NITROGEN TRANSFORMATIONS AND NITRATE ' LEAGHING FOLLOWING s'LIIDGE APPLICATION TO 11. i FOUR MICHIGAN FOREST TYPES MICHIGAN STATE UNIVERSITY _. - ANDREW .IAMES BURTON IllllltllllllllllllllllllllllllIlHllHllIlHllllllIIlIlllII I, 1293 00884 NITROGEN TRANSFORMATIONS AND NITRATE LEACHING FOLLOWING SLUDGE APPLICATION TO FOUR MICHIGAN FOREST TYPES By Andrew James Burton A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Forestry 1986 ABSTRACT NITROGEN TRANSFORMATIONS AND NITRATE LEACHING FOLLOWING SLUDGE APPLICATION TO FOUR MICHIGAN FOREST TYPES By Andrew James Burton Nitrogen transformations following sludge application to four Michigan forest types were studied by aerobically incubating intact cores containing the forest floor and upper 10 cm of mineral soil. Net nitrification following surface application of anaerobically digested sludge was Glower in pine cores than in cores from aspen, northern hardwoods and oak sites. Net nitrification was reduced in oak cores receiving incorporated sludge, limed undigested sludge and liquid sludge prepared from freeze-dried sludge. Results suggested bacteria responsible for a majority of net nitrification were added with the sludge, and the surface sludge layer provided the most favorable zone for nitrification. Net nitrification differences among types could not be used to predict differences in NO3--N leaching following field sludge application. Groundwater NO3T-N concentrations following sludge application at 9 Mg/ha solids and 500 kg/ha N were compatible with the 10 mg/L public health standard for NO3T-N in drinking water. ACKNOWLEDGEMENTS I would like to thank Dr. James B. Hart, Jr., my major professor, whose advice, guidance and support were invaluable throughout the duration of this study. Thanks also goes to Dr. Kurt's. Pregitzer, Dr. Frank N. D'Itri and Dr. Dean H. Urie for serving on my committee and reviewing this thesis. Additional thanks goes to Dr. Urie for his advice during the planning of this study and his help in field sample collection. A special thanks goes to Dr. Phu Van Nguyen for his invaluable assistance during all phases of this research. I also gratefully acknowledge my fellow graduate students Neil MacDonald, Dennis Nerkel, Eunice Padley and Robert Cheney for their advice and for helping me maintain a proper perspective and a productive attitude. Thanks also goes to Connie Bobrovsky and Theresa Clark for their help during the often tedious analytical phase of this research. I would like to express my gratitude to my parents for their encouragement and assistance during all stages of my education. Finally, I thank Laurie Greenwood for her patience and encouragement during this labor. iii TABLE OF CONTENTS LIST OF TABLES . . . . . . . . . . . . . LIST OF FIGURES . . . . . . . . . . . . . Chapter I INTRODUCTION . . . . . . . . . . II REVIEW OF LITERATURE . . . . . . SLUDGE NITROGEN COMPOSITION . SLUDGE NITROGEN CYCLING . . . Methods of Investigation . . Mineralization . . . . . . . Volatilization . . . . . . . Nitrification . . . . . . . Denitrification .. . . . . . Immobilization . . . . .I. . Nitrate leaching . . . . . . III STUDY SITE CHARACTERIZATION . . SITE DESCRIPTIONS . . . . . . Aspen Site . . . . . . . . . Northern Hardwoods Site . . Oak Site . . . . . . . . . . Pine Site . . . . . . . . . FOREST FLOOR AND SOIL CHEMICAL AND PHYSICAL PROPERTIES . . iv Page vii l4 17 21 24 26 33 33 36 37 37 39 4O Chapter . IV INCUBATION EXPERIMENTS . . . . . MATERIALS AND METHODS . . . . Experimental Designs . . . . Sludge Characteristics . . . Sample Collection and Incubation Treatment Application . . . Sample Analysis: 1984 Experiments Sample analysis: 1985 experiments Statistical Analysis . . . . . . . RESULTS AND DISCUSSION . . . . Forest Type Effects . . . . Incubation Method Effects . Sludge Type Effects . . . . Sludge Loading Rate Effects Sludge Application Method Effects Effects of Time Between Application and Incubation Sludge N Composition Effects Sludge Acidity Effects . . . V NITROGEN LEACHING . . . . . . . FOREST SLUDGE FERTILIZATION DEMONSTRATION PROJECT . . . Materials and Methods . . . Results and Discussion . . . Aspen site . . . . . . . . Northern hardwoods site . Oak site . . . . . . . . . V Page 43 43 43 48 50 53 54 55 55 56 56 61 67 70 73 73 77 82 84 84 84 85 90 92 96 Chapter Page Pine Site 0 O O O O O O O O O O O O O 96 Relationship of leaching to incubation results . . . . . . . . . 99 LEACHING CORES . .. . . .. . . .. . .. 107 Materials and Methods . . . . . . . . . 107 Results and Discussion . . . . . . . . . 109 VI SUMMARY AND CONCLUSIONS . . . . . . . . . . 116 SUMMARY: INCUBATION EXPERIMENTS . . . . . 116 SUMMARY: NITROGEN LEACHING . . . . . . . 121 CONCLUSIONS . . . . . . . . . . . . . . . 123 APPENDIX A Core pH Data . . . . . . . . . . . . . . 126 APPENDIX B Core Moisture Data . . . . . . . . . . . 129 APPENDIX C Field Incubation Temperatures . . . . . . 133 LIST OF REFERENCES . . . . . . . . . . . . . . . . . 135 vi 4.8 4.9 4.10 4.11 LIST OF TABLES First year sludge N mineralization rates 0 O O O O O O O O O C O C O O O NO '-N concentrations in soil Ieachate and groundwater following forest sludge application . . . . . . Stocking for the northern hardwoods, oak and pine stands . . . . . . . . . Mean forest floor and surface soil characteristics . . . . . . . . Summary of forest type eXperiment . . . Summary of incubation method experiment Summary of sludge type experiment . . . Summary of sludge loading rate experiment . . . . . . . . . . . . . Summary of sludge application method experiment I I O O C C I C O O O C 0 Summary of time since application experiment 0 O O O O O O O O O O O 0 Summary of sludge N composition experiment . . . . . . . . . . . . . Summary of sludge acidity experiment . Sludge characteristics . . . . . . . . Sludge loading rates . . . . . . . . . Mean N contents for control cores of forest type experiment . . . . . . . vii Page 13 27 38 41 45 45 46 46 47 47 49 50 51 53 57 Table 4.12 4.13 4.14 4.15 4.16 4.17 4.18 4.19 4.20 4.21 4.22 5.1 5.4 5.5 5.6 Mean N contents for sludge treated cores of forest type eXperiment . . . . . Mean NO T-N contents for sludge treated cores of the incubation method experiment . . . Mean TIN contents for sludge treated cores of the incubation method experiment . . . . . . . . . . . . Mean NO T-N contents for control cores of the incubation method experiment Mean TIN contents for control cores of the incubation method experiment . Mean N contents for sludge type experiment . . . . . . . . . . Mean N contents for sludge loading rate experiment . . . . . . . . . . Mean N contents for sludge application method experiment . . . . . . . . . Mean N contents for time since application experiment . . . . . . Mean N contents for sludge N composition experiment . . . . . . Mean N contents for sludge acidity EXperillent e e e e e e s e e s s 0 Characteristics of well locations . . Characteristics of sludge treatments applied in forest fertilization demonstration project . . . . . . . Aspen well NO3T-N concentrations . . Aspen lysimeter NO3T-N concentrations Northern hardwoods lysimeter N03 -N concentrations . . . . . . . Northern hardwoods well NO3--N concentrations . . . . . . . . . . Oak lysimeter N03T-N concentrations . viii Page 58 63 65 66 68 69 71 74 75 78 83 87 88 91 93 94 95 97 Table 5I14 Pine well N03T-N concentrations . . . . . Pine lysimeter NO3--N concentrations . . Groundwater NO3T-N site comparisons . . . Soil leachate NO3T-N site comparisons . . Chemical composition of simulated rainfall I I I I I I I I I I I I I I I Cumulative net NO “-N and NR4T-N contents leached for sludge N composition experiment I I I I I I I I I I I I I I Cumulative net NO3T-N and NH4T-N contents leached for sludge acidity experiment I I I I I I I I I I I I I I Core forest floor pH values for 1984 incubation experiments . . . . . . . . Core soil pH values for 1984 incubation experiments . . . . . . . . . . . . . . Core soil and forest floor pH values for 1985 incubation experiments . . . . . . Soil and forest floor moisture contents at -0.10 bars for the four forest types I I I I I I .I I I I I I I I I I I Core forest floor moisture contents for 1984 incubation experiments . . . . . . Core soil moisture contents for 1984 incubation experiments . . . . . . Core soil and forest floor moisture contents for 1985 incubation experiments . . . . . . . . . . . . . . Field incubation temperatures . . . . . . ix Page 98 100 103 104 108 110 111 126 127 128 129 130 131 132 133 5.3 LIST OF FIGURES The sludge N cycle . . . . . . . . . . . Locations of stands used in forest sludge fertilization demonstration project . . Locations of study sites within demonstration project stands . . . . . Sludge-control NO3--N content differences for the forest type experiment I I I I I I I I I I I I I I Sludge-control TIN content differences for the forest type experiment . . . . NO3T-N contents in sludge treated oak cores . . . . . . . . . . . TIN content increases over time for the sludge N composition experiment . . . . Locations of demonstration project wells and lysimeters . . . . . . . . . Cumulative net NE +--N content leached vs. NE4 -N content in destructively sampled cores of 1985 incubation experiments . . . . . . . . Cumulative net NO —-N content leached vs. N03 -N content in destructively sampled cores of 1985 incubation experiments . . . . . . . . Page 34 35 60 62 79 81 86 114 115 CHAPTER I INTRODUCTION Wastewater treatment, in addition to producing clean water safe for discharge, yields a significant quantity of residue material--s1udge.81udge production in the United States was expected to double from 3.6 to 7.3 million metric tons between 1970 and 1985 (Walsh 1976), creating a growing need for environmentally sound disposal methods. Current practices include incineration, surface impoundment, landfilling, ocean dumping and land application. In 1978 these methods accounted for the disposal of 22,11, 33, 10 and 24 percent of sludge produced in the United States, respectively'(U.S.EPAq 1980). Virtually all current land application is associated with agriculture, but interest in forest land application is growing. Two main reasons for this are: l) the availability of forest land to communities far from large agricultural areas; and 2) the ability of sludge to increase forest productivity (Bledsoe and fasoski 1978; Hinckley et a1. 1983; Zaaoski et al., 1983). Additional advantages have been recognized. Bledsoe and Zasoski (1978) state forested areas reduce chances of human contact with waste material and remove metals and potential pathogens from the human food chain. Reynolds and Cole (1981) note forests are perennial, allowing for flexibility in application timing, 2 and forest soils typically have high infiltration and permeability, minimizing surface runoff problems. Cost effectiveness and growth response can both be increased by using higher application rates, but maximum rates need to be determined in order to avoid potential pollution hazards. The limiting factor is often leaching of nitrate to groundwater (King and Morris 1974; Brockway and Urie 1983, Harris et a1. 1984L.A.major reason for this is methemoglobinemia, a condition in which fixation of nitrite to bloodstream hemoglobin prevents oxygen transport, causing a clinically detectable cyanosis (Craun en: a1. 1981). Reduction of nitrate to nitrite in the gastrointestinal tract by microorganisms is the causative factor (Lee 1970). The disease is common in infants less than six months old due to higher gastrointestinal tract pH, which allows growth of nitrate reducing bacteria, and incomplete development of methemoglobin reductase enzyme systems (Fraser and Chilvers 1981). The condition can also be fatal to livestock ingesting nitrate rich water (Lee 1970). A public health standard of 10 mg/L for NO3'-N in drinking water has been established because of the potential health hazard (0.8. EPA, 1977). The possible formation of carcinogenic N- nitroso compounds in the gut has also been noted (Fraser et a1. 1980), but this probably involves nitrate concentrations higher than the 10 mg/L standard. Knowledge of factors influencing nitrate leaching beneath sludge amended forest land aids determination of 3 safe application rates. Amounts and forms of nitrogen in sludge, as well as transformations undergone by applied nitrogen, influence nitrate leaching. Little information is available regarding the processes undergone by sludge N following forest application. Therefore, incubation studies examining factors affecting N transformations following surface sludge application to forest land were initiated, and nitrogen concentrations in soil leachate and groundwater beneath sludge treated forest areas were monitored. Objectives were to determine if: 1) N transformations following sludge application are different for forests of aspen sprouts, northern hardwoods, oak and pine; 2) sludge type, application rate, application method, sludge N composition, sludge acidity and time since application affect N transformations for a mature oak forest; 3) laboratory and field incubation results for pine and oak forests are comparable; and 4) N contents in incubated samples are related to those in soil leachate and groundwater beneath sludge treated areas. The studies were conducted to provide information that would aid interpretation of results of an operational scale forest sludge fertilization demonstration project conducted by Hichigan State University between 1981 and 1985. Two related sets of experiments are discussed in this thesis following a literature review (Chapter II) and study site descriptions (Chapter III). They are: 1) investigations of N transformations following sludge 4 application to forest land through incubation techniques (Chapter IV); and 2) monitoring of nitrogen leaching from sludge treated forested areas (Chapter V). Relationships between the two sets of experiments are discussed in Chapter V. Readers not interested in one of the topics may wish to skip appropriate sections. CHAPTER II REVIEW OF LITERATURE Knowledge of the sludge N cycle provides a basis from which potential nitrate leaching following sludge land application can be estimated. In this chapter sludge N composition and cycling are introduced; after which methods used in studying sludge N cycling and factors affecting individual processes in the sludge N cycle are discussed. SLUDGE NITROGEN COMPOSTION Three major nitrogen forms are found in sewage sludge. These are organic nitrogen, ammoniunn(NH4+-N) and nitrate (N03_-N). The majority of sludge N is usually organic and ammoniacal, but relative concentrations vary considerably with sludge type and source. Sabey et al.(19750 indicate that 30 to 50 percent of N in anaerobically digested sludges is NR4+-N with virtually no NO3--N present. Sommers (1977) found organic N, NH4+-N and N03--N comprised 60, 38 and 2 percent of N in anaerobically digested sludges and 88, 8 and 4 percent of N in aerobically digested sludges, respectively. Sommers and Nelson (1981) state inorganic N can constitute from <10 to >90 percent of sludge N. Total sludge N content varies with sludge type and solids content and has median values ranging from two to four percent (Sommers, 1977). SLUDGE NITROGEN CYCLING Six processes undergone by sludge nitrogen which must be considered. when. determining application rates are mineralization, nitrification, volatilization, immobili- zation, denitrification and leaching (Figure ZLIL. Sludge NR4+-N can be lost in) the atmosphere through ammonia volatilization, oxidized to nitrate by soil bacteria (nitrification) or converted to organic ‘N through immobilization (including incorporation into the living microbial biomass and plant uptake). Nitrate contained in sludge or produced by nitrification can be immobilized, denitrified under anaerobic conditions to nitrous oxide and nitrogen which are lost as gases, or leached. Sludge organic N can be mineralized to NH4+-N after which it is subject to the transformations listed previously. !££h21£.2££Buuuu££££isa Nitrogen transformations following land application of sludge have been studied primarily through aerobic incubation of samples in the laboratory at controlled temperature and humidity (Wilson 1977; Parker and Sommers 1983; Lindemann.and Cardenas 1984). Net nitrification in such incubations is determined as the increase in sample N03'-N content over the incubation period and net mineralization as the increase in total inorganic N (N03'-N + N02'-N + NH4+-N). Changes in N contents over time in N2 NH 3 Mic 4? Volatilization Denitrification NH} Nitrification fi> N 05 4 Ci .2 0 I... .0 g .5 .42? = 4- °\\\ 3 a ,o" E g \6‘ 5 as .E 2 ’ V7 Orgaric Nitrogen Leaching Figure 2.1 The sludge N cycle 8 incubation studies have been measured in two ways. One involves destructive sampling of replicates, followed by extraction with strong salt solutions (eg. 2 N [61) and analysis of extracts.for N forms (Ryan et.al.1973; Epstein et a1. 1978; Parker and Sommers 1983). The other uses periodic leaching of samples with dilute salt solutions (eg. 0.01! CaClz) and analysis of leachate for N forms (Epstein et a1. 1978; Hagdoff and Amadon 1980; Lindemann and Cardenas 1984). Samples analyzed by the latter method have sometimes been mixed with silica sand to aid leaching (Parker and Sommers 1983; Lindemann and Cardenas 1984). Ammonia volatilization has been monitored by using R2804 to trap NH3 evolved during incubation in sealed vessels (Ryan and Keeney 1975; Terry et a1. 1978, 1981). Denitrification has been measured using gas chromatography to analyze incubation vessel atmospheres for N20 (Guenzi et a1. 1978); and both immobilization and denitrification have been investigated using 15N labeled synthetic sludge and determining in what forms sludge N exists at the termination of incubation (Epstein etial.19784 Terry et‘a1.l981). Virtually all incubation studies of N transformations following land sludge application have involved agricultural soil, and in most, sludge was mixed with disturbed samples. Only occasionally have intact cores been utilized (Sommers et a1. 1979). Experiments discussed in the remainder of this chapter are agricultural unless otherwise noted. Nitrogen transformations in unamended forest soils 9 have been studied in the field by performing in situ incubations using sealed polyethylene bags (Hatson and Vitousek 1981; Pederer 1983), but no reference to use of this technique in sludge amended soil has been found. Nitrate leaching following sludge application to forest land has been monitored in two primary ways: 1) soil leachate samples collected from the unsaturated zone using lysimeters (Sidle and Kardos 1979; Brockway and'Urie 1983; Wells et al. 1984); and 2) groundwater samples collected from the upper portion of the saturated zone using wells (Brockway and Urie 1983; Harris et a1. 1984). Mineralization Mineralization occurs as bacteria rapidly decompose organic nitrogen to ammonium. Various mineralization rates for sludge organic N have been cited in the literature. Epstein et al.(1978) report 41 percent of organic N in a digested sludge mixed with agricultural soil mineralized during fifteen weeks of incubation. Ryan et al. (1973), found 4 to 48 percent of organic N in aerobically digested sludges mineralized over sixteen weeks of incubation. Mineralization rates decrease with time following sludge application. Pratt et a1. (1973) cite a decay series of 35, 10, 6 and 5 percent of residual organic N mineralized in the first, second, third and fourth years fallowing sludge application to agricultural land in California. Wisconsin agricultural sludge application 10 guidelines are based on mineralization rates of 15 - 20, 6, 4 and 2 percent for the first four years following application (Reeney et al., 1975). High initial mineralization rates are attributed to decomposition of very labile organic nitrogen (Lindemann and Cardenas, 1984).AJ this nitrogen is depleted, mineralization rates slow. Temperatureris one of the factors responsible for the variability of mineralization rates cited in the literature. Cassman and Munns (1980) measured an increase in soil N mineralization with increasing temperature between 15°C and 30°C. Terry et al. (1979) found decomposition of a synthetic anaerobically digested sludge increased with temperature over the same range during a 336 day incubation involving both incorporation and surface application of sludge; and Edmonds and Mayer (1981) attributed slower sludge decomposition in a forested area than an adjacent clearcut in part to lower temperatures under forest cover. Moisture availability also influences mineralization rates. Cassman and Munns (1980) found Optimal moisture content for net mineralization in unamended soil occurred at -0.3 bars water potential (approximately field capacity). Less mineralization occurred under both wetter and drier conditions. Near the optimum mineralization rates are fairly consistent. Terry et a1. (1979) found water potentials in the range of -0.25 to -l.00 bars did not affect decomposition of synthetic anaerobically digested sludge incubated with agricultural soil for 336 days. 11 Moisture can also influence mineralization through formation of smaller, more labile organic molecules during frequent wetting and drying cycles (Focht and Verstraete, 1977). Carbon to nitrogen (C:N) ratios of soil, forest floor and sludge affect sludge N mineralization rates. Foth (1978) states that immobilization exceeds mineralization at C:N greater than 30 , causing a net decrease in amount of inorganic nitrogen found in a system; immobilization and mineralization proceed at approximately equal rates in the C:N range of 15 to 30; and mineralization exceeds immobilization at C:N less than 15, as is generally the case with sewage sludge. This is in agreement with the finding of Tester et a1. (1977) that net sludge mineralization decreased from 11 to 3 percent as sludge C:N increased. Sludge application method can influence mineralization. In surface applications, C:N ratio of the forest floor takes on more importance as it is there sludge is deposited. Forest floor material, especially the upper layer, often has a wide C:N ratio (Pritchett, 1979) and could immobilize sludge inorganic N. Sabey. et al. (1975) found immobilization occurred in soils treated with mixtures of bark (C:N - 133), wood (C:N . 650) and sludge when the wood plus bark to sludge ratio exceeded 1:1. If sludge is incorporated into soil, the C:N ratio of the sludge-soil mixture will determine whether net immobilization or mineralization occurs. Sludge incorporation can affect mineralization rates in 12 other ways as well. Edmonds (1979) found unincorporated sludge applied to cleared and forested Douglas-fir sites in Washington exhibited lower decomposition rates than that disked into soil. He attributed this to low porosity and poor aeration found in the deep (5 to 25 cm) surface sludge layer. Terry et al. (1979), however, found decomposition of surface applied sludge exceeded that of incorporated sludge during a 336 day incubation in which moisture potential was maintained at -1.00 bar. In the field, drying of moderate sized surface sludge applications is expected to slow mineralization to rates lower than those for incorporated treatments. Soil texture and pH ‘have little effect on mineralization in sludge treated soils (Terry et a1. 1979). Sommers et al. (1979) state decomposition of anaerobically digested sludge mixed with soil and incubated for one year was similar for five different soils. Miller (1974) found that at high sludge loading rates (90 and 224 Mg/ha) soil properties in incubated columns were effectively masked, resulting in a sludge-soil system that behaved as a sludge system regardless of soil type. Sludge type and source can significantly effect mineralization rates. Magdoff and Chromec (1977) state net mineralization of sludge organic N was 14 to 25 percent for anaerobically digested sludge and 36 to 41 percent for aerobically digested sludge over a 13 week laboratory incubation. Stephenson (1955) reported that amounts of 13 nitrogen mineralized in raw, digested and activated sludges were 7, 21 and 60 percent, respectively, for a 42 day incubation, and King (1984) found greater nitrogen availability from aerobically digested municipal sludges than from anaerobically digested ones. Differences in amounts of Nlnineralized are the result of factors such as C:N ratio, forms of organic N present, and the amount of organic N mineralized during sludge stabilization processes (eg. digestion). As a result, 0.3. EPA (1983) recommends use of the rates of sludge organic nitrogen availability shown in Table 2.1 when determining sludge application rates. Table 2.1 First year sludge N mineralization rates1 Sludge Type Organic N Available in 1st Year Raw, primary or waste activated 402 Aerobically digested 301 Anaerobically digested 151 Composted 101 1 From 0.3. EPA (1983) Mineralization rates listed in Table 2.1 are decreased by'50 percent for each additional year until a stable rate of 3 percent of remaining organic N mineralized per year is reached. Lower initial mineralization rates are more desirable as they result in nitrogen being made available more evenly over time. Mineralization rates in Table 2.1 14 are for agricultural applications in which sludge is incorporated. For surface applied anaerobically digested sludge in Washington forests, Reynolds and Cole (1981) suggested lower mineralization rates of 10, 2 and 1 percent of sludge organic N during the first three years following application. This was done to account for expected reductions in mineralization rate under the forest canopy. A final factor that can influence mineralization of sludge organic N is application rate. In general, the quantity of sludge organic N mineralized has been found to be proportional to application rate (Terry et a1. 1979, 1981). Sommers et a1. (1979), however, found the percentage of sludge organic N mineralized during one year of incubation decreased from 24 to 112 as loading rate of sludge solids increased from 22.4 to 89.6 Mg/ha. V 1 .1. . n Ammonia volatilization, the gaseous liberation of ammonium as ammonia, is another portion of the nitrogen cycle that influences potential nitrate leaching following sludge application. Beauchamp et a1. (1978) measured volatilization losses in the field in Ontario using an aerodynamic method based upon horizontal windspeed and atmospheric NR3 concentration profiles. They found 602 of NR4+-N (150 kglha) in anaerobically digested municipal sludge applied to bare soil volatilized over 5 days in May, and 562 of sludge NR4I-N (89 kg/ha) applied in October 15 volatilized within 7 days. Flux of NR3 in the experiments was closely related to air temperature at one meter. Sommers and Nelson (1981) state approximately 502 of sludge u34+-N is volatilized following application to soil surfaces. In laboratory experiments involving surface sludge application, Ryan and Keeney (1975) measured volatilization losses of 11 to 692 of applied NR4+-N, and Terry et al.(1978) found losses ranging from 10 to 352 of NR4+-N applied. For design purposes, 502 of NE4+-N contained in surface applied sludge is often assumed to volatilize (0.8. EPA 1983; Cole et a1 1984). One factor affecting ammonia volatilization is pH. Ammonia loss following land application of sludge is related to the equilibrium hydrolysis of N83 to NR4+z na4* + 03‘ -- NE3(g) + 320 Log x - 4.76 At pH 9.24 ammonium and ammonia exist in equal concentrations, but at the low pH values typically found in forest soils, very little ammonia exists. ‘Effects of soil pH on volatilization following sludge application have been investigated in several laboratory experiments. Volatilization during a 49 day incubation was 612 greater from liquid sludge surface applied to a pH 7.5 soil than from applications to the same soil with pH values adjusted to 5.3 and 6.0 (Terry et a1. 1978), and Donovan and Logan (1983) state ammonia loss from a soil with an initial pH of 7.5 was significantly higher than that from soils with pH 16 values of 6.7 and 5.1 following surface application of sludge at 5 Mg/ha. Sludge pH affects volatilization losses. Greater gaseous ammonia losses have been measured from a surface application of lime stabilized sludge (pH 12) than from treatments involving anaerobically digested and aerobically digested sludges (Donovan and Logan 1983; Logan et al. 1982). Sommers et a1. (1981) found less than five percent of sludge NH4+-N volatilized following surface and incorporated applications of acidified sludge (pH 5.0 to 5.5). Buffering capacity of the sludge/soil system can also influence volatilization losses, as illustrated by findings of experiments with unamended soils in which NR3 loss increased.‘with increasing soil buffering, capacity (Avnimelech and Laher 1977; Vlek and Stumpe 1978). Laboratory research involving surface application of anaerobically digested sludge to bare soil has also shown volatilization rates to increase with: 1) increasing temperature (Logan et al.1982; Donovan.and Logan 1983);29 increasing soil moisture content (Logan et a1. 1982; Donovan and Logan 1983); 3) decreasing soil clay content (Ryan and Keeney 1975; Terry et a1. 1978); and 4) increasing sludge application. rate (Terry' et al. 1978). Greater volatilization losses have also been measured when several small applications were used rather than a single large one (Ryan and Reeney 1975), and when vegetative coverage of straw or sod prevented sludge particles from contacting the 17 more acidic soil (Logan et a1. 1982). Sludge incorporation greatly reduced volatilization rates (Terry et al. 1978; Donovan and Logan 1983). Sommers et a1. (1979) found less than one percent of applied N was lost through volatilization during a one year incubation of soil cores in which anaerobically digested sludge was incorporated. Niggificatign Nitrification is the stepwise oxidation of ammonium, which is tightly held on soil cation exchange sites, to nitrite and then nitrate, both of which can be leached from a soil profile. Most nitrification in soil systems is carried out by two types of chemoautotrophic bacteria. These primary nitrifiers are Nitggsggm spp., which oxidize NR4+ to N02-; and Nitgghggtgg spp., which oxidize N02' to NO3-. The reactions involved are expressed by the following equations (Schmidt, 1982) NE4+ + 1.5 02 == noz' + H20 + 23* N02 ‘5’ 0.5 02 .- N03- Secondary autotrophic nitrifiers are present in far smaller numbers in soil than the primary nitrifiers, and cannot survive as wide a range of temperatures and acidities (Focht and Verstraete 1977). Heterotrophic nitrification is carried out ‘by soil. organisms including bacteria, actinomycetes and fungi, but occurs at rates 1000 to 10000 18 times slower than those of the autotrophs (Focht and Verstraete, 1977). Maxiumum nitrite and nitrate concentrations achieved by these organisms are 100 to 1000 times lower than those of their autotrophic counterparts. One factor controlling nitrification is pH, which affects both steps in the conversion of ammonium to nitrate. Nigrgbactgr spp. and Nitrosomonas spp. both exhibit optimum growth and metabolism rates under slightly alkaline conditions (pH 7 to 8) (Focht and Verstraete, 1977). Nigrobactg; app. are especially susceptible to variation in pH as they are affected by toxicities to free ammonia at alkaline pH and nitrous acid at acid pH (Terry et al., 1981). Morrill and Dawson (1967) tested a wide diversity of soils and found four common nitrification patterns related to pH. These were: 1) rapid ammonium oxidation and nitrate accumulation, characterized by a pH of 7.9; 2) rapid oxidation of both ammonium and nitrite at pH 6.4; 3) a pattern similar to 2 but having markedly reduced rates of both processes occurring, at pH 5.4; and 4) no detectable oxidation at pH 5.1. Many investigators have reported reductions in nitrification at lower pH. Gilmour (1984) found a linear increase in net nitrification with pH during a 31 day incubation of unamended silt loam soils from the same series with pH values of 4.9 to 7.2. Terry et a1. (1981) found laboratory nitrification was faster following sludge incorporation in p11 7.5 soil than in soils with pH values 19 of 6.0 and 5.3, and Thorne and Hamburg (1985) found a high correlation (r2 I 0.96) between initial forest floor pH and total NO3'-N produced during incubation of forest floors from a seven stand sequence in New Hampshire. Nitrification does not occur in many forest soils, a fact often attributed to the acidity of the organic layer and soils associated with forests (Theobald and Smith 1974; Reeney 1980). However, nitrification has been measured during incubation of forest soils with pH values lower than 4J)(Federer 1983; Robertson and Tiedje 1984). Evidently, nitrifying bacteria become acclimated to site acidity. Robertson (1982) found that, although nitrification rates in unamended samples from 10 forest sites varied widely and were not correlated with site pH, rates for all individual sites responded to raising and lowering native pH by as little‘as(L3 units. Addition of alkaline pH sludge to a forest soil creates microsites with higher pH and thus possibly increases the ability of native bacteria to carry out nitrification. Moisture and temperature both affect nitrification. Optimum moisture for nitrification is similar to that for mineralization, approximately field capacity. Terry et al. (1981) found higher nitrification rates in soils adjusted to -0.25 and -0.5 bar moisture tensions than in soils at -1.0 bar. Gilmour (1984) found nitrification rates in unamended soil increased with temperature between 16°C to 28°C and declined linearly as soil moisture was decreased from 20 to 20 12 percent by weight. Robertson (1982) states NO3‘-N production was stimulated by both increased temperature (30°C vs. 20°C) and moisture content (10, 30, so and 70: of water holding capacity) during incubation of unamended forest soils from Indiana sand dunes and the New Jersey piedmont. Sludge application rate does not generally influence the percentage of applied N nitrified (Ryan et a1. 1973; Terry et a1. 1981; Lindemann and Cardenas 1984). Total nitrate production over time in these experiments was proportional to sludge loading. Several investigators have found nitrification was reduced during the first one to four weeks of incubation following heavy sludge applications. These temporary inhibitions of nitrification were attributed to toxic materials contained in the sludge such as heavy metals (Wilson 1977) and organics (Premi and Cornfield 1969, 1971; Ryan et a1. 1973). Nitrification rates in the experiments increased rapidly following initial lag periods, and final NO3--N concentrations were proportional to sludge loading rate. Nitrification is sometimes delayed due to low initial population sizes of nitrifying bacteria. This can be caused by competition for NH4I-N among roots, mycorrhizae, nitrifiers and other nitrogen users, and has been forwarded as an explanation for lack of nitrification and delays in nitrification during incubation of forest soils (Heilman 1974; Vitousek et al. 1982). When ammonium is made 21 available, populations of nitrifying bacteria can grow rapidly. Ardakani et a1. (1974) found pOpulation sizes of Nitggggggngg spp. and Nitggbgggg; spp. were one and two orders of magnitude greater 100 days after addition of ammonium and nitrite to field soils. Maxiumum population sizes two and four orders of magnitudge larger than initial sizes were found two to four weeks, respectively, following addition of NH4+-N and N02'-N solutions. Heilman (1974) found nitrification was delayed from one to three weeks while papulations of‘autotrophic nitrifying bacteria grew during incubation of soils from three Douglas-fir sites in Washington amended with 400 ug/g of urea N. Some authors have concluded lack of nitrification in soils from climax forest ecosystems is the result of allelopathic inhibition of nitrifiers by site vegetation (Rice and Pancholy 1972, 1973, 1974; Bormann and Likens 41979; Robertson 1982). Inhibitory substances have been extracted from plants at such sites (Rice and Pancholy 1973, 1974; Theobald and Smith 1974). D . .E. i Denitrification, the reduction of NO3'-N and N02'-N to nitrogen (N2) and nitrous oxide (N20) gases from nitrite and nitrate can lessen nitrate groundwater contamination following sludge land application by reducing soil nitrate levels. Denitrification occurs under anaerobic (reducing) conditions and can proceed by either biotic or abiotic 22 pathways. Since abiotic denitrification requires high nitrite levels and low pH, it is not considered to be important under normal circumstances (Keeney, 1980). Biological denitrification involves the use of NO3' and N02' by bacteria as terminal electron acceptors during respiration in the absence of oxygen, resulting in production of N2 and N20 gases. Payne (1973) lists the following sequence of nitrogen forms N03 -- NOZ- -- NO -- N20 -- N2. The general equation for complete reduction of nitrate is - + Reducing conditions under which denitrification occurs are commonly expressed in terms of Eh, the millivolt difference in potential between a platinum electrode and the standard hydrogen electrode. Latimer (1952) states ideal Eh for the NO3'IN02- couple is 421 mV, but in biological systems, nitrate reduction occurs at lower potentials of 300 to 400 mV. Eh for the NOZ'INZ couple is 996 mV (McCarty, 1972). Such conditions do not normally exist in soils drier than field capacity (Focht and Verstraete, 1977), but denitrification can occur under apparently well-aerated conditions due to formation of anaerobic microsites within the soil matrix. Creation of such microsites is dependent on: 1) oxygen consumption rate within a microsite; 2) oxygen diffusion rate; and 3) system geometry (Focht and 23 Verstraete, 1977). Simultaneous nitrification and denitrification have occurred in incubations involving soil (Robertson and Tiedje 1984) and soil-sludge mixtures (King 1973; Sommers et a1. 1979; Lindemann and Cardenas 1984). In addition to moisture, both temperature and pH affect denitrification. Focht and Verstraete (1977) state rates increase at higher temperature and are greatest at slightly alkaline pH. Neither factor has as great an influence as it does on nitrification, due to existence of many forms of denitrifying bacteria. Fine textured soils drain more slowly than coarse textured soils, resulting in longer time periods over which denitrification can occur. Working with fifteen California field soils previously used for disposal of beef feedlot manure, Lund et al. (1974) found that 862 of the variability in NO3'-N concentrations below the rooting zone could be explained by soil texture in control sections. Olsen et a1. (1970) measured NO3--N movement in fallow Wisconsin soils amended with NH4NO3. They found NO3'-N movement through a sand soil was more rapid than through a silt loam soil, and evidence of denitrification losses was greater in the silt loam soil. Soil properties can also influence denitrification through creation of temporary saturated zones in and above different textured bands in a soil profile as wetting fronts pass (Lund et a1. 1974). Finally, sludge application rate has been shown to influence denitrification, Lindemann and Cardenas (1984) 24 measured an increase in the percentage of added N denitrified as sludge loading rate increased from 15 to 30 grams of sludge per kilogram of incubated soil. In field experiments conducted in Washington Douglas-fir forests, McRane (1984) found reducing conditions required for denitrification persisted for much greater lengths of time in areas receiving heavier surface sludge applications and appearance of NO3'-N in leachate as sludge Eh levels rose above 400 mv. Imm ' iz ion Immobilization, uptake of inorganic nutrient ions by living organisms, influences levels of various nitrogen forms in soil. Two mechanisms of immobilization affecting nitrogen levels following sludge amendment of land are: l) incorporation of inorganic nitrogen ions (NOz'-N, NO3'-N and NH4+-N) into the soil microbial biomass; and 2) uptake of inorganic nitrogen by higher plants. Vitousek and Matson (1985) found these two N sinks were the most important factors controlling N03'-N leaching losses from intensively managed loblolly pine plantations in North Carolina. A major factor controlling microbial immobilization is C:N ratio. At C:N ratios greater than 30, immobilization will exceed mineralization (Foth 1978). Net immobilization commonly occurs during incubation of high C:N materials such as forest floor and papermill sludge (Parker and Sommers 1983; King 1984).Sludge and soil organic matter, however, 25 have low C:N ratios and mineralize readily. Microbial immobilization is affected by temperature, moisture availability and sludge application rate. Terry et al. (1981) found immobilization rates were: 1) greater at higher temperatures; 2) proportional to sludge application rates; and 3) fairly similar over a wide moisture range. Greatest immobilization occurred at moisture potential of -0.25 bars (approximately field capacity), but only under very dry conditions was immobilization severely inhibited. The second form of immobilization, N uptake by higher plants, also influences nitrate leaching following sludge application.In studies involving wastewater irrigation, annual N uptake rates of 100 to 300 kg/ha have been measured (0.8. EPA 1983). Nitrogen uptake in these studies varied with tree species, stocking and age, as well as extent of vegetative understory. Cole and Henry (1983) measured average N uptake of 80 kg/ha/yr over a four year period following sludge application to a 55 year old Douglas-fir stand in Washington, but felt substantially higher N uptake and greater growth response could have been achieved if a stand 5 to 30 years in age had been used. Brockway and 0rie (1983) suggested different sludge application rates for Michigan forests containing different tree species. They also attributed lower NO3--N concentrations in soil leachate and groundwater under a stand of aspen sprouts, as compared to 40 year old pine plantations, to the ability of the young vigorous aspen to utilize larger amounts of nitrogen. 26 Zasoski et a1. (1984) attributed higher levels of NO3--N in leachate collected beneath a 55 year old Douglas-fir forest in Washington than beneath an adjacent clearcut area to more active uptake by young vigorous vegetation which rapidly occupied the clearcut area. Plant species differ in their ability to use the various forms of N. Townsend (1967, 1969) found lowbush blueberry preferred NH4+-N. Haines (1977) found NO3'-N uptake decreased and NHAI-N uptake increased with succession in South Carolina forests. McFee and Stone (1968) measured greater growth and N uptake in radiata pine and white spruce seedlings grown in a solution culture containing NH4+-N than those grown with a NO3'-N source. Durzan and Steward (1967) found laboratory grown jack pine seedlings exhibited greater growth and had higher N content when provided with NH4+-N as a N source; while white spruce seedlings grew better on NO3'-N but contained more total N when NHAI-N was used. Nitrgtg ngching Nitrate not immobilized or denitrified can be leached from a soil profile to groundwater where it presents a potential pollution hazard. NO3'-N concentrations in soil leachate and groundwater beneath areas involved in demonstration projects and plot studies investigating feasibility of forest sludge application are shown in Table 2.2. Excessive NO3--N leaching occurred following heavy sludge applications high in available N (NH4+-N and NO3--N) 27 .uum mu sewn Assesses .eu» a mafia massages mono .mmaou nooaoooum mufiaumnouod om .uowuauuaooaoo mamas» mama newsman m .uowuauuaoouoo manuuoa mama unuawam m .voaw~wnauo mafia m .uowumuucounoo owauo>a use» n o .ofinagfimps uoz m .gaflauomam voumowwmsb e .oaflu mnmamaao Hasvfi>wmnw as you nowuauunoouoo aqua uaonmwu n .ouanuaoH amen uoodfioo ou mofldauuaw uuouoawamq N .gsmmofiuma vsuuowwm hgaaowaouomud a so co" Asumuouoo soauuso so was an aumomv av-0e N~.nn no.sv a. a»; o.o «a «no a.a¢ assessaua «mesa. mm< .ezaH ao cc~ asuwfiouuo commune so was an susomv meadow N~.nm mc.ev an .5; o.o «a «no a.ae saaeaoaum «mesa. «ma .eHzH A\wa inllllan\mxilllil mn\w= some cosmos zlnoz alemz z apwaOu Auowumoodv uuoauaouu codenamed zinc: statement: annoy as: can seem smegma Avuauwumoov N.N manna (Ill: I'lv 1| lllll‘ | I) I l I III" lltlul l 'II' '\ ( ilk. II III (Ill (I 'l‘ ‘I'Il I I . lull (l ‘ lulu] I’ll t s .I: \ l|1.\| 4411‘ . .\|I|\ J .1 l 28 au cam .auh n Aacfiaoumo commune no use an mafia suaomv meadow Nu.mm no.sv an a»; Redefines o.o «z «no a.ae usaeasssm «muses cease .uane So so" .mu» ma Assauouuo commune no mo.se was an «sea a._ mum sow ~.- sesame sense. an.~ nc.e a. .»a massage; m.c ass «as o.n oasesoanm sauna. =a< .uans ao oc~ .uu» a Anom~ouao commune so nc.au at. an mafia 0.x man can ".23 genome sumac. an.“ no.¢_v an a»; mazeszos m.° ass «as o.n easesoaam omega. zn< .eans so ocu .uu» n Amufifioumo commune so mc.aa can on «sea a." can so» 3.3a ssaome sumac. an.“ «ass no.cav as .»a sameness m.o sea «as a.n assuauzum manna. =a< .Hs so .aasz a e co oommuue do m an masseuse sumac. un.n sass no.5 mamas mama sown <2 ez <2 as Aaumwnuezv amends xn< .m« as manage usoumoau as an aw .uuh N commune no ac.m~ a. use saunasamaon «2 ans cco~ LN incessansuze «seams :94 .uaaa an on .uu» an commune so «mad .m« as ao.an a. she uaau.aaw=oa <2 one econ LN xaosmuaa.sae omens. ma< Lasagna A\ma Illlllanxmxluiiul aa\mz anon venues mono Zinc: alemz z ammaou Acomuaoo~v uuoaumouu codenamed znnoz «annoyance sauce use use Lao» «mesa» Avoaawuuoov ~.N manna 29 2222 222 2222 2222 222 222222222222 2222222 no 2222 2222 so 222 222 2222 2222 22 2222222222 .2222. 22.2 0222222222 2222 22 .22 222 2222 2222 22 022.22. 222:22 2:2 22222222 A.>222=ummv 22.222 to 222 222232222 22 2222 2222 2.22 222222222 «222222 so 2222 222222 22.22 2. 222 22222 22 222 2222 2.22 22222 22222. 222 222 02222 A.mamm 3ozv commune no 22.2 as 22 .222 22:22 <2 22 222 2.22 22222222222 222222 222 2222 .22 22 22.2 22 .22 222222222 .2 <2 22 22 2.2 22222222222 222222 222 2222222 ao cmu Aaouwuwnomzv ouumuao no 22 222 223222 222 <2 <2 222222222222 222222 22.22 22.222 22 222 222-2222222 <2 <2 2222 222 2222a2 «22:22 22< .2222 as 222 222222222222 22 222222 02 ona uaoumoHo unannoouuuha 222202 nn.N« 22.222 22 222 22212222222 <2 <2 2222 222 0222.22 22222. 22< .2222 as 922 Accuwaws2aav ooamuza no 02 on~ uuoumoao amounoouuamn meagoe Nn.NN 22.22 22 222 222-2222222 <2 <2 2222 222 02222.2 222222 22< .2222 as com Auoumc2semsv commune no 22 222 223222 222 2222222222 222222 22.22 22.22 22 .22 222-2222222 <2 <2 2222 222 02.2.22. 02222. 22< .2222 A\wa Illlllun\wxiinlll mn\wx x202 moguoa mono zanoz zucmz z 222202 Acowumoo2v unusuaouu sensuouou Zimoz mmfiuouamox aauoh Mun mum fiwom mwmudm AvoaumuaooV ~.~ canny 30 a. 222 22..2222..22 22 2.2.22 .. 222 .2.22.2. 2.222.22.2 .222.. 22.22 22.22 .. .22 .22-..222.2 <2 <2 2222 222 .2222 .2222. 22< .2222 Be and Aaouwawneesv eeemuse :0 22.22 .2 222 22.2..2. <2 <2 22222 222 2.2.2.2222 .222.. 22.22 2222 22. 22.222 .2 .22 222-..222.2 <2 <2 2222 222 .2222 .2222. 22< 2222 22.2.22 emuwameee Aeeeeeuaeav 02 003220 a. 22 .222 .22222222 .222.. 222 2222 .2. .. 22.22v 2. .22 222.22.2 2<2 22v 2222 2.22 .2222 .2222. 22< ..22.22 22.22 2.22 222 2222 2.22 22.22 ..22 22 2.22 22 2222 2.22 22.222.222 ...222. 2. 22.2 a 2 2. .22. 2.2 2.2 22 222 2.2 2.2.2.2..2 .222.. 22.2 22.2 .22.: 2.2...2222 2.2 22 222 2.2 .2222 .2222. 2222 .2222 22.22 ...2 22 .222 2.2 222 2222 2.22 22.222.222 ...222. 2. 22.2 a. 222 ..22a-2.2 2.2 222 222 2.2 22.22..2222 .222.. 22.2 22.2 2. .22 2.2.....22 2.2 22 222 2.2 .22... .2222. 22< .2222 22.2. 2.2 222 2222 2.22 22.222.222 ...22.. 2. 22.22 a. 222 22.2..2. 2.2 222 2222 2.22 2.2...22.2 .222.. 22.2 2222 .222 22.2 .. 2.22 ..2.< 2.2 222 222 2.22 .222< .2222. 222< 22. 2.22..22 2222 -n----22\22--a--- 22222 seem monuea 2020 Zlnoz zlemz z 202202 Auowueeoav uueaueeuu eemeueuea 2-222 2222.222.2 2.2.2 222 22. 22.2 .2222. 00220022220 0&0022 uoeuou muwaoauom 2020320002» use eueneee2 2202 02 euowueuuueonoe atlnoz ~.N eaneh 31 (SidLe and Kardos 1979; Stednick and wooldridge 1979; Riekerk 1981; Brockway and Urie 1983). As a result, more recent experiments have been designed with sludge solids loading rates in the 10 to 20 Mg/ha range (Cole and Henry 1983; Urie et al.19840. Length of time for which NO3'-N concentrations remained above the 10 mg/L public health standard has ranged from never exceeding the standard following low sludge dosages (Brockway and Urie 1983; Koterha et a1. 1979) to concentrations still in excess of 100 mg/L two and three years following excessive applications (Riekerk 1978, 1981; Stednick and Wooldridge 1979). Sludge characteristics influence NO3‘-N leaching, as is illustrated by the data in Table 2.2. Leaching was common following application of anaerobically'digested municipal sludge, but Koterha et a1. (1979) measured virtually no increase in NO3'-N concentrations in soil leachate at the 45 cm depth following surface treatment of a northern hardwoods forest in New Hampshire with limed stabilized sludge. Little 803'-N was also found in soil leachate beneath areas in South Carolina treated with an aerobically processed solid sludge containing virtually no inorganic N and having a fairly wide C:N ratio of 20 (Wells et a1. 1984). The undigested papermill sludge used by Brockway and Urie (1983) promoted N03'-N leaching losses resembling those following application of anaerobically digested municipal sludge to similar sites, but the sludge had been N enriched, lowering 32 its C:N ratio to 9, and improving its biodegradability. Repeat applications of sludge to the same area have promoted increased NO3--N leaching losses. Zasoski et a1. (1984) measured a yearly average N03'-N concentration of 37 mg/L 50 cm beneath a forested area in Washington receiving 2.5 cm of dewatered anaerobically digested sludge. In the year following reapplication of 2.5 cm of sludge (applied one year after initial treatment) average concentration in leachate increased to 54 mg/L. In Michigan, Urie et a1. (1978) found peak NO3'-N concentrations in soil leachate 120 cm beneath one year old aspen sprouts increased from 25 and 75 mg/L following single applications of municipal sludge at 23 and 46 Hg/ha of sludge solids, to 125 and 150 mg/L when the sludge was applied in two increments 12 months apart. Slower water movement in fine textured soils causes nitrate flushes to occur over a longer period of time and peak at lower concentrations (Olsen et a1. 1970). Riekerk and Zasoski (1979) found NO3'-N leaching losses were greater following sludge application to coarse than fine textured soils in Washington forests. Bands of different textures in a soil will also influence the amount of nitrate leached, as was discussed in the section dealing with denitrification. Brockway and Urie (1983) found soil leachate 803'-N concentrations following sludge application to a Michigan pine plantation were lower in soil containing textural bands. CHAPTER III STUDY SITE CHARACTERIZATION Study sites used in the experiments are located in Montmorency County, Michigan, on the Atlanta Forest Area of the Mackinaw State Forest (45°N, 84°10'W), in control areas of stands used in a forest sludge fertilization demonstration project conducted by Michigan State University from 1981 to 1985 (Figures 3.1 and 3.2). Four different forest types were involved: aspen, northern hardwoods, oak and pine. Precipitation in the area averages 69.1 cm per year, and mean annual temperature is 6.3°C (Strommen 1971). SITE DESCRIPTIONS Vegetation and soils data for the four stands were collected by Michigan State University as part of the demonstration project. Overstory data and soil survey information presented in this chapter were collected in 1981 (Hart et al. 1984). Regeneration and ground flora data were collected in 1985 (Hart et a1. 1986). Soils information given is for study site locations indicated in Figure 3.2. Vegetation data are averages for demonstration project control plots (Figure 3.1). 33 34 E N Tm Lao A ' Aspen H = Northern hardwoods O = Oak P - Pine Figure 3.1 Locations of stands used in forest sludge fertilization demonstration project 3S magnum muonoua :oMuauumcoamv cmnufla mmufim zmaum mo «gawumooq ~.n shaman ouwm osam 3.1a ous . Hum 01“ - - ' _ 01¢ WHIO . allul an: —l_-l_ voosvumm llll! _ Hue male male m Hum HIN 01H _ 22.; 33m “0 1 Av omvaflu van and udmmua "me «aways “a .28. douuaoo no , mama noam< mafia xmo nzuumg m yum yum u cum Hum mans one maun menu .70 Ill! main sin A one 1 w 11.1. 131 1 o. E . maid male 01 onu _ IIIL - 36 11am ___Site The aspen site was located in a stand of 12 to 13 year old aspen sprouts. Bigtooth aspen (ngulug grandidentggg Michx.) predominated, with scattered quaking aspen (Populua mmgloideg Michx.), oak (Quercug spp. L.), cherry (Pruggg spp. L.), and other species occurring. The stand was clearcut during 1972 and 1973 for wildlife habitat improvement. To promote aspen suckering the eastern half of the area was burned in 1973, and the entire area was burned in 1975. The site was previously occupied by an open mixed hardwood stand containing aspen, red oak (Quercus ££h££.1u)p red maple (Age; ggbrgg L.) and white birch (£2531; papyrifgra Marsh.). Common ground flora species in 1985 included hracken fern (agrigigg gagiligug (1..) Kuhn), wintergreen (Egglghggig pgggggbgg; In), early low bdueberry (laggigigg gnggggifglium Ait.), sweetfern (figmptonia peregring L.). asters (Aster spp. In) and raspberries (Rubus spp. I”). Vegetative coverage was high, often approaching 1002. Soils were a mixture of the Rubicon and Montcalm series. The Rubicon series (sandy, mixed frigid Entic Raplorthods) are deep, excessively drained soils formed in sandy glacial drift deposits (Soil Conservation Service 1979a) and the Montcalm series (coarse-loamy, mixed, frigid Eutric Glossoboralfa) are deep, well drained soils formed in sandy and loamy glacial drift deposits (Soil Conservation 37 Service 1984). Northern Hardwoods Site The northern hardwoods study site was situated in an uneven-aged stand of red maple and sugar maple (Age; aggghargg Mmrsh.). Associated species included American beech (Fggus grandifolia Ehrh.), yellow birch (Begglg gllgghanignsis Britton), paper birch (Betulg papyrifgga Marsh), red oak, American basswood (Tilia aggricgng L.), eastern hemlock (Tang; cgngdensis (Lu) Carr.) and white ash (11.15.119.19. american; L.) (Table 3.1). Ground vegetation coverage was sparse, usually less than 101. Common species included starflower (Trientglig boggalig Raf.), asters, bracken fern, violets (Viola spp. In) and Canada mayflower (Mgignghgmgg gangdgnge Dest. Sugar maple, american beech and red maple seedlings were present. The study location was situated on soils of the Mancelona series (sandy, mixed, frigid Alfic Haplorthods), deep, somewhat excessively drained soils formed in glacial drift deposits (Soil Conservation Service 1982a). 23L.§i££ The oak study site was occupied by a 70 year old oak stand containing red oak, black oak (Qggrcus yelgtina Lam.), white oak (Qggrggs 51h; L.), red maple and scattered pines (Ping. spp. L.) and aspen (Popglgg spp. L.) (Table 3.1). 38 Table 3.1 Stocking for the northern hardwoods, oak and pine stands1 Hardwoods Oak Pine Species 32 8A3 N BA N BA Sugar maple 129 5.69 Red maple 101 4.64 152 5.06 American beech 25 1.31 Basswood 33 1.98 White oak 118 7.12 Red oak 118 8.36 Jack pine 413 11.12 Red pine 144 6.14 1 Based upon trees greater than 10 cm diameter at 1.3 m height on control plots, 2 Number of trees per hectare. three plots per type. 3 Basal area in square meters per hectare at 1.37 m height. 4 Includes some black oak. 39 Ground flora cover averaged about 20%. Common species included bracken fern, wintergreen, asters and Canada mayflower. Red maple seedlings were abundant. White oak, red oak and cherry seedlings were common. Soils belonged to the Graycalm series (mixed, frigid Alfic Udipsamments), deep, somewhat excessively drained soils formed in sandy glacial drift deposits (Soil Conservation Service 1979b). Ping Site The pine study site was situated in a plantation of jack pine (Pinus banksiana Lamb.) and red pine (Pinug :gsinoga Ait.) which contained minor amounts of northern pin oak (Querggs ellipsoidalis E. J. Hill) (Table 3.1). Vegetative ground cover was typically greater than 502. Common species included early low blueberry, bracken fern, wintergreen, carex (955;; pensylganica Lam.) and bearberry (Arctggggphzlos uva-ursi 1”). Regeneration was sparse. Species occurring included northern pin oak, red maple, cherry and jack pine. Soils at the site belonged to the Grayling series (mixed, frigid Typic Udipsamments), deep excessively drained soils formed in deep sandy deposits on outwash and lake plains (Soil Conservation Service 1982b). 4O FOREST FLOOR AND SOIL CHEMICAL AND PHYSICAL PROPERTIES Samples taken at each site for characterization of chemical and physical properties included five forest floor samples collected using a 0.09 square meter metal frame and samples of mineral soil beneath each forest floor sample. Forest floor material was divided into fractions designated as 01, intact organic material that is recognizable and not discolored by decompositional processes; and O2, finely divided decomposed organic materials. Samples were oven dried at 65°C, weighed, ground, and subsampled for analysis of total N, organic carbon and pH. Organic carbon was determined using a Walkley-Black titration method (Black 1965). Total N was determined using a micro-Rjeldahl procedure with analysis on a Technicon AutoAnalyzer II system (Technicon 1977a), and pH was measured in a 1:5 forest floor-water mixture. At each sampling point five cores of the upper 10 centimeters of mineral soil collected using a soil probe were composited, oven dried at 105°C, passed through a 2 mm seive and subsampled for analysis of pH, total N, and organic carbon. Soil pH was measured in a 1:1 soil-water mixture. Two 20 cm3 bulk density cores were also taken at each point. A major difference among forest floors of the four types was weight (Table 3.2). Northern hardwoods and oak forest floors were heavier than those at aspen and pine, ‘llll'lll'l’ 41 Table 3.2 Mean forest floor and surface soil characteristics Forest type Component mean1 FF weight 01 total N 02 total N kg/ha -------------- Z --------------- Aspen 28600a 1.72a 1.18a N. hardwoods 72000c 1.55b 0.92b Oak 59200c 1.54b 0.71b Pine 36700b 1.10c 0.91b ............. z----------_-- Aspen 43.3 24.3 25.2a 20.6a N. hardwoods 45.2 22.8 29.4a 20.7ab Oak 46.2 21.0 30.1a 30.3bc Pine 49.3 29.4 45.1b 34.7c 01 pH 02 pH 8011 p8 Soil bulk density Aspen 5.11a 5.24a 4.73b 1.35 N. hardwoods 5.18a 5.42a 5.08c 1.37 Oak 5.06s 4.55b 4.43ab 1.34 Pine 3.98b 3.91c 4.20a 1.36 Soil total N Soil organic C Soil C:N ratio .............. z--------_---_-- Aspen 0.083s 1.48s 18.2 N. hardwoods 0.027b 0.70b 23.8 Oak 0.026b 0.61b 23.4 Pine 0.043b 1.08ab 23.1 1 Means in the same column within subtables followed by a different letter are significantlydifferentat the .05 level of probability. 42 with pine forest floor also heavier than that at aspen. Aspen forest floor had higher total N concentrations in both the 01 and 02 than did forest floors of the other types. Pine 01 had lower total N content than found in oak and northern hardwoods 01 layers. Organic carbon percentages of the four types were similar in both the 01 and 02 layers. Pine 01 had a higher C:N ratio than 01 of the other three types. C:N ratios measured in the aspen and northern hardwoods 02 were less than those in pine. Aspen 02 C:N ratio was also less than that of oak. Aspen and northern hardwoods C:N ratios in both the 01 and 02 were in a range where neither mineralization nor immobilization should predominate. Oak 01 and 02 C:N ratios suggested immobilization may exceed mineralization, and pine 01 and 02 C:N ratios indicated net immobilization would occur. Pine forest floor was more acidic than those at the other sites in both the 01 and 02 layers. Oak 02 was more acidic than those at the northern hardwoods and aspen sites. Aspen site surface soil had higher levels of total N and organic carbon than those at the other three sites; however, C:N ratios were not significantly different (Table 3.2L.Soil C:N ratio at all four sites was in the range in which neither mineralization nor immobilization are reported to dominate. Pine site soil was significantly more acidic than soil at the aspen or northern hardwoods sites. The northern hardwoods site had less acidic soil than the other three sites. CHAPTER IV INCUBATION EXPERIMENTS Incubation experiments investigating nitrogen transformations following sludge application to forest land were conducted in the laboratory at Michigan State University and in the field at the oak and pine sites. Eight separate experiments investigated the influence of: 1) forest type; 2) incubation method; 3) sludge type; 4) sludge application method; 5) sludge application rate; 6) time between sludge application and incubation; 7) sludge N composition; and 8) sludge acidity. The sludge N composition and sludge acidity experiments were conducted in 1985, nine months after the other experiments. Due to differences in experimental procedures used, they are discussed separately in several sections and are referred to as "1985" experiments. MATERIALS AND METHODS Expggi;gg§§1 Design; The incubation method experiment was designed as a two factor analysis of variance (ANOVA). The others were each designed as a one factor ANOVA. Sludge treatments mentioned in experimental designs are described in detail in the following section. The forest type eXperiment had four levels: aspen, 43 44 northern hardwoods, oak and pine. Both control cores and cores treated with anaerobically digested sludge were incubated so sludge treatment effects could he‘determined (Table 4.1). The incubation method experiment used two levels of an incubation factor, laboratory and field, and two levels of a forest type factor, oak and pine. Treated and control cores were again used so that affects of sludge treatment could he examined (Table 4.2). The sludge type experiment was designed with three levels: 1) no sludge; 2) anaerobically digested municipal sludge from Alpena; and 3) limed undigested sludge from Grand Ledge (Table 4.3). The freeze-dried sludges used in the sludge N composition and sludge acidity experiments provided an additional sludge type that was used for comparative purposes. The sludge loading rate experiment had treatment levels of 0.0, 4.2, 10.5, and 16.8 Mg/ha of sludge solids (Table 4.4). The sludge application method experiment had four levels: 1) surface application to intact cores; 2) incorporation of sludge and forest floor into the soil; 3) removal of forest floor followed by sludge incorporation into soil; and 4) unamended control cores (Table 4u5). The time since sludge application experiment had three levels: 1) cores which received Alpena sludge on the day incubation was initiated; 2) cores which were taken from an 45 Table 4.1 Summary of forest type experiment Year performed Forest types used Sludge used Application rates Application method Incubation method Sampling schedule Variables analyzed Statistical method Summary of 1984 Aspen, northern hardwoods, oak and pine Anaerobically digested municipal sludge from Alpena 0.0 and 4.2 Mg/ha of solids Surface application of liquid sludge Lab incubation at 25°C and 801 RR 0, 2, 4 and 8 weeks Contents of NH +-N, No3'-N and TIN One factor ANO A comparing the four forest types. Untreated and treated cores were statistically analyzed as separate experiments Table 4.2 incubation method experiment Year performed Forest types used Sludge used Application rates Application method Incubation methods Sampling schedule Variables analyzed Statistical method 1984 Oak and pine Anaerobically digested municipal sludge from Alpena 0.0 and 4.2 Mg/ha of solids Surface application of liquid sludge Lab incubation at 25°C and 802 RH and field incubation in polyethylene plastic bags 0, 2, 4 and 8 weeks Contents of NH +-N, No '-N and TIN Two factor AND A with incubation method and forest type as factors. Treated and untreated cores were statistically analyzed as separate experiments. 46 Table 4.3 Summary of sludge type experiment Component Description Year performed 1984 Forest type used Oak Sludges used Anaerobically digested municipal sludge from Alpena and limed undigested sludge from Grand Ledge Application rate 4.2 (Alpena) and 10.2 (Grand Ledge) Mg/ha of solids Application method Surface application of liquid sludge Incubation method Lab incubation at 25°C and 802 RH Sampling schedule 0, 2, 4 and 8 weeks Variables analyzed Contents of NH +—N, N03 -N and TIN Statistical method One factor ANOGA with the two sludge types and an unamended control as factor levels. Table 4.4 Summary of sludge loading rate experiment Component Description Year performed 1984 Forest type used Oak Sludge used Anaerobically digested municipal sludge from Alpena Application rates 0. 0, 4.2, 10.5 and 16. 8 Mg/ha of solids Application method Surface application of liquid sludge Incubation method Lab incubation at 25°C and 801 RH Sampling schedule 0, 2, 4 and 8 weeks Variables analyzed Contents of NH -N, N03 -N and TIN Statistical method One factor ANOéA with the four sludge loading rates as factor levels ------------------------------------------------------------ 47 Table 4.5 Summary of sludge application method experiment Component Description Year performed 1984 Forest type used Oak Sludge used Anaerobically digested municipal sludge from Alpena Application rate 4.2 Mg/ha of solids Application methods Liquid sludge surface applied, incorporated with the forest floor and soil, and incorporated into soil following removal of forest floor Incubation method Lab incubation at 25°C and 801 RH Sampling schedule 0, 2, 4 and 8 weeks Variables analyzed Contents of NH +-N, NO3'-N and TIN Statistical method One factor ANO A with the three application methods and an unamended control as factor levels Table 4.6 Summary of time since application experiment Component Description Year performed 1984 Forest type used Oak Sludges used Anaerobically digested municipal sludges from Alpena and Rogers City Application rates Alpena sludge at 4.2 Mg/ha of solids immediately prior to incubation and Rogers City sludge at 5.0 Mg/ha of solids 2.75 years prior to incubation Application method Surface application of liquid sludge Incubation method Lab incubation at 25°C and 801 RR Sampling schedule 0, 2, 4 and 8 weeks Variables analyzed Contents of NH +-N, NO '-N and TIN Statistical method One factor AND A with incubation 0.0 and 2.75 years after application, and an unamended control as factor levels 48 area that had received sludge 2.75 years earlier; and 3) control cores (Table 4.6). The sludge nitrogen composition experiment had four levels. These were a control and three liquid sludges prepared from freeze-dried sludge and having identical total N content but different proportions of organic N and NH4I-N (Table 4.7). The sludge acidity experiment had four levels including pH values of 4.5, 6.0 and 7.5, and a control (Table 4.8). Sludgg.Chg;acteristics Liquid sludges used in the experiments included: 1) anaerobically digested municipal sludge from Alpena, Michigan; 2) limed undigested municipal sludge from Grand Ledge, Michigan; and 3) liquid sludges prepared from freeze- dried anaerobically digested municipal sludge of known composition. Five 100 ml liquid samples of Alpena and Grand Ledge sludge were weighed to determine sludge density, dried at 65°C, reweighed to determine percent solids, and analyzed for total N (Technicon 1977a) and organic carbon (Black 1965). Five additional 5 ml samples were extracted with 2 5 [Cl and analyzed for NR4+-N and NO3'-N on a Technicon AutoAnalyzer II system (Technicon 1971, 1977b). Three sludges 1with different solids content were prepared from the freeze-dried sludge. Sludges with lower solids content were amended with NH401 so that all had the same total N content. Sludge pH was adjusted to 7.5 by 49 Table 4.7 Summary of sludge N composition experiment Year performed Forest type used Sludges used Application rates Application method Incubation methods Sampling schedule Variables analyzed Statistical method 1985 Oak Anaerobically digested municipal liquid sludges prepared from freeze-dried sludge and having same total N content but different proportions of organic N and NH4+-N Freeze-dried l: 226 kg/ha organic N 20 kg/ha NR +-N 10.0 Mg/ha so ids Freeze-dried 2: 150 kg/ha organic N 95 kg/ha NH +-N 6.7 Mg/ha so ids Freeze-dried 3: 75 kg/ha organic N 170 kg/ha NH +-N 3.3 Mg/ha so ids Surface application of liquid sludge Lab incubation at 25°C and 801 RR 0, 1, 2, 4, 6, 8, 10 and 12 weeks Contents of NH +-N, NO3'-N and TIN One factor AND A with the three freeze- dried sludges and an unamended control as factor levels 50 Table 4.8 Summary of sludge acidity experiment Component Description Year performed 1985 Forest type used Oak Sludge used Freeze-dried sludge 2 (see Table 4.7) Application rate 6.7Mglha solids Application method Surface application of liquid sludge Incubation methods Lab incubation at 25°C and 802 RH Sampling schedule 0, 1, 2, 4, 6, 8, 10 and 12 weeks Variables analyzed Contents of NH -N, N03 -N and TIN Statistical method One factor ANOgA with sludge pH values of 7.5, 6.0 and 4. 5, and an unamended control as factor levels adding RC1 or NaOR. Additional treatments of the medium solids content sludge (freeze-dried sludge 2) were adjusted to pH 6.0 and 4.5 for use in the sludge acidity experiment. Sludge characteristics are summarized in Table 4.9. Somolo Collection and Inoobation Intact cores containing the forest floor and upper 10 cm of mineral soil were collected in lengths of 3.81 cm inside diameter PVC pipe and served as the experimental unit for the incubation studies. Cores used in laboratory incubations were transported on ice to the laboratory and placed in a cold room. On the following day treatments were applied and incubations were initiated. Laboratory incubations were performed at 25°C and 802 relative humidity, with polyethylene plastic secured over both core 51 Table 4.9 Sludge characteristics Sludge Component1 Organic N N84 -N N03 -N Organic C ------------------- mg/L-----------------—--— Alpena 395 717 6.2 4305 Grand Ledge 1070 203 10. 9780 Freeze-dried 1 1130 99 NA 11280 Freeze-dried 2 752 475 NA 7520 Freeze-dried 3 376 851 NA 3760 pH Solids C:N ratio of solids 2 Alpena 7.5 2.1 10.9 Grand Ledge 12.0 5.1 9.1 Freeze-dried 1 7.5 5.0 10.0 Freeze-dried 2 7.53 3.3 10.0 Freeze-dried 3 7.5 1.7 10.0 1 Values for freeze-dried sludges l, 2 and 3 are based upon analyses of 0.8. EPA (1976). 2 Analysis not available. 3 Additional treatments of freeze-dried sludge 2 were adjusted to pH levels of 6.0 and 4.5 for use in the sludge acidity experiment. 52 ends to keep contents in place.Aeration.holes were placed in the top covering. Field incubated cores were treated at the time of collection, placed in polyethylene plastic bags and then returned to their original location for incubation. On August 1, 1984, twenty adjacent pairs of cores were collected at the aspen and northern hardwoods sites for use in the forest type experiment; and 40 pairs of cores were taken at the pine site, with 20 randomly selected pairs assigned to the forest type experiment and 20 designated for field incubation as part of the incubation method experiment. On the same date 20 adjacent groups of nine cores were collected at the oak site. Each group consisted of a circle of eight cores surrounding a center core. From each group, a randomly chosen pair of adjacent cores was assigned to the forest type experiment and a second randomly selected pair was designated for use in the incubation method experiment.‘The remaining cores were each randomly designated to receive one of the five additional treatments involved in the application method, application rate and sludge type experiments. Twenty cores were also taken from an area at the oak site sludge treated in November 1981, as part of the forest sludge fertilization demonstration project conducted by Michigan State University. These were used in the time since application experiment. On April 30, 1985, 240 intact cores were collected at the oak site for use in the sludge N composition and sludge acidity experiments. Forty randomly selected cores were 53 assigned to each of the six treatments used in performing the two experiments. Treatmoot Aoolicagion Cores designated for sludge treatment normally received 22.8 ml of sludge. This value was designed to achieve a target loading rate of 10 Mg/ha of sludge solids and add enough moisture to bring cores to approximately field capacity. Actual loading rates depended upon sludge solids content and are shown in Table 4.10. Two sludge treatments were exceptions to this application rate. These were treatments of 10.5 and 16.8 Mg/ha of sludge solids used in the sludge application rate experiment. For those treatments, 57.0 and 91.2 ml of sludge were applied, creating loading rates 2.5 and 440 times those indicated for Alpena sludge in Table 4.10. Table 4.10 Sludge loading rates Sludge Solids Organic N NH4I-N NO3'-N ------------------ kg/ha-------------------- Alpena 4200 79 143 1.24 Grand Ledge 10200 214 40.6 2.1 Freeze-dried 11 10000 226 19.9 NA Freeze-dried 21 6670 150 95.1 NA Freeze-dried 31 3330 75.2 170 NA .-------------------------------------------~---‘-- . "-'- --—--- 1 Values for freeze-dried sludges 1, 2 and 3 are based upon analyses of U.S. EPA analyses (1976). 2 Not available. 54 Control cores and cores from the oak area sludge treated 2.75 years earlier received 21.7 ml of deionized water. This amount approximated that added with sludge treatment. All treatments were surface applied except the two in the application method experiment in which sludge was incorporated. In those treatments core contents were removed, mixed with sludge, and returned to the core for incubation. Somole Analysis: 1984 Experiments Five sample replicates from each treatment were destructively sampled for analysis at 0, 2, 4 and 8 weeks. In sampling intact cores, forest floor and soil fractions were separated and each was thoroughly mixed. Subsamples of 5 grams for forest floor and 20 grams for soil were extracted by shaking in 100 ml of 2 N RC1 for one hour.? Extracts were filtered through Whatman No. 2 filter paper and analyzed for NH4+-N and NO3--N (H: a Technicon. AutoAnalyzer II system (Technicon 1971, 1977b). Duplicate; 5 and 20 gram subsamples were oven dried at 65°C to determine dry weights of extracted samples as well as core moisture contents and pH values. Blanks consisting of 100 m1 of 2 N KCl were also shaken, filtered and analyzed._ Samples in which sludge and core contents were mixed as part of the sludge application method experiment were analyzed as described for soil. 55 Site average forest floor weights and soil bulk densities (Table 3.2) were used to convert extract NO3'-N and NH4+-N concentrations to contents expressed as kilograms per hectare. Total inorganic nitrogen (TIN), calculated as the sum of NO3'-N and NHAI-N, was used to estimate net mineralization. NO3'-N contents were used to estimate net nitrification. The analytical procedure for NO3'-N also detected. N02'-N, but. periodic sample N02--N' analysis detected no concentrations exceeding two percent of sample (NO3' + N02-)-N. Consequently, results are reported simply 88 NO3--Ns Somole Analysis: 1985 Experiments Sample replicates from the sludge N composition and sludge acidity experiments were analyzed at 0,1” 2,14,6, 8, 10 and 12 weeks. Procedures are as described in the preceding section, with the exception that all forest floor and soil materials not extracted were oven dried at 65°C. This was done to determine total core contents and dry weights for use in converting extract concentrations to contents in kilograms per hectare. Sgotisticol Anolysis Statistical analyses were performed using SPSS statistical programs (Nie et a1. 1975, Bull and Nie 1981) on the Control Data Corporation main computer system at Michigan State University. Data from: each incubation 56 experiment for each sampling period was statistically analyzed using an analysis of variance. Logarithmic transformations were applied when needed to meet the assumption of homogeneity of variance. Means were separated using Duncan's multiple range test with a 0.05 level of significance. RESULTS AND DISCUSSION Porosg Tyoe Effects Net nitrification did not occur in control cores during the eight week incubation period, even though final NR4+-N levels exceeded half those created by sludge application (Table 4.11). Significant net nitrification, however, did occur in sludge treated cores (Table 4.12). 'This suggests either: 1) organisms responsible for nitrification were introduced with the sludge, or 2) sludge application created pH and nutrient conditions which promoted activity of existing nitrifying populations. Evidence supporting the first alternative is presented in later sections. Similar nitrification patterns were found in sludge treated cores of all four types. Three phases were evident: l) slowly increasing NO3'-N contents while nitrifying populations inhibited by anaerobic sludge conditions grew in the aerobic cores; 2) rapid NO3'-N production; and 3) decreasing NO3'-N production as the environment for nitrifying organisms became less favorable. This type of pattern was found by Heilman (1974) during laboratory 57 Table 4.11 Mean N contents for control cores of forest type experiment Content for forest typel Incubation time Aspen N. hardwoods Oak Pine weeks -------------------- kg/ha ------------------- 593:25 0 3.37h 5.75c 3.16b 1.46a 2 0.82 0.65 0.50 0.74 4 2.02 1.64 1.59 3.01 8 2.00 1.99 1.26 1.19 0 8.4ah 13.8c 11.7bc 6.2a 2 5.4a 16.6b 17.2b 14.7b 4 30.4a 45.9ab 56.3b 31.1a 8 62.4 50.2 69.8 73.9 0 11.7b 19.5c 14.8bc 7.7a 2 6.2a 17.3b 17.7b 15.4b 4 32.4a 47.6ab 57.9b 34.1a 8 64.4 52.2 71.1 75.0 1 Means in the same row followed by a different letter are significantly different at an alpha - .05 level. 58 Table 4.12 Mean N contents for sludge trestled cores of forest type experiment time Aspen N. hardwoods Oak Pine weeks -------------------- kg/ha ------------------- 1932:! 0 4.8b 5.7h 3.2a 3.5a 2 7.2a 12.5b 13.7b 5.2a 4 38.1 41.1 34.1 24.0 8 47.3b 53.1b 48.5b 20.1a + 554.21 0 80.4 94.2 110.3 101.9 2 62.2a 111.0b 101.8b 144.0c 4 110.0a 112.4a 109.9a 157.8h 8 89.7a 82.0a 144.2b 153.4b TIN 0 85.2 99.9 113.5 105.4 2 69.4a 123.5b 115.5b 149.2c 4 148.0 153.6 144.1 181.8 8 137.0a 135.1a 192.7b 173.5b 1 Cores were surface treated with anaerobically digested municipal sludge from Alpena at 4.2 Mg/ha of solids. 2 Means in the same row followed by a different letter are significantly different at an alpha . .05 level. 59 incubation of urea amended forest soils in Washington and is generally associated with autotrophic nitrifying bacteria (Alexander 1965). Net nitrification in sludge treated pine cores was about half that inicores from the other three sites (Table 4.12). This is illustrated in Figure 4.1 which shows differences between NO3'-N contents in treated and control cores over time. Lower net nitrification in sludge treated pine cores is attributed to the more acidic conditions existing at that site. It is hypothesized the greater pH change undergone by nitrifiers contained in the sludge upon addition to pine cores inhibited nitrification more than the pH change resulting from addition to cores from the other ‘ three sites. (See Appendix A for core pH data.) This would agree with the findings of Robertson (1982) that raising and lowering native pH of ten forest soils by as little as 0.3 units significantly increased and decreased net incubation nitrification. Also, it appeared sludge solids penetrated the pine litter more readily and formed less of a surface sludge layer, possibly reducing occurence of zones favorable for nitrification. Although not measured, denitrification losses likely occurred. Anoxic microsites can exist in well aerated soils (Greenwood 1961) and evidence of denitrification has been found during incubation of sludge treated columns (King 1973; Sommers et a1. 1979). Such losses, however, are felt to be small compared to measured net nitrification at ueoawuoaxo mama unouom emu now noonouomuwv unsunoo 21 no: aouuaoolowmnam e.e assess m2... < 56 0 80033412 + zmnm< a 9.003 5 0:5. m m e m o _ _ P _ _ _ _ Am. 0 o. 0 6 : on on 9. on on 614/6» u! enuaaamp iuaiuoo N—aioJuN 61 moisture levels present during incubation (Appendix B). Furthermore, core moisture contents do not suggest denitrification differences that would account for reduced net nitrification in sludge treated pine cores. Total inorganic nitrogen (TIN) content differences between treated and control cores showed a variable but steady trend over time (Figure 442). As a result, such differences could not be used to estimate net mineralization rates of sludge organic N for the four types. TIN contents in treated cores were expected to increase more rapidly than those in control cores. The fact they did not is attributed to N losses from: 1) volatilization in high pH surface sludge zones; 2) immobilization; and 3) denitrification. Others have found similar TIN patterns following incubations involving surface application of sludge (Ring 1973; Ryan et a1. 1973). Although mineralization of sludge organic N was not estimated, it apparently was of minor importance in controlling core NO3'-N and NH4+-N contents. Due to the high NH4+-N and low organic N contents of the sludge used, mineralization of all sludge organic N would produce only half the ammonium originally contained in the sludge. Iooooogion Mothod Efgocts Incubation method and forest type both significantly affected nitrification rates in sludge treated cores (Table 4413). NO3'-N contents in sludge treated pine cores were 62 uaoafiuoaxo mama unouow any new mooauuomuwv uaouaou zHH douunoolowvafim ~.e seamen on... 4 no o 883.80; .2 + :32 a 9.003 c. 0.5... .1 Oh 7 . 1' ..\ .1 2: r ca. 1. OH— om— oq/Sa u! aouaaamp iuaiuon NLL 63 Table 4.13 Mean NO3'-N contents for sludge treated fores of the incubation method experiment Forest Incubation type method 0 2 4 8 -------------- kg/ha----------------- Pine Lab 3.5 5.2 24.0 20.1 Pine Field 3.5 2.7 2.5 3.4 Oak Lab 3.2 13.7 34.1 48 4 Oak Field 3.2 4.2 17 2 33 7 Aoolyoio of yoriooco Incubation method (IM) NS ** ** ** Forest type (FT) NS ** ** ** ET 3 IN NS ** NS NS ** Significant at the 0.01 level. 1 Cores were surface treated with anaerobically digested municipal sludge from Alpena at 4.2 Mg/ha of solids. 64 less than those in oak cores for both field and lab incubations, and N03'-N levels were less in field incubated cores than lab incubated cores for both types. Significant net nitrification did not occur in sludge treated pine cores receiving field incubation. Data did not support existence of interactions, as such an effect was indicated for only the two week sampling period. The lower nitrification rate for sludge treated pine cores is attributed to the more acidic conditions at the pine site and creation of fewer microsites favoring nitrification as sludge solids infiltrated the pine litter. Cooler average temperature and diurnal temperature fluctuations encountered by field incubated cores (Appendix C), are likely the reasons that field net nitrification rates were lower than those in the laboratory. TIN data for sludge treated cores indicate a significant effect only for incubation method at two weeks (Table 4.14). Mineralization of sludge organic N was likely less in field incubation than lab incubation for the same reasons nitrification was lower, but high sample variability and limited replications prevented detection of such small differences. NO3'-N contents in control cores were lower for pine than oak at time of sample collection, but no significant effects were detected following incubation, due to lack of nitrification in all control cores (Table 4415). Net mineralization in control cores was lower during 65 Table 4.14 Mean TIN contents for sludge treated cpres of the incubation method experiment Forest Incubation type method 0 2 4 8 -------------- kg/ha----------------- Pine Lab 105 149 182 173 Pine Field 105 104 155 156 Oak Lab 113 115 144 160 Oak Field 113 107 131 157 Mu. 9.: 2.2.—Jeri“ Incubation method (IM) NS * NS NS Forest type (FT) NS Ns Ns Ns FT 8 IN NS NS NS NS * Significant at the 0.05 level. 1 Cores were surface treated with anaerobically digested municipal sludge from Alpena at 4.2 Mg/ha of solids. 66 Table 4.15 Mean NO3--N contents for control cores of the incubation method experiment Forest Incubation type method 0 2 4 8 -------------- kg/ha----------------- Pine Lab 1.5 0.7 3.0 1.2 Pine Field 1.5 0.7 2.0 1.0 Oak Lab 3.2 0.5 1.6 1.3 Oak Field 3.2 1.4 1.4 1.9 Analysis of gagiaoco Incubation method (IM) NS NS NS NS Forest type (FT) ** NS Ns NS FT 1 IM NS NS NS NS ** Significant at the 0.01 level. 67 field incubation than lab incubation for both types, as evidenced by lower TIN contents in field incubated cores at four and eight weeks (Table 4.16). This, again, is thought to result from lower average temperature and diurnal temperature fluctuations encountered by field incubated cores. Lower TIN contents in pine control cores at time of sample collection may explain the lower contents in pine cores at four weeks. It is possible, however, that differences in mineralization rates among the forest types exist. Significant interaction effects were not indicated. Sludgo Tyoe Effocgs The only treatment for which net nitrification occurred over the eight week incubation period was anaerobically digested municipal sludge from Alpena (Table 4.17). Cores treated with limed undigested sludge from Grand Ledge had ammonium levels, pH values (Appendix A) and moisture contents (Appendix B) as favorable for nitrification as those in cores receiving Alpena sludge, but net nitrification did not occur. The high pH (12.0) of the Grand Ledge sludge would destroy any nitrifiers it contained, indicating autotrophic bacteria responsible for high NO3--N contents in cores receiving Alpena sludge were added with the sludge. Breuer et a1. (1979) came to a similar conclusion regarding nitrification at a wastewater irrigated forest site in Washington using evidence including: 1) most probable number (MPN) estimates of 68 Table 4.16 Mean TIN contents for control cores of the incubation method experiment Forest Incubation type method 0 2 4 8 -------------- kg/ha----------------- Pine Lab 7.7 15.4 34.1 75.0 Pine Field 7.7 10.9 15.2 27.5 Oak Lab 14.8 17.7 57.9 71.1 Oak Field 14.8 21.0 24.2 35.1 Analysio of v i n Incubation method (IM) NS NS ** ** Forest type (FT) ** NS * NS FT x IN NS NS NS NS 69 Table 4.17 Mean N contents for sludge type experiment time Control Alpena sludge2 Grand Ledge sludge3 weeks -------------------- kg/ha ------------------- 193:25 0 3.2 3.2 4.0 2 0.5a 13.7c 3.2b 4 1.6a 34.1b 1.2a 8 1.3a 48.4b 1.4a fissizs 0 11.7a 110.3b 69.7b 2 17.2a 101.8b 86.2b 4 56.3a 109.9b 94.8b 8 69.8a 144.2b 136.3b TIN 0 14.8a 113.5b 73.7b 2 17.7a 115.5c 89.4b 4 57.9a 144.1b 96.0b 8 71.1a 192.6c 137.8b 1 Means in the same row followed by a different letter are significantly different at an alpha - .05 level. 2 Anaerobically digested municipal sludge surface applied at 4.2 Mg/ha of solids. 3 Limed undigested municipal sludge surface applied at 10.2 Mg/ha of solids. 70 numbers of autotrophic nitrifying bacteria present in control and irrigated soils; and 2) results of incubations involving wastewater irrigated soil, unamended soil, and soil amended with inorganic NH4+-N. Increases in TIN over time were too variable to allow estimation of net mineralization of sludge organic N for the two sludge types (Table 4.17). Lack of nitrification in cores treated with the Grand Ledge sludge suggests NO3'-N leaching may not occur following field applications to areas similar to the oak site. Minimal increases in NO3--N leaching found by Roterba et a1. (1979) following application of lime stabilized sludge (pH 12) to a northern hardwoods site in New Hampshire may be the result of lack of nitrification similar to that measured in the incubation. Sludgo Loading Rate Effects Differences in NO3--N content among sludge treated cores occurred only at the initial sampling time (Table 4.18). Higher NO3'-N content found at that time in cores receiving 16.8 Mg/ha of sludge solids is a result of higher NO3--N loading received by these cores. Core NO3'-N contents were expected to remain constant or increase with increasing loading rate, due to elevated loading levels of ammonium and nitrifying bacteria and creation of a thicker surface sludge layer. Instead, mean NO3'-N contents decreased (although not significantly) with increasing 71 Table 4.18 Mean N contents for sludge loading rate experiment time 0.0 4.2 10.5 16.8 weeks ------------------ kg/ha ------------------- 593-2! 0 3.2a 3.2a 2.0a 6.1b 2 0.5a 13.7b 15.0b 9.7b 4 1.6a 34.1b 28.2b 19.4b 8 1.3a 48.4b 67.5b 76.3b + 554.:! O 11.7a 110.3b 259.8c 455.6d 2 17.2a 101.8b 188.4c 312.4d 4 56.3a 109.9b 254.3c 341.6c 8 69.8a 144.2b 163.0bc 209.3c 0 14.8a 113.5b 261.7c 461.6d 2 17.7a 115.5b 203.5c 322.1d 4 57.9a 144.1b 282.5c 361.0d 8 71.1a 192.6b 230.6bc 285.6c 1 Cores were surface treated with anaerobically digested municipal sludge from Alpena. ‘ 2 Means in the same row followed by a different letter are significantly different at an alpha - .05 level. 72 loading rate at two and four weeks. Moisture contents in cores receiving the two higher application rates were well in excess 10f field capacity, evidently inhibiting nitrification and promoting denitrification. Only at the eight week sampling, after these cores dried to moisture contents nearer field capacity, did net nitrification tend to increase with loading rate. The cores were allowed to drain to help alleviate the moisture problem. Others have attributed lags in net laboratory nitrification at higher sludge loading rates to toxic materials contained in sludge (Premi and Cornfield 1969, 1971; Ryan et a1. 1973; Wilson 1977), but in this case it appears to be a result of moisture conditions and denitrification. Initial TIN contents were greater at higher loading rates, as expected. By week eight, however, differences among sludge treatments were greatly reduced, with cores receiving sludge at loading rates of 10.5 and 16.8 Mg/ha exhibiting net TIN losses over time (Table 4.18). This is attributed to: 1) denitrification caused by core saturation; 2) increased volatilization losses due to thicker surface sludge layers and higher moisture contents; 3) immobilization; and 4) losses of inorganic N through core drainage. Relative importance of these factors cannot be separated using available data. II'I. Ire-1'7 'l‘ 73 Slodgo Aoolication Method Effocgs NO3'-N contents in cores in which sludge was incorporated were lower than those in cores receiving surface application but greater than those in control cores (Table 4.19). Lower net nitrification rates for these two application methods are attributed to destruction of sludge- dominated microsites during the mixing process. Such microsites would have higher pH and greater ammonium availability, and therefore would promote higher nitrification rates. Removal of forest floor generally did not have any effect. King (1973) found higher net nitrification during an 18 week laboratory incubation in samples receiving surface sludge application than in those in which sludge was incorporated, but soil used in his experiment was agricultural (pH 6.0) and exhibited significant net nitrification during incubation without sludge amendment. TIN and NH4+-N data for the initial samples indicate differences in sludge loading rate existed (Table 4.19). Differences in NH4+-N availability, however, do not explain observed differences in net nitrification. Effoooo o;_gigo Boggoon Aoolicogion ond Iooobogion Significant net nitrification occurred in oak cores receiving sludge treatment 2.75 years prior to incubation (Table 4n20). These cores had NH4+-N and TIN contents 74 Table 4.19 Mean N contents for sludge application method experiment Incubation Control Surface Incorporated Incorporated time applied no FF weeks ------------------- kg/ha -------------------- “03-"! O 3.2a 3.2a 2.1ab 1.4b 2 0.5a 13.7c 3.5b 5.3b 4 1.6a 34.1c 2.0a 11.4b 8 1.3a 48.4c 13.4b 9.3b NHQI-N O 11.7a 110.3b 165.2c 125.0bc 2 17.2a 101.8b 144.0b 139.1b 4 56.3a 109.9b 164.6c 154.2c 8 69.8a 144.2b 176.4b 167.7b TIN 0 14.8a 113.5b 167.2c 125.0bc 2 17.7a 115.5b 147.5b 144.3b 4 57.9a 144.1b 166.7b 154.2b 8 71.1a 192.6b 189.9b 167.7b 1 Sludge treated cores received anaerobically digested municipal sludge from Alpena at 4.2 Mglha of solids. 2 Means in the same row followed by a different letter are significantly different at an alpha - .05 level. 75 Table 4.20 Mean N contents for time since application experiment Incubation Control Treated 0.0 years Treated 2.75 years time before incubation2 before incubation weeks -------------------- kg/ha --------------------- "03:2! 0 3.2 3.2 3.4 2 0.5a 13.7c 1.9b 4 1.6a 34.1c 12.1b 8 1.3a 48.4b 35.0b Na4*-N 0 11.7a 110.3b 11.2a 2 17.2a 101.8b 17.6a 4 56.3a 109.9b 45.9a 8 69.8a 144.2b 50.8a TIN 0 14.8a 113.5b 14.6a 2 17.7a 115.5b 19.6a 4 57.9a 144.1b 58.0a 8 71.1a 192.6b 85.8a 1 Means in the same row followed by a different letter are significantly different at an alpha - .05 level. 2 Cores were surface treated with anaerobically digested municipal sludge from Alpena at 4.2 Mg/ha of solids. 3 Cores were taken from an area receiving surface application of anaerobically digested sludge at 5.0 Mg/ha solids and 374 kg/ha N. 76 statistically similar to those in control cores, but had greater N03'-N contents at all samplings following initiation of incubation. These NO3--N contents were lower than those in cores receiving sludge immediately prior to incubation at two and four weeks, and were lower, but not significantly, at eight weeks. Net nitrification in these cores suggests viable populations of nitrifying bacteria, introduced with sludge, still existed. This has implications with regard to reapplication of sludge to similar sites. NO3'-N concentrations in soil leachate samples collected 120 cm beneath this area indicated production of excess nitrate occurred only in the first year following sludge application (Urie et al. 1984). Lack of available ammonium for nitrifiers in subsequent years evidently prevented NO3'-N leaching. Immediately following sludge application ammonium would be available for nitrifying bacteria. However, after the initial ammonium excess was utilized, nitrifying bacteria, would not be able to compete with other ammonium users for that made available through mineralization. As a result nitrate production would be severely reduced and leaching losses would cease. Reapplication of sludge would create an ammonium excess that could be utilized not only by the nitrifying population added with the sludge, but also by the population still existing at the site. This could lead to increased nitrification and high NO3’-N leaching losses, such as those measured by Urie et al.(1978) following reapplication to 77 aspen sprouts on sandy Michigan soils. Slodgo N Comoosioion Effects Core N03--N contents were expected to increase with increasing sludge ammoniumlloading, at least during early sampling periods. Instead, virtually no nitrification occurred for any treatment during the first eight weeks of the experiment (Table 4.21). This is illustrated in 4.3 which compares NO3-—N contents of cores used in this experiment with those of oak cores treated with anerobically digested municipal sludge from Alpena and limed undigested municipal sludge from Grand Ledge in the sludge type experiment. Over the last four weeks of incubation, when nitrification finally did occur, cores receiving the sludge containing virtually all organic N (freeze-dried sludge 1) had highest NO3'-N contents. The sludge used for this treatment had the highest percent solids of the three and thus produced the thickest surface sludge layer. It is postulated that this layer provided an environment which allowed small native nitrifying populations to grow, finally reaching a size after eight weeks where measurable net nitrification could occur. This agrees with results of incubation experiments performed by other investigators in which net nitrification following addition of NH4+-N substrate to forest soils was delayed as nitrifying papulations grew (Heilman 1974; Theobald and Smith 1974; 78 Table 4.21 Mean N contents for sludge N composition experiment Incubation time Control F-dried l2 F-dried 23 F-dried 34 weeks --------------------- kg/ba --------------------- E9322! 0 0.43 1.40 1.12 0.79 1 1.57 1.45 1.60 1.34 2 1.28a 1.39a 1.47a 2.20b 4 2.42ab 1.52s 4.39h 1.50s 6 3.10a 2.67a 4.65b 5.16b 8 2.23ab 4.91bc 4.8lc 1.67a 10 1.88a 44.09b 4.19a 3.70s 12 3.32 25.81 9.64 6.08 524::5 0 6.6a 30.9b 98.7c 171.7d l 16.4a 43.1b 104.1c 172.5d 2 17.5a 51.7b 118.5c 168.4d 4 33.4a 81.2b 168.7c 226.4d 6 88.9a 153.7ab 206.6b 280.2b 8 91.1a 121.1ab 194.9bc 222.1c 10 88.6a 160.3b 224.9c 227.3c 12 102.4a 169.1b 245.3c 281.8c El! 0 7.0a 32.3b 99.9c 172.5d 1 18.0a 44.5b 105.7c 173.8d 2 18.8a 53.1b 120.0c 170.6d 4 35.8a 82.7b 173.1c 227.9d 6 92.0a 156.4ab 211.2b 285.4b 8 93.4a 126.0ab 199.7bc 223.8c 10 90.5a 204.4b 229.0b 231.0b 12 105.7a 194.9b 254.9bc 287.8c 1 Means in the same row followed by a different letter are significantly different at an alpha - .05 level. 2 226 kg/ha organic N and 20 kg/ha NRA: N, surface applied. 3 150 kg/ha organic N and 95 kg/ha NH4: -N, surface applied. 4 75 kg/ha organic N and 170 kg/ha NH4 -N, surface applied. 79 ounce xmo vouaouu «woman aw nunoucoo zllmoz m.e spawns .xu D n_Dm x «.mm 4 P an. “.053 + 0.0 c< D 3.00; c. 0.5... m w N #1 _ _ _ _ _ m , ‘10s. .1‘li‘1’b“ ell! 111 ' 1 1| .1} u a L‘ 1. ow ON on on 01-1/6» U! zuauoo N—azmzm 80 Robertson 1982). Ideal temperature and moisture conditions under which cores were incubated are not likely to exist in the field for such an extended period of time; thus it is doubtful that the treatments used in this experiment would induce high nitrification rates under field conditions. TIN content increases over the incubation period were variable among treatments but tended to be greater for treatments with higher loading rates of sludge solids (Table 4.21). This was expected as these cores had more sludge organic N available for mineralization. Increases in TIN were greater in cores receiving freeze-dried sludges 1 and 2 than in control cores at all times, and greater for cores receiving freeze-dried sludge 3 than for control cores at 4, 6 and 12 weeks (Figure 4.4). This indicates that sludge addition can increase availability of inorganic nitrogen to plants through both mineralization of sludge organics and direct addition of inorganic N. Low loading of sludge organic N associated with freeze-dried sludge 3 is believed to be the reason that it did not always exhibit greater increases in TIN than the control. Larger increases in TIN content over time in cores treated with sludges higher in organic N caused TIN content differences among sludge treatments to decrease over the twelve week incubation (Table 4.21). 81 unoawumexo nofiuflmomaoo z savage on» new mafia uo>o oommouoaw amounoo zHa e.¢ ouswwm n O... 4 N On. 0 P On. + 35:00 D 9.00; 5 SEE NP O— O O v N O F F . t _ _ L _ _ . _ _ Am) nu Owl O 9 ON on O... on O0 Oh OO Om OO p O p p ON — on — O* F on p on 9 Oh F on p 014/651 u! asoasoug iueiuon NLI. 82 Sludgo Acidity Effeots There were no clear trends with regard to N03'-N contents during the first six weeks of the experiment (Table 4.22). At weeks 8, 10 and 12, cores treated with pH 7.5 sludge had highest NO3--N contents, but these were low in comparison to those in cores receiving anaerobically digested municipal sludge from Alpena in the forest type experiment. Evidently, the pH 7.5 sludge created microsites with acidity levels more favorable for nitrifying bacteria. Sludge pH might have had a greater effect if it had been varied for the Alpena sludge which contained nitrifiers capable of immediately utilizing available ammonium. TIN data indicate higher net mineralization rates for sludge treated cores than controls, a result of mineralization of sludge organic N. Differences related to sludge pH, however, were not detected. 83 Table 4.22 Mean N contents for sludge acidity experiment Totol inoggonic N time Control pH 4.5 pH 6.0 pH 7.5 weeks --------------------- kg/ha --------------------- £23-:E 0 0.43s 2.34b 1.61b 1.12b 1 1.57 1.47 1.75 1.60 2 1.28a 1.95c 1.75bc 1.47ab 4 2.42ab 2.47ab 1.48s 4.39h 6 3.10s 5.17b 5.34b 4.65b 8 2.23a 2.32a 2.96ab 4.81b 10 1.88a 2.61a 2.67a 4.19b 12 3.32 3.53 3.71 9.64 .g. 154.25 0 6.6a 95.7b 100.0b 98.7b 1 16.4a 107.7b 105.5b 104.1b 2 17.5a 124.6b 129.0b 118.5b 4 33.4a 156.8b 142.7b 168.7b 6 88.9a 245.6b 174.8b 206.6b 8 91.1a 206.4b 217.1b 194.9b 10 88.6a 214.7b 183.0b 224.9b 12 102.4a 222.1b 268.1b 245.3b 0 7.0a 98.0b 101.6b 99.9b 1 18.0a 109.1b 107.2b 105.7b 2 18.8a 126.6b 130.7b 120.0b 4 35.8a 159.3b 144.2b 173.1b 6 92.0a 250.8b 180.1b 211.2b 8 93.4a 208.8b 220.0b 199.7b 10 90.5a 217.3b 185.7b 229.0b 12 105.7a 225.7b 271.8b 254.9b l Cores received surface application of freeze-dried sludge 2 containing 150 kg/ha organic N and 95 kg/ha NH4+-N. 2 Means in the same row followed by a different letter are significantly different at an alpha - .05 level. CHAPTER V NITROGEN LEACHING Leaching of NO3--N and NH4+—N following sludge application was monitored through: 1) wells and lysimeters installed in the forest sludge fertilization demonstration project conducted by Michigan State University; and 2) leaching of incubated cores receiving treatments used in the 1985 incubation experiments with simulated rainwater. FOREST SLUDGE FERTILIZATION DEMONSTRATION PROJECT Magogials ond Methods Water quality monitoring for the project entitled "Fertilization of State Forestland in Michigan with Municipal Wastewater Sludge: A research demonstration project to assess the impact of sludge fertilization upon plant production, nutrition, soil fertility, and water quality in four forest ecosystems" was conducted by the U.SJLA~ Forest Service during 1981 and 1982, and continued by Michigan State University from 1983 until 1985. The experiment for each forest type was a completely random design involving three treatments: control (C); application trails only (T); and application trails with sludge fertilization (TS) (Hart et a1. 1984). Water samples were collected using wells seated with a perforated screen section extending 1.5 m below the water table and pressure 84 85 vacuum lysimeters installed at 1.2 m. Monitoring wells were not installed at the oak site as the water table was below a convenient sampling depth. Locations of wells and lysimeters are indicated in Figure 5.1, and characteristics of well locations are shown in Table 5.1. Sludge treatments received by each type are summarized in Table 5.2. Sample analysis for NO3'-N and NRA-N was performed using a Technicon AutoAnalyzer II system (Technicon 1971, 1977b). Statistical analyses were performed using SPSS statistical programs (Nie et a1. 1975, Hull and Nie 1981) on the Control Data Corporation main computer system at Michigan State University. Water sample concentrations over selected time periods were analyzed. using 1ANOVA. Logarithmic transformations were applied to data when needed to meet the assumption of homogeneity of variance. Means were separated using Duncan's multiple range test with a 0.05 level of significance. Resulos and Discussion Results for the four individual forest sites are discussed in detail following a description of overall findings. N03--N concentrations in lysimeters at all four sites peaked in the first 6 to 18 months following sludge application, after which they dropped to background levels. This pattern suggests N03"-N leached was produced by 86 muouoamnma one made: uommouo acmumuumnoaov mo oaofiumooq L.n seamen moan oewm manm on“ $0. oufim noosossm e n one man AV mane m mQ O, O Amvuouoamuma "0 23oz "Au sounds one In on~ ngweua “my p%¢ agmeuh "H .Eap douuooo no NNAV mama monm< mama me Ozmomq Hno 4 sna O ono Hnw man“ one no e w m BIO fiIP. nn anm a one o. :50... 0 03L onn OIN .lIIIIL 87 Table 5.1 Characteristics of well locations Well No. Treatment Water table depth2 Geology Asoen sito 1 T 5.9 m Sand 3 C 9.1 m Sand 4 TS 7.0 m Sand 5 TS 3.9 m Sand 7 TS 5.3 m Sand Noyohoyn hagdwoods sigo 1 C 1446 m Sand to 6 m, clayey sand below 21 T 1.3 m Clay loam 22 T 1.4 m Clay loam 4 TS 15.8 m Sandy loam to 8 m, clayey sand below 9 TS 3.6 m Loamy sand to 4 m, loamy clay below Pino sito 2 T 7.2 m Sand 4 T8 7.8 m Sand 5 T8 7.0 m Sand 6 TS 6.1 m Sand, clayey sand at 5.5 to 6 m 8 T 4.1 m Sand, clayey sand at 5 m 1 C .- control. T - application trails only. TS - trails with sludge application. 2 Wells were seated with a perforated screen section extending 1.5 m below water table at time of installation. 3 Geology information from notes taken at time of well installation (Urie et al. 1984). 88 Table 5.2 Characteristics of sludge treatments appliedlin forest fertilization demonstration project Forest site Characteristic Source of Application Loading rate sludge date of solids kg/ha Aspen Alpena Oct. 1981 9980 N. hardwoods Rodgers City July 1982 9210 Oak-plot l Alpena Nov. 1981 13964 Oak-plots 5 and 7 Rodgers City2 Nov. 1981 5047 Pine Alpena June, 1982 8119 Sludge N in wet N loading solids sludge rate ----------- 2----------- kg/ha Aspen 3.21 0.17 560.6 N. hardwoods 5.05 0.43 783.1 Oak-plot 1 5.85 0.19 453.5 Oak-plots 5 and 7 2.23 0.16 374.1 Pine 2.62 0.12 379.4 1 From Urie et a1. (1984). 2 Alpena sludge was applied to portions of plots 5 and 7, but not in areas where lysimeters were located. 89 nitrification of NH4+-N existing in sludge at time of application. Ammonium produced by mineralization of sludge organic N in subsequent years was evidently unavailable to nitrifying bacteria due to competition from plants and non- nitrifying microorganisms. Groundwater NO3'-N flushes occurred over longer periods of time and had delayed, reduced peaks; a result of the additional time required for leaching NO3--N to reach groundwater and dilution occurring as this took place. Groundwater NO3--N concentrations were still elevated in 1985, three to four years following sludge application. These patterns are similar to those found by other researchers following sludge application to forest land (Riekerk 1981; Zasoski et al. 1984; Brockway and Urie 1983). NO3'-N data from the four types indicate that the sludge application rates used in the demonstration project were compatible with the 10 mg/L public health standard for NO3--N in drinking water. Further monitoring of NO3--N at these sites is desirable as concentrations in several wells had not returned to background levels by 1985. Unvolatilized NH4+-N was evidently bound tightly to soil exchange sites where it was immobilized or nitrified; as elevated levels were not detected in wells or lysimeters (Urie et a1. 1984). Others have found similar low NH4+-N concentrations beneath sludge treated forests (Urie et a1. 1978; Roterba et a1. 1979; Stednick and Wooldridge 1979). In interpreting groundwater data, locations of 90 individual wells in relation to treated areas (Figure 5.1) and characteristics of surrounding soil materials (Table 5J0 must be taken into account. Some wells located in or downslope from control plots exhibited a nitrate flush as groundwater from beneath nearby sludge treated plots reached the area. In other instances, wells located in sludge treated plots showed no nitrate flush due to the location of the well in fine textured material through which water movement from the surrouding aquifer was slow, delaying or preventing detection of a nitrate flush. A£2£2.£i££- NO3'-N concentrations in samples from well 1 represent levels under aspen sprouts not receiving sludge fertilization. Mean N03'-N concentration for the well was 0.19 mg/L with a range of 0.00 to 0.36 (Table 5.3). 'These values are similar to those for all wells during the first year after sludge application before leaching NO3'-N reached the saturated zone. Samples from all other wells had significantly higher N03'-N concentrations during 1983, 1984 and 1985 than in 1982 or in samples from well 1. NO3'-N concentration in well 3, located in a control plot, reached a peak of 5.61 mg/L in the spring of 1984. This was evidently a result of nitrate enriched groundwater from beneath adjacent sludge treated plots 4 and 7 flowing into the area. Wells 4, 5 and 7, located within plots receiving application trails and sludge treatment, began showing elevated NO3'-N 91 Table 5.3 Aspen well NO3'-N concentrations Sampling date l-T 3-c a-rs s-rs 7-rs ----------------------- mgIL----------------------- 11-16-81 0.00 0.29 0.13 0.00 0.00 12-7-81 0.00 0.00 0.12 0.00 0.00 5-82 0.00 0.00 0.00 6-82 0.08 0.09 0.10 0.10 0.24 7-82 0.00 0.00 0.11 0.45 0.16 8-82 0.00 0.00 0.09 0.17 0.00 9-82 0.00 0.00 0.00 0.43 0.00 9-82 0.09 0.12 0.15 0.14 0.19 4-9-83 0.12 0.40 0.25 1.98 4-22-83 0.12 0.29 2.10 0.97 0.59 6-17-83 0.36 0.89 4.75 0.85 0.80 9-13-83 0.32 4.13 0.57 10-28-83 0.01 2.18 3.34 0.51 11-11-83 0.04 0.60 11.14 1.98 4-13-84 0.07 5.61 5.88 1.53 0.99 5-20-84 0.12 1.06 3.77 0.44 0.68 6-84 0.17 0.33 2.63 0.85 0.72 9-25-84 0.09 0.12 3.04 1.02 0.96 10-30-84 0.08 0.97 1.61 12-6-84 0.11 1.02 1.69 1.54 1.38 4-23-85 1.73 4.89 0.67 0.20 9-3-85 1.66 0.48 6.13 1.87 10-19-85 1.01 0.21 3.04 1.57 Yoarly a er es1 19822 0.02a,x 0.07a,x 0.09a,x 0.16a,x 0.07a,x 1983 0.16a,y 0.87b,y 4.29c,y 1.14b,y 0.70b,y 1984 0. 1a,y 1.52b,y 3.10c,y 1.08b,y O.95b,y 1985 NA 1.47a,y 1.86a,y 3.28a,z 1.21a,y 1 Values followed by different letters are significantly different at the 0.05 level of probability. Letters a, b and c compare values within a row. Letters x, y and 2 compare values within a column. 2 Includes 1981 data. 3 Not available. 92 concentrations in April 1983, approximately 18 months following sludge application. NO3--N concentrations in well 4 were several times higher than those in wells 3, 5 and 7. NO3'-N concentrations in soil leachate collected at the 120 cm depth declined from an average of 11.53 mg/L in 1983 to 2.52 mg/L in 1984 and 0.17 mg/L in 1985 (Table 5.4). Brockway and Urie (1983), working with aspen sprouts on a sandy soil in Michigan found similar NO3'-N concentrations in soil leachate 120 cm beneath areas receiving surface application of 23.0 Mg/ha of anaerobically digested municipal sludge. Norghern oogogoogo,oi;o. Sludge was applied to the northern hardwoods site in July 1982. During early spring 1983, NO3I-N concentrations in leachate beneath sludge treated plots reached maxiumum average concentrations of 0.99 and 4.17 mg/L for sludge treated plots 4 and 5 respectively, and 0.69 mg/L for control plot 1 (Table 5.5). After this time, concentrations fell quickly to background levels. Highest groundwater NO3--N concentrations were found in samples from well 1 (Table 5.6), which is located along an access trail north of sludge treated plots 4 and 5. A slight northerly component of flow would allow groundwater from beneath the two adjacent sludge treated plots to reach this well. The highest NO3'-N concentration measured was 3.92 mg/L in September, 1985. Additional monitoring is 93 Table 5.4 Aspen lysimeter NO3'-N concentration Sampling date 4l-TS 42-TS 43-TS 44-TS 45-TS ----------------------- mgIL------------------------ 4-9-83 3.70 20.94 28.83 20.43 14.04 4-22-83 2.47 17.89 14.03 4.48 13.71 6-17-83 1.90 4.80 13.18 12.87 10-28-83 0.37 21.04 11-11-83 1.32 4-21-84 10.35 5-20-84 2.55 12.15 9-25-84 0.01 0.05 0.01 10-30-84 0.01 0.02 0.03 12-6-84 0.01 4-23-85 0.33 10-19-85 0.00 L.“ r 1 W3 1983 2.11b,x 19.42a,x 15.892 l4.78a,x 10.49a,x 1984 0. 1b,y 6.45a,y 12.151 0.04b,y 0.02 ,y 1985 NA NA 0.33 NA 0.00 1 Based upon one sample, statistics cannot be performed. 2 Not available. 3 Values followed by different letters are significantly different at the 0.05 level of probability. Letters a, b and c compare values within a row. Letters x, y and z compare values within a column. 94 Table 5.5 Northern hardwoods lysimeter NO3--N concentrations 7-82 4-9-83 4-22- 6-17- 83 83 10-28-83 11-11-83 4-21- 5-20- 8-13- 9-25- 84 84 84 84 10-30-84 12-6- 4-23- 84 85 9-3-85 1982 1983 1984 1985 1 Values 2 Based upon one sample, in Yoarly avoragos 0.002 0.09b,x 0.00b,y 0.04a,x parentheses indicate number of which average concentrations are based. 3 Not available. 4 Values followed 0.99 0.19 0.01 0.00 0.01 0.03 0.00 0.00 0.04 0.02 NA3 0.29 0.02 0.02 b,x ,x 0.61 X l.32a,x 0.08a,y 0.02a,y Letters a, b and c compare values within a row. Letters x, y and 2 compare values within a column. statistics cannot be performed. by different letters are significantly different at the 0.05 level of probability. Northern hardwoods well NO3'-N concentrations Ta 95 ble 5.6 date 9-13-83 10-28-83 11-11-83 4-13-83 5-20-84 6-84 9-25-84 10-30-84 12-6-84 4-23-85 9-3-85 10-19-85 1982 1983 1984 1985 0.22 0.28 0.28 0.69 0.64 0.86 1.09 0.85 1.20 1.59 1.43 2.99 3.92 2.06 0.15.1 0.50a,z 1.23a,y 2.99a,x 0.18 0.02 0.16 0.04 0.06 0.25 0.03 0.14 0.11 0.10 0.21 0.18 0.03b,y 0.12bc,xy 0.28ab,x 0.11b,xy NA 0.16b,x NA Yearly averages 0.02b,y 3 0.01 0.01 0.00 0.00 0.03 0.01 0.00 0.00 0.01 0.02 0.02 0.04 0.06 0.02 NA2 0.01c,y 0.01c,y 0.04c,x 0.16a,x 0.28ab,x 0.29b,x 0.20b,x 1 Based upon one sample, 2 Not available. 3 Values followed different at the 0.05 level of probability. Letters a, b and c compare values within a row. statistics cannot be performed. by different letters are significantly Letters x, y and z compare values within a column. 96 needed to ensure that maximum N03--N concentrations have been reached. NO3--N concentrations in groundwater beneath plots 2, 4 and 9 remained essentially at background levels through 1985. Well 4 is located near the center of a sludge treated plot, but depth to the water table (15.8 m) and clayey strata at the water table depth have evidently prevented leaching nitrate from reaching the well. NO3'-N in samples from well 9, located in a sludge treated area with a water table at 3.6 m, increased to about 0.5 mg/L in the summers of 1983, 1984 and 1985. Average yearly concentrations for this well, however, were not significantly different than those in wells monitoring groundwater beneath plot 2 which received no sludge. 94.! gigs, Soil disturbances caused by lysimeter installation produced a short lived 1-2 mgIL increase above background NO3--N levels in control plots (Table 5.7). For sludge treated areas, the average increase in NO3'-N concentration was several mg/L higher than that due to disturbance alone. Peak NO3--N concentrations occurred at the time excess sludge NH4+-N would have nitrified and leached. Between 1983 and 1985 NO3'-N concentration from all lysimeters were at background levels. Pioo gigs. Sludge was applied to the pine site in early summer 1982. During that year N03'-N concentrations remained at background levels in all wells (Table 5.8). 97 Table 5.7 Oak lysimeter NO3'-N concentrations Mean lysimeter NO3'-N concentration for plot1 Sampling date 1-TS 2-C 3-C 5-TS 7-TS ---------------------- mgIL----------------------- 11-16-81 0.00 (1) 0.10 (1) 12-7-81 0.00 (2) 0.22 (1) 0.50 (2) 4/82 0.19 (l) 0.08 (1) 3.53 (2) 0.48 (4) 5/82 0.96 (2) 0.21 (l) 0.60 (2) 2.01 (3) 6/82 1.89 (1) 0.14 (1) 1.17 (2) 3.01 (2) 1.22 (4) 7/82 5.46 (1) 0.26 ( 0.99 (l) 5.72 (1) 0.85 (3) 8/82 5.34 (2) 1.67 ( 0.00 (2) 6.35 (1) 0.09 (2) 9/82 2.21 (1) 4/9/83 0.04 (1) 0.00 (l) 0.08 (2) 0.20 ( ) 4/22/83 0.02 (2) 0.13 (2) 0.01 (2) 0.11 (3) 0.01 (2) 6/17/83 0.04 (1) 0.14 (3) 0.01 (2) 0.09 (2) 0.03 (1) 10/28/83 0.01 (2) 0.09 (2) 0.00 (3) 0.03 (2) 0.00 (6) 11/18/83 0.00 (1) 0.03 (3) 0.02 (3) 0.02 (3) 0.01 (4) 4113/84 0.03 (1) 4/21/84 0.01 (2) 0.10 (3) 0.00 (2) 0.07 (6) 0.01 (7) 5/20/84 0.00 (2) 0.11 (3) 0.00 (2) 0.05 (5) 0.00 (7) 8/13/84 0.01 (2) 0.02 (2) 0.00 (2) 0.01 (3) 0.00 (4) 9/25/84 0.00 (2) 0.01 (3) 0.00 (2) 0.00 (2) 0.00 (3) 10/30/84 0.00 (2) 0.01 (3) 0.00 (1) 0.04 (6) 0.00 (6) 12/6/84 0.01 (2) 0.02 (2) 0.01 (2) 0.00 (3) 0.01 (3) 4/23/85 0.01 (2) 0.09 (2) 0.01 (2) 0.04 (6) 0.01 (5) 9/3/85 0.00 (1) 0.01 (1) 0.00 (1) 0.02 (2) Yooyly oyoyogesz 19323 2.03a,x 0.47b,x 0.65b,x 3.18a,x 0.92b,x 1983 0.02bc,y 0.09a,y 0.02c,y 0.07ab,y 0.01c,y 1984 0.00b,y 0.05a,y 0.00b,y 0.04a,y 0.00b,y 1985 0.01a,y 0.06a,y 0.01a,y 0.04a,y 0.01a,y 1 Values in parentheses indicate number of samples upon which mean concentrations are based. 2 Values followed by different letters are significantly different at the 0.05 level of probability. Letters a, b and c compare values within a row. Letters x, y and 2 compare values within a column. 3 Includes 1981 data. 98 Table 5.8 Pine well NO3--N concentrations Sampling date 2-T 4-TS 5-TS 6-TS 8-T ----------------------- mg/L----------------------- 6-82 0.10 0.09 0.08 0.00 0.00 7-82 0.00 0.00 0.00 0.00 0.15 8-82 0.00 0.00 0.07 0.00 0.00 9-82 0.11 0.12 0.18 0.15 0.16 4-9-83 0.10 0.01 0.12 0.17 0.02 4-22-83 0.21 0.01 0.05 0.05 0.01 6-17-83 0.37 0.01 0.00 0.05 0.01 9-13-83 3.17 0.82 0.00 10-28-83 3.85 0.03 1.49 0.05 0.00 11-11-83 4.91 0.61 1.23 0.11 0.01 4-13-84 1.20 2.57 2.51 0.10 0.00 5-20-84 0.80 3.03 2.37 0.06 0.00 6-84 0.96 1.77 0.75 0.08 0.00 9-25-84 2.60 0.25 1.19 0.34 0.04 10-30-84 1.62 0.39 1.39 0.10 0.07 12-6-84 1.35 0.90 1.39 0.11 0.03 4-23-85 0.71 0.03 1.09 0.49 0.02 9-3-85 1.73 0.41 0.49 0.23 0.01 10-19-85 1.07 0.87 0.27 0.13 0.01 Yoogly oyorogeol 1982 0.05a,y 0.05a,y 0.08a,z 0.04a,y 0.08a,x 1983 2.10a,x 0.13b,y 0.62ab,yz 0.07b,y 0.01b,x 1984 l.42a,x 1.49a,x 1.60a,x 0.13b,xy 0.02b,x 1985 1.17a,x 0.44abc,xy 0.62ab,y 0.28b,x 0.01c,x 1 Values followed different at the 0.05 level of probability. Letters a, b and c compare values within a row. Letters x, y and z compare values within a column. by different letters are significantly 99 NO3--N concentrations in samples from well 2 were significantly greater in 1983 than in 1982 and reached a peak of 4.91 mg/L in November, 15 months following sludge application. Groundwater flow from beneath nearby sludge treated plot 5 is presumably responsible for this increase. NO3'-N in groundwater below sludge treated plots 4 and 5 was significantly higher in 1984 than in 1982 or 1983. Peak concentrations of 3.03 and 2.51 mg/L, respectively, occurred in spring 1984, 23 months after sludge was applied. Well 6, located down gradient from sludge treated plots 5 and 6 had not shown significant increases in sample NO3'-N concentration through 1985. The well is finished in a clayey layer through which water movement may have been so slow that pore liquid had not yet equilibrated with changes in the surrounding sand aquifer. NO3'-N concentrations in soil leachate beneath sludge treated strips decreased from a mean of 11.1 mg/L in 1983 to 1.74 mg/L in 1984 and 0.43 mg/L in 1985 (Table 5.9). Maximums recorded in groundwater and soil leachate collected at the pine site were consistent with those found by Brockway and Urie (1983) in plot studies using equal dosages of other sludges on similar sites. 5.11.111an 9.: lashing. 5.9. ineuhatiea fuels..- Variables used to compare NO3'-N concentrations in wells and lysimeters at the four sites included: 1) peak concentration for sludge treated plots; 2) average peak 100 Table 5.9 Pine lysimeter NO3'-N concentrations Sampling date 51-TS 52-TS 54-TS 55-TS -------------------- mg/L-------------------- 4-9-83 5.84 18.52 4-22-83 12.68 12.68 6-17-83 3.93 5.41 10-28-83 13.27 13.27 11-11-83 9.11 15.91 4-13-84 2.46 5-20-84 2.13 1.74 9-13-84 2.16 1.95 9-25-84 1.22 2.17 1.52 10-30-84 1.33 1.98 1.10 12-6-84 1.31 1.59 4-23-85 1.65 9-3-85 0.05 0.46 0.35 10-19-85 0.03 0.02 0.46 0.41 Yeayly ovoragos 1983 11.19a,x NAl 10.33a,x 12.20a,x 1984 1.51a,y 2.083 2.06a,y l.58a,y 1985 0.04b,z 0.02 0.86ab,z 0.38a,z 1 Not available. 2 Based upon one sample, statistics cannot be performed. 3 Values followed by different letters are significantly different at the 0.05 level of probability. Letters a, b and c compare values within a row. Letters x, y and 2 compare values within a column. 101 concentration for sludge treated plots; 3) average peak concentration for selected plots; 4) yearly average concentration for sludge treated plots; 5) overall average concentration for sludge treated plots; 6) yearly average concentration for selected plots (wells only); and 7) overall average concentration for selected plots (wells only). In determining concentrations for selected plots, wells in C and T areas experiencing a N03'-N flush due to groundwater flow from beneath nearby sludge treated plots were included; while lysimeters dry at the time of suspected NO3'-N leaching and wells in treated areas not exhibiting a NO3'-N flush due to location of subsurface clay deposits were excluded. Selected wells were 3-C, 4-TS, 5-TS and 7-TS at the aspen site; l-C and 9-TS at the northern hardwoods site; and 2-T, 4-TS and 5-TS at the pine site. Selected lysimeters were 42-TS, 43-TS, 44-TS and 45-TS at the aspen site; 41-TS, 51-TS, 53-TS and 54-TS at the northern hardwoods site; ll-TS and 12-TS for oak plot 1; 52-T8, 58-TS, 72-TS, 73-TS and 78-TS for oak plots 5 and 7; and Sl-TS, 54-TS and 55-TS at the pine site. Oak plot 1 was statistically analyzed separately form oak plots 5 and 7 because of differences in source of sludge used. Groundwater NO3'-N concentrations following sludge application were greatest at the aspen site, intermediate at the pine site, and lowest at the northern hardwoods site (Table 5.10). A similar trend was found in soil leachate 102 samples. Aspen samples had NO3--N concentrations similar to or greater than those found in pine samples, which generally contained more NO3'-N than samples from the oak and northern hardwoods sites (Table 5.11). These trends cannot be predicted using results of the forest type incubation experiment. Net nitrification for the pine type in that experiment was about half that for the other three types. Differences in treatments applied to the types (Table 5.2) and portions of the N cycle other than nitrification evidently need to be taken into account. Source of sludge can affect the amount of nitrate available for leaching. The sludges from Alpena and Rodgers City may have contained different sizes of populations of nitrifying bacteria and thus may have had differential Vabilities to promote nitrification. NO3'-N concentrations in lysimeters fromnplot l LAlpena sludge) at the oak site did have higher concentrations than those in plots 5 and 7 (Rodgers City sludge) (Table 5.11), but differences were only significant for average peak concentration. It should also be noted that there were only two lysimeters in plot 1, while there were 16 in plots 5 and 7; many of which produced no samples during 1982 when peak concentrations were expected to occur. Those collecting leachate in 1982 produced samples with concentrations similar to those in lysimeters from plot 1. Differences in loading rates could be important. A higher solids loading rate, such as that received by oak 103 Table 5.10 Groundwater NO3--N site comparisons Measurement Aspen N. hardwoods Pine ------------- mg/L-------------- Peak, sludge treated 11.14 0.58 3.03 Avg. peak, sludge treated 6.38s 0.32b 2.01ab Avg. peak, selected 6.19a 2.25a 3.48a 1982 avg., sludge treated 0.14a 0.16a 0.08a 1983 avg., sludge treated 2.43s 0.15b 0.28b 1984 avg., sludge treated 1.80a 0.16c 1.07b 1985 avg., sludge treated 2.12s 0.12c 0.45b Overall avg., sludge treated 1.48a 0.15c 0.52b 1982 avg., selected 0.13a 0.16a 0.08a 1983 avg., selected 2.02s 0.39c 1.00b 1984 avg., selected 1.72s 0.72b 1.50s 1985 avg., selected 1.96a 1.60a 0.74a Overall avg., selected 1.35s 0.68b 0.92ab 1 Values within a row followed by different letters are statistically different at the 0.05 level of probability. Soil leachate 104 Table 5.11 N03--N site comparisons Measurement Aspen Peak-sludge treated Avg peak-sludge treated Avg peak-selected 1982 avg-sludge treated 1983 avg-sludge treated 1984 avg-sludge treated 1985 avg-sludge treated Overall avg-s1. treated 0.17ab 7.64s Northern Oak hardwoods 1 7.05 9.60 2.36bc 7.53b 3.38b 7.53b 0.61a 2.79a 1.11b 0.02c 0.06c 0.00c 0.02bc 0.01bc 0.48c 0.68c 18.52 12.47ab 15.90a NA 11.06a 1.74b 0.43a 4.41b 1 Values within a row followed by different letters are statistically different at the 0.05 level of probability. 2 Not available. 105 plot 1, would create a thicker sludge layer and may thereby promote greater nitrification. Variation in N loading could also promote differential nitrate leaching losses due to differences in NO3'-N loading or ammonium availability for nitrifying bacteria. Higher NO3'-N concentrations in wells and lysimeters at the aspen and pine sites may be due simply to Alpena sludge applied having higher NO3'-N content than Rodgers City sludge used at oak and northern hardwoods. Unfortunately, it is not known what proportions of the N applied at each site were organic N, NH4I-N and NO3'-N. Time of application can influence nitrate leaching in several ways. Late fall applications, such at those at aspen and oak, could promote either: 1) decreased leaching losses as a result of reduced nitrification rates caused by low temperature; or 2) higher leaching losses due to lessened plant uptake of both nitrate and ammonium. Higher temperatures following early summer applications, such as those at northern hardwoods and pine, would promote greater nitrification rates; but this would be counteracted by higher plant N uptake at that time of year. Also, lack of groundwater recharge during summer months would allow more timefor plants to utilize nitrate before it is leached. Depth to water table and soil textural properties can influence NO3'-N concentrations in well and lysimeter samples. As soil texture becomes finer, length of time needed for water containing leached nitrate to reach wells and lysimeters increases, causing nitrate flushes to occur 106 over a longer period of time (Olsen et al. 1970) and peak at a lower concentration (Lund et al. 1974). Nitrate flushes detected in wells are influenced in a similar manner as water table depth increases. Zones favoring denitrification are more likely to form in finer textured soils (Shaw 1962), and presence of different textured bands in soils can promote temporary zones of saturation as wetting fronts pass, producing conditions favoring dentrification (Lund et a1. 1974). None of the possibilities discussed thus far can consistently explain observed differences in NO3'-N leaching at the four sites. Therefore, it is hypothesized that plant uptake was a major factor controlling N03--N leaching losses at the four sites. Lower N uptake at the aspen and pine sites due to less complete site occupation and inability of plant species at the pine site to utilize NO3'-N are possible factors that may have contributed to higher NO3'-N leaching losses at those sites. The pattern of NO3'-N leaching observed may also have been influenced by differences among the four types in volatilization, denitrification and competition for NH4+-N between nitrifiers, other microorganisms and plants. There are likely many other factors that could influence the amount of NO3'-N leached following sludge application to forest land. Until accurate models can be developed, data on NO3'-N concentrations in soil leachate and groundwater from plot studies and demonstration projects 107 will remain the best source of information on which to base guidelines for proper application rates. LEACHING CORES Materials ond Methods Incubated cores 7.62 cm in diameter receiving the treatments involved in the 1985 incubation experiments were leached using a Buchner funnel with 2 cm of simulated rainfall weekly (except for week 7) over a 12 week incubation period to see if incubation nitrate and ammonium contents were related to the amount of nitrate and ammonium leachable in the absence of plant roots. Thirty intact cores containing the forest floor and upper 10 cm of mineral soil were collected from the oak site on April 30, 1985, in lengths of 7.62 cm inside diameter PVC pipe for use in the experiment. Five randomly selected cores received each treatment used in the 1985 incubation experiments: 1) control; 2) freeze-dried sludge 1; 3) freeze-dried sludge 2 at pH 7.5; 4) freeze-dried sludge 3; 5) freeze-dried sludge 2 at pH 6.0; and 6) freeze-dried sludge 2 at pH 4.5. Core transportation and incubation were as described in Chapter IV. Cores designated for sludge treatment received 91.2 ml of sludge, with control cores receiving 86.8 ml of distilled deionized water. This produced loading rates identical to those used in the sludge N composition and sludge acidity 108 incubation experiments. Cores were leached with 2 cm of simulated rainfall weekly (except for week 7) over the 12 week incubation period. Leaching was performed using Buchner funnels. Simulated rainfall was prepared as outlined by MacDonald (1983) and had chemical composition typical of rainfall in the study area (Table 5.12). Table 5.12 Chemical composition of simulated rainfall Component Concentration mg/L Mg2+ 0.10 Ns+ 0.27 Ca2+ 0.41 x+ 0.04 NH‘+-N 0.39 Cl 0.23 304'-s 0.52 NO3--N 0.42 Leachates were analyzed for NO3'-N and NH4+-N on a Technicon AutoAnalyzer II system (Technicon 1971, 1977b). Net contents leached were calculated as contents in leachate minus those added with simulated rainfall. Statistical analyses were performed using SPSS statistical programs (Nie et a1. 1975, Hull and Nie 1981) on the Control Data Corporation main computer system at Michigan State University. Leaching core data were analyzed 109 using ome factor ANOVA *with experimental designs corresponding to those of the sludge N composition and sludge acidity experiments. Logarithmic transformations were applied to data when needed to meet the assumption of homogeneity of variance, and means were separated using Duncan's multiple range test with a 0.05 level of significance. Regression analysis was used to compare nitrate and ammonium contents in the 1985 incubation experiments with those leachable in the absence of plant £00118. Resulos and Discussion NO3'-N leached from incubated cores over time (Tables 5.13 and 5.14) followed patterns similar to those of NO3--N contents in destructively sampled incubated cores(Tmb1es 4.21 and 4422). In both the sludge N composition and sludge acidity leaching experiments, NO3'-N leached was low during early stages of the experiment and increased rapidly over the last four to six weeks. Over the last five weeks, significantly higher amounts of NO3'-N were leached from cores receiving freeze-dried sludge 1 than from control cores or cores receiving freeze-dried sludges 2 and 3 (Table 5.13). These higher leaching losses correspond to higher NO3--N contents found at 10 and 12 weeks in destructively sampled cores receiving that sludge (Table 4.21). In the sludge acidity experiment NO3'-N contents in 110 Table 5.13 Cumulative net NO ”-N and NH4+-N contents leached for sludge N composition experiment Incubation Control Freeze- Freeze- Freeze- time dried 12 dried 23 dried 34 weeks -------------------- kglha --------------------- 593:2! 1 -0.02a -0.02b -0.03ab -0.03ab 2 -0.08 -0.01 0.00 -0.04 3 -0.08 0.03 -0.03 -0.03 4 -0.05 0.19 -0.06 -0.06 5 0.07 0.65 -0.09 -O.11 6 0.43 1.84 0.05 -0.14 8 1.63a 5.40b 1.17a -0.07a 9 3.63s 10.53b 3.01a 0.02s 10 6.11s 17.35b 5.64a 0.33s 11 9.06s 24.66b 8.93a 1.32s 12 12.59a 32.73b 12.67a 2.88s 5541:! 1 0.2a 2.8a 16.6b 24.2c 2 0.4a 5.1a 27.3b 44.6c 3 0.8a 7.6a 35.4b 57.8c 4 1.4a 10.4a 42.9b 70.0d 5 2.1a 13.2b 48.7c 78.2d 6 3.0a 16.2b 53.8c 85.5d 8 4.4a 20.0b 58.5c 91.6d 9 5.9a 24.5b 62.9c 96.7d 10 7.5a 29.3b 67.1c 100.9d 11 9.1a 34.4b 71.5c 105.0d 12 10.8a 39.4b 75.9c 109.1d 1 Means in the same row followed by a different letter are significantly different at an alpha - .05 level. 2 226 kglha organic N and 20 kglha NH4+-N, surface applied. 3 150 kglha organic N and 95 kglha NH4+-N, surface applied. 4 75 kglha organic N and 170 kglha NH4+-N, surface applied. 111 Table 5.14 Cumulative net NO3'-N and NH4+-N contents leached for sludge acidity experiment Control Freeze- Freeze- Freeze- Incubation dried 2 dried 2 dried 2 time pH 7.5 pH 6.0 pH 4.5 weeks -------------------- kglha --------------------- 193::! 1 -0.02 -0.03 -0.02 -0.02 2 -0.08a 0.00b -0.04ab -0.02b 3 -0.08 -0.03 -0.03 0.00 4 -0.05 -0.06 -0.06 -0.05 5 0.07 -0.09 -0.06 -0.08 6 0.43 0.05 0.07 -0.05 8 1.63 1.17 1.34 0.40 9 3.63 3.01 3.88 1.37 10 6.11 5.64 7.84 3.40 11 9.06 8.93 13.40 6.59 12 12.59 12.67 20.62 11.36 114::5 1 0.2a 16.7b 16.6b 17.5b 2 0.4a 27.5b 27.3b 29.86 3 0.8a 35.6b 35.4b 39.6b 4 1.4a 43.2b 42.9b 48.5b 5 2.1a 49.1b 48.7b 55.6b 6 3.0a 54.3b 53.8b 61.5b 8 4.4a 59.0b 58.5b 66.8b 9 5.9a 63.5b 62.9b 72.1b 10 7.5a 67.8b 67.1b 77.2b 11 9.1a 72.3b 71.5bc 83.0c 12 10.8a 76.8b 75.9bc 89.2c 1 Means in the same row followed by a different letter are significantly different at an alpha I .05 level. 2 Surface applied at 150 kglha organic N and 95 kglha NH -N l; 112 destructively sampled incubated cores were higher at several sampling periods in cores receiving pH 7.5 sludge (Table 4w22). This was not evident, however, in leachate, as quantity of NO3-IN leached was not significantly affected by sludge pH (Tables 5.14). The amount of NH4+-N leached from cores corresponded to that added during sludge treatment (Tables 5.13 and 5.14). Sludge acidity generally had no significant effects, but data did indicate higher cumulative amounts of leached NH4+- N for pH 4.5 sludge than pH 7.5 sludge at 10 and 12 weeks (Table 5.14L. This trend for somewhat higher losses from cores treated with pH 4.5 sludge is likely due to: 1) less NH3-N and more NH4+-N being present at low pH; and 2) increased availability of Cl', as an ion for NH4+ to pair with in leaching, and H+, for replacing NH4+ on exchange sites, due to use of HCl in sludge acidification. It is probable that NH4+-N leached through the 10 cm of mineral soil contained in cores would not leach below the rooting zone in the field as it would be bound to exchange sites below the 10 cm depth. Regression analysis was performed using data from the six treatments involved in the two experiments. Content of destructively sampled cores served as the independent variable, and net cumulative content leached from incubated cores acted as the dependent variable. For NH4+-N, a significant relationship existed with a correlation coefficient of 0.93 (Figure 5.2). The variables were not as 113 well correlated for NO3--N (r I 0.66), but a significant relationship still existed (Figure 5.3%. Elimination of the week 10 data point for cores receiving freeze-dried sludge 1 improved the relationship (r I 0.77; P I 4.38 x 10-9); but deletion of both the 10 and 12 week data points for that treatment reduced the correlation coefficient (r I 0.40) and level of probability for which significance was indicated (P I0.01) to levels more representative of the data set. The relationship for NO3--N would presumably have been similar to that for NH4+-N had nitrification rates for the freeze- dried sludges been higher, such as those for anaerobically digested sludge from Alpena used in the forest type experiment. nunoawuoouo.aowuansoaw moo“ we nouoo omamaen >~o>fiuoauunoo aw unoueoo zn+¢mz .n> venueoa unsunou zn+¢mz no: o>flueaoa=o ~.n ensues notoo moiEon Enzuuabnoo Zlvzz oc\ox OON O¢N OON OO— ONp OO O? O p _ . b _ b _ _ #1 P _ . . 114 Mled*°MsH l m 25 n s + it. ~.~N n N¥~¢.o u w + + 1 oo— & OP— peuaotn N-nrn-nN Inn/6» 115 nunoafiuooxo.aoauan=onw mama we «once vodaaem >Ho>muo=uunoo aw unounoo 21 ~92 .m> assumed uaoucoo 21 ~02 um: o>wumgna=o m.n ouawwm notoo “02¢an >_o>_uon.zaon zanZ o:\ox OV ON ON O— O — h — — — _ _ _ 111.3311 1. + OIOMNON.N .- m H. H. W s n. H o o ++ + T Om.o + Nkao.c u w + 1 r1 + + + 1 F +.OP x003 9 On I + I T +9 eon; F o... N— wp O— Op ON NN ¢N ON ON on NO tn p-uaoen N-rON 011/6» CHAPTER VI SUMMARY AND CONCLUSIONS Application to forest lands is an alternative that shows much promise as a method of sewage sludge disposal. Leaching of NO3'-N to groundwater will often limit rate of application; therefore, studies were initiated in which N03--N leaching following sludge application to four Michigan forest types was monitored, and incubation experiments investigating sludge N transformations that might affect such losses were performed. SUMMARY: INCUBATION EXPERIMENTS Intact cores containing the forest floor and upper 10 cm of mineral soil were collected in lengths of 3.81 cm inside diameter PVC pipe, treated and aerobically incubated. Incubations were performed in the laboratory at 25°C and 802 relative humidity and in the field in polyethylene plastic bags. During August and September 1984, experiments were performed in which: 1) differences in N transformations in cores from aspen, northern hardwoods, oak and pine forest sites following surface application of anaerobically digested sludge were investigated in the laboratory; 2) field and laboratory results were compared for the oak and pine sites; and 3) effects on laboratory N transformations of sludge type, application rate, application method and 116 117 time between sludge application and initiation of incubation were investigated using cores from the oak site. Additional laboratory incubation experiments, conducted using cores from the oak site during May, June and July 1985, investigated effects of sludge N composition and sludge acidityu Unless otherwise noted, all treatments involved surface application of anerobically digested municipal sludge. Five replicate samples from each treatment were destructively sampled for analysis at 0, 2, 4 and 8 weeks in 1984 incubation experiments and 0, 1, 2, 4, 6, 8, 10 and 12 weeks in 1985 incubation experiments. In the analysis procedure, forest floor and soil materials were separated and subsamples of each were extracted by shaking with 2 N RC1 for one hour. Extracts were filtered and analyzed for NO3'-N and NH4I-N. Increases in core N03'-N content over time were used to estimate net nitrification, and increases in core total inorganic nitrogen (TIN) content over time were used to estimate net mineralization. TIN was calculated as the sum of NO3'-N and NH4+-N. In the forest type experiment net nitrification occurred in sludge treated cores but not in control cores. Evidence suggested autotrophic bacteria responsible for a majority of nitrification in treated cores were added with the sludge. Net nitrification in treated pine cores was about half that in treated cores from the other three types. This was attributed to the greater acidity at the 118 pine site and creation of fewer sludge dominated microsites having conditions favorable for nitrification as sludge infiltrated pine litter more readily. Mineralization of sludge organic N could not be determined, but NH4+-N derived from such mineralization appeared to be of minor importanceein comparison to NH4+-N initially contained in the sludge as a substrate for nitrifiers. In the incubation method experiment, type of incubation affected both net nitrification in sludge treated cores and net mineralization in control cores; and forest type affected net nitrification in treated cores. Lower NO3'-N contents in sludge treated pine cores than in treated oak cores in both field and laboratory incubations were attributed to the factors discussed above. Lower rates of net mineralization in control cores and net nitrification in sludge treated cores during field incubation than lab incubation were likely a result of lower average temperature and diurnal temperature fluctuations encountered by field incubated cores. In the sludge type experiment, net nitrification did not occur in control cores or cores from the oak site treated with limed undigested municipal sludge. Net nitrification, however, did occur in cores receiving anaerobically digested sludge. The high pH of the limed undigested sludge (12.0) would destroy any nitrifying bacteria it contained. Thus the fact that net nitrification did not occur in cores treated with that sludge supports the 119 hypothesis that the nitrifying population responsible for high NO3--N contents in cores treated with anaerobically digested sludge was introduced with the sludge. NO3'-N contents in. cores receiving sludge at application rates of 4.2, 10.5 and 16.8 Mg/ha of sludge solids were not significantly different over the eight week incubation period. During the early stages of the experiment NO3'-N contents tended to decrease (but not significantly) with increasing loading rate. This was attributed to denitrification in cores receiving sludge at the two higher loading rates. These cores had initial moisture contents in excess of that desired and were allowed to drain to alleviate the moisture problem. Net nitrification rates in these cores increased as they became dryer, so that after eight weeks, core NO3'-N contents increased (but not significantly) with increasing loading rate. In the application method experiment, higher NO3'-N contents were found in cores receiving surface sludge application than in those in which sludge was incorporated. This was attributed to destruction during incorporation of the surface sludge layer and other sludge dominated zones favorable for nitrification. . NO3'-N contents in cores collected from a portion of the oak site receiving sludge 2.75 years prior to incubation were much higher than those in control cores. NO3'-N contents in these cores were lower than those in 120 cores receiving sludge treatment immediately prior to incubation, but not significantly so by the end of the experiment. Evidently, nitrifying populations added to the site during sludge application 2.75 years earlier were present and capable of producing significant quantities of NO3'-N when NH47-N was made available. Sludges used in the sludge N composition and sludge acidity experiments were prepared from a freeze-dried sludge of known composition. The sludges were prepared with: 1) virtually all organic N; 2) approximately 2/3 organic N and 1/3 NH4I-N; and 3) approximately 2/3 organic N and 1/3 NH4I-N. The sludge containing approximately 2/3 organic N and 1/3 NH4I-N was prepared with pH values of 7.5, 6.0 and 4.5 for use in the sludge acidity experiment. Sludges used in the sludge N composition experiment had the same total.Nncontent but varying proportions of NH4+-N and organic N. It was expected that net nitrification would be higher in cores receiving the sludge high in NH4+-N than in cores receiving the sludge containing virtually no NH4+- N, at least in the early portions of the experiment. Instead, virtually no net nitrification occurred for any treatment during the first eight weeks, and when net nitrification finally did occur, highest NO3--N contents were found in cores receiving the sludge containing virtually no NH4+-N. Lack of net nitrification during the first eight weeks is attributed to destruction during freeze-drying of nitrifying bacteria originally contained in 1’. LI ll 1| 121 the sludge. This provides further support for the hypothesis that nitrifiers responsible for a majority of net nitrification in cores treated with anaerobically digested sludge were added with the sludge. It is postulated that higher net nitrification during the last four weeks of the experiment in cores treated with the sludge containing virtually all organic N was a result of creation of a thicker surface sludge layer, which provided an environment that allowed small native nitrifying populations to grow to a size where measurable net nitrification could occur. This agrees with the conclusion from the application method experiment that the surface sludge layer and other sludge dominated microsites provide important zones favorable for nitrification. In the sludge acidity experiment, sludge pH had little influence on net nitrification and net mineralization. NO3-IN contents in cores receiving pH 7.5 sludge were slightly higher during the final four weeks of the twelve week experiment, but were still much lower than those in cores treated with anaerobically digested sludge in the forest type experiment. Had sludge pH been varied for that sludge, it might have had a greater influence on net nitrification rates. SUMMARY: NITROGEN LEACHING Leaching of NO3--N and NH4+-N from sludge treated areas was monitored through: 1) wells and lysimeters installed to 122 monitor water quality in the forest sludge fertilization demonstration project conducted by"Michigan State University; and 2) leaching of incubated cores receiving the treatments used in the 1985 incubation experiments with simulated rainwater. In the demonstration project, NO3'-N concentrations in lysimeter samples reached peak levels 6 tun 18 months following sludge application after which they fell quickly to background levels. This supports the hypothesis that NO3'-N produced following sludge application to these sites was formed primarily through nitrification of NH4+-N existing in the sludge at the time of application. NO3--N concentrations in well samples reached peak values two to three years following sludge treatment and were still elevated in 1985, three to four years following application. NH4I-N did not leach beneath sludge treated areas as that not volatilized was evidently held tightly to soil exchange sites where it was immobilized or nitrified. NO3'-N concentrations in soil leachate and groundwater were highest for the aspen type, intermediate for the pine type and lowest for the oak and northern hardwoods types. These results can not be predicted based solely upon results of the incubation experiment comparing the four forest types in which net nitrification for the pine type was about half that for the other three types. Differences in the sludge treatments received by the four types and portions of the nitrogen cycle other than nitrification need to be taken 123 into account before observed differences in N03'-N leaching can be explained. Incubated cores receiving treatments used in the sludge N composition.and sludge acidity experiments were leached with simulated rainwater to see if NO3-IN and NH4+-N contents in destructively sampled cores were related to contents leached in the absence of plant roots. In both the sludge acidity and sludge N composition experiments, NO3'-N contents leached followed patterns over time similar to those of NO3'-N contents in destructively sampled cores. Cumulative net contents leached and contents of incubated cores were significantly correlated for both NO3'-N (r I 0.66) and NHAI-N (r - 0.93). CONCLUSIONS Net nitrification in laboratory incubations could not be used to predict differences in NO3'-N leaching losses following sludge application to the four forest sites. Quantification of differences among forest types in portions of the N cycle such as plant uptake of NO3'-N, volatilization, denitrification and microbial immobilization is evidently needed before NO3'-N leaching losses from sludge treated forest sites can be accurately modeled. Incubation results may be useful, however, in comparing the way different sludge treatments will behave following application to a specific site. Reduced net 124 nitrification in oak cores in which sludge was incorporated and lack of net nitrification in oak cores treated with limed undigested sludge suggest NO3'-N leaching losses following field application of such treatments might be less than_ losses following surface application. of the anaerobically digested municipal sludge from Alpena. Care should be taken, however, in extrapolating incubation results to field situations. The treatments might promote high rates of net nitrification and leaching if applied to sites having large native nitrifying populations. NH4+-N produced by mineralization of sludge organic N appeared to be of minor importance in comparison to NH4+-N initially contained in the sludge as a substrate for nitrifiers. This suggests that NO3'-N production and leaching following application of sludge to forest land may be minimized by using sludges low in inorganic N. Results of experiments using cores from the oak site suggest that the surface sludge layer provides a favorable zone for nitrification. Therefore, to lessen N03--N leaching, it is recommended that conservative application rates be used at sites having many high spots and depressions and sludge applications be applied as evenly as possible. The findings that: l) N03--N concentrations in groundwater were still elevated three to four years following sludge application; 2) nitrifiers responsible for a majority of nitrification in cores treated with 125 anaerobically digested sludge were added with the sludge; and 3) cores from areas receiving sludge treatment 2.75 years prior to incubation were capable of significant net nitrification upon incubation; suggest caution should be exercised in determining frequency of reapplications to sites such as those studied. Sludge application rates used in the forest sludge fertilization project conducted by Michigan State University (approximately 9 Mg/ha of sludge solids and 500 kglha N) were compatible with the 10 mg/L public health standard for NO3'-N in drinking water. Lower leaching losses beneath the northern hardwoods and oak sites indicate that they could have safely received heavier sludge applications. Until more research on the factors affecting NO3'-N leaching following sludge application to forest lands is performed, data from trial applications, such as the demonstration project, will provide the best source of information on which to base sludge application rates. APPENDICES APPENDIX A 0033 pH DATA Table A.1 Core forest floor pH values for 1984 incubation experiments Forest type Treatment 0 2 4 8 Aspen Control 5.23 4.99 5.28 5.16 Aspen Sludge 22 6.02 5.42 5.37 5.12 N. hardwoods Control 4.75 5.33 5.26 4.73 N. hardwoods Sludge 2 5.31 5.54 5.19 4.81 Oak Control 4.52 4.71 4.62 4.69 Oak Sludge 2 5.23 4.99 5.13 5.03 Pine Control 3.75 3.98 3.84 3.87 Pine Sludge 2 4.94 4.62 4.35 4.42 Oak Control-field 4.52 4.69 4.59 4.54 Oak Sludge 2-field 5.23 5.17 5.01 5.27 Pine Control-field 3.75 3.69 3.97 3.83 Pine Sludge 2-field 4.94 4.75 4.40 4.33 Oak Sludge 33 5.73 5.67 5.30 5.28 Oak Sludge 44 6.12 5.81 5.26 5.38 Oak Sludge 55 6.99 6.59 6.10 5.90 Oak Sludge 66 4.70 4.59 4.72 5.00 1 All treatments lab incubated unless otherwise noted. 2 Alpena sludge surface applied at 4.2 Mglha of solids. 3 Alpena sludge surface applied at 10.5 Mglha of solids. 4 Alpena sludge surface applied at 16.8 Mglha of solids. 5 Grand Ledge sludge surface applied at 10.2 Mglha. 6 Area treated with anaerobically digested municipal sludge at 5.0 Mglha solids and 374 kglha N, 2.75 years prior to incubation. 126 127 Table A.2 Core soil pH values for 1984 incubation experiments Forest type Treatment1 0 2 4 8 Aspen Control 4.38 4.19 4.39 4.67 Aspen Sludge 22 4.67 4.26 4.34 4.71 N. hardwoods Control 4.19 4.23 4.32 4.35 N. hardwoods Sludge 2 4.34 4.26 4.27 4.38 Oak Control 4.27 4.16 4.03 4.33 Oak Sludge 2 4.34 4.13 4.19 4.59 Pine Control 3.78 3.88 3.76 3.72 Pine Sludge 2 3.83 3.86 3.91 3.79 Oak Control-field 4.27 4.21 4.44 3.93 Oak Sludge 2-field 4.34 4.40 4.40 4.15 Pine Control-field 3.78 3.67 3.77 3.77 Pine Sludge 2-field 3.83 3.78 3.89 4.04 Oak Sludge 33 4.37 4.44 4.58 4.82 Oak Sludge 44 4.68 4.74 5.00 4.71 Oak Sludge 55 4.64 4.72 4.70 4.74 Oak Sludge 66 5.30 5.21 5.10 5.05 Oak Sludge 77 4.07 3.88 4.33 4.34 Oak Sludge 88 4.04 3.96 4.11 5.20 1 All treatments lab incubated unless otherwise noted. 2 Alpena sludge surface applied at 4.2 Mglha of solids. 3 Alpena sludge surface applied at 10.5 Mglha of solids. 4 Alpena sludge surface applied at 16.8 Mglha of solids. 5 Alpena sludge incorporated into forest floor and soil at 4.2 Mglha of solids. 6 Alpena sludge incorporated at 4.2 Mglha with forest floor removed. 7 Grand Ledge sludge surface applied at 10.2 Mglha. 8 Area treated with anaerobically digested municipal sludge at 5.0 Mglha solids and 374 kglha N, 2.75 years prior to incubation. 128 Table A.3 Core soil and forest floor pH values for 1985 incubation experiments Contfol 4.01 4.41 4.27 4.33 4.19 4.46 4.23 4.30 an 1 4.33 4.48 4.29 4.14 4.51 4.26 4.73 4.56 so 22, pH 7.5 4.50 4.46 4.19 4.71 4.49 4.38 4.23 4.41 20 33 3.98 4.21 4.19 4.03 4.31 4.09 4.13 4.26 20 2, pH 4.5 4.46 4.21 4.36 4.56 4.17 4.21 4.16 4.29 PD 2, pH 6.0 4.43 4.31 4.26 4.16 4.25 4.27 4.42 4.31 Control 4.85 4.67 4.72 5.05 4.59 4.63 5.16 5.02 FD 1 5.38 5.21 4.98 5.22 5.42 5.34 5.58 5.27 PD 2, pH 7.5 4.95 5.01 5.13 4.89 5.21 5.17 5.59 5.35 FD 3 5.21 4.98 5.12 4.99 4.87 5.03 4.66 5.22 FD 2, pH 4.5 4.54 4.67 4.63 5.19 4.91 5.07 5.15 5.20 FD 2, pH 6.0 4.99 5.19 5.07 5.26 5.37 5.18 5.38 5.23 l Freeze-dried sludge l. 2 Freeze-dried sludge 2. 3 Freeze-dried sludge 3. APPENDIX B CORE MOISTURE DATA Table B.l Soil and forest floor moisture contents at -0.10 bars for the four forest types Mean gravimetric moisture content and (std. dev.) for forest type Material Aspen N. hardwoods Oak Pine -------------- g H20] g dry materia1----------- Soil 0.16 (.019) 0.18 (.021) 0.20 (.035) 0.18 (.017) Forest floor 1.04 (.324) 1.29 (.479) 1.27 (.432) 1.33 (.414) 129 130 Table 8.2 Core forest floor moisture contents for 1984 incubation experiments Forest type Treatment1 0 2 4 8 ------ g H20] g dry forest floor------ Aspen Control 0.77 0.72 0.77 0.82 Aspen Sludge 22 1.08 0.79 0.73 0.77 N. hardwoods Control 1.20 1.30 1.23 0.92 N. hardwoods Sludge 2 1.29 1.44 1.85 1.23 Oak Control 1.28 1.21 1.41 1.00 Oak Sludge 2 1.80 1.38 1.36 1.28 Pine Control 0.85 1.35 1.26 1.44 Pine Sludge 2 1.68 1.43 1.55 1.46 Oak Control-field 1.28 1.26 1.22 1.92 Oak Sludge 2-field 1.80 1.33 1.06 1.33 Pine Control-field 0.85 0.83 1.22 1.61 Pine Sludge 2-field 1.68 0.94 1.53 1.66 Oak Sludge 33 2.30 1.68 1.47 1.28 Oak Sludge 44 2.30 2.09 1.47 1.05 Oak Sludge 55 1.74 1.40 1.19 1.16 Oak Sludge 66 1.42 1.00 1.14 1.19 1 All treatments lab incubated unless otherwise noted. 2 Alpena sludge surface applied at 4.2 Mglha of solids. 3 Alpena sludge surface applied at 10.5 Mglha of solids. 4 Alpena sludge surface applied at 16.8 Mglha of solids. 5 Grand Ledge sludge surface applied at 10.2 Mglha. 6 Area treated with anaerobically digested municipal sludge at 5.0 Mglha solids and 374 kglha N, 2.75 years prior to incubation. 131 Table B.3 Core soil moisture contents for 1984 incubation experiments Forest type Treatment1 0 2 4 8 ---------- g HZO/g dry soil----------- Aspen Control 0.17 0.15 0.16 0.15 Aspen Sludge 22 0.17 0.13 0.17 0.13 N. hardwoods Control 0.19 0.18 0.18 0.10 N. hardwoods Sludge 2 0.16 0.13 0.20 0.13 Oak Control 0.26 0.26 0.19 0.15 Oak Sludge 2 0.25 0.24 0.20 0.23 Pine Control 0.15 0.19 0.19 0.18 Pine Sludge 2 0.18 0.20 0.18 0.15 Oak Control-field 0.26 0.27 0.23 0.30 Oak Sludge 2-field 0.25 0.23 0.20 0.26 Pine Control-field 0.15 0.09 0.18 0.20 Pine Sludge 2-field 0.18 0.08 0.18 0.22 Oak Sludge 33 0.27 0.26 0.27 0.24 Oak Sludge 44 0.28 0.24 0.24 0.20 Oak Sludge 55 0.39 0.16 0.12 0.14 Oak Sludge 66 0.31 0.16 0.14 0.12 Oak Sludge 77 0.22 0.22 0.22 0.19 Oak Sludge 88 0.19 0.18 0.16 0.15 1 All treatments lab incubated unless otherwise noted. 2 Alpena sludge surface applied at 4.2 Mglha of solids. 3 Alpena sludge surface applied at 10.5 Mglha of solids. 4 Alpena sludge surface applied at 16.8 Mglha of solids. 5 Alpena sludge incorporated into forest floor and soil at 4.2 Mglha of solids. 6 Alpena sludge incorporated at 4.2 Mglha with forest floor removed. 7 Grand Ledge sludge surface applied at 10.2 Mglha. 8 Area treated with anaerobically digested municipal sludge at 5.0 Mglha solids and 374 kglha N, 2.75 years prior to incubation. 132 Table 8.4 Core soil and forest floor moisture contents for 1985 incubation experiments Control PD 1 FD 22, P0 33 FD 2, pH PD 2, pH Control PD 1 FD PD 3 FD 2 PD 2 4 6 pH 7.5 5 .0 0.19 0.17 0.19 0.19 0.19 0.19 0.73 0.80 0.63 1.03 0.79 0.77 0.19 0.17 0.15 0.17 0.16 0.17 0.90 1.09 0.95 0.88 0.89 0.97 2 4 6 8 Soil 0.21 0.19 0.17 0.16 0.20 0.19 0.16 0.14 0.16 0.19 0.17 0.16 0.18 0.21 0.15 0.15 0.18 0.16 0.21 0.12 0.19 0.16 0.19 0.20 Fogosg gloo; 1.09 0.94 1.27 1.11 1.40 1.41 1.07 1.02 1.03 1.13 1.01 0.98 1.28 1.38 1.19 1.24 1.08 0.99 1.24 0.70 1.16 1.06 1.07 1.09 0.19 0.17 0.17 0.18 0.16 0.16 0.20 0.17 0.18 0.19 0.14 0.18 l Freeze-dried sludge 1. 2 Freeze-dried sludge 2. 3 Freeze-dried sludge 3. APPENDIX C Table 0.1 Field incubation temperatures Date Daily maximum Daily minimum ................ 03------_--_----_-_ 08-01-84 77 63 08-02-84 69 61 08-03-84 82 65 08-04-84 79 59 08-05-84 84 63 08-06-84 87 67 08-07-84 78 63 08-08-84 83 62 08-09-84 73 63 08-10-84 87 57 08-11-84 79 58 08-12-84 72 48 08-13-84 75 52 08-14-84 80 56 08-15-84 83 58 08-16-84 84 62 08-17-84 78 53 08-18-84 79 60 08-19-84 76 54 08-20-84 71 50 08-21-84 79 58 08-22-84 80 63 08-23-84 80 53 08-24-84 66 44 08-25-84 73 48 08-26-84 78 53 08-27-84 81 62 08-28-84 75 63 08-29-84 85 62 08-30-84 90 NA2 08-31-84 NA NA 09-01-84 NA NA 09-02-84 NA NA 09-03-84 NA NA 09-04-84 NA NA 09-05-84 57 37 09-06-84 59 40 09-07-84 68 49 134 Table C.1 (continued) 09-08-84 09-09-84 09-10-84 09-11-84 09-12-84 09-13-84 09-14-84 09-15-84 09-16-84 09-17-84 09-18-84 09-19-84 09-20-84 09-21-84 09-22-84 09-23-84 09-24-84 09-25-84 Daily maximum Daily minimum ................ 03--------_-------_ 65 52 76 61 74 53 70 51 73 45 68 54 73 43 57 41 57 36 63 43 67 48 71 53 77 58 67 38 65 48 81 53 73 50 71 NA 1 Data from Atlanta, Michigan climatological station (NOAA 1984). 2 Not available. 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