- I. ‘nq . I, ,v, ‘ . II , ll. VIN“, ,' >{,- “.0 ‘1. “U“ :."' , I V THIS/i“ I! I: H11 " , ‘ - ~-~vm.—v~mm EFFECTS OF LONG-TERM APPLICATION OF HIGH RATES OF NITROGEN CARRIERS ON SOIL ACIDITY, EXCHANGEABLE CATIONS AND SOIL ORGANIC MATTER Thesis for the Degree of M. S. MICHIGAN STATE UNIVERSITY EBINIMI F. A. BURUTOLU 1977 IIIIIIIIITZIIIIITITIIIITIM ‘ If A :1 ~— ABSTRACT EFFECTS OF LONG-TERM APPLICATION OF HIGH RATES OF NITROGEN CARRIERS ON SOIL ACIDITY, EXCHANGEABLE CATIONS AND SOIL ORGANIC MATTER BY Ebinimi F. A. Burutolu Residual effects of 14 annual applications of eight nitrogen carriers at rates of 300 lb N/A were studied on a Hodunk sandy loam soil. Data collected by others over a period of 16 years from initia- tion of the experiment are summarized. Data collected by the author in two succeeding years are presented. The eight nitrogen carriers were applied in a randomized com- plete block design with four replications. Corn (Zea mays L.) was grown each year from 1959 to 1972. A basal fertilizer control and an unfertilized check were included. The ten treatments were discon- tinued in 1973 when wheat (Triticum.aestivum L.) was grown with uniform fertilization on all plots, followed by soybeans [Glycine max (L.) Merr.] in 1974, 1975 and 1976. Dolomitic lime was applied on two of the four replications in 1965 and again in 1966. The total for the two applications was two times the requirement determined by the SMP buffer test on each plot. Soil pH in the plow layer was initially about 6.0. With soil pH had declined to a limiting low value of about 4.2 (NH4)ZSO4, in 1962 after four annual applications. A similar limiting value ‘-'e Mu Ebinimi F. A. Burutolu was reached by other acidifying carriers in the order: NH4C1 (1965), NH4N03 (1967), urea and ureaform (1970). Occasional values of less than 4.2 were encountered from time to time, indicating the presence of free mineral acid at the time of sampling. With anhydrous NH3, a limiting low value of 4.5 was reached in 1971. Ca(NO3)2 had little residual effect on soil acidity, but NaNO maintained a consistently 3 higher pH than in control plots which received only basal fertilizer. Lime requirement (potential acidity) increased rapidly in the plow layer at about pH 5.0 and then progressed quickly into the sub- soil. By 1971, the increase in potential acidity to a depth of 30 inches was two to three times greater than the expected residual acidity from acidifying N carriers. It appeared that acidity which had accumulated in polymeric Al complexes before the experiment was initiated in 1959 was quickly released as exchangeable Al when the pH dropped below 5.0. Bray P in the plow layer increased in several treatments in l unlimed and limed plots over time. Significant differences were mainly between no fertilizer and plots that received basal fertilizer. The capacity of the soil to retain exchangeable basic cations was reduced by the high levels of exchangeable Al indicated by the high lime requirement. Exchangeable Ca and Mg were depleted to very low levels throughout the 30" profile by 1975. Similar depletion of exchangeable K did not occur, probably because of rapid release from non—exchangeable forms. Levels of exchangeable Ca and Mg were restored by addition of dolomite, but a significantly lower level of exchangeable Mg was maintained after liming with NH Cl and Ca(NO3)2 than with other 4 carriers. Liming did not completely neutralize accumulated acidity Ebinimi F. A. Burutolu in (NH4)ZSO4 and NH4Cl plots by 1975. Specific carrier ion effects on persistence of acidity and on retention of cations were observed for C1. XE $04= and for Ca2+ X§_Na+. There was evidence that nitrification of ammonium was retarded in very acid soils. Liming increased nitrification because it pro- vided suitable environmental conditions for the nitrifying bacteria. Detection of substantial quantities of nitrate in acid unlimed plots indicates the presence of acid tolerant strains of bacteria or the spontaneous formation of nitrate from nitrite at very acid pH. Residual organic matter was higher and had wider C:N ratios in unlimed acid plots than the limed plots, although return of residues as indicated by yields of corn and soybeans had been reduced drasti- cally below pH 5.0 and was restored by liming. EFFECTS OF LONG-TERM APPLICATION OF HIGH RATES OF NITROGEN CARRIERS ON SOIL ACIDITY, EXCHANGEABLE CATIONS AND SOIL ORGANIC MATTER BY Ebinimi F: A. Burutolu A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Crop and Soil Sciences 1977 TO MY PARENTS This thesis is dedicated to my beloved parents for their prayers and encouragement all these years. ii ACKNOWLEDGEMENTS The author would like to express his profound gratitude to Dr. A. R. Wolcott for his wonderful and most rewarding guidance through all phases of the research. The amount of time we spent together in preparing the thesis has been quite invaluable. The author also wishes to thank the Rivers State Government of Nigeria and Michigan State University for their financial support. My thanks are due to Dr. C. Cress and Dr. D. D. Warncke, who served on my guidance committee, for their advice and useful suggestions. iii INTRODUCTION. . . . . . . LITERATURE REVIEW . . . . TABLE OF CONTENTS Soil Acidity and Nitrogen Carriers . Relationship Between pH and Nutrient Availability. Phosphorus and Potassium. Calcium and Magnesium . Liming and Nutrient Availability . Phosphorus and Potassium. Calcium and Magnesium . Effect of Anions of Nitrogen Carriers on Ion Reten- tion and/or Losses . Mineral Nitrogen . Organic Matter as Affected Crop Yields as Affected by MATERIALS AND METHODS . . Field Treatments . Sources of Data. . Soil Sampling. . . Laboratory Procedures. Statistical Analysis RESULTS AND DISCUSSION. . History of Corn and Soybean Yields by Nitrogen Carriers. Nitrogen Carriers . Soil Test Changes Over Time. Soil pH and Lime Requirement. Available P and Exchangeable K. Exchangeable Ca and Mg. Profile Changes After Treatments Were Discontinued Soil pH and Lime Requirement. Available P and Exchangeable K. Exchangeable Ca and Mg. Relationship Between Lime Requirement and Exchange- able Cations . . Mineral Nitrogen in 1975 . Ammonium N. Nitrate-N . Soil Organic Matter in 1975. Organic Matter Levels iv 0 Page 10 12 12 14 14 15 16 19 21 21 23 24 24 26 28 28 29 29 40 44 56 57 60 63 68 71 71 73 75 75 C:N Ratios and Organic Nitrogen SUMMARY AND CONCLUSIONS . . . . . . . . . . . BIBLIOGRAPHY. . . . . . . . . . . . . . . . . APPENDICES. . . . . . . . . . . . . . . . . . A HODUNK SERIES. . . . . . . . . B TOTAL N PROCEDURE. . . . . . . C TOTAL C PROCEDURE. . . . . . . Page 77 81 87 94 94 96 99 ([1 VB CT‘ I LI ST OF TABLES Table Page l-a Crops and amounts of nutrients used in nitrogen carrier study from 1959 to 1976. . . . . . . . . . . . . 22 l-b Percent N and relative residual acidity of the nitrogen carriers in the field experiment. . . . . . . . 22 2 Representative yields and stands of corn on plots which received 300 1b N/a/yr from various sources, beginning in 1959. . . . . . . . . . . . . . . . . . . . 3O 3 Residual effects on soybean yields of 14 annual appli- cations (1959 to 1972) of nitrogen carriers (300 lb N/a/yr) BK) + NH4+202—->No c) Increase in potential acidity (lime requirement): NH4(soil) + 2 02 —-—> N0; + 520 + H(soi1) + 3* [51 + . . 2+ 2 H + Ca(3011) -—-—-\H2(son.1) + Ca [6] active‘ potential acidity acidity + Reactions [1] and [2] show that either NH3 or NH4, when added to soil that is not highly alkaline, will be adsorbed immediately 4. on the exchange complex as NH4. Reactions [3] and [4] show that the 5 expected production of acidity (H+ ions) will be twice as great from nitrification of NH: as from NH3. The nitrifying bacteria in soil probably have access only to the + adsorbed NH4 formed by reactions [1] or [2]. Nevertheless, the essential reactions of nitrification involve NH3, as shown in reac- tion [3]. As a result, when adsorbed NH: is nitrified, as in equation [5], part of the acidity produced appears initially as exchangeable H+ and part of it as H+ ions in solution. The equilibrium in equation [6] is very much in favor of adsorp- tion of H+ from solution onto the soil exchange complex. Thus, much of the acidity produced by nitrification appears initially as exchangeable H+ on soil mineral and organic colloids. Further reac- tions are slower, but they lead to incorporations of H+ ions into complexes with hydrated A1 oxides and hydroxides already present in the soil or released by continuing decomposition of alumino-silicate minerals. In equations [5] and [6], the 8+ ions in solution represent "active” acidity which can be measured with a glass electrode as pH. The H+ adsorbed on soil represents ”potential" acidity or "buffer" acidity. Potential acidity may be defined as the soil's capacity to feed H+ ions back into solution, by reversal of equation [6], when lime is applied to produce a desired change in pH. Potential acidity, or "lime requirement", can be estimated from the pH change in a standard buffer when soil is added to it. According to Jackson (1963), the principal form of potential acidity in soils from pH 4.2 to 5.0 or 5.2 involves complexes of exchangeable A1 with H+. From pH 5.2 to 7.0, the principal forms of . . + . potential acidity include organic matter and Al-H complexes which 6 are not exchangeable but which carry positive charge and serve to counter the negative charge at exchange sites. Both exchangeable and non-exchangeable Al-H+ complexes serve to reduce the soil's capacity to retain other cations on the exchange complex. For this reason, accumulating potential acidity is usually accompanied by depletion of exchangeable nutrient cations such as Ca2+ and "92+. The roles of different forms of aluminum in soil acidity, as well as the roles of other mineral colloids and organic matter, have been treated extensively in the literature (Mirasol, 1920; Paver and Marshall, 1934: Howard and Coleman, 1954: Jenny, 1961: Jackson, 1964: McLean et al., 1964). The increase in soil acidity with application of amonium sulphate has long been recognized (Wheeler, 1893: Allison and Cook, 1917: Ruprecht and Morse, 1915: Morgan and Anderson, 1928; White, 1931: Leo et al., 1959). Pierre (1928) compared the relative effects on acidity of sources of nitrogen fertilizers and found it to be of this order: ammonium sulphate > ammonium phosphate > leunasalpeter > urea > ammonium nitrate. A similar result was reported by Kolbe and Scharf (1967). Brown (1934) reported that application of sodium nitrate increased pH while ammonium sulphate caused a decrease in soil acidity when materials were applied in amounts equivalent to 21 and 63 pounds of nitrogen per acre, respectively, in a greenhouse study. In the dry- land regions of the Northern Great Plains, Power et a1. (1972) reported the greatest reduction in pH with (NH4)ZSO4 in an experiment where corn (Zea mays) and bromegrass (Bromus inermis) were grown on aisandy loam soil of pH 6.5. Soil pH values for Ca(N03)2 treated h! (I) .7 plots were higher than (NH4)ZSO treated plots but similar to those 4 for the check. 0n red sandy loam soils of Bangalore, India, Rao et a1. (1971) found that at high rates of (NH4)ZSO4 and NH Cl application, pH 4 decreased in both leached and submerged soils. In the submerged soils, the decrease in pH was directly related to the depletion of exchangeable Ca2+ and Mg2+ and inversely to the increase in exchange- able 3* in the soil. At high rates of application of urea and ammonium nitrate, Volk (1955) found low pH with ammonium nitrate. He attributed this to differential adsorption by plants of bases such as calcium, or to movement of bases along with the nitrate ion into the subsoil. Nitrogen carriers have been shown to have immediate, but tem- porary, effects on soil acidity. Residual effects may be counteracted by release of bases through weathering of soil minerals or through additions of liming materials. The CaCO3 equivalent of residual acidity or basicity is an important property of fertilizer materials. Thus, anhydrous NH3 is strongly basic initially but, when it nitrifies, residual acidity equivalent to about 1.8 lb CaCO is produced for each pound of N. 3 The equivalent residual acidity from NH3NO3, urea and ureaform is similar. Residual acidity from (N34)ZSO4 and NH4C1 is considerably greater because much of the SO 2- and Cl- is not removed by plants 4 and these surplus anions promote leaching of bases. Commonly accepted residual acidities are 5.5 lb CaCO3 per lb N for (NH4)ZSO4 and 5.3 for NH4C1 (Wolcott, 1964). Residual acidity from the sulphate salt is greater than for the chloride because H2504 tends to form complexes 8 with aluminum compounds in soils and is retained as an acidic residue to a greater extent than HCl. In the case of Ca(N03)2 and NaNO , nitrate is absorbed more 3 2+ + , extensively by plants than Ca or Na . The surplus cations tend to be retained on the exchange complex and leave a basic residue with a neutralizing value of about 1.8 lb CaCO per lb N. 3 Relationship Between pH and Nutrient Availability Phosphorus and Potassium Brown (1934) found that application of (NH4)ZSO4 as nitrogen source reduced pH but had no effect on phosphate availability. Fudge (1928) reported that (NH4)ZSO did not only cause an increase in 4 acidity but also caused a marked decrease in phosphate availability, along with some negative effects on calcium. Trogdan and Volk (1949) reported that availability of phosphate depended upon whether the nitrogen fertilizer was banded or broadcast. Banding of N decreased while broadcasting had little effect on availability of applied phos- phate. Davis (1938), using Truog's method for determining available P, reported the availability of P decreased with an increase in soil acidity associated with the application of nitrogen fertilizers. Schafer et al. (1968b) reported that all nitrogen carriers, especially anhydrous NH and (N84)ZSO4, promoted the release of soil phosphorus. 3 The effect of N33 was ascribed to the fact that the hydroxyl ion formed from hydrolysis of NH is effective in displacing absorbed 3 phosphorus . Potassium is an important macronutrient in the soil. It is much greater in content than nitrogen and phosphorus in mineral soils. It exists in exchangeable, soluble, interlayer and primary mineral forms. 9 The latter two forms may be classified as non-exchangeable. These forms are in equilibrium as shown below: Feldspars Primary Mineral l\ \. slowly a slowly Interlayer K .___~. 'Efiféfi': K ..__~. ‘S'\ ‘ [_ "-J V_____ { .-J‘ L oluble K J moderate fast Removal of K in one form shifts the various equilibria in accordance with mass action. Among other factors, the type of col- loid, soil pH, wetting and drying, and temperature affect the K equilibria in soils (Tisdale and Nelson, 1975). Potassium availability is low at low pH. It is likely that K+ and other cations move down the profile in company with surplus anions. However, Crowther and Basu (1931) reported no evidence that intense acidity caused by nitrogen fertilizers decreased the level of exchange- able K. Prince et a1. (1941) reported no apparent nitrogen fertilizer effect on the amount of exchangeable K in a 40—year study of nitrogen fertilizers. The availability of P and K were studied by determining their solubility as indicated by their concentration in displaced solutions and in 1:5 extract using 0.04 N_H CO or 0.2 N_H NO 2 3 2 3' (1928) concluded that basic fertilizers decrease the amount of water Fudge soluble K while acid forming fertilizers caused an increase. W61cott et a1. (1965) studied the patterns of acidification associated with eight sources of nitrogen applied at annual rates of 40 to 300 1b N per acre in long-term experiments, including the one used in the present study. 10 They reported that all acidifying carriers maintained exchangeable K at levels higher than basal fertilizer, but that exchangeable K continued to decline over the three-year period beginning the third year after annual applications of N carriers were initiated. Calcium and Magnesium In acid, humid region soils, greatest quantity on the exchange Plants absorb Ca largely from the soil systems the exchangeable and equilibrium. There is a definite amounts of exchangeable Ca and Mg 4. Ca, A1 and H ions occur in the complex (Tisdale and Nelson, 1975). . . 2+ soil solution as the ion Ca . In solution forms are in dynamic correlation between pH and the in humid region soils. A decrease in soil pH is marked by a decrease in the amount of Ca and Mg in the soil solution. It is then to be expected that nitrogen carriers which have significant effect on soil pH will encourage the loss of Ca and Mg if applied in heavy amounts over periods of time. Crowther and Basu (1931) reported significant reduction of replaceable calcium by (NH4)ZSO4 compared to NaNO 3. The differential effect on replaceable magnesium was so small as to be within experi- mental error. Davis (1938) also reported a decrease in soil bases ‘with an increase in soil acidity in Olivier silt loam in Louisiana. Prince et a1 . (1941) summarized results of a 40-year study of the comparative effect of various carriers of nitrogen on nitrogen Inscovery and on the status of the exchange complex in Penn loam.soil i1: Alabama. They reported that the use of (NH4)ZSO4 caused a reduc- tion of exchangeable Ca. Mg. There were similar effects on exchangeable 11 Results of long-term treatments with (NH4)ZSO4 on the soil- calcium status under field conditions in the Northeastern tea growing region of India showed that there was a significant reduction in the calcium content of the soil (Gokhale and Bhattacharyya, 1958). In the tropics, where high rates of nitrogen fertilizers are applied in order to get maximum yields, the residual acidity from (NH4)2SO4 can cause rapid changes in soil nutrient status. Pearson et a1. (1962) reported the use of high rates of acidifying N fertilizers caused a significant downward movement of Ca and Mg in the profiles of typical latosolic and red-yellow podzolic soils used for the produc- tion of forage grasses in Puerto Rico. On the other hand, Chaudhry and Vachhani(l965)reported no effect of long-term applications of (NH 504 on exchangeable Ca in 4’2 rice soils when moderate rates were applied. Yield response of rice increased with increasing rates up to 40 lbs N/a, and continued applications did not affect soil pH. In the third, fourth, and fifth years of the long-term experiment used in the present study, Wolcott et al. (1965) reported significant losses of exchangeable Ca and Mg where acidifying carriers had been applied annually at 300 lbs N/a. In the eighth year of the same study (1967), Schafer et al. (1968b) observed extreme depletion of exchangeable Ca and Mg as soil pH dropped below 5.0. It was noted that levels of Ca and Mg were influenced by the anion or cation asso- ciated with N in the different carriers. For example, the calcium in Ca(N03)2 maintained soil calcium but accelerated depletion of soil magnesium. 12 Liming and Nutrient Availability Liming is an important management practice that has long been recognized. The methods of liming are as varied as the liming materials. The ability of crops to make effective use of applied fertilizers through the influence of liming on plant growth is due to one or more of the following: "supplying Ca and Mg as nutrients: maintaining availability of applied nutrients: improving availability of native soil nutrients: enhancing desired types of microbiological activity: improving root development: and reducing toxic effects of Mn or Al" (Pearson, 1958). These effects may be direct or indirect. The effects of liming have been extensively studied. Phosphorus and Potassium One of the anticipated benefits of liming is to increase the availability of phosphorus. Salter and Barnes (1935) reported that liming increased the availability of phosphorus in soil. Over a two— year period on La Terraza and La Vega clay loam soils at Zamorano in Honduras, Awan (1964) observed a significant increase in soil P liber- ated from the organic fraction with liming. Similar results were reported by Stewart and Pearson (1952) and Davis (1938). Liming increased the availability of phosphate and corrected the detrimental effects of acid-forming nitrogenous fertilizers (Fudge, 1928). Schafer (1968) reported no significant increase in available P where lime had been applied the year before in amounts equal to two times the lime requirement by buffer test. In fact, he found more extractable P in unlimed than in limed plots. This may have been due to interaction effects of anion exchange. 13 It may also be pointed out that the availability of P with liming depends on what governs the solubility of phosphate in a given soil, the method of extraction and the type of phosphate ion in solu- tion. Phosphate solubility diagrams predict the changes that may be expected with the application of lime where phosphate equilibria are dominated by Fe or Al in the presence of different phosphate minerals (Lindsay and Moreno, 1960). The availability of K as influenced by liming has been a subject of much confusion. Bradley (1910) found that liming gave increases in soluble K. Gaither (1910) reported that liming did not have any liberating effect on K. Bradfield (1924) noted that the above disputes were caused by the failure of investigators to consider soil acidity. He said that, unlike CaSO the Ca in CaCO cannot appreciably liberate other soil 4' 3 bases until the acidity of the soil is neutralized. MacIntyre et a1. (1930) showed a repressive effect of lime on the solubility of K. Jenny and Shade (1934) reported that addition of CaOO3 liberated K. After extensive further studies, Peech and Bradfield (1943) con- cluded that the addition of lime to soils containing neutral salts may have no effect, may decrease, or may increase the concentration of K in soil solution, depending on the initial degree of base saturation of the soil. York and Rogers (1947) studied six soils in Alabama with wide ranges of exchange capacity, total K content and exchangeable bases. They concluded that the addition of lime could result in an increase or decrease in available K depending on the ability of the soil to fix K and, also, on the amount, kind and solubility of Kr bearing minerals in the soil. Bonnet (1946), working with lateritic l4 soils from.Puerto Rico, showed a significant increase in available phosphorus and calcium and a decrease in available iron 15 and 23 months after the application of lime. Calcium and Magnesium Duley (1924) reported an increase in the concentration of Ca, with liming, in displaced solutions. Rest and Zetterberg (1932) con- ducted a study on the effect of liming on the exchangeable Ca and Mg content in Southeastern Minnesota. They found that Ca and Mg con- tent increased with liming and that replaceable bases decreased from the surface with depth. Schafer (1968) assessed the nutrient status of soils in the long term N carrier experiment used in the present study. Samples were taken in the eighth year of the experiment, one year after half of the plots were limed. He found that the limed plots contained more exchangeable Ca and Mg than unlimed plots. In plots treated with Ca(NO3)2, Ca suppressed exchangeable Mg in limed and unlimed plots. Effect of Anions of Nitrogen Carriers on Ion Retention and/or Losses The nature and concentration of anions in percolating soil solu- tion influence the vertical movement of exchangeable bases in the soil (Pearson et al., 1962). Gillingham and Page (1965) reported that the enhancing effects of anions on vertical movement of Ca and Mg through the profile and into the leachate were in the order of solubility of their respective salts: No; > C1. > so: > Poi. Anions may also affect the adsorption of cations by the soil exchange complex. It appears that the surface charge density of soil materials does not remain constant, but varies with the surface 15 environment. Anions are not considered by some authors to signifi- cantly affect adsorption characteristics of soil materials (Eaton, 1950: Marshal, 1949). However, it has been indicated by others (Kelly, 1957: Bower and Truog, 1941; Sommerfeldt, 1962) that such effects may be significant. Mineral Nitrogen welcott et a1. (1965) reported the effect of various nitrogen carriers on the nitrate levels in the long-term experiment used in the present study. They found no evidence of interference of nitri- fication at low pH in soils. Weber and Gainey (1962) found that nitrate may be produced in soils with pH as low as 4.0. They suggested the presence of acid tolerant strains or that the nitrifying organisms may be protected from acid effects by other mechanisms. Alexander et a1. (1960) defined nitrification as the "biological conversion of nitrogen in organic or inorganic compounds from a reduced to a more oxidized state.” This definition includes the possibility of nitrate formation from other compounds such as amides, amines, hydroxylamine, and oximes (Tisdale and Nelson, 1975). It is not known how important the direct production of NO3 from organic N substrates may be in nature. The generally accepted sequence of events, according to Alexander (1961) and Campbell and Lees (1967), is the following: Organic N ——-> N83 -—-> N02 -——> N03 According to this sequence, organic N is released by decay 3° 2 bacteria (Nitrosomonas spp.). The N02 is oxidized to N03 by another organisms as NH The NH3 is oxidized to NO by a specific group of no te 9n Val fro v01 fer- a1k. bioj wet che: min ”in the ‘ 16 specific group (Nitrobacter spp.). The two oxidation steps together are referred to as nitrification. Under normal conditions, nitrification is rapid. Neither NH: nor NO2 accumulates in appreciable concentrations unless environmental conditions are unfavorable for one or both groups of nitrifying bac- teria. Whether NM: or no; accumulates will be determined by which group is more severely restricted in its activity. Any of the mineral forms of N (NH3, MHZ, NO- 2, N03) can be taken up by crops (Allison, 1973). Excessive concentrations of the incom- pletely oxidized forms can have unfavorable effects on some plants. Under normal conditions, NO- is the principal form available through 3 much of the growing season because nitrification is so rapid in warm, moist, well-aerated soils. In addition to removal by crops, mineral N forms can be lost from soils in various ways (Allison, 1973). NH3 can be lost by volatilization if anhydrous N83 is improperly injected or if ammoniacal fertilisers or livestock manures are tapdressed, particularly on ‘ alkaline soils. Nitrite and nitrate can be lost by leaching or by biological denitrification (reduction to N O or N2) under excessively 2 2 chemical denitrification due to chemical reactions of undissociated wet conditions. Under acid conditions, N0 can be lost also by nitrous acid (HNOZ). Erosion by wind or water can, of course, lead to losses of both organic and mineral forms of N. Organic Matter as Affected by Nitrogen Carriers In absence of fertilizers, soil organic matter is important pri- marily as a source of nitrogen. Except in newly tilled virgin soils, the rate of release of N is too low to support a high level of 17 production of cultivated crops. Numerous technologies have evolved to augment or replenish soil organic matter as a source of N: use of livestock manures, legumes, shifting agriculture and, within the last 50 years, the large scale use of nitrogen fertilizers produced industrially. The use of industrially fixed nitrogen for fertilizer has increased many-fold since WOrld War II, with the result that inten- sive management systems have developed which make little or no pro- vision for practices that will maintain soil organic matter or retain unused fertilizer N in the soil. However, at the present time, energy shortages and concern for environmental pollution are arousing new interest in the role of soil organic matter in recycling of N and other nutrients. Declining organic matter is suspected to be one of the causes for problems of reduced infiltration, impeded aeration and restricted root development in many intensively cropped soils. Soil organic matter content of any horizon depends partly on how much organic matter from crops or other vegetation is turned over to the soil every year and partly on what percentage of the organic matter decomposes during the year. The organic matter content is stable when the two processes are balanced, plus or minus allowances for eluviation of humus (Rich and Obenshain, 1943). They reported that fertilizer and cropping practices which tended to increase crop yields tended to increase soil organic matter and cation exchange capacity. 0n the other hand, Salomon and Smith (1947) found that, (Respite higher yields in limed plots, more organic matter accumulated in.the more acid soils of unlimed soils which received N from.the sane sources. Apparently the effect of lime was to increase annual si the lat pla cro loss tell trea on t that crop} ti1i: 0f tl‘ {litre find 1 ”eh I 18 decomposition rates to an even greater extent than the annual return of crop residues. Because soil pH can influence both the production of residues and their rate of decomposition, reported effects of liming on soil organic matter are varied and often conflicting. White and Holden (1924) found that soils which received lime treatments showed a sig- nificant increase in N above that found in untreated soils. Greater loss of nitrogen was reported on limed plots than unlimed plots (Mooers et al., 1912). Potter and Snyder (1916) reported basically similar findings. It may be noted that there is a general lack of treatment in the literature of effects of specific nitrogen fertilizers on organic matter. It is generally assumed that any carrier that increases plant growth will increase the organic matter by way of increased crap residues. This may not always be the case. Dodge and Jones (1948) concluded that there had been a continual loss of soil nitrogen and carbon over the period 1915-1945 in a long- term management experiment, regardless of cropping system or fertilizer treatment. It was found that fertilizer treatment had no influence on the nitrogen trends in the soil or C:N ratios. It may be noted that only NaNO was used as the source of nitrogen. In a 7-year 3 cropping study, Mazurak and Conrad (1966) found that nitrogen fer- tilizers either minimized the losses or increased the total-N content of the plow layer (0-6”). Scharf (1967) reported a decrease in soil nitrogen which was greatest in plots that received NaNO or Ca(N03)2 3 .and least in plots that received calcium-ammonium nitrate and ammonium sulphate . 19 There is not much literature on changes in the C:N ratio with the application of nitrogen carriers. Waksman (1942) considered C:N ratio as the factor that controls most of the liberation of nitrogen in available forms during the decomposition of plant residues. Leo 80 caused a downward movement of et al. (1959) reported that (N114)2 4 organic matter and there was a wider C:N ratio in the subsoil. Crop Yields as Affected by Nitrogen Carriers Nitrogen is regarded as one of the primary elements in plant growth. Investigations have been carried out not only to test the effects of rate but also the effects of sources of nitrogen. These research objectives arise from the fact that different types of nitrogen carriers undergo remarkable soil reaction which should cause concern to those who ”dump” heavy amounts of fertilizers to get maximum yield. Tidmore and Williamson (1932) conducted 222 tests, during a 5-year period, with (NH ) SO and NaNO . They reported that 4 2 4 3 (11345804 produced lower yields than NaNOa. They attributed it to low pH caused by the continued use of acid forming fertilizers, and to depletion of soil bases. Prince et a1. (1941) reported that nitrate of soda was the most effective carrier of nitrogen. The average crop yields were greater from the use of this material per unit of nitrogen applied than any other source of nitrogen. Scarbrook and Cope (1957) summarized the results, from 1925 through 1955, of field experiments on sources of nitrogen for cotton and corn. They reported that a primary cause of reduced yields was the low pH produced by the acid-forming sources of nitrogen, without "h 20 the addition of lime, would eventually cause reduced yields on nearly all soils in Alabama. Sodium nitrate, at rates applied, maintained the soil pH at approximately constant level without the addition of lime. Chaudhry and Vachhani (1965) reported that (NH4)ZSO4 may not be deleterious on a long-term basis, if applied at moderate rates. They found that yield response of rice increased with increasing up to 40 lbs N/a, on a silt loam soil, but did not 4 affect soil pH, total-N or C. rates of (NH4)ZSO Power et a1. (1972) found greater corn (Zea mays) response to (NH4)ZSO4 than Ca(N03)2 at 110 Kg/ha than at 55 Kg N/ha. This was due mainly to leaching of the nitrate fertilizer. Data reported by Schafer (1968) for the eighth season in the long-term N carriers experiment used in the present study show drastic reductions in corn yields where cumulative acidity from N fertilizers at 300 lbs N/a/yr had reduced soil pH to about 5.0 and virtually barren plots at a pH of about 4.0. Corn with the same car- riers responded dramatically to lime applied one year earlier. In an adjacent experiment on similar soils, Starr (1970) observed only moderate reductions in soil pH after three annual applications of NH NH NO and urea at 255 lbs N/a/yr but not at lower rates 3' 3 3 which did not exceed the maximum yield response range of the corn. 51': Vex (61 MATERIALS AND METHODS Field Treatments An experiment was initiated in 1959 on the Soil Science Experi- mental Farm at Michigan State University to study the residual effects of nitrogen carriers on soil and on crop yields. The crop- ping and basal fertilization history for these plots is given in Table l-a. Basal fertilizer was broadcast and plowed down before planting. The nitrogen carriers in Table 1-b were applied annually on corn (Zea mays L.) from 1959 to 1972 at 300 lbs N/a/yr (336 Kg/ha/yr). Solid carriers were broadcast after plowing and disced in before planting. Anhydrous NH was injected in row middles when corn was 3 knee-high. These eight treatments, plus an unfertilized check and a control treatment which received only basal fertilizer, comprise the ten treatments for which residual effects are reported in this thesis. The application of different carriers on different plots was discontinued after 1972. Only the basal fertilizers in Table 1-a were applied on wheat (Triticum aestivum L.) in 1973 or on soybeans (Glycine max (L.) Merrill) in 1974, 1975, and 1976. The ten treatments on corn from 1959 to 1972 were replicated four times in a randomized complete block design. Each plot was 14 x 25 ft (4.3 x 7.6 m). In the spring of 1965 and again in 1966 applications of dolomitic agricultural limestone were made on all 21 22 Table l-a. Crops and amounts of nutrients used in nitrogen carrier study from 1959 to 1976 Basal fertilizer Ratio Annual nutrients Year Crop Annually N-PZOS-KZO N P K a lb/a lb/a 1959-72 Corn 200 5—20—20 10 17 33 1973 Wheat 150 6-24—24 9 16 30 1974 Soybeans 350 12-12-12 42 18 35 1975 Soybeans 350 12-12-12 42 18 35 1976 Soybeans 100 0-26-26 0 ll 22 “lb/a x 1.12 = kg/ha. Table 1-b. Percent N and relative residual acidity of the nitrogen carriers in the field experiment Carrier used Relative residual on corn“ % N acidityB (NH4)2504 20.5 5.5 NH4C1 28.0 5.3 NH4NO3 32.5 1.8 NH3 82.2 1.8 Urea 46.0 1.9 Ureaform 48.0 1.9 Ca(N03)2 15.5 —l.3 NaNO3 16.0 -1.8 “Supplemental N carrier applied at 300 lb N/a/yr (336 kg/ha) on continuous corn 1959 to 1971. BLbs of CaCO3 to neutralize a weight of carrier containing one pound of nitrogen (Wblcott, 1964). 23 plots in two of the four blocks. The two applications on each plot totalled 2 times the lime requirement by the SMP buffer test on that plot. Michigan 480 Hybrid corn was used in the early years, but in later years Michigan 300 was grown. The row spacing in early years was 42 inches, but 28—inch rows were adopted in 1967. In 1970, the row spacing changed again to 42 inches when Pioneer 3773 corn hybrid was grown. In early years, an initial plant population of 25,000 plants per acre was thinned to 16,000 plants per acre. In 1970, plant popur lation was thinned from 21,000 to 18,000 plants per acre. Due to dry weather at planting time in 1971, emergence on most plots was less than 16,000 plants per acre. No observations were made in 1972. Sources of Data A number of people have been involved in this study over the years. The field experiment was established by J. F. Davis and H. D. Path in 1959. Representative soil test data for 1961, 1962 and 1963 were reported by wolcott et a1. (1965). Corn yields, foliar analyses and soil tests in 1967 were reported by J. W. Schafer in a PhD thesis (1968). The 1967 results were summarized at national meetings by Schafer et a1. (l968a,b), but never were published. Corn yields and extensive data on foliar analyses and soil tests in 1970 and 1971 were collected by A. R. Wolcott and B. D. Knezek, and recorded in the 1971 Research Report of the MSU Soil Science Farm. Additional data have been collected at various times by students of E. C. Doll, H. D. Foth, J. C. Shickluna and A. R. Wolcott. Many of NE NE at 24 these data were found in files of A. R. Wolcott and have been drawn on for historical background prior to 1975. Soybean yields in 1975 and 1976 were taken by the author. Soil samples in 1975 were taken and analyzed by the author. Raw data for September 1966 and July 1971 were also reduced and subjected to analysis of variance by the author. Soil Sampling On September 25, 1975, soil samples were taken. Twenty cores were taken randomly from the plow layer (0-10") between the center rows of the plot. For the 10-20" and 20-30" depth, 5 core samples were taken from plots treated with basal fertilizer, (NH4)ZSO4, NH4C1, Ca(N03)2 and NaNO3. A composite sample for each plot was obtained after passing the core samples through a 4-mesh (5 mm) screen. The moist samples were stored at 5°C until analyses for + I NH4, NO2 and N03 were completed. They were then air dried for 8 days. For total C, CO -C and Kjeldahl N analyses, an aliquot of the 3 air-dry sample was ground to pass through an 80-mesh screen (0.18 mm). For other analyses, air-day soil which had passed through a 2 mm screen was used. Laboratory Procedures Soil pH was measured with a glass electrode pH meter, using a 1:1 soil-to-water suspension. Available P was extracted with the Bray P extractant using a 5-minute extraction. Exchangeable K, Ca 1 and Mg were extracted with neutral 1 N_NH OAc (5 minutes, 1:4 soil- 4 to-extractant ratio). The extracted nutrients were determined after filtering through Whatman No. 1 filter paper, by procedures used 25 routinely in the Soil Testing Laboratory, Michigan State University, East Lansing. Available P was determined from the color developed, accomplished by utilizing Ammonium Molybdate — Ascorbic Acid Method (Watanabe and Olsen, 1965). The Technicon Auto-Analyzer was used. Exchangeable Ca and Mg were determined after addition of La to an aliquot of 203 the NH4OAc extract, using the Perkin-Elmer 303 Atomic Absorption Spectrophotometer. Lanthanum was added to prevent ion interference associated with the ground state and excitement of electrons. Exchangeable K was determined in a separate aliquot of the same extract, using a Coleman Model 21/22 Flame Photometer (no lanthanum was added as was done for Ca and Mg determinations). Lime requirement was estimated, using the pfnitrOphenol, triethanol- amine buffer (pH 7.5) of Shoemaker et a1. (1961). Lime requirement, as CaCO3, was calculated from the decrease in pH of the buffer from neu- trality after equilibrating with soil (1:2 ratio of soil to buffer, 4. 30 minutes). The acid equivalent of the buffer is 14.4 me H /100 g per unit pH, as given in Ohio Ext. Bul. 472 (1970-71): me H+/100 g = 14.4 (7.0 - buffer pH). 2 + Total N (excluding NO 4 and N03) and NH N were determined by semi- micro methods described by Bremner (1960), Bundy and Bremner (1972), and Bremner (1965). Potassium sulphate-selenium mixture was used as catalyst in the Kjeldahl digestion for total N. The clear digestion mixture was made alkaline with NaOH, and NH3 was distilled over into + boric acid. See Appendix B. Exchangeable NH4 was determined by distil- lation of a 1:1 suspension of soil in 2 N KCl in the presence of NaOH, and NH3 was collected in boric acid. In both cases, NH3 collected in 26 boric acid was titrated against standard acid, using a mixed indica- tor. Organic N was taken as the difference between Kjeldahl N and an}-.. Organic-C was determined by difference between total-C and carbonate-C. Total-C was determined using a LECO carbon analyzer (Belo, 1970: Appendix C). Carbonate-C was determined by the titri- metric method of Bundy and Bremner (1972), using 2 M_HC1 at room temperature. Nitrate-N was determined on moist samples which had been stored at 5°C for two weeks after they were taken from the field. An auto- mated procedure for the Technicon Auto-Analyzer (1972) was used. These soluble ions were extracted into saturated CaSO4 solution (1:1 soil-to-extract ratio, 30 minutes). Nitrite in the extract is determined directly and nitrate after reduction to nitrite in a copper-cadmium reactor column. Nitrous acid then reacts with sulf- anilamide under acidic conditions to form a diazo-compound. The compound then couples with N-l-naphthylethylenediamine dihydrochloride to form a reddish azo dye which is measured photometrically. Statistical Analysis Analysis of variance was performed on raw data from 1966, 1971, 1975 and 1976, using facilities of the Michigan State University Computer Center. Data summarized here for years prior to the applications of lime in 1965 and 1966 had been analyzed in accordance with a randomized complete block design, with four replications. Treatments were randomized within each block. Since the two center replications were first limed in 1965, the data have been treated as for a split 27 plot design, with lime or no lime as main plots and N treatments as sub-plots. Replications were, thus, reduced from four to two when lime was applied. In general, split plot design may be used in experiments where the experimental units are large and/or the experimenter wants to compare subsidiary treatments. Also, it is used where the experi- menter wants more precision in the sub-plot effects and interactions than the main plot effects (Cochran and Cox, 1965; Federer, 1955: Snedecor and Cochran, 1974; Steel and Torrie, 1960). Characteris- tically, the sub-treatments have larger degrees of freedom and generally smaller experimental error. In the present experiment, the original plots were too small (14 x 25 ft) to split for lime on half of each plot. The loss of useful plot area to border effects would have been excessive. The loss of replication has resulted in LSD values which frequently exclude what must be considered to be a real difference. The basis of statistical inference with only one degree of freedom for lime is very weak. To help overcome this serious weakness in design of the field experiment, data that have been collected over the course of the experiment are presented, in addition to those collected personally by the author. Changes over time serve to support differences which may not be statistically significant in any given year. RESULTS AND DISCUSSION History of Corn and Soybean Yields Yields of corn in many years of the experiment were not taken or were of doubtful value because of damage from wildlife entering from an adjacent orchard. Representative yields in Table 2 reflect changes which were observed visually in the vegetative development of corn with different carriers, as noted in reports by Schafer (1968) and Schafer et al. (1968b). Yields without lime with the two non-acidifying carriers, Ca(N03)2 and NaNO3, represent near maximum response of corn to nitrogen on this sandy loam soil without irrigation. By contrast, yields with the three ammonium salts declined sharply. The rate of decline from 1961 to 1971 was in the order: (NH4)ZSO4 > NH4C1 > NH4NO3. In the early years of the experiment, maximum yields were obtained with anhydrous NH , urea and ureaform. By 1971, the effec- 3 tiveness of these carriers had declined to the point where yields were no different than for no fertilizer or for basal fertilizer only. Addition of lime in 1965-66 did not affect yields on plots which received Ca(NO3)2, NaNO or no supplemental N. Yields were 3 increased dramatically by lime on all plots where acidifying carriers were used. The long term trends in corn yields and the responses to lime reflect observed changes in germination and in survival and vigor <3f emerged plants, as is seen in the data for plants per acre in 1971 28 29 (Table 2). As will be seen, declining yields in plots which received acidifying carriers without lime were associated with declining soil pH and depletion of Ca and Mg. Analyses of seedlings in 1971 showed deficient levels of Mg and toxic concentrations of Mn for these treatments (Wolcott et al., 1971). Both of these nutri- tional imbalances were corrected where lime had been applied. The nitrogen carrier treatments were discontinued after 1972. Nevertheless, residual effects of carriers were still apparent in soybeans in unlimed plots in 1974 and 1975 (Table 3). These residual effects were not apparent in limed plots. In 1976, soybean yields on all plots were very low. This may have been due, in part, to the fact that no fertilizer nitrogen was applied in 1976 (Table l-a). Also, the weather was very dry at flowering and during the pod setting period (rainfall in August was 0.56” and 1.85" in September, compared with the lS-year average for these months of 2.95" and 2.64”). Additional factors may have been build-up of disease due to growing soybeans three years in a row and declining fertility due to the low annual return of residues from soybeans. Soil Test Changes Over Time Soi1_pH and Lime Requirement Some of the variation in pH values given in Tables 4-a,b and c is due to the fact that the determinations were performed by dif— ferent analysts in different years. The determination is sensitive to variation in manipulation of the sample. The author found varia- tions as great as 0.3 pH units between duplicate soil samples. 3O oumuuon\mucmam u ev.m x ouoc\muccam ououoon\macucado u no. 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Residual effects on soybean yields of 14 annual applica- tions (1959 to 1972) of nitrogen carriers (300 lb N/a/yr) on continuous corn Soybean yields Lime Soybean yields Carrier used No lime Applied“ Plus lime on corn 1974 1975 1976 T/a 1974 1975 1976 ———-Bu/aY-—-—- -—-Bu/ a No fertilizer B 19.3 15.9 5.9 4 20.4 15.3 9.3 Basal fertilizer 17.6 13.9 5.3 6 18.9 17.3 8.0 (NH4)ZSO4 2.1 6.9 3.8 12 16.6 16.5 8.0 NH4C1 4.4 4.6 1.9 10 17.5 14.2 5.8 NH4NO3 5.4 5.8 2.4 8 17.8 16.9 8.1 NH3 8.9 10.9 2.8 6 24.9 17.8 8.0 Urea 8.0 14.1 5.5 8 19.5 17.4 10.0 Ureaform 12.5 14.8 7.0 8 18.7 15.3 7.7 Ca(NO3)2 20.6 11.9 4.4 4 22.6 15.7 7.6 NaNO3 23.7 10.0 4.2 4 16.9 17 4 7.3 LSD (.05) carriers within 2.2 4.1 3.1 2.2 4.1 3.1 lime LSD (.05) lime 2.4 4.4 ns within carriers “Lime applied in two applications (1965 and 1966) to supply 2 times the lime requirement by buffer test. (T/a x 2.24 = TM/ha). BBasal fertilizer: 200 lb/a 5-20-20 (N-P-K=10-18-33). YBu/a x .67 = quintals/ha. 32 «A:FIOVOBOH ehwmfl “hemlovoomfl .momH .mmmH «hemlovmomfl tiebuocaoos "momma an msumoo now some .A:OHlovmhmH .obmfl .Hhma » .immimauoauzuouz. omnomum o\oa oom "woueeauuou Homomo >64 odes canoes m.o m.o m.o o.H o.o e.o e.o oz m.o v.0 m.o muoauuoo imo.ooma b.m e.m o.m m.b e.o ~.b e.o ~.o ~.o o.o o.m mozmz m.m m.m m.m m.m m.m e.m o.m o.m m.m m.m o.m mimozooo m.e m.e H.e m.e ~.e o.e m.e o.m o.m m.m e.m snowman: e.e e.e o.m m.e ~.e m.e e.e m.v o.e o.e H.m nous m.e m.e o.e e.e m.e m.m H.m o.m H.m e.m ~.m mmz ~.v m.e m.m m.e ~.e H.e e.e v.v m.e m.e e.m mozemz e.v ~.e e.m m.e m.m o.e o.e m.e e.e o.e o.e Hoemz ~.e v.v m.m H.v m.m m.m o.m H.e o.e «.e m.v eommiemzo H.m e.m H.m m.m o.m m.m o.m b.m o.m o.m e.m muonaHsouoo semen m.m m.m m.m H.o m.m m.m o.o ~.m e.m o.m o.m noueaauuoo oz me on so an op so me mood no we so «enemas men 900 are mm: was Hon mom and and Hon shoe :0 muoam coaaacs no r momma scam,onu cw mm,awom 00w” HOflHHflU mhma cu Hood .mHOquooEHHcs .womca 30am .mm Haom cw momcsno .suv sands 33 .Aaoalovmhma .vwma .ahma «AthlovamH .hwmd “Acmlovmmmd .mmmH .immnmauoauzuouzc omuomum exam oom "macaw an mammoo now some "Houaaauueu aemmm r m .umou summon an ucoEmuwsowu mama one mafia» m Samoan on “wood can moody mcowumowammc o3u ca woodman dawns >o< dams canoes m.o m.o m.o o.H e.o e.o o.o oz muoauuoo imo.oomq oK e8 mo ms mg mo oK me e mozmz m.b m.b m.o o.e o.» e.o e.o ~.o e mimozomo o.m o.o m.o o.b e.o ~.o o.m o.m m snowman: e.o e.o e.m o.o m.o e.m o.m o.e m «on: ~.b o.m m.m ~.b H.o H.b e.m a.m o mmz e.o e.o o.m m.o o.o o.m m.m o.m m mozvmz m.m e.m o.e o.m o.m o.m b.e m.e om Hoemz m.o o.b m.m m.m e.m H.m e.e ~.e NH eOmmiesz m.o m.o o.o o.o o.o m.o o.o m.o b Housmauuom demon e.o o.o e.o o.e N.e e.o m.o m.m e Houasaouoo oz me as He as on so be meme «\9 monomoa mom boo Hon me: one Hon mom cooaammc choc so mean poms Hoauuou 82.32 as oosfl 32o mo Roses 32a. are as am flow mama on mood .moomm noses .uosea some .mc snow to momccnu .oiv manna 34 oAsONIOHVmFOH eHhmH “Asmaloavmoma .momH .momH “AemHINH vHomH “mucom How sumac Haomomm Home: omagacmr .immImHIoanIaIzo oanmIm o\na oom "monaaauuom Homcm m .umoo woumon mo ucosouwoowu mafia emu mesa» a madman cu “mood was moody mcowumowammm 03» ca meadows means mane ensues o.H b.H a.o m.H o.H e.o m.o b.o m: mooauuoo .mo.comq oo To be e6 mo So so o.o so mozmz o.b m.o e.b e.m o.o m.m m.m o.m m.o mimozvoo III o.m o.m III e.m s.m o.m e.m m.m snowmen: III o.m e.m III e.m m.e m.e e.m m.m eons III e.m H.m III o.m H.m H.m m.e o.m mmz III e.m m.m III m.e H.m ~.m H.m o.b mozezz m.e o.v m.e m.v o.e e.e m.e ~.m m.m Hoemz e.m m.e e.e m.e o.e m.e o.v m.e m.m commiomzv o.o e.o o.b e.m o.o H.b o.m m.m m.o aboueaeuuoo Human III o.o ~.b III m.b e.o e.m m.m v.o bonaaaouou oz me He ob me as be no no so moIomoH mom he: new mom as: new Han and Hon once :0 seems mafia uses oz coma uoauuoo >Haomosm woods on» ma mm,awom mama cu Home .muon oofiaa one mosque: .HAOmnsn momma .mm deem cw monsoon .onv edema 35 Another source of variation is the season of the year when soil samples were taken. Except in highly buffered soils, pH declines during the forepart of the growing season because of the nitric acid produced by nitrification (Eno and Blue, 1957). As nitrification slows down, accumulated acidity is slowly neutralized by various soil buffer systems so that, by the spring of the following year, soil pH tends to return to the level of the previous spring. This annual fluctuation is apparent in plow layer data for several treatments over the sequence August 1970, May 1971, July 1971 (Table 4-a). According to Jackson (1963), the ultimate buffer system in soils is the release of bases by decomposing primary and secondary sili- cate minerals. Because of mineral decomposition, most soils cannot remain long at a pH less than the "ultimate" pH of 4.2 unless free acids, such as sulfuric or nitric, are present. This ultimate pH had been reached in the plow layer by 1962 4)ZSO4 at the rate of 300 lbs after four annual applications of (NH N/a/yr (Table 4-a). This pH was approached less quickly by other carriers but had been reached by 1970 with all acidifying carriers except NH3. The rate of decline in soil pH over this period was approximately in the order: (NH4)ZSO4 > NH4C1 > NH4NO3 > urea > ureaform > NH3. The order of declining pH parallels rather well the order of declining corn yields (Table 2). After the last application of N carriers at high rates in 1972, there was a tendency for the very low pH develOped earlier to increase. However, the data for 1975 indicate that soil acidity was still being controlled mainly by decomposition of soil minerals at near the ultimate pH of 4.2. 36 Residual basicity from NaNO maintained pH in the plow layer at 3 levels distinctly higher than control plots which received only basal fertilizer. Ca(NO3)2 had little residual effect on soil pH at any time. The lime applied in 1965-66 produced immediate increases in plow layer pH (cf. Tables 4-a and 4-b). However, by September 1966, full correction to the desired pH of 6.5 to 6.8 had been achieved only with the two control treatments and with Ca(N03)2 and NaNO3. The lime reacted very much more slowly with the acidity produced by acidifying carriers. With (NH4)ZSO4, NH4C1 and NH3, full correction was never achieved through 1975. Soil pH in the plow layer of limed plots (Table 4-b) reached a maximum for several carriers in the May 1971 sampling. This spring sampling represents a seasonal high and should be ignored in assessing long-term trends. If only summer and fall samples are considered, it would appear that lime applied in 1965-66 was still reacting with residual acidity from several carriers through the last sampling in 1975. Residual acidity from acidifying carriers moved quickly from the plow layer into the upper subsoil (Table 4-c). The rate of downward movement through May 1971 was greater for (NH4)ZSO4 and NH4C1 than for other carriers. Lime applied in 1965-66 had resulted in substantial correction of subsoil pH by 1971. Additional increases in pH of the upper sub- soil had occurred by 1975. These findings are in agreement with reports of Blair (1934), Brown and Munsell (1936) and Brown et a1. (1956) that lime applied to the plow layer had marked effect in reducing acidity in the subsoil. 37 Lime requirements from 1961 to May 1971 in Tables 5-a and S-b were recalculated to make them directly comparable with those for later samplings. The recalculations included changing the assumed acid equivalence of the buffer from 10.0 to 14.4 me H+/100 g, and conversion of T/a for varying sample depths to a common basis (T/a - 6 2/3', or ppm x 103). Data from 1964, 1965 and 1967 could not be adjusted to a common basis because buffer pH values were not recorded, and lime requirements greater than 5 T/a were recorded at 5 T/a. Lime requirement in the plow layer increased dramatically when soil pH dropped to 5.0 or less (cf. Tables 4-a and 5-a). The increase occurred earlier with (NH4)ZSO4 than with other carriers. By August 1970, lime requirement with all six acidifying carriers had reached the range of 9 to 14 x 103 ppm at soil pH values of 4.5 or less. In most cases, lime requirement remained in this range as long as high annual applications of N were being made. In the case of NH , the relatively low value of 4.3 x 103 ppm in July 1971 may 3 reflect alkalinity from the injection of NH in late June. 3 The N treatments were discontinued in 1973, and all plots have been fertilized uniformly at much reduced N rates since then (Table l-a). Lime requirements in unlimed plots which had received acidi- fying carriers had fallen sharply by 1974 (Table S-a). Further decreases occurred in 1975 for several treatments which had been discontinued in 1973. These decreases in lime requirement may have been due, in part, to leaching of exchangeable Al and other mobile components of poten- tial acidity. The greatest downward development of lime requirement by 1971 had occurred with (NH 50 and NH Cl (Table 5-b). The plow 4)2 4 4 layer with these two carriers had been very strongly acid (pH 4.5 or 38 .A:OHIovmbmH .vnma .Hhma «A:0IOVOBmH «A3mlOvm0mH .AMMImHIOHflMImIzv ONIONIm M\QH con .50 he I mc\az u m\m o I e\a n uA=mIOVNOOH «AEQIOvHQmH «when» an mammoo wow sumo "HoNfiHauHom acmmm x Emu mIoH e > m .umou acumen an ucoaouwsoou mama ecu mesa» N maomsm on Aooma 0cm moody mcowucowammm osu ca woodman oawqc ms v.m ~.m m: o.m o.~ m: N.m m.n o.m vum m.~ m.H Amo.comq. 0.0 v.0 0.0 0.0 0.0 v m.m m.v 0.N m.o m.o N.N m.m m.m mozmz 0.0 v.H 0.0 0.0 0.0 v m.m m.v o.m m.v m.¢ o.m 0.~ o.~ Namozvcu 0.0 m.m 5.0 v.a N.H m m.m m.o m.o m.0a v.vH N.o >.m m.m snowmen: 0.0 5.0 o.m >.0 v.H m v.m 0.m 0.m o.m 0.mH ~.h ~.m 0.v cow: 0.0 o.m ~.m 0.N m.v o 0.m m.m m.v «.ma 0.ma 0.o o.o m.v mmz o.o o.o o.~ o.H e.H m m.e o.m e.o o.e e.o ~.e m.e m.m mozemz o.a m.v o.m m.o m.0a 0H 0.m m.o v.m 0.NH 0.MH o.m m.v m.v dovmz m.~ N.m o.m m.m 0.m NH m.m m.m m.HH 0.0 ~.~H m.0 m.m 0.0 vOmmxvmzv 0.0 0.0 v.0 v.0 0.0 0 m.m m.v m.v o.m m.¢ m.m m.~ o.m moonaaauwom demon 0.0 0.0 0.0 ¢.0 0.0 v 0.m m.v 0.m 0.H m.o m.e 0.m m.~ umuaaauwmm oz OH x EQQIIIII MI0H x 5mm. n me on an an on M\B me or an an on no we do NhImmmH mom poo H50 he: use sooaammc new one Hon as: com H50 and H50 choc so mafia msam mafia used 02 com: wowwwsu >uo>ma 30am ecu ca oceaouaooou mama r momma 30am on» cw ucosouwsoou mafia meme cu Hood .muoao nosed pom ooaaaco .wohoa 30am .usosouasoou mama ca moocscu .oIm oases 39 .Atomloavmhma .Hhma « A: maloavowma .momH .NmmH «AstINHVHmmH .AMMImHIOHuMImIzv omlomlm M\QH com me ucoamua5oou mead ecu mesa» m mamm5m .so as I oe\e= I .m\~ o I axe I cm x sod MI 0 ounce» How cameo Hwomoom Homm5 ooaoacw> “Houaawuumm Hommm u .umou bounds on “boos one moose meoaoooaamdo can as commode usage o.o m: 5.5 e.o H.m 5.5 o.o m.H m.H Amo.ooma o.o o.H o.o o.o o.o e.o o.o v.5 e.o mozoz o.o o.o o.o o.o o.o o.H o.o e.s o.o Nxmozcoo III o.H o.o III m.m o.5 o.o o.o o.o snowman: III o.o ~.~ III m.m o.H e.~ o.H o.m mono III m.m N.~ III m.e o.~ m.e m.m o.m mmz III ~.e «.5 III o.o o.o o.o o.H o.o mozemz v.5 o.o o.~ o.o m.HH o.~ m.m o.o m.m Hoezz o.m o.o o.~ o.o «.ms o.o o.m m.m o.m «OmNAezzo o.o v.5 «.5 o.o o.o o.H o.o ~.H ~.m Monoueaauuoo semen III o.o e.H III o.o o.o ~.~ ~.~ o.o nouaaaouoo oz 0H x Rom m..- e me as be me as be no Nb Ho NeIomoH mom has new new an: new H50 054 H50 choc co defied m5Hm mafia oz oom5 Howwueo » HwOmo5m HoommIocu ca ucosouw5oou mama whoa ou Home .nuon oosaa one oofiwas5 .HaOmosn noom5 .ucuaoww5oou some so nomsecu .oIm manna 40 less) for a longer period than with other carriers (Table 4-a). Very high levels of potential acidity had accumulated earlier also (Table 5-a). It is reasonable to expect that downward movement of potential acidity would have occurred with other carriers but somewhat later in time. The data for 1971 (Table S-b) are consistent with this expectation. Unfortunately, subsoil samples were not taken for the other acidifying carriers in 1975. Lime applied in 1965-66 reacted slowly with the potential acidity from (NH4)ZSO4 and NH4C1 (Table S-a). Data for subsoils in limed plots of NH4N03, NH3 and urea in 1971 (Table S-b) suggested that one effect of liming may have been to displace exchangeable Al and promote its downward movement. Available P and Exchangeable K There are significant differences in available P among treat- ments over the years, except in 1961, 1962 and 1974, both in unlimed and limed plots (Tables 6-a and 6-b). The significant differences were mainly between no fertilizer and all other plots which received basal fertilizer. Bray P1 levels increased in all treatments in unlimed and limed plots over time. In unlimed plots, this increase over time paralleled the record of increasing acidity. However, phosphate normally is less available at the very low pH levels which developed with acidifying carriers in this study. Looking at the data for 1967, Schafer et al. (1968b) suggested that nitrogen carriers, especially NH3 and (NH 4,280 4, pro- nmsted the release of soil phosphate by displacement with anions thCh were at high concentration because of the annual rates of application of N carriers. They noted that sulphate is particularly 41 .50 hH I co\0M a vm.m x 5mm km\~ 0 I o\nH u N x Ema e .AeoHIocmooH .veom .Heoa aieeIovoooH .emos liemIocoomH .mmoH liemIocmooH ligoIooHomH "memos an meadow boo some» .immImHIoHIzIoIzc omIomIm exam ooN .uoumamuuom Homomm m.e~ me e.m~ e.me m.om o.om m.~m o.~H me me .mo.vomq mm mom mm mm mm as me me am we mozoz mo «NH OHH «OH om on em em mm om Nimozcoo HOH oo mos ooH mom as we om on me snowman: mo ago was NOH mam as ea mm mm om «on: ooH 5H5 mom >55 mm mm om mm He Hm mzz 055 mm eos mmH owe om mm am so me mozemz OHH mom has HHH mo om mo oo me me v Naovzz mos oHH mom mom «He no mo em ee he om mezzo so om eoH HHH Nod mm on mm on me muouHHmuuom Homom mm me me me em om me mm mm on nonmamouou oz 3mm. e me vs so H» on am we no no Ho weImmmH mom poo H50 mm: 05¢ H50 mom H50 05¢ H50 once so oaHH oz oom5 onHumu r HomoH son ecu cH m oHocHHe>¢ mama on Home .muon ceased: .uoon scam .o oHneHHoad .er oHooe 42 .EU 0H I nc\0x n VN.N x 3mm mm\N o.I M\nH n N x ammo .ieoHIoomsoH .eeos .HooH “AIAIoooemH .oooH aPmIocomoH ”memos so meadow boo some» .immImHIoHuzIoIzo oNIoNIom o\oH oom "noumHHuuom Humane .umou summon mo ucoEmHH50ow oaHH ecu moaHu N mHmm5m on AoomH occ momHv chHucoHHmmm can cw ooHHmmc oEHHo m.>N v.00 0.mN N.Nv m.0N 0.0N 0.Nm “m0.vomq on mod mm as mm mm vb mozaz mm mom mm on be no so Nimozcoo mm oma em mos No so om snowmen: mm owe ode om no me so eons mm me oom mm as mm mm mzz mm mam eos om HoH om No mozezz mo mom mos om Hoe om em Hoezz 5H5 ems mm nod mom as as eOmmiezzo 00 HHH v0 00 on He 00 muouHHHuuou Hommm no mm mm mm em so on uonmaaouou oz somII, e me we as as on . no mo ueIomoH mom poo H50 he: 05¢ H50 mom once so coaHH m5Hm oen5 usHuwso »uozea some on» do o oHooHHoae moms ou moms .ouon edema .uoNoH son .o oHnoHHoba .oIo oases 43 .A:ONIOva00H .HO0H «AzmHIOHvommH .mmmH .NmmH .80 NH I c£\0M u vN.N x 8mm a:m\N o I c\oH u N x 5mm aAthINHVHmmH .AMMImHIOHuxamIzV ONIONIm M\nH com o "momma How compo HHomo5m nomo5 oonacm» “nouHHHuueu Hommm u .uoou Hoodoo mo ucoEoHH500H oEHH ecu moSHu N szo5m o» AnomH one momHv mcoHucoHHmmc oz» :H ooHHmoc oEHHo m: n: mm mm mm m: 0.NH m: m: Am0.vomH mm mm om mm mm mm AH mH on mozoz mm eH om oe mm Ae mm Am ov mimozooo II mm on II mm on mH HN mm suoooouo II mm on II mm mH NH MH mm mono II Am Am II om mm AH mm on mzz II AN AN II ov on mm mm on mozezz 0m Am mm mm mm mm Hm mm om Hoezz mm mm mm on mm mm on mm em eomwivzzo mm mm mm mm Hm em mm mm on muouHHHuuoo Homom II AH mH II mH em mH Hm mm nouHHHuuou oz ,amml. 0 mA HA ob mA HA be no no Ho NAImmmH new me: new new mom mom H50 05¢ H50 shoe :0 soBHH m5Hm oaHH oz o0m5 HoHuHoo AHHomnam some: on» em a oHndHHo>4 onH on HooH .muon ooaHH can oosHHoa .HHomoeo nomad .o oHouHHnad .oIo oHoos 44 effective in displacing adsorbed phosphates as are hydroxyl ions released from the hydrolysis of NH3. Extractable P levels were lowered rather consistently by liming (of. Tables 6-a and 6-b). However, the reduction was not statisti- cally significant in. any year. There were scattered significant differences among nitrogen carriers, but there were no consistent differences relative to the basal fertilizer treatments. Most of the available P was retained in the plow layer because low levels of phosphorus were found in the subsoil for all treatments over the years (Table 6-c). There is some evidence that more of the subsoil P remained in extractable forms with Ca(NO3)2 than with other carriers. Statistically significant differences in exchangeable K were found in both unlimed and limed plow layer soils (Tables 7-a and 7—b). All treatments that received basal fertilizer maintained exchangeable K at higher levels than the no fertilizer treatment. There is some evidence that the retentive capacity for K in the plow layer was maintained at a higher level with the NaNO3 treatment than with other carriers. Liming appears to have increased the retention of exchange- able K, especially after the large annual applications of acidifying carriers were discontinued in 1973. Exchangeable K levels in the upper subsoil were much lower than in the plow layer but do reflect the annual additions of basal fer- tilizer (Table 7-c). Elchangeale Ca and Mg Exchangeable Ca (Tables 8—a, b and c) and Mg (Tables 9-a, b and c) were affected much more dramatically by residual acidity from 45 .van .HhmH «A:0I00000H .000H .so AH I sexes.» e~.~ x and t.m\~ b I oon I N x sum NA:mIoV©©0H .mmmH «AsmlovmomH «ArmlovamH 0 .A:0HI00mA0H amuse» 0o ocumoo won some A .HHMIbHIoHIzIdIzo oNIomIm eon ooN ”nouHHHuuob Hdoomo osHH cquHz o.bH «.me ~.b~ A.vm o.Hm o.b~ A.me b.mH ~.m~ o.Hm muoHuueo Hmo.oamd HA HmH ooH meH «NH bmH mNH ooH ooH mHH mozoz mm AHH HOH emH Ab bA ooH Ab Hb AHH Nimozceo om mNH AOH Am no bA mo eoH ob mo snowman: Am bmH AHH omH bm bA boH HoH bb moH mono mm ooH moH mm bb oHH ooH moH moH eHH mmz Hm mm mm moH HA bA mm moH mmH bHH mozezz bm «NH bb bb HA Am boH moH AHH ooH Hoezz be mHH mm HA mA vA no Ho mHH mNH vommxezzb eb mHH em. ooH mm Ab ooH bb No mHH muouHHHuuob Homes be mm om bb em me Am be Av Ab nouHHHuuob oz Ema! b mA «A HA HA oA Ab bb Mb Nb Hb NAIomoH mom uoo Han so: and Han com Hon 0:4 Han :uoo :0 oaHH oz oom5 HoHuuco wommH son ecu 5H m oHoso0cscoxm mAmH ou HboH .buoHo_oosHHea .quuH .son .M 0Hoe00cscoxm .eIA oHoea 46 .so AH I nexus I e~.~ x and l=m\~ b I ebu I N x ado .A=0HIon00H .obmH .HhmH AA=0IOVONmH ehomH «HemlovoomH .AMMImHIOHNMImIzV omlowlm m\nH CON 0 Hakeem an moumoo wow sumo» u HQNfiHflHHOH Hflmflm m .wmou Homm5o mo ucoaonH50oH oEHH ecu mosHu N mHmm5m cu AbomH oss momHv mcoHuboHHmme 03D cH ooHHmmc oSHHo osHH dHeuHa o.bH mo N.b~ A.em o.Hm o.b~ A.oe muoHuuoo Hmo.oomq AA mmH NmH meH bmH emH HNH mozmz bb mHH bNH mHH mo bA moH Nimozcoo Hb oNH mo omH em vb bm abdomen: bb omH bNH HeH vo vb NoH mobs HA mHH bHH AoH mm Hm omH mzz eb «NH mNH oNH AA vb Am mozvzz mb mmH em bo mm ob em Hoemz om NOH AoH be AA Hm Nb eomNHezzb MA AOH eHH mHH mHH mo boH muooHHHuuob Human no mo Am Nb em me Am wouHHHuuob oz Emmi. b mA eA HA HA oA Ab bb NAImmoH mom poo H50 an: 05¢ H50 mom cuoo so cuaHH m5Hm oom5 uoHuweU ruoth onm ecu ca x oHoso0cscoxm onH on bde .muoHc oesHH .ucon toad .z oHndomddeoam .bIA pobe 47 .A=ONIOva00H .Han aAthIOHvoomH .mmmH .NmmH «AngINHVHomH .EU 0H I mn\0x n vN.N x 5mm .HmmIbHIoHIzImIzo oNIoNIm man oON “.me b I o\oH I N x and nausea mom cameo HHomnnm Homm5 oonEsm "woNHHHuuom Hemom 0 r m .unou nomw5n he unoaoHH50on wEHH on» mosHu N mHmonm ou AbomH one momHv mnoHuMOHHmmc can nH ooHHomc onHHo a: me me a: o.bm o: b.mH b.NH me .mo..omn mm NA bb mm bA Hb mw Nw AA mozoz Am ob Nb Am wb oA Nw ww oA Nimozbwo II No Hb II wm wb Nw Nw mA snobooub II no bb II moH Nb bw Nw Nb mono II wA mm II wb ob Aw No NA mzz II wA NA II NA bb bw ww mb mozwzz ow NA NA wm NHH wA mb mm bb Howzz Nw ow bb mm wm NA Nb Nb mb wobNszzc Hb mA bb Hm ob bb mw ww ,mb nuouHHHuuou Human II mw mw II Am Hw Hm mm Hm uoNHHHuuob oz. anew mA HA bb mA HA bb nb .Nb Hb NAImmoH mom as: new new an: new H50 05¢ H50 nwoo no IosHH msHo osHH oz eons uoHuuoo >HHonn5m Hommr on» nH M oHnso0nenoMm onH o» HboH .muon oosHH can oosHHaa .HHoobsu some: .z anaoodusouu .oIA oHoue 48 .au AH I bn\mx u wN.N x 5mm «gme b I mxaH u N x ammb .Accalovmhma .qhma .Hhmd «A:hlovonma .hmma «Azmlovmwma .mmmd «Asmuovmmmfi «Asmlovammd "mumou >n mnumwv HON mama» .AmmlmHIoHuMImlzv owlomlm M\AH com "Hmuudwuuflu Amman m m.HON m.mAH m.AmH m.HHm m.ebH o.bmH be N.HA A.be m: Hmo.vabq NHe HAN bmm Obm one ONm omm mNe eom bmb mozbz mow bom wa Nbe cme ebm omm mmm beb oNA NHmozvbo bb eOH mA bNH AMH emN mbm ebN ban bme auobeouo mA owH HNH NNN AMH emN mbm Hem bbm bbm emu: bb NOH AbH NNN bAH mmN moe oAN ebm on mm: mA NOH HNH eAH mm mbH obN HNN obm bNm mozwmz om mb HNH bNH AMH mbH oem me mmm be Howmz me NOH mA bNH mm bNH oeN bmH HmN bmm webNmezv bmm bom AbH Abm wom Nme ome bHe bme wa bubuHHHuubb Human bbm NAN mam obm bAm ONm 0mm - bmm omw wa noNHHHuubb oz anmI b mA eA HA HA oA Ab bb Nb Nb Hb NAImmmH mum #00 1.6 an: 9.2 HHS mmm HHS and Hum. 500 no oaHH oz can: uoHuueo EH93." 30.3 on» 5.. no manommcmsoxu mAmH on beH .uuon_basHH:s .uuNuH :on .oo oHnaooaonuxn .oIb oHnua 49 .A:OHIovmhmH .whma .ahma “AthOVOFmH .homa «Asmalovmomd .50 AH I mn\mx u v~.N x 3mm .AMMIwHIOHnMImIzV ONIONIm m\QH CON «gme b I b\oH u N x sum 0 "mummh >9 mnumuo How mama» "Hmuwdfiuuom Human m .umou Hobbso an unmamufiavmu mafia osu moawu N hammdm on Ammma can mwmdv mcowumowammm 039 :w omwammu mamas osHH oHnoH3 m.H0N b.mAH m.AmH m.HHm m.ebH o.bmH A.Amm muoHuuoo Amo.vobH bmm wa ome obm NAe wbm omm mozmz me mwm AbA Hob Nbb Amm Nob szozvbo mHm Nwm wa HHm bAm bAw mbn auobmouo mbe www bmm mbe bAm bob own bozo MHm oem ome HHm bAm ebm bom mzz owe mew omw mbw bAm bAe obm mozwzz oom bom Nmm Abm NbN bAe omm Hoezz me Nem ban mbe won bAw ebN wobNszzv mNb Aww bmm AOb me bmb eob buouHHHuuob Hombm bNm wa ome HHm one ebm mme uoNHHHuuob oz goo b mA wA HA HA oA Ab bb NAImmmH mom uoo Han aw: mad .Hnb. .mom choc :0 > aafidd afldm uohoa 30am 0:» ca no mandomcdgoxu 0mm: umwnunu mAmH ou bbmH .buon ooaaH .uoNoH oon .oo oHnuooounuxm .nIb «Home 50 .A30NIOHthmH .Hhma «Agmaloavmwma .mmma .Nomd «Azmfllmavammfl .30 ha I ms\mx u QN.N x 5mm N:m\N o I m\nH I N a sum 0 «munch How sumac aflomnsm mommy voamammr .AmmImHIOHuMImIZV ONIONIm M\nH CON "Hmuwawuuwm Amman m .vmou nmmman xn ucmsouwnwmu mafia an» mmfiwu N hamm9m on Aboma can mead. mcowumowammd can cw vowammd oawqo m.obN mg m: m.ebN no mo N.HA m: on Amo.vobq eb mbe Abm eb Abm Nmm NAN can Nme mozoz oom mmA mAm bmm mbe oee AHe Nmm mAm szozvbo III HHm ome III mbe own mNm Hbm bow snobbouo III Abm ome III Obm mmw eAm bbw emm bozo III NNN 0mm III mHe own mmN emN ebm mmz III Abm mmw III bNH own men HAN me mozezz mHH HAN mbN me emN oem eHm on obe w Hoezz bmH NNN owm mm mbH mbN AAN mmN obm oszwzzv ome mAe Heb mNm AbA mow bbm eHe Nae buouHHHuuob Human III Abm ANm III HHm mme on bmm Ne uoNHHHuuob oz ammI b mA HA bb mA HA bb Nb Nb Hb NAImmmH mom an: mom mom was mom Han and Han choc co soaHH mon oaHH oz boos uoHuuoo >HNOmasm momma «nu cw no mandoucanoxu mhmd cu Hmmd .muoam GQEHH find vafifldna .Hdounbu Rama: .60 0Hndomcdnoxfl .oIb «Home 51 .au AH I banz u eN.N x 5mm «NNM\N O I M\fl n N K EQQ b .zgoHIonANH .eANH .HANH “AgAIoVOANH .AbNH NAngSbbNH .NbNH NAgbISNbNH N.gbISHbNH "bosom No bzumob now some» .ANNINHIoanINIzV ONIoNIm «\oH ooN «nouNHHouob Hambmb N.AN mo b.AN N.mw o.bN o.NN b.Nm A.NH N.wN m: AmomvobH Nb ew em HA Nm eb NA Ne oA bm Nozmz bN NN 0N mN NN HN mN NN Am Nm NzNozvbo mH mH NH wH NH HN HN HN om bN snowman: oH 0N bH HN NH bN HN oN Ne be boo: NH OH NH AH bH NN bN NN Ne mN sz NH N NH AH 0H eH NH NN om Nb Nozemz NH m bH eH bH bH NH NH NN om w NHoezz N b NH A 0H A e OH bN mN ob Awmzv ow NN NH be bN be be Ne NA mm NuoNNHHuuob Human be ow bm NA bm Ab Nb be Nb mN NNNNHHuuou oz EQQWI b mA eA HA HA oA Ab bb Nb Nb Hb NAINmNH mom poo Han an: 094 and mmm duh and Han :uoo co wENH oz coma uoNHHmu > “mama 30am on» :w m: manwmmcmnoxu mbma 0» Homa .muon omawans .mema 3OHQ .mz wanmomcmnoxm .mfm wanna 52 .30 ha I mn\mM n vN.N x 5mm Nam\N m I o\nH u N x ammo .A=0HIovaNH .eANH .HANH uAgAIoVoANH .AbNH uAsmISbbNH "muooN No anamoo Nob boon» .AmmImHIoHnMImIzv ONIONIm M\na CON ”Honwafiuumm Hmmmmm .ummu Hummus ma ucmsmuwavmu mafia may mQENu N hammsm ou Homma can mmmav mcoNumoNHmmm 03» ca cwuammm usage oaNH :quHs N.AN m: N.AN N.me o.NN o.NN mo NubHuuoo Amo.vobq beH NNH bHH HNH wHH NNH NN Nozmz NHH NOH NA HA NA eA mb NzNozvoo NmH HHH mNH NmH AHH HNH Nm auoboouo bNH bNH mNH mNH AHH beH bb mono meH AN mNH AHH . HHH bNH NN Nmz beH NNH NNH bNH AHH bNH Nb Nozezz NoH bb beH Nb bb NwH NA Hoemz beH beH AeH NNH AHH wbH mA eoszwmzv NbH NHH NNH HNH oHH HNH mN buouHHNuuob Human mmH mNH meH ova NMH NHH Na Houwawuumm oz somI b mA eA HA HA oA Ab bb NAINmNH flow 900 Han . an: and Han mam ch00 co ooaNH ooHN bobs uoNuuoo rumaua 30am may :N as candomcdnuxu mANH on bbNH .Nuon ooaaH .uoNuH oon .Na oHnoomougoxm .oIN «Home 53 .Azomioavmhma .Hhma «A:mHIOHv©mmH .mmma .Nmma “NomHINHVHmmH "mumma How numwo NNONQsm uwmm: vmamamm .20 NH I mn\mM u vN.N x 5mm N..N\N b I «\oH u N x sum .AmmINAIoanMImIzV ONIONIm m\nH CON uuouwawuuom Hammm o r m .ummu Mommas an ucwamuflswau mENH may mmENu N hammnm ou Awmma can mmmav mcoflumowammm 03» GN wowammm QBNQU m .Qm .012 mn— m .qm WC ma FIN." man mC AmOIVn—mfl mN NNH NN Nm Nm Ne ow Ne Nm Nozbz 0N Ab NA NH mN HH AN Nb om NzNonNo II omH NA II be mN ow me Ne snowmouz II AHH NA II HA Ne He Nm Ne mono II Nb we II NHH HN HN AN em Nmz II bN NA II wH NN Ne me HA Nozezz Nw wA Nm N mN me HN Ae be Howmz NA Nm Nm b A mN NN Ne NN eoszemzb oN HA bN ow Ne AN Ne Hm em NuoNHHHuuob HNNNN II NNH bN II Ab Nm AN NN Hm uoNHHNuuob oz samll N mA HA bb mA HA bb Nb Nb Hb NAINmNH mom an: now now an: mmm Han mam H96 shoe :0 soENH maam «HHH oz can: Huwuumo mANH on HbNH .Nuon ooaNH can buaNHoa .HNoNnom mommy .Nz oHnooNouaoxm .oIN oHoNa 54 N carriers than was exchangeable K. The capacity of soils to retain these cations in the plow layer decreased as potential acidity increased. A comparison of Tables 4-a, S-a and 8-a indicates that large increases in lime requirement did not occur until exchangeable Ca had decreased to less than 400 ppm at a pH of about 5.0. Below that pH rapid adsorption of protons by exchangeable Al would have reduced the capacity of the soil to retain basic cations, but accel- erating decomposition of soil minerals would have served to maintain K levels at the expense of Ca and Mg (Wolcott et al., 1965; Schafer, 1968). Marked depletion of exchangeable Ca was first observed with (834)2804 (Table 8-a). Depletion progressed more rapidly with the three ammonium carriers as a group than with NH urea or ureaform, 3I but all were at the same low level by 1971. Additional decreases have occurred in the plow layer since annual application of these acidifying carriers was discontinued in 1973. Ca added in Ca(N03)2 tended to maintain exchangeable Ca at higher levels during the early years of the study. However, since 1966, values for both Ca(NO3)2 and NaNO3 in unlimed soil have been similar and somewhat higher than for no fertilizer or for basal fer- tilizer only. The additions of lime in 1965-66 had restored exchangeable Ca in the plow layer by 1967 to levels comparable to those found in 1961 (cf. Tables 8-a and 8-b). In the case of Ca(N03)2, exchangeable Ca after liming was higher than for any other treatment and remained higher through the last sampling in 1975. In the case of (NH ) SO 4 2 4 and NH Cl, maximum values were obtained in 1971 and have shown a 4 marked tendency to decline since then. 55 Marked evidence for depletion of Ca from upper subsoils (Table 8-c) was obtained only for the three ammonium salts and NH Reduc- 3. tions for (NH ) SO and NH were significant in 1963 and for (NH SO 4 2 4 3 4’2 4 and NH C1 in 1975. It must be recognized that levels found in the 4 subsoil represent a balance between illuviation and eluviation. There were variations from year to year, but no evidence that Ca lost from the plow layer had accumulated in the upper subsoil. There have been both increases and decreases in subsoil Ca since lime was applied. The largest increases were in Ca(NO3)2 plots. Smaller increases in (NH4)2804 and NH4C1 plots may reflect reduced capacity to retain basic cations due to exchangeable A1 retained in the subsoil as potential acidity (Table S-b). Exchangeable Mg in the plow layer (Table 9-a) was depleted in much the same pattern as Ca. The levels at the beginning of the experiment were already rather low in all plots. Mg deficiency symptoms were observed in corn on (NH4)2504 In 1967, foliar analyses for Mg were at deficient levels for corn in plots as early as 1961. unlimed plots of all carriers except NaNO (Schafer, 1968). Exchange- 3 able Mg for the same treatments (Table 9-a) remained at the 1967 levels, or dropped still further, during the remaining years of the study. The Na in NaNO appears to have had a sparing action on dis- 3 placement of Mg, similar to that noted earlier for exchangeable K. Mg released from dolomitic lime applied in 1965-66 increased exchangeable Mg to levels 3-fold or more greater than 1961 (cf. Tables 9-a and 9-b). The increases by July 1967 were related in a general way to the quantities of lime applied (Table S-a). However, levels in Camoa)2 plots were less than in NaNO plots and have remained so, 3 even though both treatments received 4 T/a of lime. Mg is adsorbed 56 less strongly than Ca in cation exchange reactions and would not have displaced Ca previously adsorbed from Ca(NO3)2. The greater reten- tion of Mg in NaNO plots again reflects the sparing action of Na 3 which is adsorbed less strongly and remains in solution as the dominant complementary cation accompanying nitrate as it leaches through the profile. With acidifying carriers, Mg in limed plots fluctuated con- siderably from year to year, with no consistent tendency to increase or decrease. Levels were frequently significantly lower in NH4C1 plots than with other carriers. This may reflect differences in the exchange reactions of Al complexes with Cl- as compared with Al complexes with polyvalent anions such as sulphate or phosphate (Jackson, 1963). Evidence for progressive depletion of Mg in the upper subsoil of unlimed plots was obtained only for the three ammonium carriers (Table 9-c). Year to year fluctuations with NHB' urea and ureaform suggest that there were periods of net eluviation and net illuviation. The sparing action of Na relative to Ca is again expressed in the data for the two nitrate salts. There is evidence that Mg from the dolomitic limestone had moved quickly into the upper subsoil, but that less was retained in the very acid plots. These differences are undoubtedly real even though statistical significance was achieved only in 1975 because of inadequate replication of the lime treatment. Profile Changes After Treatments Were Discontinued In May 1971, all plots were sampled in 10" increments to 30". In September 1975, the same depth increments were sampled for the 57 basal fertiliser control and for the two most acidifying carriers, (NH $04 and NH4C1, and the two non-acidifying carriers, Ca(NO3)2 4’2 and NaNOa. Soil tests for these two samplings (Tables 10 to 15) provide a picture of changes that have taken place in the profile since annual applications of the different carriers at high rates were discontinued in 1973. In Tables 5 to 9, lime requirements and nutrients in the 0-10" and 10-20' increments were given in units of concentration. These have been converted in Tables 11 to 15 to T/a or lb/a in each 10" increment so that totals to 30“ can be compared. The English units were used because they are still the basis for lime and fertilizer recommendations in Mich. Ext. Bul. E-SSO (1976). Soil pH and Lime Reguirement The striking change in Table 10 from 1971 to 1975 is the sharp decrease in pH at 20930” for (NH4)2504 and NH4C1. These decreases occurred in both limed and unlimed plots. In unlimed plots, decreases in pH at 20-30" for both acidifying carriers were accompanied by decreases in lime requirement at each depth and in the total to 30” (Table 11). In limed plots, much of the accumulated potential acidity from NH Cl had disappeared by 1975, 4 even though pH at all depths remained low. By contrast, in limed (NH4)2804 plots it seems that potential acidity displaced from upper soil layers had accumulated at the 20-30” depth. The greater reten- tion of potential acidity from (NH4)ZSO4 than from NH4 limed and unlimed plots, is consistent with the greater stability of C1, in both exdhangeable Al complexes with sulphate than with monovalent anions (Jackson, 1963). The sulphate complexes also have a greater tendency 58 Table 10. Soil pH, profile changes, 1971 to 1975 Carrier Soil pH Lime“ Soil pH used on No lime Plus lime“ corn T/a 1959-72 0-10" 10-20" 20-30" 0-10" 10-20" 20-30" Y A. May 1: 1971 No fertilizer 6.1 6.3 6.2 4 7.0 6.7 5.8 Basal fertilizer 5.5 6.0 5.8 6 6.9 6.7 6.6 (NHN)2SOu 4.1 4.0 5.0 12 5.8 4.8 5.6 NHeCL 4.3 4.0 5.7 10 5.6 4.6 6.2 NH4N03 4.5 4.5 4.8 8 6.5 5.4 5.9 NH3 4.7 5.0 4 6 6 6 2 5.4 5.0 Urea 4.5 5.4 6 2 8 6 6 5.6 6.2 Ureaform 4.5 5.4 5 2 8 6 6 5.6 6.0 Ca(N03)2 5.8 6.0 6.0 4 7.0 6.8 6.0 NaNO3 6.5 6.8 6.4 4 7.2 6.4 6.8 LSD(05) Carriers within lime 1.0 1.6 NS 1.0 1.6 NS LSD (05) Lime within carriers - - - 1.8 ns ns B. §gptember 25, 1975 No fertilizer B 5.3 - - 4 6.7 - - Basal fertilizer 5.1 5.4 6.6 6 6.8 6.9 6.6 (NHe)250“ 4.2 4.2 4.4 12 6.2 5.4 4.8 NHgCl 4.4 4.5 4.8 10 5.3 4 9' 4.9 NHgNO3 4.2 - - 8 6.7 - - NH3 4.5 - - 6 6.2 - - Urea 4.4 - - 8 6.7 - — Ureaform 4.3 - - 8 5.9 - - C8(N03)2 5.3 5.7 5.7 A 6.8 6.9 7.2 NaN03 5.6 6.4 6.8 4 7.0 6.6 6.3 LSD(.05) Carriers within lime 0.83 0.83 1.90 0.83 0.83 1.90 LSD(.05) Lime within carriers 0.79 ns ns 0 Lime applied in two applications (1965 and 1966) to supply 2 times the 8 Basal fertilizer: Y lime requirement by buffer test. (T/a x 2.24 - TM/ha). 200 lb/a 5-20-20 (N-P-K-lO-18-33). Data for 1971 from 1971 Research Report. M.S.U. Soils Farm, East Lansing, Michigan. 59 Table 11. Lime requirements, profile changes, 1971 to 1975 Carrier Li used on Lime requirement Limea me requiremsnt corn No lime Plus lime 1959-72 0-10" 10-20" 20-30" 0-30" T/a 0-10" 10—20" 20-30" 0-30" ----------- T/a6 ---------- ----------- T/a ----—-—-- A. May 1, 19717 No fertilizer 1.5 0.0 0.6 2.1 4 0.6 0 0 0.6 1.2 Basal fertilizer 8.4 1.5 1.6 11.5 6 0.6 2 1 0.0 2 7 (NHu)ZSOQ 14.4 18.3 10.2 42.9 12 8 7 6.0 2.7 17.4 NHuCI 18.0 17 2 2 7 37.9 10 9 8 10.2 3.7 23.7 NH4N03 4.8 5 8 S S 23.1 8 1.5 10.8 3.7 16.0 N33 18.3 6.4 14.5 39.2 6 4 4 8.7 7 6 20.7 Urea 12.9 5.0 2 7 20.6 8 1 0 5.8 1.2 8.0 Ureaform 16.2 5.0 5 S 26.7 8 2 1 1.5 0 6 2.9 Ca(NO3)2 6.4 2.8 2.7 4.9 4 0.0 0 6 0.0 0.6 NaN03 11.2 0.6 1.6 12.4 4 0.0 2 8 1.2 4.0 LSD(OS) Carriers within lime 11.2 12.1 9.4 22.3 NS NS NS 22.3 LSD(05) lime within carriers - - - - NS NS NS 21.3 B. September 25) 1975 No fertilizer 3.9 - - - 4 0 - - - Basal fertilizer 3.2 0 0 3 2 6 O 0 0 0 (NHu)250u 8.6 7.6 4.3 20.5 12 3.2 S 4 10.8 19.4 NHuCl 7.6 5.4 2.2 15.2 10 2.2 2 2 0 4.4 NHqN03- 6.5 - - — 8 0 - - NR3 7.6 — - - 6 0 - - - Urea 7.6 - - - 8 0 - - - Ureaform 8.6 - - - 8 0 — - - Ca(NO3)2 4.3 0 0 4.3 4 0 0 0 0 NaN03 3 2 0 0 3 2 4 0 0 0 0 LSD(.05) Carriers within lime 2.6 5.4 NS 13.0 NS 5.4 6.0 13.0 LSD(.05) Lime within carriers NS NS NS NS c Lime applied in two applications (1965 and 1966) to supply 2 times the lime re- quirements by buffer test. (T/a x 2.24 - MT/ha). B Basal fertilizer: 200 lbs/a 5—20-20 (N-P-K-- 10-18—33). Y Data for 1971 from 1971 Research Report, M.S.U. Soils Farm, East Lansing, Michigan. 6 T/a x 2.24 - MT/ha 60 to fbrm immobile polymers with increasing pH than does exchangeable Al itself. As will be seen, decreases in pH from 1971 to 1975 in Table 10 were accompanied by extensive depletion of exchangeable cations, notably Ca and Mg. It is likely that'these basic cations were dis- placed by exchangeable Al and its complexes as they moved downward through the profile. Available P and Exchangeable K Profile totals and profile distributions for available P in 1975 were remarkably similar to those found in 1971 (Table 12). Uniform fertilization on all plots in 1973, 1974 and 1975 had not eliminated the significant differences in the plow layer between plots which had previously received no fertilizer and all other treatments which had received basal fertilizer. There is no theoretical explanation for the uniquely high level of P at 20-30” with ureaform.in 1971. It is probably not practically significant and cannot be taken seriously since no subsoil samples were taken in 1975 to verify it. Exchangeable K was much lower in September 1975 than in May 1971 for most treatments at all depths. This difference probably reflects both seasonal variation and differences in laboratory techniques of different analysts. Significant differences in the plow layer in 1975 still reflected the differences observed over the years of the experiment between no fertilizer and other treatments and the greater retention of exchangeable K with NaNO and with lime applied to very 3 acid soils. 61 Table 12. Available P, profile changes, 1971 to 1975 Carrier used on Bray P1 A corn No lime Plus limeu 1959-72 0-10" 10-20" 20—30" 0-30" 0—10" 10-20" 20-30" 0-30" ----------- 1b/a6 - - — - - - - - - - - - - — - - A. May 1, 1971Y No fertilizer 136 56 36 227 78 40 36 154 Basal fertilizer 334 93 33 459 294 108 45 448 (NHu)2804 345 105 36 484 321 98 39 458 NHuCl 333 105 39 477 297 82 28 407 NH4N03 376 120 39 535 288 82 30 401 NH3 351 60 66 478 258 110 42 410 Urea 306 68 30 404 270 74 39 382 Ureaform 321 117 108 546 316 66 36 418 Ca(N03)z 306 104 32 441 237 42 44 322 NaN03 288 72 36 396 231 66 51 349 LSD(05) carriers within lime 128 NS 56 212 128 NS NS 212 LSD(05) lime within carriers - - - - NS NS 56 NS B. September 25, 1975 No fertilizer B 155 - - - 188 - - - Basal fertilizer 290 113 53 455 287 167 108 561 (NHu)2804 305 90 62 456 296 114 54 464 NHuCl 329 86 60 474 333 89 56 477 NHuNOa 329 - - - 288 - - - N83 299 - - - 255 - - — Urea 296 - - - 267 - — - Ureaform 303 - - - 258 - - - Ca(N03)2 296 119 53 467 254 69 54 377 NaNO3 246 84 59 389 236 116 59 410 LSD(.05) carriers within lime 82.4 NS NS NS 82.4 NS NS NS LSD(.OS) lime within carriers NS NS NS NS a Lime applied in two applications (1965 and 1966) to supply 2 times the lime re- quirement by buffer test. B Basal fertilizer: 200 1b/a 5-20-20 (N-P-K-10-18-33). Y Data for 1971 from 1971 Research Report, M.S.U. Soils Farm, East Lansing, Michigan. 6 lb/a x 1.12 - kg/ha. (32 Table 13. Exchangeable K, profile changes, 1971 to 1975 Carrier Exchangeable K used on No lime Plus limea corn 1959-72 0-10" 10-20" 20—30" 0-30" 0-10" 10-20" 20-30" 0—30" -------------- lb/ad - - - - - - - - - - - - - - A. May 1I 1971Y No fertilizer 8 198 171 178 548 186 130 130 448 Basal fertilizer 360 267 177 803 354 224 192 770 (Nflu)2SOq 213 162 268 643 288 147 204 638 NHuCI 255 338 321 915 288 234 244 767 NHQNO3 306 220 272 798 360 222 177 760 NH3 255 192 303 752 321 222 225 768 Urea 360 309 234 903 423 250 162 834 Ureaform 261 162 202 625 360 276 177 813 Ca(NO3)2 372 192 182 745 354 240 166 760 NaN03 428 228 182 838 429 234 222 886 LSD(05) Carriers within lime 164 168 NS NS 164 NS NS NS LSD(05) Lime within carrier - - - - NS NS NS NS B. September 25, 1975 No fertilizer 8 139 - - - 130 - — - Basal fertilizer 193 152 135 480 222 182 109 512 (N82)u802 143 113 116 372 177 125 138 440 NHuCl 168 102 146 415 188 120 160 469 NHgNOa 152 - - - 192 - — - NH3 173 - - - 213 - - - Urea 171 — - - 199 - - - Ureaform 149 - - - 182 - - - Ca(N03)2 178 160 133 471 197 171 125 550 NaNOg 220 140 182 484 231 159 90 481 LSD (.05) Carriers within Lime 48.0 NS NS NS 48.0 NS NS NS LSD (.05) Lime within carriers 21.8 NS NS NS a Line applied in two applications (1965 and 1966) to supply 2 times the lime re- quirement by buffer test. B Basal fertilizer: zoo lblacre 5-20-20 (N-P-K-10-18-33). Y Data for 1971 from 1971 Research Report, M.S.U. Soil Science Farm, East Lansing Michigan. 6 1b/a x 1.12 - kg/ha. 63 The effect of NaNO3 is apparent in both limed and unlimed plots. Sodium is adsorbed less strongly than K by cation exchange and is more likely to move with anions in percolating soil solution. Thus, Na would have a sparing action on displacement of K and other cations. Also, at the higher pH in NaNO plots and in all plots after liming 3 the concentration of charged Al compounds would have been less and these are mainly responsible for displacing basic cations in very acid soils (Jackson, 1963). Exchangeable Ca and Mg Residual effects of N carriers had extended through the soil profile between 1971 and 1975, as shown by data for exchangeable Ca and Mg in Tables 14 and 15. These changes were related to changes in pH (Table 10) and lime requirement (Table 11). In the unlimed plots, levels of exchangeable Ca in the plow layer were substantially higher for the two controls and for Ca(NO3)2 and NaNO3 than all the six acidifying carriers (Table 14). These differences, which were obvious in 1971 (the last application of N carriers was made in 1972), had increased by 1975. There were sub- stantial reductions (or losses) of exchangeable Ca in the plow layer and subsoils in all treatments except in plots that received basal fertilizer. The greatest reductions were associated with the acidify- ing carriers. The profile totals indicate reductions from 1971 to 1975 in all three layers, especially in the 20-30" layer of (NH ) SO 4 2 4 and NH Cl plots. Losses from plots that received Ca(NO3)2 and NaNO 4 3 were mainly from the 20-30' layer and were greater for Ca(NO3)2 than for NaNO3. Table 14. Exchangeable Ca, profile changes, 1971 to 1975 Carrier Exchangeable Ca used on corn No lime Plus lime“ 1959-72 0-10" 10-20" 20-30" 0-30" 0-10" 10-20" 20-30" 0—30" ------------ — - 1b/a6 - - - - - — - - - - - - - - - A. May 11 1971 Y No fertilizer B 1680 1534 2402 5615 1534 1101 1245 3881 Basel fertilizer 1101 1534 1389 4025 1822 957 1968 4748 (NHq)280u 378 378 1389 2146 1390 666 2691 4748 NBnCI 378 668 2979 4025 1101 812 2980 4893 NHuN03 622 378 1534 2435 1390 1101 2256 4748 N83 666 1245 957 2869 1534 666 957 3158 Urea 666 1680 522 8506 1390 1101 2402 4893 Ureaform 378 1390 1245 2291 1534 1534 2256 5326 Ca(N03)2 1390 1389 2258 5038 2402 2258 2256 6916 NaN03 1680 1101 1101 3881 1680 1389 1534 4603 LSD (05) Carrier within lime 934 NS NS NS 934 NS NS NS LSD (05) Lime within carrier - - - — 909 NS NS NS B. September 25, 1975 No fertilizer 1163 - — - 1583 - - - Basal fertilizer 1013 975 4508 6495 2475 1470 1328 5272 (NHu)280u 135 105 210 450 773 413 795 1980 NHuCI 150 128 525 803 900 338 923 2160 NHuN03 225 - - - 1440 - - - NH3 263 - - - 1538 - - - Urea 225 — - - 1388 — - - Ureaform 263 - - - 1545 - - - Ca(N03)2 1215 1013 675 2903 1845 1500 3863 7208 NaNOa 1238 1013 555 2805 1613 1013 1238 3863 LSD (.05) Carriers within line 604 781 NS 3942 604 781 NS 3942 LSD (.05) Lime within carriers 1178 NS NS NS 0 Lime applied in two applications (1965 to 1966) to supply 2 times the lime requirement by buffer test. B Basal fertilizer: 200 1b/acre 5-20-20 (N—P-K-lO-18—33) Y Data for 1971 from 1971 Research Report, M.S.U. Soils Farm, East Lansing. 6 1b/a x 1.12 - kg/ha. (55 Table 15. Exchangeable Mg, profile changes, 1971 to 1975 Carrier Exchangeable Mg: “Bed °° No lime P1 1i corn us me 1959-72 0-10" 10-20" 20-30" 0-30" 0-10" 10-20" 20-30" 0—30" ------------ lb/as - - - - - - - - — - - - - - A. May 1, 1971* No fertilizer 234 201 376 808 438 309 286 1033 Basal fertilizer 138 147 244 530 363 212 354 937 (NHu)230~ 21 21 147 190 286 159 513 958 NHuCI 42 74 288 403 266 222 549 1037 NHgNOa 52 42 255 350 384 288 450 1121 N83 52 357 159 567 351 190 213 754 Urea 63 213 406 682 405 351 405 1162 Ureaform 42 138 74 254 460 450 428 1337 Ca(N03)2 74 105 266 445 . 212 201 276 688 NaN03 213 159 234 604 362 309 330 1000 LSD (05) Carrier within lime 136 NS NS NS 136 NS NS NS LSD (05) Lime within carrier 204 NS NS NS B. September 25, 1975 No fertilizer 143 - - - 473 - - - Basal fertilizer 120 120 383 623 489 270 263 1022 (NH“)280~ 26 18 49 93 443 233 323 998 NHu01 38 5 90 133 308 128 323 758 NHHN03 38 - - - 443 - - - NN3 38 - - - 435 - - - Urea 30 - - - 413 - - - Ureaform 45 - - - 473 - - - Ca(N03)2 83 38 90 210 353 240 413 1005 NaN03 188 173 210 451 443 255 218 916 LSD (.05) Carriers _ within lime 82 103.4 NS NS 82 103.4 NS NS LSD (.05) Lime within carriers 182 204 NS NS o Lime applied in two applications (1965 and 1966) to supply 2 times the Lime re- requirement by buffer test. 3 Basal fertilizer: zoo 1b/acre 5-20-20(N-P-K!10—18-33) Y Data for 1971 from 1971 Research Report, M.S.U. Soils Farm, East Lansing, Michigan. 6 lb/a x 1.12 I kg/ha. 66 There were less dramatic losses in exchangeable Mg from 1971 to 1975 in the plow layer of unlimed plots, though differences for treat- ments were statistically significant in both years (Table 15). In the subsoils, recoveries of exchangeable Mg were substantially lower in (N84)ZSO4, NH4C1 and Ca(NO3)2 plots in 1975 than in 1971. Quanti- tative changes in the subsoil and in the profile totals were less for Mg than Ca, but the relation to carriers was essentially the same as described for Ca. Losses of bases from the different soil layers are most likely due to displacement by exchangeable Al which moved down the profile along with the bases. This is reflected in the decrease of lime requirement from 1971 to 1975 in the plow layer and upper subsoil of (NH4)2SO4 and NH4C1 plots (Table 11). This trend would have been expected for other acidifying carriers because of the large quanti- ties of accumulated acidity in the plow layer and subsoil in 1971. However, the expected trend for these other carriers was not determined because subsoil samples were not taken for them in 1975. The very low levels of exchangeable Ca and Mg (Tables 14 and 15) which remained in 1975 may be mainly due to continuing release from decomposition of soil minerals. The effects of liming in the plow layer were significant in 1971 and 1975 for exchangeable Ca (Table 14). The greatest increases of exchangeable Ca in 1971 with liming were associated with the acidi- fying carriers in all layers. However, large losses had occurred from the total profile since 1971 for (NH4)ZSO4 and NH4C1 treated plots. There is evidence that Ca in Ca(NO3)2 plots had been displaced downward into the 20-30" layer, also. 67 In the limed plots, levels of exchangeable Mg were higher in 1975 than in 1971 in the plow layer in all treatments (Table 15). This indicates continued release from dolomitic lime applied in 1965-66. Profile totals show an increase for Ca(NO3)2 due to increases at all depths. In NH4C1 plots, the profile total shows a decrease due to decreases in both subsoil layers. The subsoils of other treatments showed either a decrease or an increase in exchangeable Mg. Exchangeable Mg in the plow layer of plots that received Ca(NO3)2 was uniquely lower over the years of the experiment than those that received NaNOB. This difference had progressed in unlimed plots, to both subsoil layers in 1975 (Table 15). This indicates interaction between Ca2+ and Mg2+ ions. Calcium has greater exchange potential compared to Mg and therefore tends to displace Mg from the exchange complex and promote its downward move- ment in the soil solution. Exchangeable Mg was displaced from both subsoil layers in plots that received NH Cl and (NH4)ZSO in unlimed plots (1971 to 4 4 1975). In limed plots, in 1975, exchangeable Mg in the plow layer and upper subsoil was lower in NH Cl plots than (NH ) SO (Table 15). 4 4 2 4 This was shown in earlier years (Table 9-b). The differential effect of the Cl- and 804- ions in moving the bases below the root zone appears to be related to differences of Al complexes formed in the presence of Cl- as against SO4 (Table 11). Complexes of A1 with SO . are very stable, and the complexed so4 4 acidity (Jackson, 1963). contributes to potential 68 Relationship Between Lime Requirement and Exchangeable Cations 3 equiva- The relationship between lime requirement and the CaCO lent sum of exchangeable K + Ca + Mg is shown in Figure l. The numbers used to identify treatments are the same as were used by Holcott et a1. (1965) in similar graphs for data obtained in 1961, 1962, and 1963. In those early years of the experiment, lime requirement increased rapidly when soils reached a pH of about 5.0 and then more slowly at lower pH. The authors of the 1965 report noted that exchangeable Al buffers strongly at about pH 5.0 or 5.2. By 1975, the ten treatments without lime had separated into two groups: (1) the six acidifying carriers with high lime requirements at about pH 4.0 to 4.5 and (2) the two nitrate salts and the two control treatments with moderate lime requirement at pH 5.1 to 5.6. Exchangeable Al has higher replacing power in exchange reactions than N, Ca or Mg. As seen in Figure l, the high levels of potential acidity at pH 4.0 to 4.5 had reduced the capacity of soils to retain cations drastically. It is likely that the very low levels of cations in this very low pH range were maintained mainly by decomposition of soil minerals. As had been seen in previous sections in this thesis, exchangeable K levels were maintained more effectively than Ca or Mg. Additions of lime in 1965-66 had fully neutralized or displaced potential acidity from the plow layer by 1975, except in (NH 2SO 4) 4 and NH4C1 plots. These two treatments had received the heaviest applications of lime (12 and 10 T/a, respectively). However, extreme acidity had developed earlier than with other acidifying carriers. From this and other data, it seems that the longer soils are allowed 69 Figure 1. Lime requirement and exchangeable bases in relation to soil pH in 1975. KEY TO TREATMENTS l (NH4)ZSO4 6 - Ureaform 2 - NH4C1 7 - Ca(NO3)2 3 - NH4N03 8 - NaNO3 4 - NH3 9 - Basal fertilizer U" l C" H m m [.5 O I No fertilizer 70 g a 9 Lu 9'9 2 g (9 ® 91 a! 0 69 g G). 3 0 2 698 e (9 ° 3 2 3 (9.0: x and d) lNJWBUIHOSN SW” .99 C96 .01. N (5w + 03 + )1) ‘AanJ awn 7- 0 6-0 6-5 SOIL P H 55 5-0 55 5-0 SOII. PH 48 4-0 Figure l 71 to remain very acid, potential acidity becomes more difficult to correct. 4 the nitrogen carriers behave fairly differently. It seems that As pointed out in earlier sections, the SO and Cl- ions of 4 pH than is the potential acidity which develops in the presence of potential acidity due to complexed SO may be more stable at higher c1“, as shown in the figure with lime. Potential acidity which remained after treatment with lime was still effective in occupying the exchange sites, reducing the capacity of the soil to retain exchangeable ions. The cations replaced in this manner may be taken up by plants or lost to the subsoils as indicated in earlier sections (Tables l3, l4 and 15). Mineral Nitrogen in 1975 Ammonium N Accumulation of NH: or of N0; (the intermediate mineral form in nitrification) is due to unfavorable conditions for one or both groups of nitrifying bacteria, Nitrosomonas and Nitrobacter. In the unlimed plots, there were small accumulations of NHz-N in September 1975 in the plow layer in all treatments, especially in plots that had received acidifying carriers (Table 16). The 42 pounds of N applied on all plots for soybeans in 1975 (Table 1-a) was probably mainly ammoniated phosphate or urea, although there are no 4. 4 were statistically significant, and there is evidence that Nitrosomonas records to verify this. Differences in NH N in the total profile may have been inhibited during the growing season in the very acid soils (pH 4.2 to 4.4) of plots which had received (NH4)ZSO4 and NH4C1 in earlier years. The first step of nitrification, itself, is 72 .ANNINHIoanIaIza oNIoNIm e\nH NNN ”Hmuwawuuom Homom .Ne\Nz I NH.H x eonN m .unou summon an unofiouwnoou one» on» need» N aammsm cu Aboma one momav mnowumofiammm can nN oofiammm means snowshoe nwnuws on on an an OSHA Amo.vomq osHH cHaoHs on on mn mn o.N an on an muowuwmo Amo.vomn N.N o.o N.N o.o m.e o.o o.o b.o Nozoz A.o N.N N.N N.N N.N o.o o.o H.H NiNozeNo N.o w.w saobeouo N.N N.N cone m.e N.m mmz N.N m.e Nozwmz A.H N.N o.o N.N N.m o.o o.o N.m e Hoezz N.N N.N N.N N.N N.N o.o o.o N.N ebwamzv N.N m.e m.e m.e o.N m.o o.o N.N muosNHNuuom Hmmmm N.o o.o nouflawusom 02 e nH b \ eoNIo =oNIoN eoNIoH goHIo =oNIo =oNIoN .oNIoH goHIo NAINmNH SOEflH mDHm 05H oz 500 CO I ZIanNnoeam owns uoNHHmU mANH .mN nonsenseb .Hmz No coHoonauuNHo oHHuoua .bH oana 73 an acidification process that tends to limit the effectiveness of the organisms that carry it out. Lime applied in 1965-66 continued to be released to effect favorable conditions for nitrification in 1975, as indicated by the + very low levels of NH4 N in the limed plots in all treatments. Nitrate-N Nitrification leads to the production of nitrite which is oxi- dized to nitrate. Soil samples taken and analyzed for N0; in 1975 did not show detectable nitrite. This may be due to delay between the time samples were collected from the field in 1975 and when actual analysis was performed on them. Soil samples collected in 1976 (about the same time as in 1975) and run immediately showed traces of N03, up to 1 ppm, in the limed plots, but no trace was found in the unlimed plots. Nitrous acid is unstable at acid pH (Allison, 1973). Mineral N can be lost by chemical denitrification in reactions of nitrous acid with organic and inor- ganic constituents of acid soils. These reactions lead to the release of oxides of nitrogen and/or elemental nitrogen as gases. Because of the production of nitrous acid as an intermediate in nitri- fication, these losses can be significant in acid soils and may have contributed to somewhat lower recoveries of nitrate in the most acid unlimed plots (Table 17). Greater leaching may have occurred in these plots also, as is indicated by significantly higher NO; in the 20-30" layer. Accumulation of nitrate in limed plots (Table 17) is evidence that nitrification of nitrite was not inhibited in the pH range of 5.3 to 7.0, which is favorable for most nitrifiers. Detection of 74 .AMMImHIOHnMIAIzv ONIONIm e\nH CON «Honwawuuom Hemem .Naxez I NH.H x «\po m .ueeu summon ms unosouNsoou saws enu moawu N hammnm on “wood one moody nnONueONHmme osu nN ooNHmme enema muefiuueo nwnuwe me No No oaHH .mo.eoNH osHH cHauma mn an an N.N an an muowwueo “mo.v0mn AN N b NN oe H b NN Nozez NN H N NN be N N mN NaNozooo mm II II . II mm auomeouo 0N " '1 all. mH “0H9 NN II II II NN Nmz II II II oN II II II AH Nozezz Ne N e bN wN m N HH Howmz bN H N NN eN N N AH webNaezz. oe N N NN NN N N NN NuouNHHuuou Henna bN Nm uoNHHHuuoo oz m P b \o4 COMIC IOMION IONIOH IOHIO IONIC IOMION IONIOfl IOHIO NFIOWGH ooaHH mcHa osNH oz cuoo co zIouoNuNz omen NONuueU mANH .mN uonsopmom .moz no coHuonHuuuHo oHNuosa .AH oHoua 7S substantial quantities of nitrate in the unlimed acid soils in the pH range of 4.2 to 4.5 may be due to the presence of acid tolerant strains of Nitrobacter, as reported by Weber and Gainey (1962). However, chemical reactions of nitrous acid in acid soils can pro- duce nitrate spontaneously in the absence of Nitrobacter, as shown in sterile soils by workers cited by Broadbent and Stevenson (1966). Soil Organic Matter in 1975 The content of soil organic matter in any horizon depends partly on what percentage of organic matter decomposes during the year and partly on the annual turnover of crop residues or other vegetation. Qgggnic Matter Levels Organic matter levels in unlimed plots in the plow layer were substantially higher than lbmed plots by a factor of 2 in several treatments (Table 18). This is unexpected since higher yields of corn and soybeans had been maintained over a period of years in limed plots than in unlimed plots of acidifying treatments (Tables 3 and 4). However, Leo et a1. (1959) also reported greater accumulations of organic matter in the acid topsoil than where pH had been raised by lime. This is an indication that the extent of decomposition of vegetative materials had been reduced by unfavorable pH in unlimed plots compared to limed plots. Organic matter declined with depth, as expected, since most of the organic residues in both cultivated and virgin soils are deposited on or incorporated in the surface layer. 76 .AmmImHIOHlKlmIzv ONIONIm e\nd OON .vNA.H x OIowneouo I Heaven oanemuo «senwawusom Hemem o m .umou Noumea mo uneaouasoou eaNH one needs N madman on Nomad one momav mnowueowaome 03» nN oeNHome means muoeuueo nwnuaz on on on «mNH Amo.vomq osHH chuHs on an on on an o.o nsewuueo Amo.vomq m.e m.e N.N N.N m.e b.H Nozez m.e N.N N.N A.o N.N A.H NzNozeeo III III o.o III III m.H fineness: III III N.N III III m.H eons III III H.H III III N.H NNz III III N.N III III N.o Nozezz N.N m.e N.H m.e m.e N.H HoeNz N.N e.o N.N N.N b.c b.H eobNaemz. m.e b.o N.N A.o w.o A.o NuouHHHuuob HNNNN III III N.N III III b.H uoNHHHuuom oz .oNIoN .oNIoH .oHIo .oNIoN .oNIoH .oHIo NAINmNH QBNH oz nwoo no moaHH NoHa whoever canemuo ooms Howuweu Amped .mN Homeownemv weasel ownemso HNom unoowom no uuewuweo nemonuwn mo museums Hesownon .mH eases 77 C:N Ratios and Organic Nitrgggg. Organic-N levels were not affected by treatments at any depth (Table 19). They did decline with depth as expected. Carbonznitrogen ratios in Table 20 were consistently wider in the plow layer of unlimed than in limed plots for all carriers except NaNO and this difference extended into the upper subsoil. The 3: effect of lime was not significant statistically, but the difference in C:N ratio is consistent with the probability that residual organic matter was quantitatively different in limed plots than in those where acidity from N carriers had been allowed to accumulate. Carbonznitrogen ratios tend to become narrower as decomposition proceeds. Thus, the wide C:N ratios in unlimed plots support the earlier inference that decomposition was less complete than at more favorable pH in limed soil. The higher C content of most unlimed, very acid soils suggests that the residual organic matter may have had a higher content of organic acids. The fulvic acid fraction of humus includes compounds which form soluble chelates with polyvalent cations (Allison, 1973). These may have promoted depletion of Ca and Mg in acid soils, as well as downward movement of both basic cations and exchangeable Al. During the formation of soils under natural conditions, fulvic acid complexes with polyvalent cations, such as Ca, Al and Fe, tend to be precipitated in the B horizon. This would account for the wide C:N ratios at 20-30' in unlimed plots of several treatments in Table 19 and of all treatments in limed plots. 78 v + .AMMIwHIOHnMImIzv ONIONIm e\nH oom "HoNNHNuwou Hemem :2 I zIHneoHenM I nemouuNn ownemuor u .uboo summon No uneaouasoow oaNN one nofiwu N magnum ou “ooma one moody mnowueowamme one nw oowamme means muowuHeo nNnuws me be No oaHH amo..oNH oaHH cHsuma on an an an on an muowuueo Amo.voma No.0 No.0 Ac.o No.o No.o HH.o Nozez No.0 No.0 No.o No.0 No.o No.0 NaNozeeo III III No.0 III III cH.o snowmen: III III Ao.o III III No.0 eons III III No.0 III III Ao.o sz III III No.o III III No.0 Nozezz No.0 eo.o oH.o No.o No.o Ao.o Hoezz No.0 No.o No.0 Ho.c No.o No.o wobNaezz. No.0 eo.o No.o No.o eo.o No.o NuoNHHNuuob HNNNN III III No.0 III III No.o aouHHHuuom oz .oNIoN .oNIoH .oHIo .oNIoN .oNIoH .oHIo NAINmNH nomad seam «HHH oz nwoo no nemouuwn ownemuo oops Hewwueo r .mhma .mN Homeownemv nooonudn ownemwo no mnemuweo nemouuNn no nucoumo Hesoween .md ouoee 79 .AmmeHIOHlMImIzv ONIONIm e\nH DON “Heuwawuuom Nemem m .uoou summon an unmseufinoeu oaNH on» umaNu N Nammsn ou Amman one momav mnowueONHome 03D nN ooNHmme oquc nuowuueo nwnuas an on an «HNH Amo.voma oaHH chuHa on on an on an H.@ muemuueo Amo.vamq N.eH H.eH o.N N.b N.HH H.N Nozez N.NH N.m N.b N.bH N.NH e.NH NzNozeeo III III H.b III III w.oH snowmen: III III N.A III III N.NH eons III III A.A III III e.HH Nmz III III A.b III III o.N Nozeez A.bH m.b N.b m.NH H.NH e.NH Hoezz N.NH N.N m.b N.N A.NH N.HH weszemz. N.HH m.A N.b m.NH A.A N.m NuoNNHHuuou Hence III III N.A III III b.N uoNHHHuuou oz .oNIoN .oNIcH .cHIo .oNIoN .oNIoH .oHIo NAINmNH unaHH NoHa oaHH oz cuoo co oHuen nomouuNzanonueo oons weNHweO AmhmH .mN ueoseuoomv oauew nomouuwnunoofieo no mnemuweo nemowudn mo museums Henowmon .ON eases 80 One further inference may be made regarding treatments and horizons with wide C:N ratios in Table 19. Jackson (1963) pointed out that humus carboxyl groups are an important buffer system over the pH range of 5.2 to 6.5 or 7.0. Carboxyl groups would have contributed to increases in potential acidity as soils which received acidifying carriers declined over this pH range during the earlier years of the experiment. When pH increased again into this range after lime was applied, humic and fulvic acids may have contributed to the persistence of potential acidity, as was observed for (NH4)280 and NH4C1. 4 SUMMARY AND CONCLUSIONS Residual effects of 14 annual applications of nitrogen carriers at rates in excess of crop needs (300 lb N/a/yr) have produced a wide range of effects on crop yields, pH, nutrients, inorganic and organic components in the soil. The nitrogen treatments produced effects in 1975 which had continued to develop after the N treatments were discontinued in 1973. Residual acidity of nitrogen carriers, especially ammonium salts, drastically reduced corn and soybean yields over the entire period. Non-acidifying carriers maintained fairly constant stable yields of corn better than the check plots. The devastating effects of acidi- fying carriers on yields of both corn and soybean were corrected by dolomitic lime applied in the seventh and eighth years of the study. It is apparent from the data that the lime should have been applied much earlier, as soon as buffer tests indicated the need. Environmental factors, such as drought, insect and disease build-up, undoubtedly influenced crop yields, especially of soybeans. Other factors, such as Mn and A1 toxicity and Mg deficiency associated with low pH, were probably directly responsible for reducing yields. Soil pH continued to decline with repeated application of acidi- fying carriers without line over the years. The rate of acidification was related to their relative residual acidities (Table l-b). The general rate of decline of pH over time was in the order: (NH ) SO > 4 2 4 NH4C1 > NH NO > urea > ureaform )INH This order is based on changes 4 3 3' 81 82 observed from.year to year and is reflected, also, in the sequence of years when the ”ultimate“ pH of 4.2 was first observed for acidi- fying carriers: (NH4)2804/l962, NH4Cl/l965, NH4NO3/1967, urea and ureaform/1970. Soil pH fluctuated near this limiting level through 1971 and showed only slight tendency to increase by 1975 after annual applications were discontinued in 1973. With NH3, soil pH reached 4.5 in 1970 and this was the limiting value through 1975. Calcium nitrate had little effect on soil pH, but residual basicity from sodium nitrate tended to maintain a pH in the plow layer somewhat higher than in plots which received only basal fertilizer. Soil pH in the subsoil decreased rapidly when the pH of the plow layer was reduced below 5.0. Lime requirements in the plow layer increased rapidly at about pH 5.0 and then increased quickly in subsoil layers. Increase in profile lime requirements greatly exceeded the acidity which could have been produced as residual acidity from N fertilizers. For example, lime requirements to 30” in 1971 (Table 11) were 42.9 T/a fer (NH4)280 and 11.5 T/a for basal fertilizer. The difference 4 between these two treatments is 31.4 T/a, or 62,800 lb. If this is divided by 3900 lb N applied in 13 annual applications (1959 to 1971) the indicated increase in potential acidity is 16 lb. CaCO3 per pound of N applied. This is about 3-fold greater than the accepted equivalent acidity, 5.5 lb. CaCOB/lb. N, for (NH4)ZSO4 (Table 1-b). This greatly accelerated increase in potential acidity below pH 5.0 has been referred to as ”runaway" acidity (welcott, 1964). It is likely that the greater than expected increase in potential acidity at low pH is due to release of hydrogen ions which had 83 accumulated in non-exchangeable polymeric complexes with A1 at pH's above 6.0 before the’experiment started. Release of acidic species of Fe may have been involved also, as evidenced by reddish crusts which formed during dry weather (Wolcott et al., 1965) and greatly increased extractability of Fe in soils below pH 5.0 (Schafer, 1968). Potential acidity which had accumulated before liming in plots which remained extremely acid for the longest periods of time in (NH4)ZSO4 and NH4C1 treatments had not been completely neutralized or displaced from the plow layer into the subsoil by 1975. Residual potential acidity was retained, after liming, at a higher pH in ($182804 plots than where NH4C1 had been used (pH 6.2 32 5.3). This is consistent with retention of sulphuric acid in complexes with exchangeable Al that are more stable than the complexes formed in the presence of Cl- (Jackson, 1963). Effects of nitrogen carriers or lime on the extractability of exchangeable potassium (K), calcium (Ca), and magnesium.(Mg) were dramatic and often statistically significant throughout the lO-year period, despite greatly reduced degrees of freedom for testing sig- nificance after lime was applied on two of the four replications in 1965-66. These effects often progressed rapidly into the subsoil. Effects on available P were less marked than for cations. How- ever, the data indicated that the release of available P was promoted by acidifying carriers. Major increases were for basal fertilizer over no fertilizer. Most of the Bray P phosphorus was retained in 1 the surface soil, which confirms the low mobility of P. However, some increased quantities from basal fertilizer were detected in the subsoil over time. 84 Exchangeable K.was higher in all treatments, including N carriers, that received basal fertilizer than in the no-fertilizer treatment. Higher levels were maintained with NaNO3 than with other carriers. Liming increased retention of exchangeable K. Exchangeable K moved into the subsoil although, in most treatments, greater levels of K were held in the plow layer. Acidifying carriers accelerated the disappearance of exchangeable Ca and Mg from the plow layer in both unlimed and limed plots. In unlimed plots, displacement of these two cations from the profile continued after applications were discontinued so that extreme deple- tion was apparent in the 20 to 30” layer in 1975. Dolomitic lime applied in 1965 and 1966 restored exchangeable Ca to levels observed near the beginning of the experiment and exchangeable Mg to levels 3-fold greater for most treatments. The recovery in exchangeable Hg was significantly less in NH Cl and Ca(NO3)2 plots. This result for 4 Ca(NO3)2 reflects the greater exchange potential of Ca2+ compared with ”92+. In the case of HR Cl, it appeared that Cl- had accelerated 4 downward movement of Mg. It did appear that unspent dolomite was continuing to release Ca and Mg and maintain or increase levels in the plow layer for all treatments through 1975. Ca applied as Ca(NO3)2 accelerated the loss of exchangeable Mg in the profile of both unlimed and limed plots. On the other hand, Na applied as NaNO3 increased the levels of exchangeable K, Ca and Mg, especially in the plow layer. The differences reflect known dif- ferences in replacing power among the four cations in exchange reactions: Ca > Mg > K > Na (Foth and Turk, 1972). Significant differences among carrier anions, such as sulphate (804.), chloride (Cl-) and nitrate (N03), were observed. Effects of 85 carbonate (C03) produced by hydrolysis of urea and ureaform, and effects of hydroxyl from hydrolysis of NH may have influenced 3 patterns of acidification also. Sulphate was more effective in reducing pH initially than the chloride. However, soil pH in chloride plots was less responsive to liming. Disappearance of exchangeable bases (Ca and Mg) was more rapid initially with (NH4)ZSO4 than with NH4C1. Both left more persistent forms of potential acidity than any of the other acidifying carriers. The data support the idea that the sulphate ion forms more stable complexes with A1 at higher pH than those formed in the presence of the chloride ion. Liming did not completely neutralize the potential acidity and that which remained reduced the soil's capacity to retain exchangeable K, Ca and Mg. Levels of mineral nitrogen in the soil in September 1975 indi- cated that nitrification may have been inhibited earlier in the season in unlimed acid soils. Lime applied in 1965 and 1966 continued to release basic components that reduced soil acidity to a favorable level for nitrification to proceed. This was confirmed by the uniformly high levels of nitrate nitrogen in the limed plots.. However, presence of substantial quantities of nitrate nitrogen in very acid unlimed soils indicates the existence of acid tolerant species of Nitrosomonas and Nitrobacter or the production of nitrate from nitrite by other processes occurring spontaneously at acid pH. Organic matter was greater in unlimed acid soils than in limed soils. This was due to higher carbon content, since the organic nitrogen level was fairly uniform for all treatments, unlimed and limed. The resulting wide C:N ratios are indicative of reduced microbial activities that cause decay and important differences in 86 quality of residual humus in acid versus limed soils. Liming pro- moted decay giving lower carbon content with consequent narrow C:N ratios. As expected, organic matter declined with depth in limed and unlimed plots . BIBLIOGRAPHY BIBLIOGRAPHY Alexander, M. 1961. Introduction to Soil.Microbiology. John Wiley and Sons, Inc., New York. . 1965. Nitrification. Ig.w. V. Bartholomew and P. Clark (ed.), Soil Nitrogen,Agronomy Mbhograph 10: 307,347, , Marshall, x. C., and Hirsch, P. 1960. Autotrophy and heterotrophy in nitrification. Trans. Intern. Cong. Soil Sci. 7th Cong. Madison 2: 256-591. Allison, P. B. 1973. Soil organic matter and its role in crop production. 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APPENDICES APPENDIX A HODUNK SERIES The Hodunk series consists of moderately well drained Gray- Brown Podzolic (Ochreptic fragudalf) soils with fragipans which developed on calcareous sandy loam glacial till. Hodunk soils are found in association with the well drained Hillsdale and moderately well drained Elmdale series which also developed on calcareous sandy loam till. Soil Profile: AP im 29 o—r' 7-16" 16-25“ 25-46” Hodunk sandy loam Dark grayish brown (10 YR 4/2) to very dark grayish brown (10 YR_3/2): sandy loam: moderately fine, granular structure: friable when moist and soft when dry: medium content of organic matter: medium to slightly acid: abrupt smooth boundary. 6 to 11 inches thick. Yellowish brown (10 YR 5/4): Pale brown (10 YR 6/3) or light yellowish brown (10 YR 6/4): sandy loam: weak, fine, granular to weak, fine subangular blocky structure: very friable when moist and soft when dry: medium acid: abrupt wavy boundary. 6 to 20 inches thick. Brown (10 YR 5/3) to pale brown (10 YR 6/3): sandy loam to light sandy clay loam: massive to weak, thick, platy structure: firm when moist and brittle when dry: weak to moderately developed fragipan: few thin clay flows: medium to strongly acid: clear wavy boundary. 4 to 12 inches thick. Brown (10 YR 5/3) to yellowish brown (10 YR 5/4) mottled with yellowish brown (10 YR 5/8) and dark brown (7.5 YR 4.4), mottles are common, medium, distinct: sandy clay loam, heavy sandy loam, or light clay loam: few thin clay flows: weak, medium, subangular blocky structure: firm when moist, strongly to medium acid in the upper part and slightly acid 94 95 in the lower part: abrupt irregular boundary. 15' to 30 inches thick. Cg 46"+ Light yellowish brown (10 YR 6/4) to brown (10 YR 5/3) mottled with yellowish brown (10 YR 5/6-5/8), mottles are common, medium, distinct: sandy loam: massive to very weak, coarse, subangular blocky structure: friable when moist and hard when dry: calcareous. Topography: , Gently to moderately sloping till plains and moraines. Drainage and Permeability: Moderately well drained. Surface runoff is slow to moderate. Permeability is moderate to slow depend- ing upon the degree of development of the fragipan. Natural Vegetation: Deciduous forest consisting of sugar maple, beech, oak, and hickories. Source: Schneider et al., 1967. APPENDIX B TOTAL N PROCEDURE 2. Reagents: 1. Concentrated H2804. 2. 10 Normal NaOH solution: a. Prepare N-free flakes in deionized water and allow to stand several days. b. Equip with aspirator bulb and ascarite tube to prevent absorption of C02. 3. Boric acid indicator: a. Heat 1800 m1 of deionized water to boiling to remove CO b. Add 40 g boric acid, stOpper, swirl to dissolve and cool in cold water bath. Add 30 m1 of Fisher's methyl purple indicator. 4. Potassium sulfate-catalyst mixture: a. Mix by grinding 100 g K2S04, 10 g CuSO4°5H20, and 1 g Se. 5. 0.01 N_HZSO4: a. Make up N/lO H SO : 3 m1 conc. H2804 made up to 1:1 with deionized wa er. b. Make up N/lOO H SO4 : 200 m1 N/lO H2804 made up to 2:1 with deionized water. c. Titrate N/100 H SO against primary Standard base (0.05 N_THAM: equivalent wt. = 121.136). 6. 30‘ H O in brown bottle with glass stopper may be needed to rinse soil particles down flask during digestion. 7. Cigarette paper. 8. Indicator. 96 97 Procedure (excluding nitrate): 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. Grind soil sample to pass 32-40 mesh screen. Weigh duplicate samples containing 0.5000 grams on weighed cigarette paper, roll and drop into Kjeldahl flask. Add 2 m1 H20, swirl, allow to stand for 30 minutes. Add 0.8 g K2504 catalyst mixture. Add 2 m1 concentrated H SO , heat cautiously on digestion stand until water is removed and frothing stops. Heat until digest clears (a light green color develops). Continue to boil gently for at least one hour, regulating heat so that the H280 condenses about 1/3 way up the neck of the flask. Allow to cool to touch. Slowly, and with swirling, add 10 ml deionized.water: con- tinue swirling until undissolved.materials are in suspension. Flush out distillation apparatus for 5 minutes with steam to clean and bring it up to temperature. (Teflon stop- cocks should be loosened during warmup to avoid freezing and possible splitting to barrels due to expansion of the teflon.) Add 3 ml of H PO solution to a 25 Erlenmeyer flask which is marked at a volume of 15 m1. Add 1 drop of indicator. Place Erlenmeyer flask under the condenser of the distilla- tion~apparatus so that the tip is about 4 cm above solution. Add 1 m1 of 10 N_NaOH to funnel at start, note height in funnel, then add 10 ml more NaOH. Insert Kjeldahl flask to distillator. Drop 10 m1 of the 10 N NaOH into the flask, close stopcock, open steam system, close steam by-pass. Collect 15 ml of distillate in 3-5 minutes. Remove Erlenmeyer flask. Flush system out. Titrate to first pink color with the 0.01 3.32504: Calculate t N. where T (02!!! 98 % N = (T-B)(N)(l400) 8 ml of sample titration ml of blank titration normality of H SO4 sample wt. in fig. APPENDIX C TOTAL C PROCEDURE Operation: One hundred milligrams of finely ground soil (80 mesh) is weighed into a special ceramic crucible and one scoop (approx. 1 gram) each of Iron Chip and Tin accelerators are added. The crucible is then placed on the combustion table of the induction furnace through which 02 is being passed. As the cycle is started, the sample is combusted at a temperature of over 1670°C, and the Carbon in the sample is oxidized to CO After leaving the induction furnace, the 2. gas mixture is passed through (1) a dust trap to filter out the solid Tin and Iron oxides, (2) a Sulfur trap containing MnO2 to absorb Sulfur gases which may have been oxidized during the combustion of the sample, and (3) a heated catalyst to convert any CO formed to 002. Moisture is removed from the gas mixture before it enters the analyzer by an anhydrone trap. After combustion and passing through the Purification Train, the gas mixture (02 and 002) is passed into a thermal conducting cell housed in a temperature-controlled oven (45°C) in the analyzer. The output of the Thermal Conductivity Cell is read on a special DC digital Vbltmeter as percent carbon (% C). The instrument is calibrated to read a one gram sample. So all readings of 100 mg sample size must be multiplied by 10 to get t C in the soil (Sale, 1970). 99 "mmm“