i thHlHlW‘ W1 “WINNIl W l Egg (IHW REMOTE STORAGE Date 0-7639 er '71.. A ram, nw-fir un‘ . IEO?! o a 4 . f—i‘ (VA '.A P ft m 19- mu. tu-ui-Ia‘frw- .' um.“ I O O E ._ Mafia-v1“ "-u‘ ‘0‘-.- This is to certify that the thesis entitled HoUiow and Soud Tine £660,012 on 30418 smotww and Tu/zfigna/sa Root Gnowth presented by Jame/s A. thphy -. has been accepted towards fulfillment ' , of the requirements for 1.; - M.S. degree in Cltop 8 $041 SC/CQVLCQA owe? ' Major professor Juzg 28, 1986 MS U is an Affirmative Action/Equal Opportunity Institution REMOTE STORAGE R3 F PLACE IN RETURN BOX to remove this checkout from your record. TO AVOID FINES return on or before date due. DATE DUE DATE DUE DATE DUE ‘QI K rm." "fifth 1., U ‘1‘le ,J l 7 I "V “\ 2m 20:: Blue F0RM'§/Date0ueForms_2or7.inad - 99.5 HOLLOW AND SOLID TINE CULTIVATION EFFECTS ON SOIL STRUCTURE AND TURFGRASS ROOT GROWTH By James Arthur Murphy 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 1986 ABS TRACT HOLLOW AND SOLID TINE CULTIVATION EFFECTS ON SOIL STRUCTURE AND TURFGRASS ROOT GROWTH By James Arthur Murphy Hollow and solid tine cultivation effects as influenced by soil compaction and moisture content during cultivation were evaluated on the basis of soil structural qualities and root growth over a 2 year period. As expected compaction resulted in pronounced detrimental effects on soil structure and root growth. Both cultivation methods resulted in positive and negative effects on soil structure. While cultivation increased the amount of large soil pores drained between 0 and -0.001 MPa, a corresponding decrease in the remaining macropores drained between -0.001 and -0.010 MPa occurred in noncompacted soil. Regardless of compaction levels, solid tine cultivation increased the amount of micropores drained between -0.010 and -0.100 MPa compared to hollow tine cultivation. Hater conductivity dropped dramatically with cultivation in noncompacted soil. Cultivation reduced surface soil strength. Initially, solid tine cultivation was more effective in loosening the surface soil than hollow tine cultivation, however this effect was reversed by the end of this study. Cultivation decreased surface rooting in noncompacted soil but had no influence on rooting in compacted soil. Greenhouse studies demonstrated the potential for cultivation to enhance rooting within the tine hole while limiting root development below the tine hole. to my family, especially Carol, for their love, support, and patience ii ACKNOWLEDGEMENTS I wish to express a sincere thanks to Dr. P. E. Rieke, chairman of my guidance committee, for his guidance, support and patience during the good times and bad. I am most grateful to Dr. A. E. Erickson, Dr. B. E. Branham, and Dr. J. M. llargas for their valuable assistance and advice as members of my guidance committee. I also wish to thank Micheal Ferkowicz for his unending perserverance and assistance during this investigation. I would like to thank my fellow graduate students, especially Roch Gaussoin, for their support which made my program most rewarding. Lastly, I would like to acknowledge the United States Golf Association and Michigan Turfgrass Foundation for their finacial support of this investigation. iii TABLE OF CONTENTS Page LIST OF TABLES...................................................... vi INTRODUCTION........................................................ 1 LITERATURE REVIEW................................................... 2 Compaction..................................................... 2 Soil Responses................................................. 2 Shoot Responses................................................ 4 Root Responses................................................. 6 Cultivation.................................................... 9 MATERIALS AND METHODS............................................... 12 Field Study.................................................... 12 Greenhouse Study 1............................................. 15 Greenhouse Study 2............................................. 17 RESULTS AND DISCUSSION.............................................. 19 Bulk Density................................................... 19 Aeration Porosity.............................................. 19 Moisture Retention............................................. 22 Soil Porosity.................................................. 26 Field Water Infiltration Rate.................................. 31 Saturated Hydraulic Conductivity............................... 31 Oxygen Diffusion Rate (ODR).................................... 35 penetromter ReadingSOOOOOOOOOOOOOOOOO...OOOOOOOOOOOOOOOOOOOOOO 37 iv ROOtTngo0000000000000...00000000000000.0000...00000000000000... 41 Greenhouse StUdy 1....OOOOOOOOOOCOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO 43 Greenhouse StUdy 2.00......0....O0..IOOOOOOOOOOOOOOOOO000...... 46 SUMMARYOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO0.0.00000000000000000000000 54 LIST OF REFERENCESOO0.00.0000...0.0.000....0.00000000000000000000000 57 Table 10 11 LIST OF TABLES Page The effects of compaction, cultivation, and soil moisture during cultivation on bulk density and -0.010 MPa aeration pOPOSity in OCtOber, 1984.00.00.00000000000000000000000IOOOOO 20 The effects of compaction, cultivation, and soil moisture during cultivation on bulk density and -0.0lO MPa aeration por051ty in OCtOber, 19850....OI.OOOOOOOOOOOO0.0.0.0.0000...O 21 The effects of compaction, cultivation, and soil moisture during cultivation on moisture retention at O, -0.0lO, -00033, afld '0.100 MPa 1" OCtODEP, 19840000000000...ooooooooo 23 The effects of compaction, cultivation, and soil moisture during cultivation on moisture retention at O, -0.0lO, “00033, afld -0.100 "Pa in OCEDDQP, 198500000.000000000000000o 24 The effects of compaction, cultivation, and soil moisture during cultivation on percent porosity within various moisture potential ranges in October, 1984................... 27 The effects of compaction, cultivation, and soil moisture during cultivation on percent porosity within various moisture potential ranges in October, 1985................... 29 The effects of compaction, cultivation, and soil moisture during cultivation on field infiltration rates and saturated hydraulic conductivity in September and October, PESPQCtTVEIy, Of 1984....0OOOOOOOOOOOOOOOOOOOOOf.0.0.0.0..00O 32 The effects of compaction, cultivation, and soil moisture during cultivation on saturated hydraulic conductivity in OCtOber’ 1985.0...OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO... 33 The effects of compaction, cultivation, and soil moisture during cultivation on ODR at -0.002, -0.003, and -00004 "Pa in OCtOber’ 1984.00.00.000000000000000000000000000 36 The effects of compaction, cultivation, and soil moisture during cultivation on areas under cone index curves at 2.5 cm intervals taken September 3 and 5, 1984............... 38 The effects of compaction, cultivation, and soil moisture during cultivation on areas under cone index curves at 2.5 cm intervals taken November 27, 1985..................... 39 v1 12 13 14 15 16 17 18 19 20 The effects of compaction, cultivation, and soil moisture during cultivation on total root weight and root density in NOVEMber’ 1985.0000000000000000IOOOOOOOOOOOOOOOOOOOOOOOOO. Cultivation effects on root length 14 days following treatment with tines for greenhouse study 1.................. Cultivation effects on root density in various zones of the core outer region 14 days following treatment with tines for greenhouse StUdy 1.0.0.0000000000000.000.00.000...O Cultivation effects on root density in various zones of the core center region 14 days following treatment with tines for greenhouse study 1................................. Cultivation effects on root length 16 days following treatment with tines at two soil moisture conditions for greenhouse StUdy 2.00.0...OOOOOOOOOOOOOOO0.00000000000000 Cultivation effects on root density in various zones of the core outer region 16 days following treatment with tines at two soil moisture conditions for greenhouse StUdy 2......0..0.0...OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO...O Cultivation effects on root density in various zones of the core center region 16 days following treatment with tines at two soil moisture conditions for greenhouse StUdy 2..00...I.OOOOIOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOIOOOO0..O The effect of a 4 hour soil moisture differential prior to treatment on root length fbr greenhouse study 2........... The effect of a 4 hour soil moisture differential prior to treatment on root density in various zones of the core center region for greenhouse study 2......................... vii 42 44 45 45 47 48 49 51 51 INTRODUCTION Most recreational turf areas experience a high frequency of use. Associated with this usage are both vehicular and foot traffic. Either form of traffic can result in soil compaction. Soil compaction can also occur during construction on such sites as golf courses and home lawns. Soil compaction decreases soil porosity with resultant increases in bulk density. As soil porosity decreases, particularly macroporosity, reductions in soil water movement, aeration, and turfgrass shoot and root growth can occur which lower the functional quality of the turf. Few alternatives are available for alleviating the problems associated with compacted soils because significant loosening of the soil cannot be accomplished without major disruption of the turf. Core cultivation, or aerification, is the most widely used practice for improving compacted soil conditions under turf. Core cultivation has traditionally referred to the mechanical removal of soil cores (plugs) from established turf. In recent years, solid tine cultivation has received attention as being a possible practice in combatting soil compaction in turfgrass management. Solid tine cultivation eliminates soil core processing time and labor requirements associated with hollow tine cultivation. However, little is known about the direct effects of solid tine cultivation on soil physical properties and turfgrass root growth. LITERATURE REVIEW Compaction The soil is a medium for plant growth and as such, its structure should not hinder the movement of water, oxygen and nutrients to plant roots. thwfavorable soil structure has the characteristics of increased soil density and decreased aeration which restrict seedling development and root proliferation (Baver et al., 1972). Soil structure can deteriorate in highly trafficked areas. Hillel (1980) described soil compaction as the compression of an unsaturated soil body reducing the soil fractional air volume. The degree to which a soil will compress is a function of the soil moisture content, antecedent bulk density, magnitude of the compactive effbrt and soil texture (Free et al., 1947; Reaves and Nichols, 1955). Forces which compact soil can originate from natural sources such as rainfall and wetting and drying cycles or mechanical sources such as traffic from people and machinery (Harris, 1971). Recreational turf areas are subjected to high usage. With the passage of people and machinery over the same sites soil compaction is an inevitable problem in turfgrass management. Madison (1971) has stated, "compaction is the foremost turf problem." Soil Responses Aeration porosity and bulk density are commonly used measures to characterize soil structure and compaction phenomona. Compactive efforts on a soil can result in decreased soil porosity (Proctor, 1933). A decrease in soil porosity has the associated effects of increased soil density (Tanner and Mamaril, 1959). A reduction in total porosity, as a result of compaction, is generally at the expense of the soil aeration porosity. Aeration porosity refers to those pores not filled with water at a given moisture tension. Swartz and Kardos (1963) observed a decrease in aeration porosity from 19.3% at the lowest level of compaction to 12.7% at the highest level compaction on several sand-soil-peat mixes differing in moisture content at the time of compaction. Capillary porosity increased from 32.2% at the lowest compaction level to 35.7% at the highest level. Water retention characteristics are influenced with alterations of soil porosity. Relative to noncompacted soil, compacted soil will generally retain greater amounts of water at a given soil matric tension as a result of increased microporosity (Baver, 1938; O'Niel and Carrow, 1982; Sills and Carrow, 1982). However, it is possible that both aeration porosity and microporosity can be reduced by compaction thereby reducing water retention at any given matrix suction (Agnew and Carrow, 1985). Alteration of the soil porosity by compaction can influence soil water movement. Baver (1938) demonstrated soil water permeability to be a function of macroporosity; as macroporosity decreased so did water permeability. Swartz and Kardos (1963) found percolation rates decreased substantially with compaction. In their study aeration porosity had a strong positive correlation with percolation rate. Akram and Kemper (1979) found infiltration rates were lowered as compacting forces and/or soil moisture content at compaction increased. Infiltration rates of a loamy sand were reduced from 20 to 0.5 cm M“1 as soil water content was increased from air dry to 1.3 times field capacity at the time of a .339 MPa compacting force. Soil oxygen movement is reduced with compaction. Agnew and Carrow (1985) found oxygen diffusion rates (ODR) in compacted soil remained below the 20 x 10"8 gm cm'2 min"1 value, considered threshold for adequate plant growth, for as long as 143 and 119 hours after irrigation at the 7.5 and 15 cm depths, respectively. Noncompacted soil reached acceptable levels within 26 and 50 hours at the 7.5 and 15 cm depths, respectively. These observations were consistent with the findings of O'Niel and Carrow (1983). Asady et al. (1985) found 00R in a Charity clay at -0.008 MPa soil moisture potential decreased from 49.0 to 10.0 gm cm"2 min"1 as soil density increased from 1.39 to 2.1 g cc‘l. This reduction in ODR also coincided with a decrease in air-filled porosity from 31.0 to 8.0%. Hughes et al. (1966) also observed reduced ODR values with soil compaction. Increases in soil density can increase soil strength. Taylor and Gardner (1963) showed soil strength increased with bulk density and moisture suction. Taylor et al. (1966) demonstrated that soil strength of a loamy sand at -0.033 MPa moisture potential increased from .6 to 1.7 MPa as density rose from 1.55 to 1.8 g cc'1. Others have observed increases in mechanical resistance as soil density increases (Asady et al., 1985; Hughes et al., 1966; Tanner and Mamaril, 1959). Shoot Responses Compaction can reduce turfgrass visual quality (Agnew and Carrow, 1985; O'Niel and Carrow, 1982; Sills and Carrow, 1982). In a field study, Carrow (1980) found a significant positive correlation between visual quality and aeration porosity at -0.010 MPa of Chase silt loam soil for tall fescue (Festuca arundinacea Schreb.) and perennial ryegrass (Lolium perenne L.). A significant positive correlation was also found between visual quality and bulk density for tall fescue, perennial ryegrass and Kentucky bluegrass (Poa pratensis L.). The influence of compaction on turf shoot density, verdure (aerial shoot material remaining after mowing) and percent cover varies among species. Watson (1950) reported increased density of Kentucky bluegrass with compaction in a fairway turf consisting of bentgrass (Agrostis palustris Huds.), red fescue (Festuca rubra L.) and Kentucky bluegrass. In studies conducted on monostands, shoot densities of perennial ryegrass and Kentucky bluegrass have declined under compaction stress (Carrow, 1980; O'Niel and Carrow, 1982; O'Niel and Carrow, 1983). However, shoot densities of tall fescue were not significantly altered by soil compaction stress (Carrow, 1980; Sills and Carrow, 1982). Verdure of Kentucky bluegrass, common bermudagrass (Cynodon dactylon (L.) Pers.) and tall fescue decline with compaction stress (Agnew and Carrow, 1985; Carrow, 1980; O'Niel and Carrow, 1982; Thurman and Porkorny, 1969). In contrast, in another study Sills and Carrow (1982) reported no effect of compaction on verdure of tall fescue. Compaction has had no influence on verdure of perennial ryegrass (Carrow, 1980; O'Niel and Carrow, 1983; Sills and Carrow, 1983). In a field study Carrow (1980) observed the percent cover of mature tall fescue and Kentucky bluegrass turfs were reduced up to 8 months after the last compaction treatment. Perennial ryegrass cover was not affected in this study. Clipping yields decline under compaction stress (Thurman and Pokorny, 1969; Rimmer, 1969; Valoras et al., 1966). O'Niel and Carrow (1983) reported total clipping yields of perennial ryegrass declined 38 and 53% under moderate and heavy compaction, respectively when compared to noncompacted turf. Compaction stress can reduce clipping yields within 8 days on a Kentucky bluegrass stand (Agnew and Carrow, 1985). Schmidt (1980) found spring clipping yields were greater on heavily compacted plots compared to lightly compacted plots. The reverse was true during the summer. Carrow (1980) found total nonstructural carbohydrates (TNC) declined for Kentucky bluegrass, perennial ryegrass and tall fescue as compaction stress was applied. However, subsequent studies have not shown TNC levels to be affected by compaction stress (O'Niel and Carrow, 1982; Sills and Carrow, 1982; Sills and Carrow, 1983). Root Responses Reported effects of compaction on root growth have been somewhat conflicting. Watson (1950) found no compaction effect on root development of a mixed species fairway turf. In a field study utilizing monostands, Carrow (1980) observed declining root growth of Kentucky bluegrass with compaction stress. He also noted perennial ryegrass root growth declined with moderate compaction but was not affected with heavy compaction. The decrease in rooting of perennial ryegrass under moderate compaction was associated with increased tillering. However, tall fescue root growth was not significantly affected with compaction in this study. Sills and Carrow (1982) observed that total root growth of tall fescue was reduced by compaction only when higher nitrogen fertilization rates where used. O'Niel and Carrow (1982) reported no influence of soil compaction on root weight or distribution of a 2 year old Kentucky bluegrass stand. In a greenhouse study O'Niel and Carrow (1983) evaluated perennial ryegrass under compaction stress and observed differences in root distribution although total root growth was not significantly affected. They found a higher percentage of roots in the surface 0 to 5 cm and a lower percentage in the 10 to 25 cm zone. Sills and Carrow (1983) observed a decline in total root growth of perennial ryegrass under compaction stress. The decline was more pronounced at higher nitrogen fertilization rates yielding a 44.6% decrease compared to noncompacted plots. Agnew and Carrow (1985) observed compaction stress over a 99 day period increased root weights in the surface S cm and lowered root weights in the 10 to 20 cm zone. Compaction stress over a 9 day period decreased root weights only in the 15 to 20 cm zone. Total root weights were not significntly affected by the 99 or 9 day compaction treatments. IHlkinson and Duff (1972) compared rooting of annual bluegrass (191 M L.). creeping bentgrass and Kentucky bluegrass at three soil densities under growth chamber conditions and found no differences among species, although root growth significantly increased for all species as soil density increased from 1.1 to 1.4 g cc‘l. They attributed the increase in root growth to increased water availibility at higher densities and the use of a sandy loam soil which prevented soil oxygen from being limiting. Inadequate soil aeration and mechanical impedance are important factors associated with poor root growth in compacted soils. Compaction can produce poor soil aeration. Letey et al. (1966) found common bermudagrass root growth was greatly reduced or stopped by ODR values less than 15 x 10'89 cm'z min-1. An ODR value of 20 x 10'39 cm"2 min'1 was reported to be limiting for Newport Kentucky bluegrass (Letey et al, 1964). Waddington and Baker (1965) found Merion Kentucky bluegrass required 00R values of 5 to 9 x lO'Bg cm'2 min'1 for adequate root growth while creeping bentgrass and goosegrass grew well at ODR values as low as 5 x 10‘8 g cm"2 min‘l. Grable and Siemer (1968) studied the effects of bulk density, aggregate size and soil water suction on oxygen diffusion and corn (Agility: L.) root elongation. Over the range of 0 to 68 cm of water suction they found diffusion of oxygen controlled the rate of root elongation. They noted oxygen diffusion was determined by air porosity and suggested 12 to 15% air porosity was needed for adequate plant growth. Also, root elongation rates tended to decrease at 48 to 68 cm of water suction. Reasons for the decrease were suggested to be due to increased soil strength. Compaction can result in greater mechanical impedance to root growth. No information is available on turfgrass root development in response to mechanical impedance. However, several investigators have evaluated agronomic crop responses to mechanical impedance and were summarized by Lutz (1952). Veihmeyer and Hendrickson (1948) showed the critical density needed to inhibit sunflower (Helianthus annus L.) root growth varied with texture. They found no roots penetrated soil of a 1.9 9 cc‘1 bulk density. The lowest density where-roots failed to penetrate was 1.46 9 CC‘1 for an Aiken clay loam. They concluded roots failed to penetrate soil due to small pore sizes rather than to a reduction in oxygen supply. Wiersum (1957) examined the relationship between size and structural rigidity of pores and root penetration. Roots can enter pore sizes of smaller diameter than the young root itself only if rigidity of the pore structure is weak enough to allow soil displacement. In examining cotton (Gossypium hirsutum L.) taproot penetration as influenced by bulk density, moisture content and soil strength, Taylor and Gardner (1963) found a highly significant negative correlation between soil strength and root penetration into prepared cores; as soil strength increased root penetration declined. They found no root penetration when soil strength was 2.96 MPa as measured by a static penetrometer. In another study Taylor et al. (1966) found cotton taproot penetration decreased drastically as soil strength increased to 2.50 MPa. With higher strength levels no root penetration occurred. Rickman et al. (1966) evaluated tomato (Lycopersicon esculentum L.) root response to oxygen supply and physical resistance. They proposed 00R to be the primary factor in limiting root growth even though the high density - high 00R (artificially maintained) treatment did slow root growth. In a similar study Tackett and Pearson (1964) found mechanical impedance was more detrimental than low oxygen at densities greater than 1.5 g cc’l. At densities lower than 1.5 9 cc"1 oxygen levels below 10% restricted cotton seedling root penetration. However, root restriction was greater with high bulk densities. Cultivation Cultivation is one practice used to combat soil compaction on high use turf sites, such as athletic fields, parks and golf courses. llther management practices used are soil modification and/or traffic control. Turf cultivation refers to the selective tillage of an established turf without excessive disruption of the turf (Beard, 1973). There are several forms of turf cultivation, such as coring, slicing, spiking and deeper subaerification (Turgeon, 1980). The most frequently used method 10 is core cultivation. In particular, the vertical operating tine (VOT) units are used extensively in golf course turf management systems. Core cultivation involves the removal of soil cores from established turf to alleviate problems of soil surface compaction, layering and thatch accumulation. Evidence to support these objectives is limited and somewhat conflicting. Murray and Juska (1977) reported reduced thatch accumulation, reduced leaf spot damage and improved turf quality in a one year cultivation study. Engel and Alderfer (1967) found no significant influence on thatch accumulation, overall turf quality or water penetration from core cultivation over a ten year period. They noted a slight increase in ODR with cultivation. Infiltration rates have increased (Waddington, 1974), decreased (Roberts, 1975) and remaimed unchanged (Byrne, 1965) as a result of coring. Alderfer (1954) reported a significant reduction in runoff on compacted aerified plots when compared to nonaerified plots. However, coring did not increase the clipping yield of the Kentucky bluegrass stand growing on compacted soil. Cordukes (1968) observed enhanced turfgrass recovery from compaction with aerification. In a 2 year field study Petrovic (1979) found core cultivation had little influence on turf quality, soil strength and oxygen diffusion rates. Studies have shown no appreciable increase in turfgrass root development with cultivaton (Engel, 1951; Harper, 1953). Alleviation of soil compaction is often the primary objective of core cultivation, however, destruction of soil structure may occur due to localized soil compaction (Engel, 1970). Petrovic (1979) examined soil density changes caused by penetration of hollow tines into laboratory prepared soil cores. With the use of computed axial ll tomographic (CT) scanning, large bulk density increases in the soil surrounding the coring hole were observed. Under greenhouse conditions, the zone of increased bulk density at the bottom of the coring hole was still evident after 93 days while compaction at the sidewall zone had dissipated due to the walls collapsing. These findings support Engel's (1970) suggestion of the deleterious effect of cultivation on soil structure. Therefore, it is proposed that routine cultivation in turf management programs might lead to induced hardpans below the cultivation zone. Petrovic (1979) also noted that smaller increases in bulk density due to tine penetration occurred in higher density soil. He thereby concluded that higher density soils maybe less suseptible to the compacting effects of core cultivation. Increasing interest has developed regarding the replacement of hollow tines with solid tines in standard cultivation operations. Reasons for the increased popularity of this practice stem from the dramatic savings in time and labor costs. Solid tine cultivation eliminates the need for soil core removal required with the traditional hollow tine practice. However, the response of turf to solid tine cultivation has not been recorded. Therefore, ‘the objectives of this research were to determine the effects of vertically operating hollow and solid tine cultivation on soil structure and turfgrass root growth as influenced by soil compaction and soil moisture at the time of cultivation. 12 MATERIALS AND METHODS Field Study A vertically Operating tine (VOT) cultivation study was initiated in May, 1984 at Michigan State University Robert Hancock Turfgrass Research Center on a 3 year old Penncross creeping bentgrass turf maintained under greens conditions. The soil under this turf was a modified loamy sand containing 83.5% sand, 10.6% silt and 5.9% clay. A 2 x 2 x 2 factorially arranged randomized complete block design was used. One check at each compaction level was also included for comparison. Factors included compaction, tine type and soil moisture at the time of cultivation. Compaction levels were: (i) NC -- noncompacted except for normal maintenance practices and (ii) C = compacted with a Ryan's Rollaire vibrating power roller. Static pressure of the roller when filled with water was 0.52 kg cm'z. Compaction treatment consisted of 6 passes per plot. The two tine types were 1.25 cm 0.0. (i) hollow and (ii) solid tines. (hrktivation was performed with a Ryan's Greensaire II at moisture levels of (i) Moist = an average soil moisture potential of -0.050 MPa and (ii) Wet = -0.003 MPa average moisture potential as measured with tensiometers (Marthaler et al , 1983) placed at the 2.5 to 7.5 cm depth zone (zone of cultivation). All plots were subjected to dry down prior to the moist cultivation treatments. Following moist cultivation treatments irrigation was applied over a 2 to 3 day period to rewet all plots to -0.003 MPa for wet cultivation treatments. In 1984 compaction treatments averaged 6 passes per week May 11 through August 14 totaling 90 passes. One set of cultivation treatments 13 was applied; moist cultivation on August 27 and wet cultivation on August 30. Moisture sampling at the time of cultivation operations yielded an average 7.5 and 19.1% soil moisture content by weight at -0.050 and -0.003 MPa, respectively. In 1985, 32 compaction treatments were performed May 1 through Sept 14 totaling 192 passes. Three sets of cultivation treatments were performed. Moist cultivation treatments were applied on June 4, July 13 and August 14 at average gravimetric moisture contents of 8.8, 9.1 and 9.7 %, respectively. Wet cultivation treatments were applied on June 6, July 15 and August 16 at average gravimetric moisture contents of 21.5, 25.3 and 17.7 %. respectively. Total nitrogen applied was 119.8 kg ha-1 and 130.7 kg ha-1 in 1984 and 1985, respectively. Fungicides were applied as necessary to control disease. Supplemental irrigation was applied as necessary to maintain an average soil moisture above -0.030 MPa except during drydown periods prior to moist cultivation operations. A cutting height of 0.6 cm was maintained throughout the study. Four undisturbed soil cores, 7.6 cm I.D. x 7.6 cm deep were taken per plot fin'laboratory measurements of bulk density, moisture retention, air porosity, saturated hydraulic conductivity and oxygen diffusion rate (ODR) determinations in October of 1984 and 1985. Cores were excavated so that the top of each core began below the bottom of the thatch layer which positioned the bottom of the tine holes at approximately the middle of the core. Moisture retention and air porosity determinations were made at 0, -0.001, -0.010, -0.100 MPa and oven dry (105 C) moisture potentials. Saturated hydraulic conductivity measures were determined using the technique described by Klute (1965). 14 ODR were measured in the labarotory at water potentials of -0.002, -0.003, and -0.004 MPa by the platinum microelectrode method of Lemon and Erickson (1952). Three readings per core were taken at the 3.8 cm depth fOr each tension level. A depth monitoring penetrometer (Davidson, 1965) was used to take 10 readings per plot on September 3, 1984 and November 27, 1985 at sodl moisture potential greater than -0.05 MPa. Infiltration rates were determined in September, 1984 using a constant head double ring infiltrometer technique; 12.7 cm inside ring and 22.9 cm outside ring. Both rings were driven to a 7 cm depth into the soil. A 1.25 cm constant head was maintained in both rings during infiltration runs. Infiltration runs lasted 4 hours and the final 3.5 hours were used to calculate hourly rates. In November 1985 five root samples 4.4 cm2 x 15 cm deep were taken per plot and sectioned at the 7.5 cm depth to form two samples. Samples were washed with the hydro-elutriation system of Smucker et al. (1982), dried at 60 C and weighed. All data were subjected to anlysis of variance and planned comparisons were made using single degree of freedom orthogonal comparisons (Steele and Torie, 1980). In 1984 five contrasts were made evaluating the noncompacted check versus the compacted check (NC-Ck vs CD-Ck), hollow versus solid tine cultivation (T), moist versus wet soil at the time of cultivation (M), tine type by soil moisture interaction (T1x M), and within compacted soil, the check versus the average cultivation effect (CD-Ck vs Cult). In 1985 nine contrasts were planned examing the 3 main effects of no compaction versus compaction (C), hollow versus solid tine 15 cultivaition (T), and moist versus wet soil at the time of cultivation (M), the 4 subsequent interactions C x T, C x M, T x M, and C x T x M, and within each level of compaction the check versus the average cultivaition effect (Ck vs Cult). Greenhouse Study 1 This study, initiated April 30, 1985, was arranged in randomized complete block design with 5 replications. Three treatments consisting of a check (no tine), hollow and solid tine penetration into prepared soil cores. The soil used was a Metea fine sandy loam consisting of 73.0% sand, 18.6% silt, and 8.4% clay. The soil was air dried and passed through a 1 nun sieve. Soil was poured at a moisture content of 1.0% by weight into 10.1 cm 1.0. by 16.5 cm high polyvinyl chloride (PVC) pipe. Container bottoms consisted of filter paper and two layers of cheesecloth held in place with a rubber band. Soil was poured to fill the entire core assembly after which the top 2.5 cm section of core assembly was removed so as to level the soil remaining in the 14.0 cm high core. Soil weights ranged from 1463.5 to 1494.4 9 (air dry) and were blocked according to weight. Cores were then put through two wetting and drying cycles (saturation to -0.1 MPa) after which the soil was compressed with a hydraulic press (Carver type, Model 20505-11) at -0.100 MPa to the required height to achieve a bulk density of 1.65 g cc'l. Sod plugs 10.1 cm diameter by 1.9 cm high were cut from a 3 year old Toronto creeping bentgrass turf and sodded onto saturated soil cores described above. Sod was allowed to root for 7 days into saturated soil 16 cores. Cores were then moved to ceramic plates and a 0.030 MPa tension was maintained for 1 day followed by 2 days at 0.070 MPa tension. Coring treatments were applied on May 9, 1985 at a soil moisture content of 6.8% by weight. Treatments were applied with a gear cutting tool (Gould 8 Eberhardt, Model 6243) which simulated the tine movement of standard VOT cultivation equipment. Hollow and solid tines 1.25 cm 0.0. were used to cultivate sodded cores creating tine holes in the center of each core 7.6 cm deep (5.7 cm into prepared soil). Following treatment all cores were watered with 50 ml of water and returned to ceramic plates at 0.030 MPa tension to permit adequate drainage. Sod was allowed to grow for 14 days with supplemental watering applied as necessary to prevent wilting. Cores were sampled at 2.5 cm intervals from the soil surface to the 10.0 cm depth. within each 2.5 cm section 2 samples were taken. One sample consisted of a 2.5 cm diameter core at the center equidistant fran the edges of the container walls, surrounding the tine hole. The second sample was a 7.6 cm diameter core surrounding and concentric to the 2.5 cm core yielding a doughnut shaped sample. Roots were then separated from the soil using the hydrOpneumatic elutriation technique of Smucker et al. (1982). After washing, the roots of each sample were counted using the line intersect method (Newman, 1966). All data were subjected to analysis of variance and planned comparisons were made using single degree of freedom orthogonal comparisons. Two comparisons were planned contrasting the control (check) versus the average tine effect and hollow versus solid tine penetration. 17 Greenhouse Study 2 This study, initiated on December 22, 1985, was arranged in a randomized complete block design with 4 replications. The three treatments used in study 1 were performed at two differing moisture contents for a total of 6 treatments. The soil used was a Metea fine sandy loam consisting of'73.0% sand, 18.6% silt, and 8.4% clay. The soil was air dried and passed through a 1 mm sieve. Soil was poured at a moisture content of 1.0% by weight into 10.1 cm 1.0. by 19.1 cm high PVC pipe. Container bottoms consisted of filter paper and two layers of cheesecloth held in place with a rubber band. Soil was poured to fill the entire core assembly after which the top 2.5 cm section of core assembly was removed so as to level the soil remaining in the 16.5 cm high core. Soil weights ranged from 1778.8 to 1829.9 9 (air dry) and were blocked according to weight. Cores were then put through two wetting and drying cycles (saturation to -0.070 MPa) after which the soil was compressed with a hydraulic press (Carver type, Model 20505-11) at -0.070 MPa to the required height to achieve a bulk density of 1.65 g cc'l. Sod plugs 10.1 cm diameter by 1.9 cm high were cut from a 4 year old Penncross creeping bentgrass turf and keep moist for "6 days. Sod plugs were then sodded onto saturated soil cores prepared as decribed above. Sodded cores were allowed to root for 8 days and then placed on plates at 0.030 MPa tension for 3 days. Tension was increased to 0.070 MPa for 2 days. Treatments were applied January 3, 1986 using a gear cutting tool (Gould & Eberhardt, Model 6243) and 1.25 cm diameter hollow and solid tines at soil moisture contents of 14.9 (-0.010 MPa) and 7.5% (> -0.070 MPa). Tine holes were made at the center of each core and 7.6 18 cm deep. On January 4 the sod was clipped to 2.5 cm. Cores were watered every three days to -0.010 MPa moisture equivalent. Sixteen days following treatments the experiment was terminated. Cores were sectioned as described previously for root analysis. All data were subjected to analysis of variance and planned comparisons were made using single degree of freedom orthogonal comparisons. Comparisons were planned contrasting moist versus wet soil conditions at the time of tine treatment. Two other contrasts were evaluated within each moisture level comparing the control (check) versus the average tine effect and hollow versus solid tine penetration. 19 RESULTS AND DISCUSSION Bulk Density Bulk density data for 1984 are shown in Table 1. The compacted check had significantly higher bulk density when compared to the noncompacted check in 1984 with compaction increasing density 2.3%. Cultivation resulted in 2.3% lower bulk densities than the compacted check. No differences were observed between individual .100 % Porosity Noncompacted (NC) Check (Ck) 3.2 10.7 5.0 14.5 Compacted (CD) Check 2.9 9.6 4.8 14.8 Hollow Moist 3.4 9.2 6.2 15.3 Hollow Net 3.2 9.5 5.7 14.9 Solid Moist 2.8 9.5 6.2 14.4 Solid Net 2.7 7.7 6.6 16.2 Comparisons Mean Squares NC-Ck vs CD-Ck 0.135 1.927 0.042 0.135 Tine Type (T) 0.963 + 1.763 0.801 0.067 Moisture (M) 0.083 1.763 0.008 1.541 T x M 0.013 3.630 0.608 3.521 * C-Ck vs Cultivation 0.043 1.014 4.320 * 0.368 Error 0.211 2.408 0.582 0.627 * and + denote signifiCance at the .05 and .01 level, repectiveTy. LSD(0.05) (TxM) at > -O.100 MPa =1.4 28 pores drained in the -0.010 to -0.100 MPa range by 28.6%. A significant tine by moisture interaction was observed in the porosity range greater than -0.100 MPa. In this interaction solid tine cultivation under wet soil conditions resulted in a 12.5% increase in the percentage of pores when compared to solid tine cultivation under drier (moist) soil conditions. This moisture effect was not evident with hollow tine cultivation. Pore size distributions for 1985 are shown in Table 6. In 1985 treatment effects on pores drained in the 0 to -0.001 MPa range were more pronounced. Compacted plots resulted in 13.1% lower porosity values compared to noncompacted plots. A highly significant tine effect was also found in this pore size range. Hollow tine cultivation yielded 25.8% greater porosity values than solid tine cultivation across all treatments. Highly significant cultivation effects were also found in this range. Cultivation in noncompacted and compacted soil increased porosity values 46.2 and 43.5% above the respective controls. Thus after 4 sets of cultivation treatments the percentage of very large pores increased with cultivation with hollow tine cultivation being the most effective in producing this response regardless of compaction or soil moisture levels at the time of cultivation. In the -0.001 to -0.010 MPa range (remaining macroporosity) compaction significantly decreased percent porosity 18.8% below noncompacted plots. Cultivation also influenced porosity in this range when performed in noncompacted soil. Porosity was reduced 12.4% with cultivation when compared to the control. This effect was not apparent in compacted soil conditions. Thus after 2 years of cultivation macroporosity has been altered with cultivation. Cultivation, 29 Table 6. The effects of compaction, cultivation, and soil moisture during cultivation on percent porosity within various moisture potential ranges in October, 1985. Moisture Potential Range (-MPa) Treatments 0-.001 .001-.010 .010-.100 > .100 % Porosity Noncompacted (NC) Check (Ck) 2.6 12.9 4.9 14.0 Hollow Moist 4.4 11.4 4.8 14.7 Hollow Net 4.1 11.3 4.8 15.0 Solid Moist 3.1 11.0 5.1 14.6 Solid Net 3.4 11.5 4.8 14.9 Compacted (CD) Check 2.3 9.7 5.0 14.8 Hollow Moist 3.6 10.4 4.4 14.6 Hollow Net 3.5 9.7 4.7 15.2 Solid Moist 2.9 9.0 4.9 15.1 Solid Net 3.0 8.4 5.3 15.5 Comparisons Mean Squares Compaction (C) 1.408 ** 34.992 ** 0.000 1.083 Tine Type (T) 3.920 ** 3.010 0.844 ** 0.135 Moisture (M) 0.010 0.304 0.120 1.042 C x T 0.220 2.600 0.260 0.375 C x M 0.004 1.170 0.350 + 0.042 T x H 0.260 0.220 0.010 0.002 C x T x M 0.050 0.094 0.050 0.002 NC-Ck vs Cultivation 3.361 ** 6.208 0.000 1.473 CD-Ck vs Cultivation 2.282 ** 0.294 0.104 0.216 Error 0.157 1.362 0.097 0.447 **, * and’+ significant at the .01, .05, and .10 TeveT, respectively. 30 particularly with hollow tines, increased the amount of very large voids. However, in noncompacted soil a loss of pores in the -0.001 to -0.010 MPa range coincided with the increase of very large voids in the 0 to -0.001 MPa range. A highly significant tine effect was found in the -0.010 to -0.100 MPa range with solid tine cultivation resulting in a 6.4% increase over hollow tine cultivation across both levels of compaction and soil moisture. Also noted in this range was a compaction by moisture interaction (P<.10). This trend indicated that micropores in this range were found in greater quantity when cultivation in compacted soils was performed under wet soil conditons. This effect was not found in noncompacted soils suggesting soil moisture content during cultivation may be more of a concern in compacted soils. The only effect on porosity in the range greater than -0.100 MPa was a trend (P<0.09) with cultivation in noncompacted soil increasing porosity 6.5% above the check. Cultivation influenced soil porosity both positively and negatively. Nhile the amount of larger pores between 0 and -0.001 MPa were increased with cultivation a decrease in the remaining macropores (-0.001 to -0.010 MPa) occurred with cultivation in noncompacted soil. Soil porosity data also show that hollow tine cultivation is more effective in increasing the amount of large pores between 0 and -0.001 MPa while solid tine cultivation is most effective in increasing the amount of finer pores between -0.010 and -0.100 MPa. 31 Field Nater Infiltration Rate Data and analysis for water infiltraton rates in September of 1984 are shown in Table 7. Interestingly, compaction had no significant effect on field infiltration rates. No significant differences were found due to the type of tine used in cultivation, although cultivation under wet conditions significantly reduced water infiltration rates by 38% when compared to cultivation under moist soil conditions. Saturated Hydraulic Conductivity Data and comparisons for 1984 water conductivity rates are presented in Table 7. Compaction had the only significant effect on conductivity in 1984 with the compacted check yielding a 50% lower water conductivity rate than the noncompacted check. No significant differences were observed between individual cultivation treatments. Data and analysis for 1985 saturated water conductivity are presented in Table 8. In 1985 compaction resulted in a 42.7% reduction in water conductivity below the noncompacted plots. A significant reduction in conductivity due to cultivation was found in noncompacted soil. Cultivation reduced water conductivity 37.7% below the noncompacted check. A similar effect was apparent in compacted soil with cultivation decreasing conductivity 40.0% below the check. However, this effect was only significant at the 8.4% level. These data indicate cultivation has a negative effect on subsurface water flow most likely due to localized compaction (reduced pore size) at the lower end of the cultivation zone. Even though macroporosity can be increased with cultivation the continuity of these large voids at the bottom of the cultivation zone is most likely interrupted by localized areas of 32 Table 7. The effects of compaction, cultivation, and soil moisture during cultivation on field infiltration rates and saturated hydraulic conductivity in September and October, respectively, of 1984. Parameter Field' Saturated Treatments Infiltration Conductivity cm hr'1 Noncompacted (NC) Check (Ck) 3.0 4.8 Compacted (CD) Check 2.3 2.4 Hollow Moist 2.3 3.1 Hollow Net ' 1.8 3.2 Solid Moist 2.5 3.1 Solid Net 1.2 1.8 Comparisons Mean Squares NC-Ck vs CD-Ck 0.602 8.640 * Tine Type (T) 0.083 1.267 Moisture (M) 2.163 * 1.141 T x H 0.563 1.541 CD-Ck vs Cultivation 0.3841 0.308 Error 0.391 1.633 ‘ significance at the .05 Tevel. 33 Table 8. The effects of compaction, cultivation, and soil moisture during cultivation on saturated hydraulic conductivity in October, 1985. Saturated Hydraulic Conductivity Treatments cm hr‘1 Noncompacted (NC) Check (Ck) 5.1 Hollow Moist 3.6 Hollow Net 3.3 Solid Moist 2.9 Solid Net 2.9 Compacted (CD) Check 3.0 Hollow Moist 2.1 Hollow Net 1.9 Solid Moist 2.1 Solid Net 1.1 Comparisons Mean Squares Compaction (C) 16.725 ** Tine Type (T) 1.402 Moisture (M) 0.807 C x T 0.060 C x M 0.375 T X M 0.107 C x T x M 0.375 NC-Ck vs Cultivation 9.362 ** CD-Ck vs Cultivation 3.313 + Error 0.994 ** and’+ signifiCant at the .01, and .10 levéT, respectiveTy. 34 reduced pore size. Nelson and Baver (1940) observed this effect on percolation rates in soil cores prepared with various sand separates. No differences could be attributed to individual cultivation methods. All cultivation treatments on compacted plots resulted in decreased hydraulic conductivity in 1985 when compared to 1984 while untreated plots increased or remained unchanged. It should be noted that the solid tine wet soil cultivation treatment had reached a conductivity rate (1.8 cm hr‘l) classed as moderately slow (Davidson, 1965) in 1984 and continued to decline in 1985 to 1.1 cm hr'l. The fact that cultivation effects were only found in 1985 suggest that the possible detrimental effects of cultivation (induced hardpan) require several treatment applications before any measurable effects develop. Therefore, long term study of these effects would be more meaningful. 35 Oxygen Diffusion Rate (ODR) Due to the fact that uniform soil moisture was difficult to maintain in the field ODR measurements were obtained in the laboratory at moisture potentials of -0.002, -0.003, and-0.004 MPa. 00R readings were made at the 3.8 cm depth in 7.6 1.0. by 7.6 cm high cores. A significant difference in ODR was found only at -0.003 MPa. Cultivation resulted in 35.6% lower ODR when compared to the compacted check plot. Although this reduction in ODR is large the reduced levels were not below values considered limiting to plant growth. However this data again indicates cultivation can have a negative effect on soil structure in the lower region of the cultivation zone. ODR decreases as soil density increases (Asady et al., 1985). The fact that 00R is not limiting below the -0.003 MPa moisture potential suggests that reduced oxygen supply would not be of great concern in restricting root growth in this soil, particularly in the surface 7.6 cm. Moisture potentials on this site rarely remain at such high moisture potentials longer than 12 hours following heavy rainfall or irrigation. 36 Table 9. The effects of compaction, cultivation, and soil moisture during cultivation on ODR at -0.002, -0.003, and -0.004 MPa in October, 1984. Moisture Potential (-MPa) Treatments 0.002 0.003 0.004 gm x 10"8 cm'2 min“1 Noncompacted (NC) Check (Ck) 8.8 42.9 75.8 Compacted (CD) Check 4.5 47.5 83.1 Hollow Moist 3.2 30.6 80.2 Hollow Net 3.6 32.5 77.9 Solid Moist 4.4 36.3 83.4 Solid Net 3.5 23.0 73.9 Comparisons Mean Squares NC-Ck vs C-Ck 27.74 29.48 80.67 Tine Type (T) 0.85 11.21 0.33 Moisture (M) 0.27 98.61 104.43 T x M 1.33 171.76 38.88 CD-Ck vs Cultivation 1.73 670.67 ** 43.35 Error 9.15 67.38 61.77 ** significant at the :01 level. 37 Penetrometer Readings The applied force required to press the penetrometer cone into the soil is referred to as the cone index. Quantitative information on soil compactness can be obtained from cone index readings taken at desired depth intervals which yield plots of cone index curves. Areas under each cone index curve at 2.5 cm depth intervals were measured for all treatments to the 15 cm depth in 1984 and 1985 and are presented in Tables 10 and 11, respectively. Compaction significantly increased areas under the curve (soil strength) at all depth zones in 1984 and 1985. In 1984, cultivation decreased soil strength in both compacted and noncompacted soil. However, the depth of this effect ended in the 7.5 to 10 cm zone in noncompacted soil while cultivation in compacted soil influenced penetration resistance as deep as the 10 to 12.5 cm zone. The type of tine used in cultivation influenced soil strength in the 2.5 to 5 and 5 to 7.5 cm depth zones in 1984. Solid tine cultivation was more effective than hollow tine cultivation in reducing soil strength in this zone. This response could be seen visually immediately following treatment. Solid tine treated plots showed considerably more surface disruption (heaving) than hollow tine coring indicating greater displacement or loosening of the soil. In 1985 cultivation again reduced soil strength. However, cultivation effects in noncompacted soil were only significant in the 2.5 to 5.0 cm zone. Cultivation in compacted soil reduced soil strength only to the 7.5 to 10 cm depth zone. Interestingly, 1985 data suggest continued cultivation has a reduced ability to lower soil strength at 38 Table 10. The effects of compaction, cultivation, and soil moisture during cultivation on areas under cone index curves at 2.5 cm intervals taken September 3 and 5, 1984. Depth Intervals (cm) 0-2.5 2.5-5.0 5.0-7.5 7.5-10 10-12.5 12.5-15 Treatments area (cm?) Noncompacted (NC) Check (Ck) 0.431 1.230 1.810 2.298 2.735 3.091 Hollow Mbist 0.396 1.092 1.465 1.896 2.557 3.085 Hollow Net 0.385 1.063 1.402 1.758 2.367 2.948 Solid Moist 0.314 0.850 1.184 1.684 2.431 2.994 Solid Net 0.350 0.971 1.293 1.695 2.396 2.999 Compacted (CD) Check 0.592 1.643 2.362 2.896 3.407 3.425 Hollow Moist. 0.419 1.103 1.500 2.086 2.907 3.465 Hollow Net 0.402 1.052 1.414 1.948 2.724 3.292 Solid Moist 0.355 0.943 1.362 2.011 2.844 3.454 Solid Net 0.402 1.069 1.402 1.839 2.563 3.137 Comparisons Mean Sguares Compaction (C) 0.025 ** 0.109 ** 0.235 ** 0.629 ** 1.151 ** 0.822 * Tine Type (T) 0.013. 0.085 * 0.109 * 0.079 0.039 0.016 Moisture (M) 0.001 0.010 0.000 0.072 0.178 0.145 C x T 0.001 0.013 0.022 0.003 0.006 0.006 C x H 0.000 0.000 0.003 0.013 0.022 0.048 T x M 0.005 0.040 0.033 0.005 0.001 0.000 C x T 0.000 0.000 0.001 0.013 0.024 0.031 NC-Ck vs Cult 0.012 *' 0.133 **' 0.539 **' 0.700 **' 0.213 0.017 CD-Ck vs Cult 0.094 ** 0.868 ** 2.131 ** 2.054 ** 1.008 ** 0.018 Error 0.003 0.012 0.019 0.040 0.064 0.114 'Cilt'denotes cultivatiOn. ** and * significant at the .01, and .05 level, respectively. 39 Table 11. The effects of compaction, cultivation, and soil moisture during cultivation on areas under cone index curves at 2.5 cm intervals taken November 27, 1985. Depth Intervals (cm) 0-2.5 2.5-5.0 5.0-7.5 7.5-10 10-12.5 12.5-15 Treatments area (cmz) Noncompacted (NC) Check (Ck) 0.379 1.276 1.977 2.402 2.856 3.218 Hollow Moist 0.305» 0.879 1.385 2.075 2.815 3.327 Hollow Net 0.293 0.914 1.488 2.218 3.028 3.585 Solid Moist 0.328 1.069 1.839 2.568 3.172 3.585 Solid Net 0.333 1.051 1.580 2.166 2.925' 3.091 Compacted (CD) Check 0.672 2.178 3.350 3.919 4.275 4.482 Hollow Moist 0.402 1.264 2.126 3.057 3.838 4.269 Hollow Net 0.362 1.143 1.982 2.930 3.735 4.195 Solid Moist 0.425 1.425 2.459 3.281 3.884 4.309 Solid Net 0.534 1.701 2.701 3.522 4.183 4.505 Comparisons Mean Squares Compaction (C) 0.172 "1.909 ** 5.674 ** 8.364 ** 7.864 ** 7.360 ** Tine Type (T) 0.025 * 0.410 ** 0.957 ** 0.594 0.209 0.005 Moisture (M) 0.001 0.011 0.001 0.008 0.010 0.005 C x T 0.007 0.057 0.096 0.053 0.022 0.129 C x M 0.002 0.007 0.024 0.052 0.020 0.048 T x M 0.010 0.045 0.000 0.012 0.001 0.087 C x T x M 0.007 0.075 0.209 0.313 0.279 0.392 NC-Ck vs Cult 0.010 0.212 * 0.391 0.051 0.040 0.077 CD-Ck vs Cult 0.140 **1.516 ** 2.559 ** 1.249 ** 0.320 0.063 Error 0.005 0.034 0.094 0.153 0.165 0.194 Tilt denotes cultivatiOn. ** and * significant at the .01, and .05 level, respectively. 40 deeper regions, particularly in noncompacted soil. This could be a result of cultivation building soil strength at the lower regions of the cultivation zone. Petrovic (1979) demonstrated the compactive effect of hollow tine coring at the lower end of the cultivation zone. Tine differences were reversed in 1985 with solid tine cultivation producing significantly greater soil strength than hollow tine cultivation in the 0 to 2.5, 2.5 to 5.0, and 5.0 to 7.5 cm depth zones. One reason for this reversal can be attributed to the time penetrometer readings were taken. Readings in 1984 were taken approximately 1 week following treatment while 1985 readings were taken approximately 15 weeks after the last cultivation treatment. During this extended period in 1985 two sets of compaction treatments were applied. Any soil loosening wdth solid tine cultivation most likely resettled by the time penetrometer readings were taken in 1985. Opposite tine effects in 1984 and 1985 suggest although solid tine cultivation can be very effective in initially loosening the soil surface this response may not be as long lived as hollow tine cultivation. 41 Rooting Root samples taken in November 1985 (ten weeks following last cultivation) show compaction reduced total root weights by 12.7% when compared to noncompacted plots (Table 12). Root densities were reduced in both the 0 to 7.5 and 7.5 to 15 cm zones by compaction. Sills and Carrow (1983) observed total root weights and root weight in all soil zones declined with compaction f0r perennial ryegrass. Cultivation in noncompacted soil reduced total root weight 15.6% compared to the check. Root density data show reductions in rooting due to cultivation occurred primarily in the 0 to 7.5 cm zone with cultivation reducing root density 16.2% below the check in noncompacted soil. This cultivation effect was not apparent in compacted soil. Reasons for reduced surface rooting with cultivation can be attributed to removal and/or destruction during the cultivation operation. Interestingly, cultivation in compacted soil does not show this type of response. Cultivation may have a more positive effect in compacted soil than in noncompacted. Soil porosity data (Table 6) showed cultivation in both compacted and noncompacted soil increased the percentage of very large voids (0 to -0.001 MPa moisture potential range). However, cultivation in noncompacted soil decreased the percentage of the remaining macropores (-0.001 to -0.010 MPa range). Areas of penetrometer cone index curves demonstrated the degree to which soil strength was reduced with cultivation was greater in compacted soil than noncompacted soil (Table 11). 42 Table 12. The effects of compaction, cultivation, and soil moisture during cultivation on total root weight and root density in November, 1985. Treatments Noncompacted (NC) Check (Ck) Hollow Moist Hollow Net Solid Moist Solid Net Compacted (CD) Check Hollow Moist Hollow Net Solid Moist Solid Net Comparisons Compaction (C) Tine Type (T) Moisture (M) C x T n-an XXX #33 x M NC-Ck vs Cultivation CD-Ck vs Cultivation Error Total Root Height Root Density 0.705 cm 705-1500 cm mg dm"2 mg dm'3 8100 930 130 6990 810 110 6610 750 120 6600 750 120 7140 800 140 6240 740 84 5890 680 93 6940 800 110 5550 630 96 6340 740 95 Mean Squaresa 60.43 ** 61020.3 * 5824.13 ** 2.37 5046.0 54.00 15.05 18704.2 580.17 4.38 3952.7 580.17 10.64 18928.2 6.00 1.64 3750.0 66.67 5.11 5890.7 280.17 38.24 * 57660.0 * 303.75 0.10 1288.1 522.15 6.93 11263.0 171.74 ** and *lEignifiCant at the .01, and .05level, respectiVéTy. a-Total root weight mean squares adjusted x 10'5. 43 Greenhouse Study 1 Root development was examined at eight locations within each core consisting of two regions (outer and center) surrounding the coring hole and within each region, four depth zones at 2.5 cm intervals. The center region was a 2.5 cm diameter core taken surrounding and concentric to the tine hole. The outer region was 7.6 cm in diameter surrounding the center region sample yielding a doughnut shaped sample. The outside edge of this outer region sample was 1.25 cm from the core wall to avoid edge effects. Total root length of the entire core was not significantly affected 14 days following treatment with tines (Table 13). However, root length of the outer region was significantly reduced 11.0% by treatment with tines. Nithin this outer region root density decreased in the 0 to 2.5 cm and 2.5 to 5.0 cm depth zones by 11.6 and 12.0%. respectively, as a result of treatment with tines compared to the check (Table 14). Reduced root development in the region outside the coring- hole may be a result of root injury incurred during treatment with tines. Considerable heaving of the soil surface can occur with cultivation. This disruption of the soil could damage roots and would be a concern in weakly rooted turf. Root length of the center region of the core was not significantly altered by treatment except in the 5.0 to 7.5 cm zone where root density was increased 41.1% by treatment with tines (Table 15). Conversely, in the center region root density at the 7.5 to 10.0 cm zone (P<.10) decreased under treatment with tines. These responses show coring soil with either hollow of solid tines can increase root density within the tine hole while root development below the tine hole can be reduced. 44 Table 13. Cultivation effects on root length 14 days following treatment with tines for greenhouse study 1. Location Entire Outside Center Treatments Core Region Region meters Check 51.55 41.67 9.88 Hollow 49.88 36.92 12.66 Solid 48.52 37.23 11.29 Comparisons Mean Squares Check vs Tines 20.82 70.20 * 14.56 Hollow vs Solid 2.80 0.25 4.71 Error 16.16 6.81 5.34 * significance at .85Tevel. 45 Table 14. Cultivation effects on root density in various zones of the core outer region 14 days following treatment with tines for greenhouse study 1. Depth Zones (cm) Treatments 0'205 2.5‘500 5.0-705 7.5-1000 km m'3 Check 1.64 1.21 0.74 0.46 Hollow 1.41 1.08 0.68 0.41 Solid 1.49 1.05 0.71 0.36 Comparisons Mean Squares Check vs Tines 0.115 ** 0.071 ** 0.006 0.019 Hollow vs Solid 0.014 0.003 0.003 0.007 Error 0.008 0.006 0.005 0.013 5* significance at the .OlleveT. Table 15. Cultivation effects on root density in various zones of the core center region 14 days following treatment with tines for greenhouse study 1. Depth Zones (cm) Treatments 0'205 205-500 500-705 705'1000 km 10'3 Check 2.75 2.40 1.57 1.01 Hollow 3.75 3.14 2.15 0.77 Solid 3.24 2.87 2.28 0.36 Comparisons Mean Squares Check vs Tines 1.870 1.244 1.387 * 0.663 + Hollow vs Solid 0.650 0.182 0.042 0.424 Error 0.733 0.461 0.201 0.146 * and + significance at the .05 andl.10ilevel, respectively. 46 Greenhouse Stugy 2 In the second greenhouse study total root length of the entire core was not significantly affected 16 days following treatment with tines (Table 16). However, there was a tendency for the solid tine treatment to decrease total root length compared to the hollow treatment under moist soil conditions (P<0.09). Treatment influences on root length in the outer region were less significant in this study. Under wet soil conditions treatment with both tines reduced root length (P<0.08) in the outer region 8.3% when compared to the check. Under drier (moist) soil conditions the solid tine treatment reduced root development 9.9% compared to the hollow tine treatment (P<0.08). Root length of the center region was unaffected by treatment with tines. However, a significant moisture effect was unexpectedly found with wet soil yielding 10.6% greater root length than moist soil. To achieve appropriate soil moisture contents prior to treatment a 2 hour period was allowed for thorough rewetting of the soil in wet coring treatment cores. Another 2 hour span was required for treatment application. During this time of differing soil moisture, rooting in the moist (drier) soil may have been restricted due to moisture stress and/or greater mechanical impedance. Noting the lower root densities found within the outer region (Table 17) as compared to the center region (Table 18) the potential for greater moisture extraction may have resulted in a moisture gradient within the core with the center being drier than the outer region. This would be an explanation for no moisture effect in the outer region. Two extra cores per replication, one at each moisture level, were 47 Table 16. Cultivation effects on root length 16 days following . treatment with tines at two soil moisture conditions for greenhouse study 2. Location Entire Outside Center Treatments Core Region Region meters Check 95.14 82.20 12.34 Moist Hollow 98.40 84.65 13.75 Solid 88.94 76.29 12.65 Check 100.69 86.76 13.93 Net Hollow 93.97 79.29 14.68 Solid 93.91 79.69 14.22 Comparisons Mean Squares Moist vs Net 24.75 2.67 11.166 * Nithin Moist Soil Check vs Tines 5.77 14.40 1.938 Hollow vs Solid 179.08 + 139.86 + 2.420 Nithin Net Soil Check vs Tines 121.50 141.14 + 0.735 Hollow vs Solid 0.01 0.32 0.414 Error 52.65 38.70 2.331 tand? significance at .05 and .10 level, respectively 48 Table 17. Cultivation effects on root density in various zones of the core outer region 16 days following treatment with tines at two soil moisture conditions for greenhouse study 2. Treatments Check Moist Hollow Solid Check Net Hollow Solid Comparisons Moist vs Net Nithin Moist Soil Check vs Tines Hollow vs Solid Nithin Net Soil Check vs Tines Hollow vs Solid Error Depth Zones (cm) 0-205 205-500 500-705 705-1000 km m'3 3.14 1.98 1.66 1.26 2.95 2.11 1.82 1.36 2.65 2.10 1.58 1.09 3.08 2.12 1.79 1.45 2.91 2.03 1.64 1.13 2.77 2.11 1.64 1.23 Mean Squares 0.000 0.004 0.000 0.007 0.311 + 0.039 0.004 0.004 0.171 0.000 0.120 + 0.143 * 0.152 0.006 0.060 0.191 ** 0.041 0.014 0.000 0.020 0.075 0.042 0.032 0.020 **, * andl+ signifitance at‘the .01, .05 and .10"level, respeétivély Table 18. Cultivation effects on root density in various zones of the core center region 16 days following treatment with tines at two soil moisture conditions for greenhouse study 2. Treatments Check Moist Hollow Solid Check Net Hollow Solid Comparisons Moist vs Net Nithin Moist Soil Check vs Tines Hollow vs Solid Nithin Net Soil Check vs Tines Hollow vs Solid Error Depth Zones(cm9 0‘205 205-500 500-705 705-1000 3.35 2.54 2.06 1.63 3.98 3.31 1.96 1.40 3.81 3.02 1.73 1.24 3.89 2.85 2.11 1.95 3.93 3.58 2.43 1.44 3.89 3.38 2.15 1.61 Mean Squares 0.226 0.574 0.589 0.350 * 0.796 1.058 0.123 0.246 + 0.063 0.168 0.106 0.050 0.001 1.054 0.083 0.482 * 0.003 0.082 0.154 0.054 0.299 0.378 0.237 0.068 * and + significance at the7705’and.10 level, respectively 50 included to evaluate the extent of rooting at the time of treatment. Root samples (Table 19) taken at this time also showed the moisture (effect with drier (moist) soil conditions resulting in 17.4% lower root length within the center region than wet soil conditions, significant at the 5.6% level. Nithin the center region root density was mainly influenced in the 2.5 to 5 cm depth zone with wet soil conditions yielding 36.9% greater root density (Table 20). Breakdown of the outer region root density into four 2.5 cm depth intervals is presented in Table 17. The effect of treatment with tines in the upper two zones was less evident relative to the first greenhouse study. There was only a tendency (P<0.06) for treatment with tines to reduce root development in the 0 to 2.5 cm depth zone under moist soil conditions. Quite possibly better rooting prior to treatment provided resistance to physical injury suggested to cause reduced root development in the first study. Better rooting would inhibit the heaving (disruptive) action caused during tine penetration by holding the soil in place thereby reducing damage to roots. Initial root samples from the two extra cores were taken on the same day of treatment application to evaluate the degree of rooting prior to treatment. Initial counts indicate that sod had rooted to approximately the same degree before treatment in study 2 as had been achieved at the conclusion of study 1 (Tables 19-20 and 13-15). A response not observed in the first greenhouse study, showed root density was significantly reduced in the 7.5 to 10.0 cm depth zone of the outer region by treatment with tines. In wet soil root density was lowered 18.6% by treatment with tines. In drier (moist) soil the solid tine treatment resulted in 19.9% lower root density than the hollow tine 51 Table 19. The effect of a 4 hour soil moisture differential prior to treatment on root length for greenhouse study 2. Location Entire Outer Center Treatment Core Region Region meters Moist 43.23 37.38 5.85 Net 49.12 42.04 7.08 Comparison Mean Squares Moist vs Net 69.50 43.52 3.026 + Error 23.84 27.41 0.331 + significance at .fU:levél, Table 20. The effect of a 4 hour soil moisture differential prior to treatment on root density in various zones of the core center region for greenhouse study 2. Depth Zones (cm) Treatments 0-205 205-500 500-705 705-1000 km 10'3 Moist 2.21 1.03 .77 .53 Net 2.69 1.41 .84 .55 Comparison Mean Squares Moist vs Net 0.466 0.293 * 0.008 0.001 Error 0.103 0.028 0.013 0.002 * signifiCance at the .O5ilevel, 52 treatment. Root densities of the center region at 2.5 cm depth intervals are shown in Table 18. Significant differences in root density were found only in the 7.5 to 10 cm depth zone. In this zone treatment with tines under wet soil conditions reduced root density 21.8% below the check. A similar trend was noted in drier (moist) soil (P<0.08). Reduced root development below the tine hole may be a result of physical injury to the roots or soil compaction incurred during tine penetration restricting subsequent root growth. Petrovic (1979) demonstrated the compactive effects of hollow tines and noted compaction below the tine hole was longer lasting than the sidewall compaction. Soil compaction (reduced pore size) in the lower region of the cultivation zone could inhibit root penetration due to increased mechanical resistance and/or aeration restriction. Model equations of Gerard et al. (1982) show that soil strength accounted for 64 and 65% of the variability in cotton seedling root growth. Another possible reason could be that root redevelopment after treatment has not yet reached this depth and therefore would only be a temporary effect. These responses suggest although tine holes formed during cultivation can increase root development within the tine hole, rooting below the zone of tine penetration can be inhibited. Over a period of years one could postulate these root responses to cultivation practices would lead to a redistribution of the root system limiting roots to the upper part of the soil. It would be important in future studies to evaluate the longevity of the responses shown here. Another point to be made about these two greenhouse studies involves the obvious root density gradient within the soil cores. In 53 future studies it would be desirable to use larger diameter cores in order to avoid this gradient in root density which could possibly have an effect on root responses. It would also be important to account for such a condition when sampling for root distribution. SUMMARY It is evident that both compaction and cultivation effects have continued to develop through the 2 years of this field study. Interpretation of these results should take into account that the responses found in this short term study may be enhanced with long term treatment. As one might expect, compaction resulted in pronounced detrimental effects on soil structure. Nhile cultivation yielded positive effects on some soil structural properties, some undesirable responses to cultivation were found as well. By the end of this investigation hollow tine cultivation reduced soil density and increased aeration porosity while solid tine cultivation showed no advantage to hollow tine cultivation when compared in these measures. Soil porosity measurements indicated cultivation increased the amount of very large voids drained between 0 and -0.001 MPa in the soil, with hollow tine cultivation being more effective than solid tine cultivation. Associated with this increase in large voids was a reducticui of the remaining macropores drained between -0.001 and -0.010 MPa with cultivation in noncompacted soil, a phenomenon not observed in compacted soil. Solid tine cultivation resulted in a greater amount of micropores between -0.010 and -0.100 MPa compared to hollow tine cultivation regardless of soil compaction and moisture levels. Based on the earlier findings of Petrovic (1979) it is suggested that the 54 55 increase in macroporosity occurs in the upper region of the cultivation zone, i.e. tine holes, while the decrease in remaining macroporosity in noncompacted soil and the increase in the amount of finer pores with solid tine usage resides at the lower end of the cultivation zone» ‘The results of hydraulic conductivity and 00R measurements in this study support this conclusion. Conductivity rates dropped dramatically as a result of cultivation, particularily in noncompacted soil. This effect was not as consistent in compacted soil and supports the idea of the compactive effect of cultivation having less influence in compacted soil, at least short term. Soil moisture content during cultivation initially affected responses to cultivation, especially solid tine cultivation. However, the influence of soil moisture after 4 cultivation treatments was apparently negligible on the soil utilized in this study. Penetrometer data in 1985 suggest cultivation in noncompacted soil developed greater soil strength in the region below the cultivation zone when compared to 1984 data. Initially, solid tine cultivation was more effective in loosening the surface soil than hollow tine cultivation, however this effect was reversed by the end of the study. Root sampling in November, 1985 found rooting declined with cultivation in noncompacted soil and had no effect on root mass in compacted soil. Greenhouse studies demonstrated short term root response to "cultivation“ increased rooting within the soil immediately surrounding tine holes, however, rooting was consistentTy'nwfibited below the depth of tine penetration. Further studies are warranted to determine the potential of cultivation to enhance and/or limit root development within and below the cultivation zone. 56 Based on the bulk density, soil porosity and soil strength responses to solid tine cultivation this practice cannot be considered as effective as hollow tine cultivation in relieving soil surface compaction. However, solid tine cultivation can decrease surface soil strength and increase the amount of large pores within the zone of cultivation. Nith this in mind, solid tine cultivation could be seen as an effective tool for short term relief of surface compaction. It is cautioned that the long term effects of solid tine use on a frequent basis is still to be determined. LIST OF REFERENCES LIST OF REFERENCES Agnew, M. L., and R. N. Carrow. 1985. Soil compaction and moisture stress preconditioning in Kentucky bluegrss. I. Soil aeration, water use and root responses. Agron. J. 77:872-878. Akram, Mohd., and N. 0. Kemper. 1979. 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Rooting of Poa annua L., Poa pratensis L., and A rostis plasturis Huds. at three soil bfiTk- densities. Agron. J. 54:55-58. IV. L RARIES ll «NW 7271 nIcwIan STRTE UN llI\Iillilllllllllllllllllllll 31293106