Soil and maize response to plow and no-tillage after alfalfa-to-maize
conversion on a clay loam soil in New York
U. Karunatilake, H.M. van Es
*, R.R. Schindelbeck
Department of Crop and Soil Sciences, Cornell University, Ithaca, NY 14853-1901, USA
Received 10 March 1999; received in revised form 11 January 2000; accepted 27 January 2000
Abstract
No-tillage in association with row crop production is generally believed to be poorly adapted to ®ne-textured soils, especially in temperate humid climates. The relative success of conservation tillage may be impacted by changes in soil structure. The objective of this study is to evaluate the performance of reduced tillage systems after rotation from a perennial sod crop. An experiment involving spring and fall moldboard plow till (PT), no-till (NT)/zone till (ZT), and ridge till (RT) under maize (Zea maysL.) production following alfalfa (Medicago sativaL.) was conducted on a Kingsbury clay loam soil (Gleyic Luvisol) in Northern New York. Soil water content, strength and temperature, plant height, leaf area and number, leaf, stem and root biomass, and root distribution were measured during the 1992 and 1993 growing seasons for spring PT and NT, while from 1994 to 1999 only yield measurements were made. Tillage in 1992 occurred under adequately dry conditions, but in 1993 under partially plastic consistency state, resulting in an underconsolidated plow layer. Soil water contents were generally higher for NT than PT in 1992, but equal in 1993. Root proliferation was good in the subsoil although soil strengths were generally above the 2 MPa level, suggesting that penetrometer measurements are not a good indicator of rooting potential in a well-structured soil. Soil strength was higher in both years under NT, and under both tillage treatments was negatively related to soil water content, except in the surface layer where soil penetrability appears mostly affected by aggregate arrangement. NT recorded higher plant heights, leaf area index and leaf numbers in 1993, while PT recorded higher per plant leaf area, stem and root biomass. Roots were generally more abundant under PT than NT at all depths, and were reduced in traf®cked inter-row areas. Maize yield was signi®cantly higher under PT in 1992, but similar to NT in 1993. Further yield data from 1994 to 1999 indicate that reduced tillage systems can perform equally or better compared to fall PT on this soil type. Spring PT generally yields lower than fall PT, NT/ZT, and RT. In general, long-term use of reduced tillage systems is economical on well-structured clay loam soils if adequate consideration is given to maintaining soil structure. # 2000 Elsevier Science B.V. All rights reserved.
Keywords:No-tillage; Zone tillage; Ridge tillage; Roots; Soil compaction; Soil quality; Clay loam; Maize
1. Introduction
Perennial crops are generally considered to improve soil structure and may help prevent land degradation. Conversion to conventional annual row cropping, *Corresponding author. Tel.:1-607-255-5629;
fax:1-607-255-6143.
E-mail address: [email protected] (H.M. van Es)
however, may degrade soil structure, and thereby negatively affect soil physical processes, crop growth potential and yield (Unger, 1975; Hermawan and Cameron, 1993). Use of conservation tillage is gen-erally believed to reduce these negative aspects of row crop production by maintaining soil structure and limiting erosion. The speci®c effects of conservation tillage practices on soil properties may nevertheless be contradictory due to variations in soil and environ-mental conditions. For example, yield differences between conventional and conservation tillage are known to vary greatly among soil types with ®ne-textured soils generally being less suitable for reduced and no-tillage (Cox et al., 1990a). Some researchers reported higher soil strength under conservation til-lage than under conventional (plow) tiltil-lage (e.g., Douglas, 1986; Braim et al., 1992; Horne et al., 1992), while others reported no differences, or even the opposite pattern (Mielke et al., 1984; Packer et al., 1984). A need for more site-speci®c tillage research is therefore warranted for the proper management of soils at any location. Generally, conventionally tilled soils tend to have lower water contents than no-tilled plots for shallower depths, as higher macroporosity and low residue levels increase atmospheric water losses (Unger and Fulton, 1990). Also, inadequate aeration generally persists longer during wet periods with untilled soils as they may not have suf®cient drainable porosity from an inadequate volume of macropores (although this may also occur in soils that received intensive secondary tillage and packing). Soil strength measured as penetration resistance has been correlated with root penetrability (Chaney et al., 1985; Braim et al., 1992; Liebig et al., 1993). It can be measured easily, rapidly, and inexpensively and is widely used for assessment of tillage effects on the rooting environment. Soil strength increases with higher soil bulk density and lower water potential (Douglas, 1986). Hill (1990) found 2±5 times higher penetration resistances within the 0.16 m depth under continuous no-till cultivation compared to conven-tional plow tillage. This ratio became smaller with the drying of soil although the absolute differences in strength increased. Reports of penetration resistances under conservation tillage that are the same or lower than under conventional tillage (e.g., Mielke et al., 1984; Packer et al., 1984; Simmons and Cassel, 1989; Hermawan and Cameron, 1993) usually involved
structurally unstable soils in which tillage increased dispersion, disaggregation and settling after heavy rainfall.
Delayed early growth of maize under conservation tillage compared to conventional tillage may be caused by higher mechanical impedance (Hughes et al., 1992). Braim et al. (1992) reported a depression in ®nal barley (Hordeum spp.) shoot mass by 20% under direct drilling and 10% under shallow cultiva-tion compared to convencultiva-tional tillage. Carefoot et al. (1990) reported cereal grain yields in a semi-arid region under no-tillage to be greater than those under conventional till on medium and ®ne-textured soils but not on coarse-textured soils. Conversely, Cox et al. (1990a) in a humid region reported better adaptability of reduced and no-tillage systems to coarse-textured soils, especially during wet years. Hughes et al. (1992) observed a 22% forage yield reduction in maize grown under no-till compared to conventional till in drier years, but not during wet years. In general, the relative success of reduced and no-tillage systems in the North Central and Northeastern USA is strongly affected by weather and soil type, with ®ne-textured and poorly drained soils generally posing the greatest challenge to their adoption (Johnson and Lowery, 1985; Grif®th et al., 1986; Lal et al., 1989; Cox et al., 1990b). It is postulated that this apparent lack of adaptability of reduced tillage is in part related to soil structural problems. The objectives of this study were to evaluate the effects of conventional and reduced tillage on soil physical behavior (water content, temperature, and strength), and maize response (root distribution, shoot growth, and yield) on a clay loam soil after conversion from a perennial sod crop, and to determine the longer-term effects of these tillage practices on crop yield.
2. Materials and methods
2.1. Experimental site
The experiment was conducted at the Cornell Uni-versity Experimental Farm at Willsboro, NY (44.228N, 73.268W). The soil at the site is a Kingsbury clay loam (Gleyic Luvisol, FAO; ®ne, illitic, mesic, Aeric Ochraqualf, USDA) with 400±600 g kgÿ1
Drainage at the experimental site has been improved with subsurface drains at 0.91 m depth and 18.3 m spacing. The site was under alfalfa sod for 5 years prior to this study.
A spatially balanced randomized complete block design (van Es and van Es, 1993) with four replicates was used for allocation of treatments to plots. The experimental design was based on four tillage treat-ments, no-tillage (NT), spring plow tillage (PT), fall PT, and ridge tillage (RT). Only two treatments, spring PT and NT, were used for intensive measurements during 1992 and 1993 as they represent extremes in terms of soil disturbance. The tillage experiment was continued from 1994 to 1999, but only yield measure-ments were made. The plots were 27.518.3 m2 in
size. Alfalfa was sprayed with glyphosate in the fall of 1991 and again immediately after planting in 1992. Moldboard plowing was performed to a depth of 20 cm in PT plots using a four-bottom moldboard plow on 21 May 1992 and 25 May 1993. Secondary tillage was performed on the same dates using offset double disks. Plots were disked a second time on the following day in 1993 to ameliorate cloddy seedbed conditions.
Maize (variety Pioneer 3751) was planted on 21 May 1992 and 26 May 1993 at 0.76 m row spacing and target populations of 68 000 seeds haÿ1
using a four-row Buffalo planter (Fleischer Manufacturing, Lin-coln, NE). The average depth of seed placement was 0.05 m. Fertilizer and herbicide applications were based on Cornell University recommendations and were identical for all tillage treatments. No nutrient de®ciencies or pest pressure was observed during the course of the experiment. Planting and harvesting were performed using four-row equipment with con-trolled traf®c. Ridges were built in late spring on RT plots using a Buffalo ridger-cultivator. Starting in 1995, the NT plots were converted to zone tillage (ZT) using a four-row Kinze zone-tillage planter (Kinze Manufacturing, Williamsburg, IA). It includes three ¯uted coulter blades and spider row cleaners to create a 15 cm wide and 10 cm deep loosened and residue-free strip around the plant row.
2.2. Weather and soil measurements
Precipitation and maximum and minimum tempera-tures were measured daily at an automated weather
station (located within 200 m from the research site) managed by the Northeast Regional Climate Center (Ithaca, NY). In both years, instruments for soil measurements were installed in the fourth and ®fth non-traf®cked inter-row from the plot border within 5 days of planting. Soil water content was measured at 0.15 m depth increments to a depth of 1.2 m using a ®eld-calibrated neutron moisture gauge (Model 503DR Hydroprobe, Campbell Paci®c Nuclear, Mar-tinez, CA). Custom-made thermistors were installed at 0.02, 0.05, 0.10, 0.15. 0.20, 0.30, 0.45, and 0.75 m depths. Digital multimeter (Radio Shack, Fort Worth, TX) readings were converted to soil temperature using individual calibration curves for each thermistor. Soil water content and temperature measurements were made in each plot during the growing season from May to October at 2-day intervals during the early part of the growing season, and less frequently during the latter part. Penetrometer measurements were taken for every 0.035 m increment to a depth of 0.49 m using a digital recording Bush soil penetrometer (Findley Irvine, Penicuik, Scotland) with a 308angle, 12 mm diameter cone. Four measurements were made in the non-traf®cked inter-rows and in the row zones in each plot. Measurements were made seven times during the season in both years and converted to cone index values (Cassel, 1983). Estimates for 0.15, 0.30 and 0.45 m depths were obtained by averaging three readings obtained from the nearest depths for each, and were used for comparison with soil water content estimates from the neutron moisture gauge.
2.3. Plant measurements
measuring leaf length from the base to the tip and leaf width at the widest place for the same ®ve plants and on the same dates as the plant height measurements. A factor to convert length and width measurements to actual leaf areas was developed at the beginning of the season from leaf measurements of 30 plants. Leaf area index (LAI) was estimated by dividing leaf areas by the equivalent surface area for each plant at the measurement location. Plant biomass was determined by cutting above-ground plant parts from ®ve plants per plot. The leaves and stems were determined separately for 23, 32, 39, 51, 60, 70 and 77 DAT after drying at 658C for 4 days.
Root weight was determined for 26, 36, 42, 53, 66, 74 and 81 DAT by excavating the entire root system and surrounding soil down to 1 m, for the same ®ve plants used for shoot weight measurements. Root and soil material were saturated for 2±3 days prior to washing with the use of a low pressure water jet. Oven dry weight was determined after drying at 658C for 4 days. The trench pro®le method (BoÈhm, 1979) was used to map root distributions in two replicates at 45 and 85 DAT. Trenches were dug perpendicular to maize rows to include the planting row, non-traf®cked inter-row, and traf®cked inter-row positions. Trench walls (2 m width1 m depth) were leveled and washed, and a plastic sheet and 55 cm2iron mesh grid were ®xed onto the wall. Visible roots were marked on the plastic sheet.
Maize grain yield for each plot was determined by harvesting ears from each of ®ve rows of 6.1 m length. Water content of a subsample of 20 ears was used to adjust plant grain yields to 15.5% moisture.
Analyses of variance were performed using the SAS GLM procedure (SAS Institute, 1985). Error mean squares were estimated based on repeated measure-ments in both time and space. The data were analyzed as from a series of experiments as described by Cochran and Cox (1957). The SAS VARCOMP procedure was used to estimate variance components and proper error mean square values. The method suggested by Satterthwaite (1946) was used to obtain approximations toF-values. Duncan's multiple range test and least signi®cant differences were carried out to compare means. Unless indicated otherwise, statistical signi®cance was based on the a0.05 error level.
3. Results and discussion
3.1. Soil aggregation
The 1993 growing season (1 May±30 September) was slightly warmer than 1992, with average tem-peratures of 18.5 and 17.28C, respectively. The 1992 and 1993 growing seasons received 272.5 and 255.3 mm rainfall, respectively (Fig. 1) compared to an estimated 30-year mean growing season rainfall of 390 mm. In 1992, only 6 mm was received during the 10-day period prior to tillage compared to 28 mm in 1993. In 1993, tillage was delayed by 5 days compared to 1992 due to wetter soil conditions. In 1992, tillage of the killed alfalfa sod occurred under friable soil consistency and resulted in a seedbed with coarse angular aggregates of 10±20 mm diameter. In 1993, soil aggregates in the surface layer had reduced to 3 mm size (unpublished data) and were also affected by compaction and smearing due to tillage when the lower part of the plow layer had plastic consistency. For the PT treatment, disking was therefore performed twice for seedbed preparation in 1993 to address underconsolidation problems, compared to only once
in 1992. Most differences in measured soil properties between 1992 and 1993 were related to different soil aggregate size distributions, apparently as a result of these varying soil water and consistency conditions at the time of tillage.
3.2. Soil water
NT had consistently higher soil water contents (expressed here as depth equivalent, i.e., volumetric water contentsoil layer thickness) for 0.075±
0.675 m depth in 1992 (Fig. 2). Signi®cant differences (a0.05) were only recorded for 0.075±0.225 m depth
interval (25 out of 46 measurement dates), where differences in aggregate arrangement between PT and NT were greatest. This may be explained for the surface horizon by a higher volume fraction of large pores providing greater gravitational drainage under PT compared to NT (Coote and
Malcolm-McGovern, 1989; Hayhoe et al., 1993). In addition, higher surface residue cover for NT than PT (78 and 17%, respectively) may have contributed to wetter soil at shallower depths, as also measured by Nyborg and Malhi (1989). Ohiri and Ezumah (1990) reported increased soil drying rates and decreased water con-tents after tillage due to vapor movement being enhanced by increased macroporosity within the plo-wed layer. This process likely played a major role in the plow layer in this study because the coarse aggre-gate arrangement resulting from tillage promoted penetration of air currents into inter-aggregate cav-ities. Total pro®le water content under NT was con-sistently higher than under PT, although these differences were only signi®cant for 12 out of 46 measurement dates (Fig. 2).
In contrast to 1992, the water contents in 1993 (Fig. 3) did not show differences between tillage treatments at individual measurement depths nor for
Fig. 2. Soil water content in 1992 for PT and NT by depth interval and days after tillage (*indicates dates with signi®cant differences ata0.05).
the total pro®le. The measurements in 1993 were for a shorter time period and may not have been suf®cient to observe differences in water uptake later in the season. Apparently, higher surface residue cover under NT was not very effective in conserving soil moisture.
Drying patterns of deeper soil layers during a growing season generally follow the root growth pattern (Hamblin, 1982). In both years, soil water at depths between 0.225 and 0.825 m decreased by the end of the season. Drying was initiated at 0.225± 0.375, 0.375±0.525, 0.525±0.675 and 0.675± 0.825 m depths on 73, 75, 78 and 90 days after tillage (DAT) in 1992 (Fig. 2) and 48, 53, 57 and 70 DAT in 1993 (Fig. 3), respectively. A similar pattern of soil drying was measured for PT and NT in 1992 above 0.525 m, (Figs. 2 and 3), but soil water extraction at 0.525±0.675 and 0.675±0.825 m depth intervals was higher under PT than NT after 90 DAT, indicating deeper and more active root growth. Under both treatments, however, apparent root activity was mini-mal below 0.675 m depth, especially in 1993.
The estimated pro®le water losses during drying periods in both 1992 and 1993 (Table 1) showed similar water extraction for NT and PT in the early season (21±33 DAT in 1992 and 29±46 DAT in 1993). In the absence of well-developed root systems at this time, soil evaporation is considered to have been the dominant process of water loss and higher surface residue cover for NT was apparently less important in reducing evaporation. The pro®le water loss under PT was signi®cantly higher in the latter part of the season
(76±103 DAT) in 1992, presumably due to water uptake resulting from a more extensive root system (Fig. 2). In contrast, a drying period between 49 and 56 DAT in 1993 did not show signi®cant tillage treatment differences in root water uptake (Fig. 3), although it may have been too early in the season to show root growth differences.
3.3. Soil temperature
Soil temperature data (Figs. 4 and 5) generally show equal or higher values at shallow depths for the NT than the PT treatment. These were signi®cant in 1992 for 32 out of 50 and 18 out of 50 measurement dates for the 0.02 and 0.05 m depths, respectively, and in 1993 for 2 out of 45 and 3 out of 45 dates at the 0.02 and 0.05 m depth, respectively. This is generally in contradiction to results by others from similar climates (e.g., Wall and Stobbe, 1983; Carefoot et al., 1990; Cox et al., 1990a), who reported lower soil tempera-tures for NT. In our study, soil temperatempera-tures were measured at daily intervals during the early part of the morning. At that time, higher soil temperatures may occur under NT due to the insulating effect of surface
Table 1
Estimated pro®le water losses from 0.075 to 1.125 m depth during soil drying periods
Year Days after tillage
Tillage Profile water loss (mm)
1992 21±33 Plow till 13.2aa
No-till 14.2a 76±103 Plow till 35.8a No-till 30.2b
1993 29±46 Plow till 15.8a
No-till 16.9a 49±56 Plow till 23.8a No-till 25.7a
aValues with same letter in a column are not signi®cantly
different between tillage treatments within each drying period at
a0.05.
residue during cooler nights. In addition, enhanced air circulation in the coarsely aggregated surface layer under PT may also have increased night-time soil cooling (Wierenga et al., 1982). The soil temperature data in this study have not been made with suf®cient temporal frequencies to evaluate the diurnal ¯uctua-tions, which are essential to relate them to crop growth.
3.4. Soil strength
Tillage can affect soil strength in various ways (Cassel et al., 1995). Fig. 6 depicts penetrometer-measured soil strength (averaged for row and non-traf®cked inter-row positions) as a function of soil water content for multiple measurement dates. The general trend was an increase in soil strength as the season progressed and the soil dried out. At 0.15 m, soil strength values were below the 2 MPa critical level above which root growth is generally considered to be slow (Taylor and Ratliff, 1969; Bengough and Mullins, 1990) for most of the growing season. Only
the NT treatment recorded values above this level during the middle and latter part of the season. For the 0.30 and 0.45 m depths, soil strength values for both tillage treatments were generally above the 2 MPa level, except during wet periods of the early 1993 season. Pikul et al. (1993) showed soil strength in the surface layer under NT exceeding that under PT by about 1 MPa in a poorly aggregated soil. In our study, soil strength differences between tillage treatments were smaller, which may be attributed to the large number of failure zones in the well-aggregated soil. Also, higher water contents in NT may have masked tillage-induced differences (Hill, 1990). Positional effects (row vs. inter-row) were generally non-signi®cant.
Although soil strengths above 2 MPa are generally considered to be the limit for root growth, Warnaars and Eavis (1972) reported that not to be the case for soils with a high degree of structural development and where roots can explore weaker failure planes between aggregates. This is supported by the data on soil water content and root distribution in this study which showed active root exploration in the subsoil despite high strengths.
Fig. 5. Soil temperature in 1993 for PT and NT by depth interval and days after tillage.
The soil-strength±water-content relationship (Fig. 6) of a soil may change subsequent to tillage due to soil settling resulting from wetting and drying cycles. Douglas (1986) reported well-de®ned relation-ships (r2>0.9) between soil strength and water content at undisturbed, deeper depths, but very erratic patterns for shallower, disturbed depths under both plowed and fallow conditions in a well-structured soil. In our study, well-de®ned negative relationships between soil strength and water content were observed for undisturbed depths (0.30 and 0.45 m) in both seasons and also for the 0.15 m depth in 1993 when the soil structural elements were more consolidated than in 1992 (Fig. 6 and Table 2). Apparently, the wetness± strength relation at the 0.15 m depth in 1992 was poorly de®ned despite wide ranges in water contents. This is presumably the result of penetration resistance being primarily de®ned by the frictional forces between individual aggregates (as the soil yields to the penetrometer force by moving aggregates), rather than the cohesive forces exerted by intra-aggregate water menisci (which provide most of the strength to aggregates). An analysis of covariance showed that only a small fraction (10%) of tillage-induced differences in soil strength could be explained by variable soil wetness, compared to 96% as reported by Weaich et al. (1992). In both years, soil strength
at the 0.15 m depth increased from the ®rst to the second measurement date despite increasing water contents, suggesting soil settling. Besides post-tillage soil consolidation, the non-unique relationship bet-ween water content and soil strength may be the result of hysteresis, because soil strength within aggregates is physically related to cohesive forces associated with soil water potential rather than to soil water content, as de®ned by Coulomb's equation. It is also notable that the wetness±strength relationship is better de®ned and has higher r2values for 1993 than 1992 due to observations from a wider range of soil water condi-tions (Fig. 6 and Table 2).
3.5. Maize growth and yield
Plant density at 32 DAT in 1993 was signi®cantly higher under NT than PT (66 193 and 57 559 plants haÿ1
), which is dissimilar to results of several other studies (e.g., Wall and Stobbe, 1983; Schneider and Gupta, 1985). This may be attributed to low moisture levels (from increased air circulation) and poor seed± soil contact in the cloddy surface layer under PT.
NT generally maintained higher plant heights in 1993 than PT throughout the season, although this was only signi®cant during the early part of the season (Table 3). Higher plant heights of maize under NT compared to PT is inconsistent with many other research efforts. Arora et al. (1991) reported that better plant growth of NT maize occurred only in coarse-textured soils as a result of modi®ed root growth. In this study, higher water losses from increased air circulation in the cloddy seedbeds under PT may be responsible for lower plant growth in the early grow-ing season. The maximum difference in plant height between tillage treatments occurred at 35 DAT when plant height under NT was 60% greater than that under PT. This coincided with the low amount of rainfall received during the period immediately before mea-surements (<1 mm for the period 28±33 DAT).
LAI is an indicator of growth and photosynthetic potential of a plant. LAI under PT was lower than that under NT during the entire 1993 growing season, although relative differences decreased toward the end of the season (Table 3). The initially higher leaf growth under NT is inconsistent with work of Swan et al. (1987) and Cox et al. (1990b). One possible explanation for this discrepancy is that the plants
Table 2
Relationship between soil strength (y in MPa) and soil water content (xin m3mÿ3) using the modelyabx
Year Depth Tillage Model parameters r2
a b
1992 0.15 Plow till 1.29 0.48 0.002nsa
No-till 1.49 0.42 0.001nsa
0.30 Plow till 4.02 ÿ4.98 0.058nsa
No-till 12.67 ÿ28.62 0.416***
0.45 Plow till 5.21 ÿ8.16 0.158*
No-till 11.37 ÿ24.66 0.273***
1993 0.15 Plow till 7.59 ÿ18.45 0.589*** No-till 7.79 ÿ17.71 0.443***
0.30 Plow till 21.18 ÿ53.77 0.794***
No-till 13.33 ÿ31.71 0.431***
0.45 Plow till 13.33 ÿ46.58 0.368***
No-till 22.14 ÿ55.84 0.636***
aNon-signi®cant. *Signi®cant at
a0.1.
under NT had an initial advantage of higher leaf numbers as a result of earlier seedling emergence from better seedbed conditions.
The per-hectare leaf biomass (Table 3) also was generally higher under NT for most of the season as a result of higher plant densities and higher growth rates. A large increase in leaf weight occurred in both treatments at 65 DAT, which was an indication of increased vegetative growth before entering the repro-ductive stage (78±82 DAT). The stem biomass was also generally higher for NT for most of the season. The highest rate of stem weight increase occurred after 70 DAT, just before silking, apparently as a result of cell differentiation for ear production. Braim et al. (1992) reported that lags in early growth and lower plant populations lead to a lower leaf-plus-stem bio-mass in maize. In this context, it is likely that higher
plant numbers and higher initial growth under NT were responsible for higher leaf and stem biomass.
Differences in root dry biomass between PT and NT were generally non-signi®cant (Table 4). The numer-ous failure zones associated with this well-structured soil presumably helped overcome higher soil strength measured by the soil penetrometer. The 1993 distribu-tion of root density, as measured using the trench pro®le method, showed no difference between tillage treatments at 45 DAT, but signi®cantly increased rooting for PT at 85 DAT (Table 5). Much of the treatment difference in root density is accounted for by the inter-row positions where PT shows higher num-bers for both traf®cked and non-traf®cked positions. In all, PT showed higher root density vertically and laterally from the planting row, especially at 85 DAT. This apparently did not result in a difference in root
Table 3
Maize growth indicators for different dates in 1993
Measurement Tillage Days after tillage
23 29 35 42 50 55 68 83
Plant height (m) Plow till 0.027ba 0.049b 0.085b 0.149b 0.270b 0.408a 1.148a 1.843a
No-till 0.039a 0.074a 0.136a 0.185a 0.319a 0.424a 1.193a 1.804a
Leaf number (per plant) Plow till 1.3b 2.4b 3.9a 5.1a 6.3a 6.9a 9.9a 11.8a
No-till 1.9a 3.0a 4.1a 4.9a 5.9a 6.6a 10.2a 11.9a
Leaf area index Plow till 0.006b 0.017b 0.064b 0.183b 0.502b 0.833a 2.377a 2.699a No-till 0.012a 0.036a 0.091a 0.246a 0.604a 0.937a 2.602a 2.869a
22 31 38 50 59 69 76
Leaf biomass (kg haÿ1) Plow till 5.75a 40.29a 97.73a 1442.9b 1339.6a 2765.3b 3017.6a
No-till 7.08a 48.92a 96.18a 1573.7a 1245.5a 3201.3a 3098.4a
Stem biomass (kg hÿ1) Plow till 0.65a 6.59a 38.91a 1186.0b 1896.2a 1854.0a 4714.7a
No-till 0.75a 7.20a 51.59a 1333.6a 1969.1a 2192.9a 4805.7a
aValues followed by the same letter in a column are not signi®cantly different between tillage treatments for a plant growth indicator at
a0.05.
Table 4
Maize root biomass for different dates in 1993
Measurement Tillage Days after tillage
25 35 41 52 65 73 80
Root biomass (kg haÿ1) Plow till 3.02aa 12.89a 35.97a 210.67a 505.17a 940.4a 1237.7a
No-till 3.48a 13.77a 34.02a 244.09a 475.33a 1110.6a 1277.4a
water uptake between the tillage treatments as mea-sured in the row position in 1993 although such a pattern was observed in the previous year (Figs. 2 and 3). Root counts in the traf®cked inter-row position were signi®cantly lower than those in the non-traf-®cked areas. PT generally showed greater in¯uence of ®eld traf®c on root distribution. Voorhees' (1992) suggestion that traf®cked positions produce less roots at shallower depth, but more at greater depth is not supported by these results.
Crop yield under a tillage system is the integrated effect of changes in soil properties and associated
plant response. Signi®cant differences in crop yields were observed in 1992 (10.07 and 9.00 Mg haÿ1
for PT and NT, respectively; Table 6) but not for 1993 (9.14 and 9.16 Mg haÿ1
for PT and NT, respectively). The higher yield for PT in 1992 may in part be related to higher root water uptake (Fig. 2 and Table 1).
This study was continued for all four tillage treat-ments without the intensive soil and crop measure-ments from 1994 to 1999, with NT converted to ZT in 1995, and with the maintenance of strictly controlled traf®c. Average yields were 7.67 Mg haÿ1
for RT, 7.26 Mg haÿ1
for NT/ZT, 7.22 Mg haÿ1
for fall PT, and 6.42 Mg haÿ1
for spring PT (Table 6). This cor-roborates the notion of the longer-term suitability of this soil type for row crop production under RT and NT/ZT when using controlled traf®c, and the problems associated with spring tillage due to dif®culties with obtaining a suitable seedbed in most years due to its high plasticity (Gerard, 1987). Considering the higher cost of production and energy use combined with lower yields for the PT systems, this soil management approach is not recommended for this soil type. The highest average yield under the RT system suggests that surface shaping improves the performance of reduced tillage systems on these soils, as was also concluded by Cox et al. (1990a).
4. Conclusions
This study provided insights into short term tillage-induced changes and resulting crop response in a clay
Table 5
Root densityaby soil depths and position for two dates in 1993
Depth (m) 45 Days after tillage 85 Days after tillage
Plow till No-till Plow till No-till
Row AIRb TIR Total Row AIR TIR Total Row AIR TIR Total Row AIR TIR Total
00±0.1 26 16 14 56 19 16 22 57 53 36 31 120 61 24 16 101
aNumber of visible roots per 25 cm2area of soil pro®le.
bAIR and TIR: non-traf®cked and traf®cked inter-row area, respectively.
Table 6
1994 11.15a 11.16a 10.53ab 10.16b
1995 5.39 b 8.21a 7.78a 8.72a
1996 6.33a 4.20b 4.95ab 6.21a
1997 8.15b 9.34ab 10.66a 9.34ab
1998 3.26b 4.08a 3.64a 5.02a
1999 4.23a 6.30a 5.97a 6.57a
Average (1994±1999)
6.42b 7.22ab 7.26ab 7.67a
aNo-till was converted to zone till in 1995.
bValues followed by the same letter in a row are not
loam soil recently converted from alfalfa-to-maize. Measured soil properties, most of the time, did not differ signi®cantly between tillage treatments, appar-ently due to limited soil degradation occurring during this short time period and the strong soil structure associated with the high clay content of the soil.
Root water uptake (as evidenced by soil water losses) was slightly higher for the PT treatment in 1992 and may have been a yield-determining factor. In 1993, soil strength was higher in the surface layer and root counts were lower under NT, yet root water uptake and yield were not signi®cantly different between the tillage treatments. Penetrometer measure-ments are perhaps not a good indicator of the mechan-ical limitations experienced by roots in a well-structured soil. Although soil tilth was excellent in the ®rst year after conversion to maize, the high-plasticity of the soil and early season wetness created an underconsolidated plow layer in the second year, which was less favorable than the surface layer of the NT soil. Early season plant growth therefore was more favorable for NT, unlike results reported in other research. This indicates that the timing of tillage is important for these soils.
The longer-term yield data revealed that well-struc-tured arti®cially drained glacio-lacustrine soils in New York appear to be adapted to long-term row-crop production under ridge and no/zone tillage systems, but poorly adapted to spring tillage systems. Fall plowing, which is typically performed on this soil type, provides intermediate yields, but also increases erosion concerns. Due to the susceptibility to compac-tion from the inherently high plasticity of the soil, controlled traf®c appears to be an important factor to its success.
Acknowledgements
This research was funded in part by the USDA-CSREES Water Quality Program under agreement No. 91-34214-6059, New York State Soil and Water Man-agement Program, and by the Northern New York Agricultural Development Program. The authors would like to acknowledge the contributions of Roel van der Veen, Timo Kroon, Delvin Meseck, Norman Wade, Michael LaDuke, David Wilson, and Robert Lucey in the execution of the ®eld work.
References
Arora, V.K., Gajri, P.R., Prihar, S.S., 1991. Tillage effects on corn in sandy soils in relation to water retentivity, nutrient and water management and seasonal evaporativity. Soil Tillage Res. 21, 1±21.
Bengough, A.G., Mullins, C.E., 1990. Mechanical impedance to root growth: a review of experimental techniques and root growth responses. J. Soil Sci. 41, 341±358.
BoÈhm, W., 1979. Methods of Studying Root Systems. Springer, New York.
Braim, M.A., Chaney, K., Hodgson, D.R., 1992. Effects of simpli®ed cultivation on the growth and yield of spring barley on a sandy loam soil. 2. Soil physical properties and root growth; root: shoot relationships, in¯ow rates of nitrogen; water use. Soil Tillage Res. 22, 173±187.
Carefoot, J.M., Nyborg, M., Lindwall, C.W., 1990. Tillage-induced soil changes and related grain yield in a semi-arid region. Can. J. Soil Sci. 70, 203±214.
Cassel, D.K., 1983. Spatial and temporal variability of soil physical properties following tillage of Norfolk loamy sand. Soil Sci. Soc. Am. J. 47, 196±201.
Cassel, D.K., Raczkowski, C.W., Denton, H.P., 1995. Tillage effects on corn production and soil physical conditions. Soil Sci. Soc. Am. J. 59, 1436±1443.
Chaney, K., Hodgson, D.R., Braim, M.A., 1985. Effects of direct drilling, shallow cultivation and ploughing on some soil physical properties in a long-term experiment on spring barley. J. Agric. Sci. 104, 125±133.
Cochran, W.G., Cox, G.M., 1957. Experimental Designs. Wiley, New York.
Coote, D.R., Malcolm-McGovern, C.A., 1989. Effect of conven-tional and no-till corn grown in rotation on three soils in Eastern Ontario, Canada. Soil Tillage Res. 14, 67±84. Cox, W.J., Zobel, R.W., van Es, H.M., Otis, D.J., 1990a. Growth
development and yield of maize under three tillage systems in the northeastern USA. Soil Tillage Res. 18, 295±310. Cox, W.J., Zobel, R.W., van Es, H.M., Otis, D.J., 1990b. Tillage
effects on some soil physical and corn physiological character-istics. Agron. J. 82, 812±860.
Douglas, J.T., 1986. Effects of season and management on the vane shear strength of a clay top soil. J. Soil Sci. 37, 669±679. Gerard, C.J., 1987. Laboratory experiments on the effects of
antecedent moisture and residue application on aggregation of different soils. Soil Tillage Res. 9, 21±32.
Grif®th, D.R., Mannering, J.V., Box, J.E., 1986. Soil and moisture management with reduced tillage. In: Sprauge, M.A., Triplett, G.B. (Eds.), No-tillage and Surface-tillage Agriculture. Wiley, New York, pp. 19±58.
Hamblin, A.P., 1982. Soil water behavior in response to changes in soil structure. J. Soil Sci. 33, 375±386.
Hayhoe, H.N., Dwyer, L.M., Balchin, D., Culley, J.L.B., 1993. Tillage effects on corn emergence rates. Soil Tillage Res. 26, 45±53.
Hill, R.L., 1990. Long term conventional and no-tillage effects on selected soil physical properties. Soil Sci. Soc. Am. J. 54, 161± 166.
Horne, D.J., Ross, C.W., Huges, K.A., 1992. Ten years of a maize oats rotation under three tillage systems on a silt loam is New Zealand. 1. A comparison of some soil properties. Soil Tillage Res. 22, 131±143.
Hughes, K.A., Horne, D.J., Ross, C.W., Julian, J.F., 1992. A 10-year maize/oats rotation under three tillage systems: plant population, root distribution and forage yields. Soil Tillage Res. 22, 145±157.
Johnson, M.D., Lowery, B., 1985. Effect of three conservation tillage practices on soil temperature and thermal properties. Soil Sci. Soc. Am. J. 49, 1547±1552.
Lal, R., Logan, T.J., Fausey, N.R., Eckert, D.J., 1989. Long-term tillage and wheel traf®c effects on a poorly drained Mollic Ochraqualf in Northwest Ohio. 1. Soil physical properties, root distribution, and grain yield of corn and soya bean. Soil Tillage Res. 14, 341±358.
Liebig, M.A., Jones, A.J., Mielke, L.N., Doran, J.W., 1993. Controlled wheel traf®c effects on soil properties in ridge tillage. Soil Sci. Soc. Am. J. 57, 1061±1066.
Mielke, L.W., Wilhelm, W.W., Richards, K.A., Fenster, C.R., 1984. Soil physical characteristics of reduced tillage in a wheat-fallow system. Trans. ASAE 27, 1724±1728.
Nyborg, M., Malhi, S.S., 1989. Effect of zero and conventional tillage on barley yield, nitrate nitrogen content, moisture and temperature of soil in North-Central Alberta. Soil Tillage Res. 15, 1±9.
Ohiri, A.C., Ezumah, H.C., 1990. Tillage effects on cassava (Manihot Esculenta) production and some soil properties. Soil Tillage Res. 17, 221±229.
Packer, I.J., Hamilton, G.J., White, I., 1984. Tillage practices to conserve soil and improve soil conditions. J. Soil Conserv. (NSW) 40, 78±87.
Pikul Jr., J.L., Ramig, R.E., Wilkins, D.E., 1993. Soil properties and crop yield among four tillage systems in a wheat±pea rotation. Soil Tillage Res. 26, 151±162.
SAS Institute, 1985. The GLM Procedure. SAS User's Guide: Statistics. SAS Institute, Inc., Cary, NC (Chapter 20).
Satterthwaite, F.E., 1946. An approximate distribution of estimates of variance components. Biom. Bull. 2, 110±114.
Schneider, E.C., Gupta, S.C., 1985. Corn emergence as in¯uenced by soil temperature, matric potential and aggregate size distribution. Soil Sci. Soc. Am. J. 49, 415±422.
Simmons, F.W., Cassel, D.K., 1989. Cone index and soil physical property relationships on a sloping paleudult complex. Soil Sci. 147, 40±46.
Sloneker, L.L., Moldenhauer, W.C., 1977. Measuring the amount of crop residue remaining after tillage. J. Soil Water Conserv. 32, 231±236.
Swan, J.B., Schneider, E.C., Moncrief, J.F., Paulson, W.H., Peterson, A.E., 1987. Estimating corn growth, yield and grain moisture from air growing degree days and residue cover. Agron. J. 79, 53±60.
Taylor, H.M., Ratliff, L.F., 1969. Root elongation rates of cotton and peanuts as a function of soil strength and soil water content. Soil Sci. 108, 113±119.
Unger, P.W., 1975. Relationships between water retention, texture, density and organic matter content of west and south central Texas soils. Texas Agric. Exp. Stn. Misc. Publ., MP-1192C. Unger, P.W., Fulton, L.J., 1990. Conventional- and no-tillage
effects on upper root zone soil conditions. Soil Tillage Res. 16, 337±344.
van Es, H.M., van Es, C.L., 1993. Spatial nature of randomization and its effects on the outcome of ®eld experiments. Agron. J. 85, 420±428.
Wall, D.A., Stobbe, E.H., 1983. The response of eight corn (Zea mays L.) hybrids to zero tillage in Manitoba. Can. J. Plant Sci. 63, 753±757.
Warnaars, B.C., Eavis, B.W., 1972. Soil physical conditions affecting seedling root growth. Plant Soil 36, 623±634. Weaich, K., Cass, A., Bristow, K.L., 1992. Use of a penetration
resistance characteristic to predict soil strength development during drying. Soil Tillage Res. 25, 149±166.
