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Agronomy Journal 94:767-774 (2002)
© 2002 American Society of Agronomy

TILLAGE

Tillage Effects on Corn Production in a Coarse-Textured Soil in Southern Ontario

Ronald P. Beyaert*, Jacqueline W. Schott and Peter H. White

Southern Crop Protection and Food Res. Cent., P.O. Box 186, Delhi, ON, Canada N4B 2W9

* Corresponding author (beyaertr{at}em.agr.ca)

Received for publication October 23, 2000.

   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
Minimum tillage has been shown to slow early corn (Zea mays L.) growth and reduce grain yields in some soil types and under some climatic conditions. To overcome these limitations, the no-till (NT) system can be modified by incorporating residues and loosening the soil in a zone over the center of the row while leaving the interrow area untilled. This study compares soil temperatures and corn growth and productivity under zone till (ZT), NT, and conventional tillage (CT) systems in a coarse-textured soil (Psammentic Hapludalf) located in southwestern Ontario, Canada. Soil temperature at the 4-cm depth decreased with decreasing tillage intensity from CT to NT during warmer years but was similar in CT and ZT during a cooler year. This resulted in reduced growing degree days in the seed zone with decreasing tillage. Lower soil temperatures in NT did not delay the initiation of corn seedling emergence but did reduce the rate of emergence compared with CT plots. Corn growth rates were found to be similar among tillage systems in the early part of the growing system but were higher for both the ZT and NT systems during late vegetative and early reproductive growth. Grain yields increased as tillage intensity decreased in a year with drier conditions at tasseling but were similar across tillage systems in the other 2 yr. These results suggest that converting a NT system to a ZT system would neither result in significantly higher yields, nor cause a serious grain yield reduction relative to CT.

Abbreviations: CT, conventional tillage • DAP, days after planting • GDD, growing degree days • LAI, leaf area index • NT, no-till • ZT, zone till


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
INCREASED INTEREST IN REDUCED TILLAGE and no-tillage (NT) systems by corn (Zea mays L.) growers has resulted from a need to conserve energy, reduce soil erosion, and improve profitability. Crop residue management associated with conservation tillage has been shown to minimize fuel costs, soil water evaporation, erosion, and temperature fluctuations (Triplett and van Doren, 1977; Wall and Stobbe, 1984; Dick et al., 1991; Wagger and Denton, 1992). A number of field studies have been conducted to determine the effects of varying tillage practices on the proportion of soil surface residue cover and soil temperature (Gupta et al., 1984; Potter et al., 1985; Shinners et al., 1994), soil water distribution (Schneider and Gupta, 1985; Steiner, 1989), and corn production. Earlier studies have reported that corn grain yields are similar with reduced tillage systems and conventional moldboard plowing on coarse-textured soils (Griffith et al., 1973; van Doren et al., 1976; Al-Darby and Lowery, 1986). More efficient moisture use and improved soil physical properties associated with NT planting have been documented (Griffith et al., 1986) and are often cited as reasons for the success of NT systems on well-drained soils. However, reductions in early corn growth and, in some cases, final grain yields have been reported and attributed to lower early season soil temperatures under NT (Vyn and Raimbault, 1993).

Residue cover appears to be the dominant factor in determining soil temperature and the availability of soil moisture across tillage systems. It has also been shown that having a large percentage of soil covered with crop residues can result in soil physical conditions that reduce plant growth and yield under some climatic conditions (Larson et al., 1961; Burrows and Larson, 1962; Mock and Erbach, 1977; Al-Darby and Lowery, 1986, 1987; Cox et al., 1990; Vyn and Raimbault, 1993). In recent years, producers have attempted to improve early season growing conditions in NT corn by removing crop residues from the row at planting. Azooz et al. (1995) reported that modifying a NT system by removing residues from a 30-cm-wide area over the row at planting resulted in soil thermal and moisture conditions that were equivalent to a conventional tillage (CT) system. This resulted in equal or higher emergence rates, growth rates, and corn yields in the modified NT system compared to CT and an unmodified NT system.

Reduced tillage systems have also been shown to increase soil mechanical resistance, which can delay root development and increase water stress if dry conditions occur early in the growing season (Bauder et al., 1981; Griffith et al., 1988; Vyn and Raimbault, 1993). Potential exists to improve corn growth by loosening the soil in a zone in the row [zone tillage (ZT)] and leaving crop residues in the untilled interrow area. Data are lacking on the effects of ZT on corn growth and productivity in coarse-textured soils. Therefore, this field study was conducted to compare the effects of ZT, CT, and NT on soil temperature and the growth and yield of corn in a coarse-textured soil.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
Experimental plots were established in 1991 on a Fox loamy sand soil (Psammentic Hapludalf) located at the Southern Crop Protection and Food Research Centre, Delhi, ON, Canada (42°52' N, 80°31' W; altitude 182 m above sea level). The experimental site is located within the Lake Erie counties climatic region (Brown et al., 1968). On average, the site receives 2950 corn heat units (Brown, 1978) and has an average of 137 frost-free days per year.

The plots were maintained in a corn–soybean [Glycine max (L.) Merr.]–winter wheat (Triticum aestivum L.) rotation managed under spring CT, mulch tillage, or NT treatments for 6 yr before initiation of this study. All other management practices were similar across tillage treatments. Three tillage systems (NT, spring CT, and spring ZT) were applied to the existing field plots to be seeded to corn in a randomized complete block design with four replications in 1997. Each plot measured 10 m long and 12 m wide. No-tillage planting of corn was performed with a double-disc planter assembly following a fluted coulter and spoked-wheel row cleaners (Martin Row Cleaner, Martin and Co., Elkton, KY), which moved residue from a 25-cm zone, centered on the row, to the interrow area of those plots previously managed under NT practices. Conventional tillage consisted of spring moldboard plowing to a depth of 15 cm followed by discing to a depth of 10 cm in those plots previously managed under CT practices. Planting in this system utilized the same planter assembly without the row cleaners. Zone-tillage treatments were applied to those plots previously managed under mulch tillage practices and consisted of a cutting coulter followed by a DMI (DMI, Goodfield, IL) minimum residue disturbance shank fitted with a NT tiger-point mounted in front of a pair of adjustable fluted coulters. The ZT system tilled a zone 25 cm wide to a depth of 20 cm. This resulted in less than one-quarter of the corn row width being disturbed. Planting operations utilized the same double-disc planter assembly used in the CT system. Corn was planted at a depth of 4 cm in all treatments.

Corn (cv. NK Max 23) was planted at a population of 61000 plants ha-1 in 90-cm rows on 13 May 1997 and on 6 May 1998. In 1999, corn was planted at a population of 61000 plants ha-1 in 75-cm rows on 7 May. Starter fertilizer was applied at planting in bands 5 cm to the side and 5 cm below the seed at a rate of 20, 10, and 30 kg ha-1 N, P2O5, and K2O, respectively, in all years. The remainder of the N (to bring the total applied to 150 kg ha-1) was sidedressed as a liquid urea ammonium nitrate mixture (28% w/w) at approximately the six-leaf stage on 25, 16, and 17 June of 1997, 1998, and 1999, respectively. Nitrogen was applied with a Yetter coulter system to reduce disturbance of the interrow area. Weed control involved a single pre-emergence application of metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methyl) acetamide] at a rate of 1.92 kg ha-1 plus cyanazine {2-[[(4-chloro-6-ethylamino)-s-triazine-2-yl]amino]-2-methylpropionitrile} at a rate of 1.80 kg ha-1 on all treatments.

Mean monthly air temperatures and monthly precipitation were calculated from daily data collected at a weather station located 300 m from the experimental site. Soil temperatures were measured with copper-constantan thermocouples embedded in epoxy within a 2-cm length of copper tubing (4 mm i.d.) mounted onto a 30-cm length of 13-mm-i.d. piece of PVC tubing. The thermocouple assembly was inserted into the void made by a 2.6-cm-diam. soil sampler in the center of Rows 4 and 5 immediately following planting in each of the 12 plots. Soil was carefully packed into the void both inside and outside the PVC tubing to ensure proper soil-to-thermocouple contact. A mark located 4 cm above the thermocouple on the PVC assembly determined the installation depth. The thermocouples were connected to a Campbell 21X data logger programmed to read soil temperatures on a 5-min schedule. These 5-min readings were averaged to estimate mean hourly temperatures and mean daily temperatures during the first 57 d after planting (DAP).

Daily seed-zone growing degree days (GDD) were calculated from the averaged hourly soil temperature at the 4-cm depth using the formula outlined by Schneider and Gupta (1985):

[1]
where Ti is the soil temperature at 4 cm at the ith hour of the day and j is the number of DAP. Cumulative GDD were calculated by summing the daily GDD accumulated to that date. The advantage of using the GDD concept is that temperature and its effect on emergence and plant growth can be combined into a single value.

Total residue cover was determined within 2 d of planting using the line-transect method (Sloneker and Moldenhauer, 1977). Measurements of seedling emergence were made by counting the number of emerged seedlings in the same two 10-m rows used to measure soil temperatures. Plant development and dry matter accumulation were determined by measuring leaf number, leaf area, and dry weight of the aboveground portion from five random plants removed from the same two rows at 4 and 8 wk after planting, at tasseling in the CT plots, and at harvest. Dry weights were determined by oven-drying the plants at 50°C to constant weight. Total leaf area per plant was determined with an area meter (LI-COR Model 3100). Leaf area index (LAI) was determined by dividing the total leaf area per plant by the area occupied by a plant determined from plant population measurements at sampling. Plant height (leaf extended) was measured on those plants sampled at tasseling. Relative growth rates (RGR) were calculated for each time period between sampling using the measured dry matter (Blackman, 1919) and the equation

[2]
where W is the dry matter of the plant and dW is the change in W during the time interval represented by dt. Grain yields were determined by machine-harvesting two adjacent rows, 10 m long, from each plot. Moisture content and test weights of the grain were determined and grain yields adjusted to a 155 g kg-1 moisture basis. Final plant population and number of broken stalks were determined in the harvested rows immediately before grain harvest.

Analysis of variance (ANOVA) for randomized complete block design was conducted using the GLM procedure of SAS (SAS Inst., 1985). Analyses combining the 3 yr of data utilized a mixed model in which year and replication were considered variable factors and tillage a fixed factor. When the year x treatment interaction was significant (P <= 0.05), analysis was completed separately for each year. All treatment means were compared using the protected least significant difference (LSD).


   RESULTS AND DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
CONCLUSIONS
 REFERENCES
 
Mean monthly air temperature and precipitation during the 1997–1999 growing seasons and for the 62-yr period from 1935–1996 are presented in Table 1. Considerable year-to-year variation in seasonal precipitation and temperature occurred. In general, only the 1997 growing season had adequate rain distribution to ensure minimal water stress. However, the 1997 growing season was marked with below-normal air temperatures, especially immediately following seeding. In contrast, mean monthly air temperatures during both the 1998 and 1999 growing seasons were above the long-term average. However, mean air temperatures during May 1999 more closely resembled those measured during the 1997 season than those of the 1998 growing season. While mean daily (data not shown) temperatures were above average during the 1998 season, minimum temperatures <0°C were experienced at 28 to 30 DAP, resulting in frost injury to the corn crop. Below-average rainfall, coupled with the above-average temperatures during 1998 and 1999, led to visual moisture stress symptoms in the corn plants at certain times in each of these two growing seasons. During the 1998 season, dry periods occurred early in the season (May and June) and during the grain-filling period (August). In contrast, a dry period was experienced during late vegetative and early reproductive growth (July and the first 22 d of August) during the 1999 growing season.


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  		Table 1. Monthly mean air temperature and precipitation during the growing season for each year of the study and 62-yr average at Delhi, ON, Canada.

 
Tillage Impacts on Residue Cover
Zone tillage resulted in less surface residue than NT but higher amounts of surface residue than moldboard plowing in all years of the study (Table 2). Lower amounts of surface residues were found in NT and ZT treatments in 1997 than in 1998 and 1999. In contrast, residue cover in the CT treatment was significantly lower in 1997 than in 1999 but did not differ from 1998. This difference in surface residue cover resulted in a significant year x treatment interaction (P < 0.05). Residue cover in the NT treatment was 75 and 12% higher than in the CT and ZT treatments, respectively. Previous research has suggested that a minimum of 20% residue cover is necessary for a significant reduction in soil erosion (Moldenhauer et al., 1983). Conventional moldboard plowing had an average surface residue cover of 9% and would not provide enough residue cover to reduce soil erosion. In contrast, ZT and NT treatments should provide sufficient residue cover to reduce soil erosion in a corn–soybean–winter wheat production system.


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  		Table 2. Effect of tillage on surface residue cover in 1997, 1998, and 1999, and the 3-yr mean.

 
Tillage Impacts on Soil Temperature and Plant Emergence
Mean daily soil temperature in the seed zone (4-cm depth) measured between planting and completion of corn emergence increased as a result of increased soil tillage (Fig. 1) . Mean soil temperatures at the 4-cm depth were lower (P <= 0.05) in the NT treatment than in the CT treatment on 75% of the days during emergence and when averaged over the emergence period. Differences in mean daily soil temperatures among the tillage treatments increased with time and were more pronounced as mean soil temperatures increased. As a result, mean soil temperatures were higher in CT than in ZT plots in the warmer, drier 1998 planting season but were similar during the cooler 1997 and 1999 planting seasons (Table 3). Within years, differences in mean soil temperatures among treatments increased as temperatures increased and decreased as temperatures decreased. Abu-Hamdeh (2000) also found that tilled soil exhibited larger temperature amplitudes compared with NT soil under similar heat flux densities. This difference in temperature amplitude was attributed to lower thermal conductivities in the tilled treatment as a result of differences in percentage of residue cover and distribution.



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  		Fig. 1. Effect of tillage systems on mean daily soil temperature (T) at corn seeding depth (4 cm), 1997–1999. Tillage systems were conventional moldboard plow (CT), no-till (NT), and zone tillage (ZT). Vertical bars represent least significant difference values ({alpha} = 0.05). The absence of vertical bars indicates that no significant difference among the treatments was determined by an F-test ({alpha} = 0.05).

 

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  		Table 3. Mean soil temperature at 4-cm soil depth averaged over the sampling periods in 1997, 1998, and 1999.

 
Percentage of corn emergence and cumulative GDD at seeding depth (4 cm) for 1997 to 1999 are shown in Fig. 2 . Initial corn seedling emergence occurred on the same day for each treatment, but the rate of seedling emergence differed slightly among tillage treatments. Percentage of corn emergence on the day of initial emergence in 1997 and 1998, 1 d following initial emergence in 1997, and on Day 5 (10 DAP) of the emergence period in 1999 was significantly higher (P < 0.05) in the CT treatment than in the NT treatment. The CT treatment had a similar percentage of emergence as the ZT treatment in the 1997 season. In contrast, emergence in the ZT treatment was not different than that in either the CT or NT treatments in 1998. While not significant at the 5% level of probability, a strong trend towards higher emergence (P < 0.10) in the CT and ZT treatments compared with the NT treatment was observed from Day 9 to 12 during the 1999 season.



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  		Fig. 2. Effect of tillage systems on corn emergence (EM) and accumulated growing degree days (GDD) at corn seeding depth (4 cm), 1997–1999. Tillage systems were conventional moldboard plow (CT), no-till (NT), and zone tillage (ZT). Vertical bars represent least significant difference values determined by an F-test ({alpha} = 0.05). The absence of vertical bars denotes no significant difference among treatments. No difference among treatments in the emergence data is shown by NS. DAP, days after planting.

 
Differences in emergence rates among treatments were attributed to differences in cumulative GDD from planting to the completion of emergence. Lower GDD in the seed zone in NT compared with CT and ZT resulted in a slower rate of emergence in NT compared with CT and ZT during the 1997 growing season (Table 4). In contrast, GDD in the seed zone during the emergence period were significantly higher in CT compared with NT in 1998 while ZT had intermediate values. This resulted in a rate of emergence for NT that was slower compared with CT but not different from ZT. Cumulative GDD were higher in the CT than in either the ZT or NT treatments in 1999, but this did not affect the rate of emergence. Similar delays in the rate of seedling emergence due to lower soil temperature at the planting depth were reported by Al-Darby and Lowery (1987) in a silt loam soil. However, larger delays in seedling emergence due to slow soil warming in NT have been reported for clay soils (Drury et al., 1999). Overall, this suggests that the negative effect of reduced tillage on seedling emergence increases in finer-textured soils but has a small impact on seedling emergence in coarser-textured soils.


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  		Table 4. Cumulative growing degree days (GDD) at 4-cm soil depth averaged across the sampling periods in 1997, 1998, and 1999.

 
Tillage Impact on Corn Growth
Response of leaf area, dry matter, and LAI to tillage treatments of plants sampled 4 wk after planting varied from year to year and led to significant year x treatment interactions for these growth parameters. Significantly higher plant leaf areas, dry matter, and LAI were measured in the CT treatment compared with NT and ZT treatments in 1998 (Table 5). While similar trends in plant growth parameters were measured in 1997 and 1999, differences in these measurements among tillage treatments were not significant (data not shown). The 1998 results could not be directly attributed to differences in soil temperature in the seed zone during plant growth. In general, soil temperature and GGD ranked CT = ZT > NT during this period of growth in all years except 1998 when the average soil temperature and GDD increased with increasing tillage intensity (Tables 3 and 4). However, significant differences among the plant parameters measured 4 wk after planting were found only during the 1998 season. The lack of plant growth response to differences in soil temperature suggests that factors other than soil temperature may have affected early season growth rates. Results reported by Al-Darby et al. (1986) suggested that a lack of difference in growth parameters may also be attributed to adequate rain distribution during the early vegetative growth period and that significant differences may be attributed to inadequate rainfall distribution during this period. In our study, significant differences in growth parameters were found in the drier 1998 season but not in those years with more adequate rain.


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  		Table 5. Effect of tillage system on corn leaf area, dry matter, and leaf area index (LAI) 4 wk after planting in 1998.

 
Moldboard plowing resulted in larger corn plants than NT after 8 wk of growth when averaged across years (Table 6). Leaf numbers, leaf area, dry matter, and LAI were all significantly higher under CT management than under NT. Plants sampled from the ZT treatment had significantly higher leaf area per plant, dry matter, and LAI than those in the NT treatment but had similar leaf numbers per plant as the NT treatment. Vyn and Raimbault (1992) also found that corn plants in ZT tended to be significantly larger than NT plants and similar to CT plants. Again, these differences in corn plant responses to tillage could not be related to soil temperature or GDD at the 4-cm soil depth (Tables 3 and 4). Stone et al. (1999) suggested that soil temperature controlled the rate of development while the meristem was underground and noted that the meristem remained underground until six fully expanded leaves had appeared. Thereafter, corn development was best approximated by air temperature.


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  		Table 6. Effect of tillage system on corn leaf number, leaf area, dry matter, and leaf area index (LAI) 8 wk after planting averaged across 1997, 1998, and 1999.

 
The trend towards higher growth-parameter values for the CT treatment found earlier in the growing season had diminished by tasseling (Table 7). However, higher leaf numbers were found under CT than under ZT and NT when averaged across years. Similar results were found in 1997 and 1998, but no difference in leaf number at tasseling was found in 1999. This may have been the result of the dry conditions experienced before tasseling (42–88 DAP) during the 1999 growing season. The effects of this drought were more visibly apparent in the CT plots but less apparent in the ZT and NT plots. Overall, these results agree with previous findings where significant differences in leaf area per plants among tillage systems in the early part of the growing season tended to disappear later (Mock and Erbach, 1977; Vyn and Raimbault 1993; Al-Darby and Lowery, 1986). This lack of difference in dry matter accumulation continued throughout the season, resulting in similar dry matter accumulation among tillage treatments at harvest (data not shown).


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  		Table 7. Effect of tillage system on corn plant height, leaf number, leaf area, dry matter, and leaf area index (LAI) at tasseling averaged across 1997, 1998, and 1999.

 
Tillage Effects on Relative Growth Rate
Relative growth rates of each treatment during the planting to 4-wk growth period and 4- to 8-wk growth period were similar (P > 0.05) for all tillage treatments (Table 8). This suggests that higher soil temperatures and GDD at the 4-cm depth during this period in CT and ZT compared with NT resulted in no difference in relative growth rates. Relative growth rates from 8 wk after planting to tasseling were found to be higher for NT plots than the ZT plots, which had higher relative growth rates than the CT plots (P < 0.05). This suggests that as soil moisture is depleted, which often occurs in these soils slightly before or at tasseling time, corn growth rates are higher in treatments that led to conservation of soil moisture through the presence of a surface residue mulch (Azooz and Arshad, 1997; Sauer et al., 1996, Opoku et al., 1997). Higher moisture availability as a result of higher surface-residue cover would support improved water availability in the ZT and NT treatments. However, relative growth rates tended to be similar (P > 0.05) among the treatments from tasseling to harvest, suggesting that there was no advantage in growth rate with reduced tillage during the period from grain filling to physiological maturity.


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  		Table 8. Effect of tillage system on relative growth rates between 0 and 4 wk after planting, 4 and 8 wk after planting, 8 wk after planting and tasseling, and tasseling and harvest.

 
Fortin (1993) showed that despite the difference in residue cover, NT and NT with residues removed from the row area had similar in-row water contents during most of the growing season. In contrast, the author found that these treatments had higher soil moisture contents than the CT treatment until silking, after which no difference among the treatments was observed. Interrow soil water contents were higher in the NT and bare-row NT treatments than in the CT treatment for the entire growing season. Fortin (1993) also found that the interrow water content was related to both the presence of a residue cover in the interrow and the type of tillage. Thus, clearing the in-row residues into the interrow area resulted in soil temperatures closer to CT than to NT and also maintained the NT advantage of lower evaporation in the interrow. Fortin (1993) concluded that in-row residue removal provided a seed-zone environment close to that provided by CT methods and an interrow environment more favorable for conserving soil water than conventional methods. Based on these results, it may be possible that dry matter accumulation during the tasseling and silking periods was greater in the NT and ZT treatments as a result of greater water availability during this period in our study. Delayed growth in ZT and NT systems compared with CT systems was confined to the vegetative period and did not influence total phytomass production at maturity. This is consistent with Al-Darby and Lowery (1986) and Cox et al. (1990), who also found that the delay in early season corn growth under NT did not influence late-season total biomass or grain dry matter accumulation if corn in reduced tillage systems attains full physiological maturity.

Tillage Effects on Corn Grain Yields
Grain yields averaged across the 3 yr of the study were not significantly different among tillage systems (Table 9). However, a significant year x treatment interaction existed due to differences in the response of corn to the tillage treatments within the individual years of the study. While grain yield was not significantly different in 1997 or 1998, it increased as tillage intensity decreased in 1999. We attribute this to soil water conservation in reduced tillage systems during the dry-tasseling and early grain-filling period in 1999. In studies of tillage systems in clay soils, fall CT or ZT resulted in significantly higher corn yield than NT systems where residues remained in the zone above the corn row (Pierce et al., 1992; Opoku et al., 1997). However, when residues were removed from the area above the corn row in the NT system, yields were similar for conventional moldboard plowing and ZT systems. This suggests that any delayed early corn growth was confined to the vegetative period and did not influence yield when residues were removed from the row area (Fortin, 1993; Azooz et al., 1995).


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  		Table 9. Effect of tillage system on corn yield and grain moisture content at harvest in 1997, 1998, and 1999.

 
Grain moisture contents at harvest decreased with increasing tillage intensity (Table 9). No-till grain moisture content was 8% higher than the that of the CT system. Grain moisture content of the ZT system was not found to differ from either the CT or NT systems. This higher grain moisture content indicates a delay in corn maturity under the NT system compared with the CT system. Opoku et al. (1997) reported 4 to 9% higher grain moisture content in NT systems than in moldboard plow systems, but no difference in grain moisture content between CT and ZT systems were found in these clay soils. In contrast, Vyn and Raimbault (1992) found corn planted with CT had lower grain moisture at harvest than strip tillage treatments and NT treatments in a sandy loam soil while no difference in grain moisture could be found between tillage treatments in either a silt loam or a clay loam soil.


   CONCLUSIONS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
REFERENCES
 
Differences in early corn growth could not be directly attributed to differences in soil temperature at the 4-cm depth associated with different tillage systems. No-tillage had soil temperatures that, on average, were lower than those found in ZT or CT. These lower soil temperatures resulted in slightly lower (1–2 d) corn seedling emergence rates in 2 of 3 yr. It appears that by disturbing a narrow strip of soil in the ZT treatment, soil temperature increased, resulting in emergence times similar to CT. In contrast, even though crop residues were removed from the soil surface directly over the seed zone in the NT system, soil temperatures were lower in the seed zone and resulted in slightly slower corn emergence rates. Zone-till and NT systems had lower corn growth rates than the conventional moldboard plow system during the early vegetative growth phase. Results from this experiment showed that the early season reduced growth was in part associated with lower soil temperatures in the seed and rooting zone. In contrast, relative growth rates were found to be higher for both the ZT and NT systems during late vegetative and early reproductive growth. This increased dry matter accumulation late in the season may be attributed to higher water availability in the NT and ZT systems due to higher surface-residue cover.

In conclusion, it appears that ZT had little effect on early growth even though it provided soil temperatures in the seed zone environment that more closely resembled those provided by the CT system than the NT system. However, faster growth in ZT later in the season was attributed to an interrow environment more favorable for conserving soil moisture during periods of high water demand and low soil moisture compared with the CT system. Overall, these three tillage practices resulted in little difference in corn grain yields despite measured differences in early corn development. This suggests that the effects of different tillage systems on early corn growth did not result in biological consequences sufficient to affect reproductive yield. Modifying the NT system by adopting a ZT system did not improve the growing conditions sufficiently for corn to produce significantly higher yields, nor did it cause a serious yield reduction relative to CT. Based on these results, selection of a tillage system for these coarse-textured soils in Ontario will likely be done based on considerations such as energy conservation, erosion control, and soil moisture conservation, rather than on yield potentials.


   ACKNOWLEDGMENTS
 
We thank E. Kent and K. Cunningham for technical assistance. Funding for this study was provided in part by the Ontario Corn Producers Association.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 




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C. K. Reddy, E. Z. Nyakatawa, and D. W. Reeves
Tillage and Poultry Litter Application Effects on Cotton Growth and Yield
Agron. J., November 1, 2004; 96(6): 1641 - 1650.
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