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© 2008 Plant Management Network. In-Row Subsoil Tillage and Planting Depth Influence on Corn Plant Population and Yield on Sandy-Textured Mid-Atlantic Coastal Plain Soils Wade E. Thomason, Assistant Professor, Department of Crop and Soil Environmental Sciences, Virginia Tech, Blacksburg 24061; Steve B. Phillips, Associate Professor, Department of Crop and Soil Environmental Sciences, Virginia Tech ESAREC, Painter 23420; Mark M. Alley, Professor, Department of Crop and Soil Environmental Sciences, Virginia Tech, Blacksburg 24061; Paul H. Davis, Extension Agent, Virginia Cooperative Extension, New Kent 23140; Matthew A. Lewis, Extension Agent, Virginia Cooperative Extension, Heathsville 22473; and Sam M. Johnson, Extension Agent, Virginia Cooperative Extension, Montross 22520 Corresponding author: Wade E. Thomason. wthomaso@vt.edu Thomason, W. E., Phillips, S. B., Alley, M. M., Davis, P. H., Lewis, M. A., and Johnson, S. M. 2008. In-row subsoil tillage and planting depth influence on corn plant population and yield on sandy-textured Mid-Atlantic coastal plain soils. Online. Crop Management doi:10.1094/CM-2008-0519-01-RS. Abstract Early-planted corn (Zea mays L.) generally has greater yield potential than later plantings in the Mid-Atlantic. However, cool, wet conditions early in the early season can delay emergence when corn is planted no-till resulting in lower yield compared to conventional tillage. Since uniform, vigorous stands are required to maximize corn yield, this research was undertaken to determine if stand establishment and yields for corn in the Mid-Atlantic Coastal Plain would benefit from in-row subsoil tillage when seeded at various depths. Experiments were conducted in 2004 and 2005 at two locations in Virginia. Main plots were no-till or in-row subsoiling using a no-till ripper with shanks 30 inches apart. Planting dates were two weeks earlier than normal, normal, or two weeks later than normal. On each date, corn was planted into soybean stubble at depths of 0.5, 1.5, or 2.5 inches. In-row subsoiling increased grain yield in only one instance. Deeper planting (2.5 inches) resulted in higher grain moisture at harvest. Grain yields were maximized and risk of stand loss minimized by planting at 1.5 inches early or at the normal time. Planting early at 2.5 inches resulted in lower grain yield in two site years and generally delayed emergence. No consistent benefit from in row subsoil tillage was noted on these sandy soils. Introduction Early-planted corn generally produces higher yields than later planted corn due to improved utilization of sunlight during the long days of June and July, assuming adequate soil moisture (3). Drying costs are reduced with early planted corn as the grain can be allowed to dry in the field longer than for late planting. However, early planting under no-till conditions is a concern because the surface mulch layer results in soil temperatures that are generally colder and warm more slowly when compared to tilled soils. These conditions can lead to slower seed germination and seedling emergence which, in turn, can lead to non-uniform corn stands (9). Careful management of seeding depth and soil temperature is necessary to obtain maximum emergence and uniform stands. In a Nebraska study, corn seeds were planted at 2.5, 7.6, 12.7, and 17.2-cm depths. Depending on environmental conditions, eight to ten days were necessary for emergence from the 2.5-cm depth and approximately one to two additional days were needed for emergence from each additional depth increment (2). Delayed emergence due to increased seeding depth has also been observed in wheat (11). While Alessi and Power (2) demonstrated that seeding depth affects the rate and time of corn emergence, they found temperature has the most control over time to emergence. Soil temperatures are influenced by tillage and impact is greater during the first five weeks after planting increasing plant height, leaf area, and overall dry matter accumulation (1). Gupta et al. (8) have demonstrated that shallower planting can decrease the time to emergence in cooler soils. The combination of warmer soil in the planting zone and shallow planting has the potential to decrease the time to corn emergence and thus increase percent stand and possibly grain yield (7). Uniform and vigorous stands of corn are required to attain optimum yields. Variable stands occur more often with no-till production due to cooler, wetter soils (7,9) and residue interference at planting (16). No-till systems typically trap and retain more moisture than conventional till systems which is of great potential benefit during the growing season (15). This tendency can be harmful to early corn growth because excess soil water delays soil warming and can cause slow growth on poorly drained soils. In spite of these potential detriments to corn growth, 74% of corn acres in the Mid-Atlantic Coastal Plain were planted without tillage in 2004 (5). Observations are that the area planted no-till is continuing to increase due to increased fuel costs and conservation awareness. Zone or strip tillage has been proposed as a possible alternative rotation tillage system combining the soil quality benefits of conservation tillage with the yield and early season growth benefits of conventional tillage (13). Tilling only in the corn row encourages more favorable soil temperature, moisture, aeration, density, and strength conditions, while retaining the increased erosion resistance, organic matter protection and reduced energy inputs of no tillage. In addition to potential seedbed preparation advantages, the opportunity to place plant nutrients below the soil surface and thatch layer exist with strip tillage. Strip tillage has been extensively tested and adopted in areas of the US northern corn belt (5,14) and in southern Canada (6,17). Corn yields on sandy loam soils in Michigan were not increased by zone tillage in a three-year study, despite substantially reduced soil penetration resistance in the surface 12 inches (13). This indicates that tillage may be less beneficial in lighter textured soils. In contrast, Chancy and Kamprath (4) found increased corn yield with deep tillage on a sandy, coastal plain soil when a compacted layer existed. Recent research in Iowa has reported higher corn seedling emergence rate index for strip tillage, yet no consistent benefit to corn yields from strip till over no-till (10). The impact of in-row subsoil tillage techniques for corn has not been extensively evaluated in the Mid-Atlantic Region since the wide adoption of no-till. This research was undertaken to determine the effect of in-row subsoil tillage and planting depth on stand establishment, early season vigor, and grain yield for corn in the Mid-Atlantic Coastal Plain. Field Studies Field studies were conducted in 2004 and 2005 in Westmoreland Co. (38°7’N, 78°49’E) and Charles City Co. (37°22’N, 78°3’E) Virginia. The soil at Charles City was a Kempsville fine sandy loam (fine-loamy, siliceous, subactive, thermic Typic Hapludult) and at Westmoreland a Wickham fine sandy loam (fine-loamy, mixed, semiactive, thermic Typic Hapludult). In all cases, corn followed doublecrop soybeans and fields were managed using continuous no-till production techniques for at least the previous five years. Prior to planting, glyphosate was sprayed on the experimental area at 1.1 lb ai/acre to destroy existing weeds. The Southern States brand corn hybrid ‘SS 691’ treated with clothianidin (0.25 mg ai/kernel) was planted in 30-inch rows at a rate of 30,000 seeds/acre in 2004 and 26,000 seeds/acre in 2005 using a four-row Wintersteiger 2600 vacuum plot planter (Wintersteiger Inc., Salt Lake City, UT). This planter features standard Kinze lower units with double disc openers behind a fluted no-till rolling coulter. Starter fertilizer at a rate of 40 lb of N per acre and 10 lb of P2O5 per acre was applied two inches below and two inches to the side of the seed at planting with additional N sidedressed at 125 to 160 lb/acre at the V6 growth stage. After maturity and field drying, the center two rows from each plot were harvested using a Massey Ferguson 8XP plot combine. Plot weight, grain moisture, and test weight were determined using a Graingage system (Juniper Systems, Logan, UT). Grain yields were adjusted to 15.5% moisture. Planting and harvest dates and total fertilizer application rates are reported in Table 1. Table 1. Planting and harvest dates and fertilizer rates, Charles City and Westmoreland, 2004 and 2005.
Experimental Design The experiments were established as a randomized complete block, split-split plot design with three replications. Main plots were no-till or in-row subsoiled. In the latter, adjacent areas 60 by 125 ft were tilled to a depth of 18 inches using a DMI in-line no-till ripper with leading smooth coulters and straight ¾ inch-wide shanks 30 inches apart or left undisturbed, respectively. Tillage was performed two to four weeks prior to planting. This implement does not significantly reduce residue. Residue coverage after tillage was over 60% across the entire experimental area. Split plots (10 by 125 ft) were planting dates equal to the long-term regional average (normal) and approximately two weeks earlier and two weeks later than normal (Table 1). On each date, corn was planted at depths of 0.5, 1.5, or 2.5 inches, resulting in a 2 by 3 by 3 factorial arrangement of treatments for tillage, planting date and planting depth (Fig. 1). Seeding depth was set using planter gauge wheels and confirmed by examining the depth of 10 consecutive seeds in the row. Each planting depth by date by tillage split-split plot was four rows wide (10 ft) and 25 ft long.
Soil temperature at planting was measured at 10 to 11 a.m. on the day of planting at three locations in the row of each subplot using a digital stem thermometer (Cole-Parmer, Vernon Hills, IL). Plant emergence date, when more than 80% of the plants within a plot had emerged, was determined for each plot. Early season plant population, as an estimate of emergence and seedling vigor was measured by counting all plants in the center two rows of each subplot at approximately three weeks after each planting date. Plant height, the distance from ground level to the tip of the longest leaf when held erect, was measured at this time. Statistical Analysis Statistical analysis was performed using the GLM procedure available from SAS (SAS Institute Inc., Cary, NC). Due to interactions among treatments and years, experimental sites and years are analyzed and presented separately. No interaction of tillage by planting date by planting depth existed; however, interactions between planting date and planting depth and between tillage and planting date were common. Therefore, data are presented by planting date and depth, averaged over tillage treatment and by planting date and tillage averaged over planting depth. Mean comparisons using a protected LSD test were made to separate treatment effects within each site year where F-tests indicated that significant differences existed (P < 0.05). 2004 Crop Season Growing season rainfall in 2004 was well above the long term average with the months of June, July, and August especially wet (Fig. 2) (Southeast Regional Climate Center, www.dnr.sc.gov/climate/sercc). The month of May 2004 was 4°F warmer than the long term average (Fig. 3) and was one of the warmest ever recorded in eastern Virginia. In response to this, corn growth and development was accelerated leading to early tasseling and maturity.
Early Season Stand and Plant Height In 2004, there were no significant main effects or interactions among planting depths, planting dates, or between tillage treatments for either soil temperature or plant population. Plant height was influenced only by the main effect of planting date. Soil temperature at 1.5 inches below the soil surface in the seed furrow measured at 10 a.m. on the date of planting and three weeks after planting is shown in Figure 4. There were no differences in soil temperature due to tillage treatment when measured on the same day. On average, soil temperature increased about 10°F over each three week period beginning with the first measurements in early April. Significant differences in plant height were observed based on time of planting with the early planting date an average of 12 inches taller than the normal date which was 11 inches taller than the late date (Fig. 5). However, by late May there were no differences in plant height when measured in all plots. At no time were there differences in plant height among tillage or planting depth treatments within a planting date
While the first planting date at both sites occurred when mid-morning soil temperatures were less than 50°F at 1.5 inches (Fig. 4), planting depth did not affect plant population measured at 3 weeks after planting in 2004 (Table 2). Time to emergence of the deepest planting depth of 2.5 inches was delayed by approximately six days compared to the more shallow plantings. There was no noticeable difference in time to emergence between the 0.5 and 1.5 inches planting depths (data not shown). No effect of tillage on the early planting date plant stand was observed at either site when averaged across planting depth (Table 3) Table 2. Corn grain yield, early season plant population, and grain moisture as affected by planting date and depth, averaged over tillage treatment, Charles City and Westmoreland, 2004 and 2005.
* Means within a column and planting date followed by the same letter are not statistically different (P = 0.05) Table 3. Corn grain yield, early season plant population, and grain moisture as affected by planting date and tillage, averaged over planting depth, Charles City and Westmoreland, 2004 and 2005.
* Means within a column and planting date followed by the same letter are not statistically different (P = 0.05). Grain Moisture and Yield In 2004, planting depth and the planting date by tillage treatment interaction significantly impacted grain moisture at Charles City. There were also significant impacts of the planting depth main effect on grain yield at both sites and the planting date by tillage treatment interaction on grain yield at Charles City. At Charles City, grain moisture at harvest averaged across tillage increased with planting depth, indicating delayed maturity (Table 2). This results in either delayed harvest or increased grain drying costs at the end of the season. No significant differences for grain moisture due to planting depth were found at the Westmoreland site. No differences in grain moisture were observed for any planting date by tillage treatment at Westmoreland but moisture was lower for the no-till treatment at the late planting period at Charles City (Table 3). At both Westmoreland and Charles City across tillage systems the shallow planting produced greater corn yield than the deeper planting (Table 2) This was particularly the case at both the early and late planting dates. This was probably due to the above average air temperatures experienced in late April and early May (Fig. 2), the rapid increase in soil temperature, (Fig. 4) and the plentiful precipitation received throughout the season. At Westmoreland there were no grain yield differences due to tillage or planting date when averaged over planting depth (Table 3). At Charles City, when averaged over planting depth, the no till planting outyielded the in-row subsoil treatment at the normal planting date, but no other differences were observed (Table 3). 2005 Crop Season Average air temperatures in early April, 2005 were much warmer than the long-term average and favored corn growth during and immediately after the early planting date but declined by the middle of the month to temperatures that were marginal for corn development (< 50°F) (Fig. 3). This resulted in slow emergence of the early planting date for all tillage treatments at both sites, but especially for the 2.5-inch depth. Soil temperature was much more stable and averaged 47°F for the early planting date and increased to over 54°F by three weeks after planting (Fig. 4). Temperature of air and soil was favorable for corn growth for both the normal and late planting dates. Rainfall for the growing season was below the 30-year mean, but adequate precipitation fell in the month of July during the critical period near corn silking resulting in average yields greater than 124 bu/acre (Fig. 2). Early Season Stand and Plant Height At both locations there were significant interactions between planting date and planting depth in measured plant population, and at the Westmoreland location there was a significant planting date by tillage interaction for early-season plant population. At Charles City, plant population, averaged over tillage treatment, for the 0.5-inch depth at the early planting date was significantly less than for the mean of the other two depths (15,385 vs. 25,142 plants/acre) (Table 2). At this low plant density, however, a number of plants produced multiple ears resulting in comparable final yields. Shallow planting and dry early conditions may have led to moisture stress that resulted in seedling mortality and decreased vigor. The 0.5-inch planting depth resulted in lower final population regardless of planting date at Westmoreland (Table 2). Seed and seedling depredation by birds was a problem at this site and the shallower planting resulted in easier access to birds and a greater effect from feeding. Bird damage was most severe in the late planting date. There were no differences in early plant stand at Charles City due to the influence of planting date and tillage, when averaged over planting depths. At the Westmoreland site, when averaged over planting depth, the lowest population was associated with no-till planting at the early date but in-row subsoil tillage resulted in the lowest plant populations for the normal and late dates (Table 3). At both locations the planting date significantly influenced plant height. Plant height in mid-May was lower at both sites than in 2004, but was again greatest for the early planting date (29 inches) (Fig. 5). Grain Moisture and Yield There was a significant interaction involving planting date and planting depth on grain moisture at Charles City in 2005. Across tillage treatments at Charles City in 2005, planting at 2.5 inches resulted in greater average grain moisture at harvest at the early planting date (Table 2). Grain moisture at Charles City did not differ due to the tillage treatment used (Table 3). No significant differences in grain moisture across tillage systems or planting depths were observed at Westmoreland (Tables 2 and 3). Grain yield was significantly impacted by the interactions between planting date and planting depth at both locations and planting date and tillage treatment at Charles City. At both sites in 2005, shallow planting generally resulted in lower grain yield than deeper planting (Table 2). These lower yields are attributable mainly to lower plant populations caused by dry surface soil conditions and bird depredation in these treatments. Shallower plantings are more susceptible to damage from preemergence herbicides, birds and other pests. Grain yields at Charles City in 2005 varied from 130 to 117 bu/acre (Table 2). When averaged over planting depths, grain yields differed only at the normal date where the in-row subsoil treatment outyielded no-till by 16 bu/acre (Table 3). No yield differences due to tillage were found for any planting date at the Westmoreland site (Table 3). Conclusions Planting depth resulted in significant differences in grain yields in 9 of 12 site-year treatment combinations. However, no planting depth consistently resulted in higher yield. When emergence was similar, shallow planting has an advantage in terms of maturity and grain yield. Shallow planting, particularly at Westmoreland in 2005, lead to reduced emergence (due to insects, birds, dry weather, etc). Grain yield was greater with the deeper planting because of reduced emergence and plant population from shallow planting, and was maximized in this study by planting at 1.5 inch. Planting at 1.5 inches either early or at the normal date offers the greatest probability of positive yield response with the least risk. No consistent benefit of increased emergence or grain yield from in-row subsoil tillage was noted on these sandy soils. When increased plant performance due to tillage has been measured, it is usually a result of warmer soil temperatures (1). In these studies, tillage did not result in increased soil temperature in the furrow at normal seeding depth. Additionally, all the experimental fields had been managed with continuous no-till practices for at least the prior five years. No compaction or surface crusting would be expected for these soils under these conditions. This lack of consistent response to tillage has also been reported by Licht and Al-Kaisi (10) and by Mehdi et al. (12). In summary: · Planting at 1.5 inches resulted in the best compromise between quick emergence and less stand loss · In-row strip tillage did not improve grain yield or any of the factors measured in this study. Literature Cited 1. Al-Darby, A. M., and Lowery, B. 1987. Seed zone soil temperature and early corn growth with three conservation tillage systems. Soil Sci. Soc. Am. J. 51:768-774. 2. Alessi, J., and Power, J. F. 1971. Corn emergence in relation to soil temperature and seeding depth. Agron. J. 63:717-719. 3. Alley, M. M., Roygard, J. K. F., and Brann, D. E. 2002. Corn planting dates in the Virginia Coastal Plain: How early is early? Virginia Coop. Ext. Pub. No. 424-033, Blacksburg, VA. 4. Chancy, H. F., and Kamprath, E. J. 1982. Effects of deep tillage on nitrogen response by corn on a sandy coastal plain soil. Agron. J. 74:657-662. 6. Drury, C. F., Tan, C. S., Reynolds, W. D., Welacky, T. W., Weaver, S. E., Hammill, A. S., and Vyn, T. J. 2003. Impacts of zone tillage and red clover on corn performance and soil physical quality. Soil Sci. Soc. Am. J. 67:867-877. 7. Gupta, S. C., Larson, W. E., and Linden, D. R. 1983. Tillage and surface residue effects on soil upper boundary temperatures. Soil Sci. Soc. Am. J. 47:1212-1218. 8. Gupta, S. C., Schneider, E. C., and Swan, J. B. 1988. Planting depth and tillage interactions on corn emergence. Soil Sci. Soc. Am. J. 52:1122-1127. 9. Kasper, T. C., Erbach, D. C., and Cruse, R. M. 1990. Corn response to seed-row residue removal. Soil Sci. Soc. Am. J. 54:1112-1117. 10. Licht, M. A., and Al-Kaisi, M. 2005. Corn response, nitrogen uptake, and water use in strip-tillage compared with no-tillage and chisel plow. Agron. J. 97:705-710. 11. Mahdi, L., Bell, C. J., and Ryan, J. 1998. Establishment and yield of wheat (Triticum turgidum L.) after early sowing at various depths in a semi-arid Mediterranean environment. Field Crops Res. 58:187-196. 12. Mehdi, B. B., Madramootoo, C. A., and Mehuys, G. R. 1999. Yield and nitrogen content of corn under different tillage practices. Agron. J. 91:631-636. 13. Pierce, F. L., Fortin, M. C., and Staton, M. J. 1992. Immediate and residual effects of zone tillage in rotation with no-tillage on soil physical properties and corn performance. Soil Tillage Res. 24:149-165. 14. Radke, J. K. 1982. Managing early season soil temperatures in the northern corn belt using configured soil surfaces and mulches. Soil Sci. Soc. Am. J. 46:1067-1071. 15. Roygard, J. K. F., Alley, M. M., and Khosla R.. 2002. No-till corn yields and water balance in the Mid-Atlantic coastal plain. Agron. J. 94:612-623. 16. Schreiber, M. M. 1992. Influence of tillage, crop rotation, and weed management on giant foxtail population dynamics and corn yield. Weed Sci. 40:645-653. 17. Vyn, T. J., and Raimbault, B. A. 1992. Evaluation of strip tillage systems for corn production in Ontario. Soil Tillage Res. 23:163-176. |
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