© 2008 Plant Management Network.
Fertilizer Management for Short-season Corn Grown in Reduced, Strip-till, and No-till Systems on Claypan Soil
Daniel W. Sweeney, Southeast Agricultural Research Center, P.O. Box 316, Kansas State University, Parsons 67357; Gary L. Kilgore, Southeast Area Extension Office, 308 West 14th St., Kansas State University, Chanute 66720; and Kenneth W. Kelley, Southeast Agricultural Research Center, P.O. Box 316, Kansas State University, Parsons 67357
Corresponding author: Daniel W. Sweeney. firstname.lastname@example.org
Sweeney, D. W., Kilgore, G. L., and Kelley, K. W. 2008. Fertilizer management for short-season corn grown in reduced, strip-till, and no-till systems on claypan soil. Online. Crop Management doi:10.1094/CM-2008-0725-01-RS.
Strip-till is an alternative conservation tillage system that may overcome the yield depression often seen with corn (Zea mays L.) grown with no-till on the claypan soils of the eastern Great Plains. The objective of this research was to determine the effect of conservation tillage systems and fertilizer N-P management on short-season corn. Continuous corn yields with no-till, strip-till in the fall, or strip-till in the spring declined with year compared with corn grown with reduced tillage. By the third year, corn yields with reduced tillage exceeded 45 bu/acre more than with the other tillage systems. In part, this can be attributed to a reduced plant stand in no-till and strip-till systems. Average corn yield was about 10% greater when N-P applications were made in the spring than in the fall. Similarly, knife (subsurface band) applications of N-P resulted in about 12% greater yield than dribble (surface band). Yield differences due to fertilizer timing or placement were related to similar increases in the number of kernels per ear. Strip-till done either in the fall or spring for corn grown in claypan soil did not improve yield compared with no-till and may be less than yields with reduced tillage. Knife applications of N-P fertilizer done in the spring may help mitigate this deficit if the producer prefers the conservation aspects of strip- or no-till systems.
Until recently, there was little corn production on the eastern Great Plains upland, claypan soils. Area rainfall patterns usually result in moisture stress during July and August and because of limited plant-available moisture storage in claypan soils, corn production had been unreliable. Short-season corn hybrids, which reach reproductive stages earlier than full-season hybrids, may partially avoid the effects of droughts in mid-summer (14) and provide equivalent (3) or greater (17) yields than with full-season hybrids. Information on tillage and fertilizer options for short-season hybrids grown on claypan soils, however, is still limited.
Tillage selection has the potential to impact short-season corn production. Although no-till corn can yield more (27) or the same (30) as with conventional tillage, on poorly drained soils (4,11), tilled conventional systems generally result in greater corn yield than with no-till perhaps because of cooler soil temperatures and excess soil moisture in the spring. Strip-till is a compromise between conventional and no-till and was designed to help improve the seedling environment by moving and incorporating residue by tillage in a narrow band, while preserving conservation benefits by retaining residue cover on the remaining soil surface. Early work done by Kaspar et al. (10), similar to the strip-till concept, showed that residue removal from a 6-inch wide band in no-till resulted in corn yields similar to those from tilled bare soil. Thus, strip-till holds promise to eliminate yield reduction often seen for corn and grain sorghum grown on claypan soils.
Fertilizer N and P management for corn is important. In previous research, injecting (subsurface band) N resulted in greater no-till corn yields than with either surface broadcast or surface band applications (9). Mengel et al. (19) also found increased corn yield with subsurface placement of N fertilizer in no-till, but to a lesser extent in conventional tillage systems. Fertilizer N uptake by sorghum and corn is most efficient with subsurface band placement across several different tillage systems (16,26). Furthermore, spring applications of N may result in greater corn yield than with fall applications (22,27). Similar to N, subsurface placement of P may increase corn yield and nutrient uptake (23). However, expected effect due to P placement is likely dependant on soil test values (12).
Producers must balance maximizing crop yield response with being good environmental stewards of the land. Data are lacking, however, regarding fertilizer N and P timing and placement management for conservation tillage systems of reduced, strip, and no-till for short-season corn grown on claypan soils of the eastern Great Plains. Thus, the objective of this research was to determine the effect of conservation tillage systems and fertilizer N-P management on short-season corn grown on claypan soil in the eastern Great Plains.
Field Experiment Description
The experiment was conducted from 2003 through 2005 near Parsons, KS, at the Southeast Agricultural Research Center of Kansas State University. The topsoil was a Parsons silt loam (fine, mixed, thermic Mollic Albaqualf) of approximately 12 inches overlying a claypan B horizon. The topsoil has an available water-holding capacity of approximately 2 inches, and the subsoil has a low percolation rate of < 0.06 inch/h (20). Selected background soil chemical analyses in the 0- to 6-inch depth were 6.6 pH (1:1 soil/water), 17 ppm P (Bray-1), 68 ppm K (1 M NH4C2H3O2 extract), 2.9 ppm NH4-N, 3.5 ppm NO3-N, and 2.9 % soil organic matter analyzed by North Central Region recommended procedures (2).
The experimental design was a randomized complete block with a split-plot arrangement of treatments in four replications. In each replication, whole plots were four tillage systems and subplots were a 2 × 2 factorial arrangement of timing and placement of N-P fertilizer. The tillage treatments were: (i) no-till, (ii) strip-till in the fall, (iii) strip-till in the spring, and (iv) reduced tillage. Strip-till was done with a commercial unit (DMI) comprised of a leading large coulter followed by a high clearance shank, berm-building double disks, and a berm-conditioning, rolling basket. Reduced tillage consisted of one pass with a tandem disk in late fall and one pass in early spring. The two N-P fertilizer placement methods were surface band (dribble) and subsurface band (knife). The two N-P fertilizer application timings were in late fall and early spring. Although commercial units are available that combine strip-till and fertilizer application, in our study to avoid potentially confounding the data we applied N-P fertilizer with a separate fertilizer unit regardless of tillage system. Individual subplot size was 10 by 40 ft.
Fertilizer rates of 120 lb of N per acre and 40 lb of P2O5 per acre were applied in each fluid fertilization scheme. Liquid N-P fertilizer sources, urea-ammonium nitrate (28-0-0) and ammonium polyphosphate (10-34-0), were metered through a positive-displacement liquid fertilizer pump driven from a tractor’s ground-speed power take-off. Knifed solutions were injected at a 4-inch depth. Both knife and dribble applications were on a 30-inch spacing applied within 4 inches from the row position in all tillage systems. This N-P fertilization occurred in fall or spring immediately prior to strip or reduced tillage. Fertilization and tillage was done on 17 December 2002, 1 April 2003, 2 December 2003, 5 April 2004, 29 December 2004, and 31 March 2005. Pioneer 35P15 corn was planted on 3 April 2003 and 6 April 2004 and Pioneer 35P12 corn was planted on 31 March 2005 at 22,700 seeds/acre in 30-inch rows with a four-row air planter equipped with trash whippers to facilitate planting in the conservation tillage systems. Annually, 78 lb K2O/acre was applied 2 inches to the side of the row and 2 inches below the soil surface with the planter’s dry fertilizer attachment. Prior to corn emergence each year, atrazine and metolachlor were applied at recommended rates for weed control. Also, strip-till and no-till plots received glyphosate at 0.75 lb ae/acre to control light pressure from previously emerged weeds.
Corn yields were harvested from the two center rows of each plot with a small plot combine on 25 August 2003, 3 September 2004, and 29 August 2005. Grain was weighed, moisture was determined, and yield was adjusted to 15.5 % moisture content. Kernel weight was determined from duplicate measures of 100 kernels from a subsample of the plot yield. Stand count of the two center rows was measured just prior to tassel. Prior to harvest, the number of ears in the harvest rows were counted. Kernels per ear were calculated using plot yield, measured ear count, plant population, and ears per plant. After kernel weight was determined, the grain subsample was dried at 140EF, ground, digested using H2SO4-H2O2 (15), and the concentration of N and P was determined colorimetrically (25). Soil temperatures were measured at 1-inch depth from in-row positions in each plot for 4 to 5 weeks after planting in 2004 and 2005 with an Omega 450-ATH (Stamford, CT) electronic thermistor temperature probe.
Data were analyzed using the Proc Mixed procedure of the SAS (SAS Institute, Inc., Cary, NC). All factors except REP were considered fixed. Year was treated as a strip-plot fixed effect, so that across years the data were analyzed as a strip-split plot. Treatment effect means for measured parameters were compared using Fisher’s LSD. Pearson product-moment correlations among measured corn variables were calculated using the CORR procedure of SAS.
Rain and air temperature data were recorded at a National Weather Service Cooperative Observer Network Site (Station ID 14-6242-09) located < 0.5 mi from the study site on the Research Center. This weather station has been active since 1948 and follows National Weather Service observational standards.
In the three years of this study, monthly rainfall totals were often different from the 30-year averages (Table 1). In 2003, rainfall totals were greater than normal in April and August, but lower than normal in July. In 2004, rainfall was 30% below normal in May, but in other months rainfall was within 20% of normal. In 2005, precipitation patterns appeared to deviate the most with April rainfall nearly 50% below normal, nearly 25% below normal in May, and nearly 60% below normal in July, but about 70% greater than normal in June and more than 30% above normal in August. Temperature patterns were somewhat near normal in April and May during each year of the study. However, in 2003 and 2004, June temperatures were cooler than in 2005 or the 30-year average. In 2004, July and August average maximum air temperatures were much cooler than in 2003, 2005, or the 30-year average.
Table 1. Precipitation and average maximum daily temperature for April through August for 2003, 2004, 2005, and the 30-year average at the Southeast Agricultural Research Center, Parsons, KS.
Tillage Effects on Corn Yield and Yield Components
Corn yield was affected by a year by tillage interaction (Table 2). In 2003, corn yield was not affected by tillage (Fig. 1) and averaged 113 bu/acre. In our study, the 2003 corn crop followed a 2002 bulk soybean crop. In rotation, corn response to tillage may be non-significant (13) and the response to strip-till may be limited compared with no-till or chisel plow (1). During 2004 in our study, yield ranged from 108 bu/acre with no-till to 154 bu/acre with reduced tillage (Fig. 1). Strip-till in either fall or spring did not result in greater yield than with no-till. Only strip-till in the fall resulted in yield that was not less than corn yields with reduced tillage. In 2005, however, reduced tillage resulted in corn yield that was 50 to 75% greater than yield with reduced tillage or with strip-till in the fall or spring. When these results are averaged across the three years of the study, corn yields ranked according to tillage were reduced > strip-till in either fall or spring > no-till, and this agreed with similar tillage rankings of four-year average yields of continuous corn reported by Vetsch and Randall (28).
Table 2. Analysis-of-variance significance levels for the effect of tillage, N-P timing, and N-P placement on yield, yield components, and grain N and P concentration.
Corn yield responses to tillage appeared to be primarily due to population and kernel weight as affected by year with little effect from tillage on the number of ears per plant or kernels per ear (Table 2). In each year, no-till resulted in lower plant population than with reduced tillage (Fig. 2). In 2003 and 2004, strip-till done either in the fall or spring resulted in corn populations at levels that were not less than with reduced tillage. In 2005, the third year of the study, population was less with either strip-till system or no-till than with reduced tillage. Additionally, in 2005, both strip-till done in the fall and no-till resulted in corn population of less than 15,000 plants/acre, but strip-till done in the spring resulted in greater population (> 18,000 plants/acre), even though not as great as with reduced tillage (> 22,000 plants/acre). Correlations showed that overall greater population resulted in greater corn yield (Table 3). In tilled treatments, corn plant populations are often greater than with no-till (21) and strip-till (8), even when compared across multiple hybrids (6). While decline in population with no-till between the first year and the third year of our study could partially be attributed to emergence difficulties because of increased accumulation of corn residue, that speculation may be inadequate to explain a similar trend in plant populations with strip-till where residue is moved from or incorporated in the tilled planting strip. However, differences in plant population in 2005 due to tillage may have been exacerbated by below normal rainfall in April (Table 1). Though no-till systems may reduce yields because of cooler spring temperatures (7) and strip-till may improve soil temperatures in the row (5), in our study, soil temperatures at a 1-inch depth measured twice weekly for 4 to 5 weeks after planting in 2004 and 2005 showed few and inconsistent differences due to tillage (data not shown). This failed to support speculation that increased soil temperature in strip-tilled or reduced tilled plots should promote better plant stands. Though kernel weight appeared to fluctuate as influenced by tillage, the only difference was found in 2005 (Fig. 3). Kernel weight was greater with reduced tillage than with no-till in 2005, but the difference was small. Thus, in general, kernel weight was not correlated with yield (Table 3). Concentration of N and P in the corn grain was unaffected by tillage (Table 2).
Table 3. Pearson correlation coefficients (r) among measured short-season corn traits.
*,** Significant at P = 0.05 and 0.01 levels, respectively.
NS = not significant.
N-P Fertilizer Timing and Placement Effects on Corn Yield and Yield Components
Corn yield was affected by N-P fertilizer timing and placement, but not by any interactions between the two factors, with tillage, or by year (Table 2). Applying N-P fertilizer in the spring as compared with in the fall increased yield by 10% (Fig. 4). Vetsch and Randall (29) found that N should be applied in the spring regardless of tillage system. In our study, this yield increase appeared to be primarily a result of a similar increase in the number of kernels per ear (Fig. 4) and this is supported by the significant correlation of the number of kernels per ear with yield (Table 3). Similarly, knife applications resulted in 12% greater yield than with dribble applications (Fig. 5). Again, this appeared to be a result of a similar increase in the number of kernels per ear. Compared with no N fertilization, N applied at optimum levels can nearly double the number of kernels per ear (24). Across a range of N levels, correlation showed that as kernels per ear increased, the yield of multiple corn lines also increased (18). Other effects of N-P fertilizer timing and placement in our study appeared to have less defined relations to corn yield and were somewhat sporadic, often the result of ill-defined interactions (data not shown). As a contrast to the effect on yield and the number of kernels per ear, fertilizer timing did not influence plant population in 2003 and 2004, but spring N-P application in 2005 resulted in 20% more plants per acre than fall N-P application. Kernel weight was relatively unaffected by fertilizer timing or placement (Table 2), except for a year by tillage by fertilizer placement interaction. In 2003, knife application of N-P fertilizer affected kernel weight inconsistently with different tillage systems, but in 2004 and 2005, kernel weight was unaffected by fertilizer treatments. Grain N was increased 8% by spring fertilizer application in 2003 compared with fall fertilization but was unaffected in subsequent years. Grain P concentration was unaffected by fertilizer timing and was variably affected by fertilizer placement with year.
Yield of short-season corn grown on the claypan soils of the eastern Great Plains is affected by conservation tillage systems, fertilizer timing, and fertilizer placement, but the response varies with year. When growing continuous corn, yields with no-till, strip-till in the fall, or strip-till in the spring declined compared with corn grown with reduced tillage. In part, this decline can be attributed to a reduced plant stand in no-till and strip-till systems. Average corn yield increased about 10% with spring compared to fall and about 12% with knife compared to dribble N-P fertilizer applications. Both of these yield increases appeared to be a result of similar increases in the number of kernels per ear. Based on these data, strip-till done either in the fall or spring for corn grown in claypan soil may not improve yield compared with no-till and may be less than yields with reduced tillage. However, knife applications of N-P fertilizer done in the spring may help mitigate this deficit if the producer prefers the conservation aspects of strip- or no-till systems.
Acknowledgments and Disclaimer
Contribution no. 08-265-J, Kansas Agricultural Experiment Station. Product names are included for the benefit of the reader and do not imply any endorsement or preferential treatment by Kansas State University. This research was funded in part by the Kansas Corn Commission. The authors would like to acknowledge and thank Bobby Myers and David Kerley for their assistance with this project.
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