Nitrogen Management in No-Tillage and Ridge-Tillage Systems Affects Short-Season Corn Grown on Claypan Soil

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Daniel W. Sweeney, Southeast Agricultural Research Center, Kansas State University, P.O. Box 316, Parsons 67357; and Douglas J. Jardine, Department of Plant Pathology, Kansas State University, Manhattan 66506

Abstract

Success of conservation tillage systems requires good fertilizer management, especially nitrogen applied to crops grown on claypan soils in the eastern Great Plains. Recently introduced, short-season corn (Zea mays L.) hybrids, that mature earlier and potentially avoid drought problems common on these soils in late summer, provide producers with another viable cropping option. However, information on N management in conservation tillage systems is lacking for short-season corn grown on claypan soils. The objective of this study was to examine the effect of fertilizer N at rates of 0, 30, 60, 90, and 120 lb/acre applied by surface broadcast, surface band (dribble), and subsurface band (knife) placement methods on short-season corn grown in no-tillage and ridge-tillage systems. Average corn yield in 1997 was about 25 bu/acre more with ridge tillage than with no tillage when fertilizer N was applied at any rate. However, this trend was not apparent in 1996 and 1998, when yields were lower because of less rainfall. In 1996 and 1998, yield was not increased at N rates greater than 60 lb/acre, but in 1997, maximum yield was obtained at the 120 lb/acre N rate. Nitrogen placement effects on yield were inconsistent. Yield improvements resulting from increased N rate can be attributed to improved yield components, especially the number of kernels per ear, which was doubled with N at 120 lb/acre compared to no fertilizer N. Increasing N rate resulted in small increases in crude protein concentration in the corn grain. Even though more samples were contaminated with aflatoxin and at higher levels in the drier years, tillage and N management had little effect on aflatoxin concentrations. Corn grown on a claypan soil can respond to increased N rate and conservation tillage systems, especially in higher rainfall years, but the effect due to N placement is inconsistent.

Introduction

Until recently, a large portion of the eastern Great Plains corn production acreage was limited to the relatively small bottom-land areas along rivers rather than the more extensive, upland, claypan soils. This limitation was likely caused by moisture stress from drought conditions in July and August, limited plant-available moisture storage in claypan soils, and the lack of aquifers for irrigation. Short-season corn hybrids, introduced in the past 15 years, reach reproductive stages earlier than full-season hybrids and thus may partially avoid mid-summer droughts. Early trials in southeastern Kansas showed that short-season corn hybrids could yield as much as 30 bu/acre more than a full-season hybrid check (13). Larson and Clegg (10) found that “a well adapted early-maturing hybrid can produce yields comparable or better than late-maturing hybrids, particularly where late-season water stress is prevalent.” However, information on cultural practices for short-season corn hybrids grown on claypan soils is lacking.

Nitrogen management and tillage selection have the potential to impact short-season corn production and quality. The importance of N management for full-season corn has been shown in no-tillage (6,8) and ridge-tillage systems (1,21). Data are lacking, however, regarding N placement and rate for short-season corn grown in ridge- and no-tillage systems on claypan soils of the eastern Great Plains. An additional factor that may limit the success of short-season corn is the potential of aflatoxin contamination of the grain. Aflatoxin, a metabolite produced by the fungus Aspergillus flavus, can reduce productivity or cause mortality in farm animals (22). Production of aflatoxin appears to be influenced by various stress factors (14), possibly including N stress (9,15). Thus, proper N management for short-season corn grown in ridge- and no-tillage systems may not only improve yield potential, but also reduce quality degradation. Therefore, the objective of this research was to determine the effect of N fertilizer rate and placement on yield, yield components, and grain quality of short-season corn grown in conservation tillage systems on a claypan soil in the eastern Great Plains.

Field Experiment Description

The experiment was conducted from 1996 through 1998 near McCune, KS on a farm owned by Calvin Flaharty. The topsoil was a Zaar silty clay (fine, montmorillonitic, thermic Vertic Hapludoll) with approximately 12 inches of topsoil 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 inches/h (17). Selected background soil chemical analyses in the 0- to 6-inch depth were 6.7 pH (1:1 soil:water), 11 ppm P (Bray-1), and 110 ppm K (1 M NH₄C₂H₃O₂ extract) analyzed by the procedures recommended by North Central Region Agricultural Experiment Stations (4).

The experimental design was a randomized complete block with a split-plot arrangement of treatments in four replications. In each replication, whole plots were ridge tillage and no tillage. In the ridge-tillage system, ridges were reformed each year approximately two months before planting with a Buffalo cultivator (Fleischer Manufacturing Inc., Columbus, NE) equipped with ridging wings. The subplots (10 by 30 ft) were a 5 × 3 factorial arrangement of N fertilizer rate and placement. The five N rates were 0, 30, 60, 90, and 120 lb/acre. The three N fertilizer placement treatments were surface broadcast, surface band (dribble), and subsurface band (knife).

The nitrogen source was urea-ammonium nitrate solution (UAN, 28% N) and was applied just prior to planting. Broadcast solutions were sprayed through flood jet nozzles. Knifed solutions were injected at a 4-inch depth. Both knife and dribble applications were on 30-inch spacings applied approximately 4 inch from the established row position in both tillage systems. Pioneer 3737 corn was planted on 11 April 1996, 23 April 1997, and 17 April 1998 at 22,700 seeds per acre in 30-inch rows. Annually, P₂O₅ at 49 lb/acre and K₂O at 49 lb/acre were 2-×-2-applied with the planter. Each year, a pre-mix of 1.2 lb/acre atrazine and 1.5 lb/acre metolachlor was applied preemergence for weed control. In 1996, dry winter conditions resulted in no weed pressure, thus a glyphosate burn-down treatment was not applied. Glyphosate was applied at planting at 1.5 lb/acre in 1997 and at 1.0 lb/acre in 1998 to control emerged weeds.

Corn yields were harvested from the two center rows of each plot with a small plot combine. 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. After kernel weight was determined, the grain subsample was dried at 140°F, ground, and analyzed for N (3) in a H₂SO₄-H₂O₂ digest (11). Crude protein was obtained by multiplying grain N concentration by 6.25. A subsample of the harvested grain was analyzed for aflatoxin using the "Veratox for Alflatoxin" test kit (Neogen Corp., Lansing, MI). In 1997 and 1998, plant stands were thinned to 20,000 plants per acre at the 8-leaf stage and before harvest the number of ears in the harvest rows were counted. This allowed calculation of the number of ears per plant and kernels per ear.

Data were analyzed using the Proc Mixed procedure of the Statistical Analysis System (12). 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. A log(x+1) transformation was conducted on the aflatoxin data prior to analysis by Proc Mixed. Regression of dependent variables against N rate was done using Proc Reg of SAS (18).

Short-Season Corn Yield

Yield was affected by a year × tillage × N rate interaction (Table 1). In 1996 and 1998, when yield was below 80 bu/acre on this dryland, claypan site, the response to fertilizer N was minimal, especially to N rates above 60 lb/acre, and the yield differences between ridge- and no-tillage systems were small (Fig. 1). On similar claypan soils, Sweeney (20) did not find differences in grain sorghum yield between ridge and no-tillage systems. However, in this study in 1997, corn yield was higher and ridge-tillage resulted in about 25 bu/acre greater yields than no-tillage at all N rates. In general, a 1-lb/acre increase in N rate resulted in approximately a 0.5 bu/acre increase in corn yield in the no-tillage system, and in the ridge-tillage system the response was even greater at the lower N rates. Nitrogen rates required to achieve maximum corn yield can vary widely (5) and this appeared true for the three years of our study. Sims et al. (19), however, reported that their data suggested that tillage may sometimes improve corn production on finer-textured soils. Thus, in our study, the tillage resulting from late winter reformation of the ridges may partially account for the response difference between no-tillage and ridge-tillage systems during the more favorable growing conditions of 1997.

Table 1. Analysis-of-variance significance levels for the effect of tillage, N placement, and N rate on yield, yield components, grain protein, and aflatoxin concentration.

Treatment	Yield	Kernel weight	Ears per plant	Kernels per ear	Grain protein	Aflatoxin conc.
Tillage (T)	NS†	NS	NS	NS	NS	NS
N placement (P)	NS	NS	NS	NS	NS	NS
N rate (R)	**	**	**	**	**	NS
T × P	NS	NS	NS	NS	NS	NS
T × R	NS	NS	NS	NS	NS	NS
P × R	*	NS	NS	NS	NS	NS
T × P × R	NS	NS	NS	NS	NS	NS
Year (Y)	**	**	**	NS	**	NS
T × Y	NS	NS	NS	NS	NS	NS
P × Y	NS	NS	NS	NS	NS	NS
R × Y	**	NS	**	**	**	NS
T × P × Y	NS	NS	NS	NS	NS	NS
T × R × Y	*	NS	NS	*	NS	NS
P × R × Y	*	NS	NS	NS	NS	NS
T × P × R × Y	NS	NS	NS	NS	NS	NS

* Significant at the 0.05 level of probability.

** Significant at the 0.01 level of probability.

† NS, nonsignificant.

Fig. 1. Effect of N rate in ridge- (RT) and no-tillage (NT) systems on short-season corn yield during 1996 through 1998. For regression equations: †, *, and ** denote significance at the 0.10, 0.05, and 0.01 levels of probability, respectively.

Yield was affected also by a year × N placement × N rate intereaction (Table 1). As a result, there was no consistent trend in yield as affected by N placement (Fig. 2). Only in 1998 at the N rate of 30 lb/acre did knife application result in greater yield than broadcast applications. In both 1996 and 1998, however, broadcast applications resulted in greater corn yield than knife applications at the N rate of 90 lb/acre. In 1997, there was no N rate × N placement interaction and, averaged over N rates, broadcasting fertilizer N resulted in greater yield than dribble applications with knifing producing intermediate yield values. Since there was no rainfall in the week following fertilization in 1996 or 1998 and only 0.15 inch during 1997 to move the N fertilizer solution into the soil and minimize potential N losses, there was no obvious reason why yield differences, though minor, were sometimes greater with broadcast applications. Corn yield can be improved with subsurface placement of fertilizer N (1,8,16), but also, differences in N application methods can be small (2) as shown in our study.

Fig. 2. Effect of rate of fertilizer N applied by different methods (BC = broadcast; DR = dribble; and KN = knife) on short-season corn yield during 1996 through 1998. For regression equations: †, *, and ** denote significance at the 0.10, 0.05, and 0.01 levels of probability, respectively, whereas NS is non-significant.

Yield Components

Nitrogen rate had the most pronounced effect on yield components (Table 1). Averaged across all three years, kernel weight increased with increasing N rate (Fig. 3). This represents an approximate 15% increase in kernel weight when N rate was increased from 0 lb/acre to 120 lb/acre. Increasing N rate from 0 to 120 lb/acre resulted in a similar 15% average increase in the number of ears per plant, although the increase was not as pronounced in 1998 as in 1997 which resulted in an N rate × year interaction (Table 1). However, the greater yields with higher N fertilization rates (Fig. 1 and 2) likely were related to increases in kernels per ear (Fig. 4). The number of kernels per ear was affected by a year × tillage × N rate interaction (Table 1). In 1997, the number of kernels per ear were greater with ridge tillage than with no tillage at the higher N rates (Fig. 4). However, this trend reversed at the N rate of 120 lb/acre rate in 1998, where no tillage resulted in more kernels per ear. Compared to no N fertilization, application of fertilizer N at 90 lb/acre nearly doubled the number of kernels per ear in 1997 and, in 1998, an N rate of 90 or 120 lb/acre more than doubled the number.


Fig. 3. Effect of N rate on kernels per lb averaged across 1996 to 1998 and on ears per plant averaged across 1997 and 1998. For regression equations: * denotes significance at the 0.05 level of probability.		Fig. 4. Effect of N rate on the number of kernels per ear of corn grown in ridge- and no-tillage systems in 1997 and 1998. For regression equations: * and ** denotes significance at the 0.05 and 0.01 levels of probability, respectively.

Grain Quality

Grain protein was affected by a year × N rate interaction (Table 1), because protein was not affected by N rate in 1998. However, across years, increasing N rate from 0 to 120 lb/acre resulted in a slight increase in protein of approximately 7% (Fig. 5). Although 3-year average yield increased greatly with the initial 30- and 60-lb/acre increments of N fertilizer, similar changes in crude protein content did not occur. At N rates exceeding 60 lb/acre, incremental gains in yield decreased, whereas crude protein increased. Even though crude protein content tended to increase at the higher N rates, calculated N recovery in grain diminished from more than 40% apparent recovery of fertilizer N at the 30 and 60 lb/acre rates, to less than 20% apparent recovery as N rate was increased from 90 to 120 lb/acre (calculated data not shown).

Fig. 5. Effect of N rate on average (1996 to 1998) yield and crude protein concentration of short-season corn grain. For regression equations: ** denotes significance at the 0.01 level of probability.

Aflatoxin was detected in some of the grain samples each year (data not shown). As evidenced by lower yield, stress conditions were greater in 1996 and 1998 than in 1997. Rainfall was 6 to 7 inches more in 1997 than in 1996 and 1998. In 1996 and 1998, more than 50% of the samples contained aflatoxin, and 18 and 13% of the samples, respectively, had concentrations greater than the established limit for human consumption of 20 ppb (7). In 1997, moisture stress was less and yield was greater and only 16% of the samples were infected with aflatoxin and no sample had a concentration greater than 20 ppb. However, aflatoxin contamination was sporadic and no treatments significantly affected concentrations (Table 1). However, at P = 0.10, aflatoxin concentration was affected by a year × tillage interaction. In 1997 at P = 0.10, no tillage resulted in greater aflatoxin concentrations in the corn grain than with ridge tillage, but average concentrations in both tillage systems were well below the 20 ppb limit (data not shown).

Conclusion

Yield of short-season corn grown on the claypan soils of the eastern Great Plains is affected by conservation tillage systems and N fertilizer placement and rate, but the response varies with year. Under better growing conditions, ridge tillage results in greater yields than no tillage. The effect of N fertilizer placement on yield tends to be variable. Even though yield may be maximized at N applied at approximately 60 lb/acre in poorer years, when growing conditions are more favorable, corn yield will increase with rates of N at up to 120 lb/acre or more. Higher N rates tend to increase all yield components, but the largest effect is filling out the ear with more kernels. Crude protein content of the grain increases slightly with increasing N, especially at higher rates. Aflatoxin detection tends to be sporadic, but is more pronounced in drier years. However, tillage and N management decisions result in little or no effect on aflatoxin concentrations each year. Corn grown on claypan soil in the eastern Great Plains responds to increased N rate and conservation tillage systems, especially in higher rainfall years, but the effect due to N placement is inconsistent.

Acknowledgments and Disclaimer

Contribution no. 04-084-J, Kansas Agricultural Experiment Station. Research supported in part by grant funds from the Kansas Fertilizer Research Fund. Product names are included for the benefit of the reader and do not imply any endorsement or preferential treatment by Kansas State University.

Literature Cited

1. Blaylock, A. D., and Cruse, R. M. 1992. Ridge-tillage corn response to point-injected nitrogen fertilizer. Soil Sci. Soc. Am. J. 56:591-595.

2. Bundy, L. G., Andraski, T. W., and Daniel, T. C. 1992. Placement and timing of nitrogen fertilizers for conventional and conservation tillage corn production. J. Prod. Agric. 5:214-221.

3. Crooke, W. M., and Simpson, W. E. 1971. Determination of ammonium in Kjeldahl digest of crops by an automated procedure. J. Sci. Food Agric. 22:9-10.

4. Dahnke, W. C., ed. 1980. Recommended chemical soil test procedures for the North Central region (rev. ed.). North Dakota Agric. Exp. Stn. Bull. 499. North Dakota Agric. Exp. Stn., North Dakota State University, Fargo, ND.

5. Eckert, D. J., and Martin, V. L. Yield and nitrogen requirement of no-tillage corn as influenced by cultural practices. Agron. J. 86:1119-1123.

6. Fox, R. H., Kern, J. M., and Piekielek, W. P. 1986. Nitrogen fertilizer source, and method and time of application effects on no-till corn yields and nitrogen uptakes. Agron. J. 78:721-746.

7. Herrman, T. 2002. Mycotoxins in feed grains and ingredients. MF-2061. Kansas State University, Manhattan, KS.

8. Howard, D. D., and Tyler, D. D. 1989. Nitrogen source, rate, and application method for no-tillage corn. Soil Sci. Soc. Am. J. 53:1573-1577.

9. Jones, R. K., and Duncan, H. E. 1981. Effect of nitrogen fertilizer, planting date, and harvest date on aflatoxin production in corn inoculated with Aspergillus flavus. Plant Disease 65:741-744.

10. Larson, E. J., and Clegg, M. D. 1999. Using corn maturity to maintain grain yield in the presence of late-season drought. J. Prod. Agric. 12:400-405.

11. Linder, R. C., and Harley, C. P. 1942. A rapid method for the determination of nitrogen in plant tissue. Science (Washington, DC) 96:565-566.

12. Littell, R. C., Milliken, G. A., Stroup, W. W., and Wolfinger, R. D. 1996. SAS system for mixed models. SAS Institute Inc., Cary, NC.

13. Long, J. M., and Kilgore, G. L. 1992. Short-season corn hybrid performance trial. Pages 57-58 in: Kansas Agr. Exp. Stn. Rpt. of Progress 654.

14. McMillian, W. W., Widstrom, N. W., Beaver, R. W., and Wilson, D. M. 1991. Aflatoxin in Georgia: Factors associated with its formation in corn. Pages 329-334 in: Aflatoxin in Corn: New Perspectives. North Central Region Res. Pub. No. 329.

15. Payne, G. A., Kamprath, E. J., and Adkins, C. R. 1989. Increased aflatoxin contamination in nitrogen-stressed corn. Plant Disease 73:556-559.

16. Randall, G. W., Iragavarapu, T. K., and Bock, B. R. 1997. Nitrogen application methods and timing for corn after soybean in a ridge-tillage system. J. Prod. Agric. 10:300-307.

17. Rott, D. E., Swanson, D. W., and Jorgensen, G. N., Jr. 1973. Soil survey of Crawford County, Kansas. USDA-SCS, Kansas Agric. Exp. Stn. U.S. Gov. Print Office, Washington, DC.

18. SAS Institute. 1990. SAS/STAT user’s guide. SAS Inst., Cary, NC.

19. Sims, A. L., Schepers, J. S., Olson, R. A., and Power, J. F. 1998. Irrigated corn yield and nitrogen accumulation response in a comparison of no-till and conventional till: Tillage and surface-residue variables. Agron. J. 90:630-637.

20. Sweeney, D. W. 1989. Suspension N-P-K placement methods for grain sorghum in conservation tillage systems. J. Fert. Issues 6:83-88.

21. Timmons, D. R., and Cruse, R. M. 1990. Effect of fertilizer method and tillage on nitrogen-15 recovery by corn. Agron. J. 82:777-784.

22. Wicklow, D. T. 1991. Epidemiology of Aspergillus flavus in corn. Pages 315-328 in: Aflatoxin in Corn: New Perspectives. North Central Region Res. Pub. No. 329.