Illinois Fertilizer
Conference Proceedings
January 22-24, 2001
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R. J. Lambert, R. W. Esgar, and D. K. Joos1
Management of fertilizer nitrogen (N) in Illinois is of economic and environmental concern to corn growers and urban populations. Response to fertilizer N by corn hybrids is affected by time of application, rates, plant densities, soil type, previous fertilizer N applications, and hybrid (Russell, 1986; Jokela and Randall, 1989; Schepers and Below, 1987; Krone and Lambert, 1995). Corn hybrids vary in their N rate that maximizes grain yields, but the soil environment also plays an important role (Gardner et al. 1990).
Preliminary data reported at this conference in 1999 indicated that grain protein content could be used to estimate N removal in the grain by corn hybrids (Lambert et al. 1999). Data obtained from the Illinois Corn Performance trials showed grain yield was the dominant factor in N removal, but location, grain protein level, and hybrid also were important factors.
There is a need to develop rapid, inexpensive methods for estimating N use of corn hybrids for on-farm use. Several Near-Infra-Red reflectance or transmittance instruments are available for this purpose. Estimates of the total amount of grain protein in whole kernels can be converted to percent N. This value can be used to estimate N removal from the soil by a corn hybrid. When information is available on factors affecting variation in these estimates the method could be adapted to on-farm use.
The objective of this research was to determine environmental effects and hybrids on N removal in the grain at three locations in Illinois during the growing seasons of 1999 and 2000.
The Varietal Testing Program of the Department of Crop Sciences of the University of Illinois offers a unique opportunity to grow a large number of commercial corn hybrids at a location and under varying environmental conditions. The three locations used in both years of the study were Brownstown, Dwight, and Urbana, IL. Characteristics of the three locations are presented in Table 1.
All plots were planted and harvested by machine. Herbicides were used for weed control. All plots were overplanted and thinned to a plant density of 26,000 plants per acre at Brownstown and 29,000 plants per acre at Dwight and Urbana in 1999 and 2000. All plots consisted of four rows 30 inches apart, with the two center rows harvested for yield and a sample saved from each plot for estimating grain protein content. Total grain protein was estimated using Near-Infra-Red transmittance (NIT), which also estimated oil and extractable starch concentration (Itynre, 1992). Protein values were converted to percent N by dividing by 0.0625. Grain yields were determined for each plot as No. 2 yellow corn. The pounds per acre of corn per plot was multiplied by percent N to estimate N removal in the grain. N removal by a hybrid was averaged for the three replications.
A field design was used that blocked hybrids within a replicate because of the large number of hybrids tested, which led to large replicates. This design adjusts for the environmental variation within a replicate. Analysis of variance procedures were used to analyze data at each location.
Data in Table 2 show the large differences in average grain yields between 1999 and 2000 for Brownstown and Dwight. These yield differences are likely the result of rainfall differences between 1999 and 2000 at these locations. Brownstown received 9 inches more rain in 2000 than in 1999, and Dwight received 7 inches more rain during the growing season (Table 1). This resulted in average yield increases of 59 bushels per acre for Brownstown and 50 bushels per acre for Dwight for 2000 vs. 1999. Yield increases observed for Brownstown and Dwight were associated with the average N removal per acre for these locations. The average increase in N removed in the grain for Brownstown was 33 pounds of N per acre and for Dwight was 39 pounds of N per acre. Little change in N removal for Urbana was observed between 1999 and 2000 (181 vs. 187). The data from 2000 for Dwight and Urbana indicate the amount of fertilizer N that was applied is close to the amount removed in the grain.
To determine if simple linear regression could be used to estimate N removal in the grain of corn hybrids group means were used at each location. The data is presented in Table 3. The three regression equations for each location were different and the b values for Brownstown and Dwight similar (+0.72 ± .03 vs. +0.48 ± .10), with Urbana being significantly greater than the other two. These differences could be the result of past management practices of fertilizer N. The Urbana location has had relatively high applications of fertilizer N for a period of 10-plus years, so there may have been a buildup of N in the soil. The regression equations were able to predict rather closely the amount of N removed at the three locations (Table 3). Using this approach on-farm would require data over several years and also would probably be site specific.
Based on data over two years (1999 and 2000) at three locations in Illinois, grain protein content can be used to estimate nitrogen removal by corn hybrids. Estimates of N removal in the grain of corn hybrids can be affected by hybrid, environmental conditions (rainfall, etc.), past fertilizer N practices, and grain protein levels.
1R. J. Lambert is Professor; R. W. Esgar is Agronomist; and D. K. Joos is Research Specialist in Agriculture, Department. of Crop Sciences, University of Illinois, Urbana, IL.
Gardner, C.A., P.L. Bax, D.J. Bailey, A.J. Cavaleri, C.R. Clausen, G.A. Luce, J.M. Meece, P.A. Murphy, T.E. Piper, R. L. Segebart, O.S. Smith, C.W. Tiffany, M.W. Trimble, and B.N. Wilson. 1990. Response of corn hybrids to nitrogen fertilizer. Journal of Production Agriculture, 3:39-43.
Itynre, R.L. 1992. Evaluation of single kernel pedigree selection for developing improved high oil corn inbreds. M.S. Thesis, Dept. of Agronomy, University of Illinois.
Jokela, W.E. and G.W. Randall. 1989. Corn yield and residual soil nitrate as affected by time and rate of nitrogen application. Agron. J. 81:720-726.
Krone, T.L., and R.J. Lambert. 1995. Maize genotypes developed at three soil nitrogen levels II. Hybrid evaluation. Maydica 40:217-222.
Lambert, R.J., R. W. Esgar, and D.K. Joos. 1999. Factors affecting the
removal of soil nitrogen by corn hybrids. In Illinois Fertilizer Conference
2000 Proceedings. (R. G. Hoeft, ed.)
Pp. 68-75.
Russell, W.A. 1986. Contribution of breeding to maize improvement in the United States, 1920s-1980s. Iowa State J. of Res. 61:5-34.
Schepers, J.R., and F.E. Below. 1987. Influence of corn hybrids on nitrogen uptake and utilization efficiency. Proc. 42nd Annual Corn and Sorghum Res. Conf. Amer. Seed Trade Assoc. Washington D.C. 42:172-186.
