Illinois
Fertilizer Conference Proceedings
January 23-25, 1995
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R.J. Lambert, R.G. Hoeft, and R.H. Teyker1
The research presented was developed from a greenhouse seedling study on different forms and rates of nitrogen (3). The seedling growth (28 days) of ten corn inbreds for response to nitrogen forms (Ca NO3 and NH4OH with nitrapyrin) at two N rates was evaluated. Based on seedling response to these variables the inbreds were classified into three groups: group 1 preferred a low N-rate of NO3-N (inbreds LH74, C103, LH51): group 2 preferred low N-rate of NH4-N ( inbreds 38-11, L317, B68, and B14): group 3 preferred a higher N-rate of NH4-N (inbreds WF9, LHE136, and Oh545).
Data has been collected over three years (1992, 1993, and 1994) to determine the effect of N placement, rates, form, and hybrids where the previous crops were corn and soybean (1, 2). The two experiments where the previous crop was corn were conducted in 1992 and 1993. The two experiments where the previous crop was soybean were conducted in 1993 and 1994.
The objective of this report is to summarize the results for the four experiments
conducted over three years. The objective of each experiment was to measure
the response of several corn hybrids to a factorial arrangement of supplemental-N,
involving placement (0" vs 15"), N-rates, and N-forms.
The experiments following corn were planted on the Agronomy Plant Pathology farm of the University of Illinois, Urbana, IL on May 18, 1992 and May 20, 1993. The experiments following soybean were planted on May 21, 1993 and May 5, 1994. Soil type for all fields was a Flanagan silt loam, with a yield potential of 140 to 160 bu ac-1 range. Soil tests on all fields had pH in the range of 6.0 to 6.4, P1 range 50 to 120 lb ac-1 and K range 350 to 450 lb ac 1. Supplemental-N was applied seven to eight days prior to planting as anhydrous ammonium with and without N-serve as the inhibitor. Application of N was at a depth of seven to eight inches below the soil surface. Planting was usually seven to eight days after application except in 1994 when planting occurred twelve days after N-application. The field was marked so the applicator placed the N underneath the row (0" placement) or in the center of a 30 inch row (15" placement). All plots were four rows spaced 30 inches apart, 17.5 feet in length and four replications. The center two rows of a plot were combine harvested for grain yield. All plots were overplanted and thinned to a plant density of 23,896 p.p. a. The corn hybrids used were LH74 x LH51, LH119 x Oh545, LHE136 x C103 in 1992 and 1993. In 1994 Oh545 x B73 was substituted for LHE136 x C103 because of the poor performance of this hybrid in 1992 and 1993. Before harvest a five ear sample was taken from each plot in two replications and the five ears used to measure yield components for a plot. Yield components measured were grain weight plant-1, ear length, kernel weight and kernels plant-1. Stalk lodging data was taken in all years but no differences were observed for this trait in the four experiments. Plant height data was also collected but only showed significant differences in 1992.
A factorial arrangement of treatments in a randomized complete block design
was used. Supplemental-N rates were 60, 120, and 180 lbs ac-1 were
used. Control plots for each hybrid, with no supplemental-N applied were used
in all experiments to measure residual soil N.
The average for grain yields for two years (1992, 1993), when the previous crop was corn are presented in Table 1. Averaged over N-rates and forms, N-placement at 0" produced 9 more bushels of grain than placement at 15". At the 60 Lbs supplemental-N rate the 0" placement was 15 bushels better and at the 180 Lb rate 9 bushel better. The average yield of all plots over the two years was 131 bu Ac-1 with the check plots being 121 bu ac-1 indicating considerable carry over N was present in soil. The three hybrids grown at the 0" placement showed an average response to supplemental-N of about 5 bu ac-1, the same hybrids grown at 15" placement had an average response of 10 bu ac-1. The yield levels of LH74 x LH51 and LH119 x Oh545 were higher at the 0" vs 15" placement.
The only hybrid to show consistent yield increases for N-form (N+N.1.) was LH119 x Oh545. This hybrid showed yield increases that varied from 4 to 10 bu ac-1 at the different placements and N-rates. (Data not shown).
The 1994 data for the experiment where soybean was the previous crop are presented in Table 2. A good response of the three hybrids was noted for N-rates. There was no difference for Nplacement when averaged for the three hybrids or when individual hybrids were compared. The average yield for the 0" placement was 182 vs 184 bu ac-1 for 15" placement. The results did not change when the data was averaged for the two years (1993-1994) Table 2. No effect for N-form was observed for the one or two year data. (Data not shown).
A study conducted over three years 1992, 1993, and 1994 involving a factorial arrangement of supplemental-N placement, rates, forms, and hybrids was grown and summarized in this report. Two of the experiments were grown on soil where the previous crop was corn (1992, 1993) and two experiments grown (1993-94) where the previous crop was soybean. No effect was observed for supplemental-N placement, or N-form when the previous crop was soybean although differences in response to N-rates was observed for hybrids. The hybrid LH182 x Oh545 (1 year data) showed the highest and most consistent response to supplemental-N rates followed by LH 119 x Oh545.
The experiments conducted in 1992 and 1993 following corn showed an average grain yield increase of 9 bu ac-' for 0" placement vs 15" placement. A grain yield increase of 15 bu ac-1 was observed at the lower supplemental N-rate (60 Lbs N ac-1), for the 0" placement vs 15" placement. Also a response was observed for N-form with supplemental-N plus the N-inhibitor showing yield increases for the LH 119 x Oh545 hybrid.
The data indicate that for corn following soybeans no advantage is obtained from supplemental-N-placement or N-form for the hybrids tested. Adequate grain yield increases were observed to the supplemental-N rates used for the hybrids tested.
The limited data indicate that in a continuous corn cropping system a yield
advantage can be obtained by supplemental placement underneath the row. However,
this response is a function of the hybrid (genotype), N-rates, and yield levels
of the previous corn crop. Additional studies using commercial hybrids are needed
before broader inferences can be made.
1R.J. Lambert and R.G. Hoeft are Professors of Agronomy in the Department of Agronomy, University of Illinois and R.H. Teyker is Project Leader for Agricultural Research and Practices at the National Fertilizer and Environmental Research Center, Muscle Shoals, Al.
Lambert, R. J., R. G. Hoeft, and R. H. Teyker. Corn hybrids response to supplemental nitrogen, placement, rates, and forms. 1993 Illinois Fertilizer Conference Proceedings. Jan. 25-27, 1993. Springfield, IL.
Lambert, R. J., R. G. Hoeft, and R. H. Teyker. Corn hybrids response to supplemental nitrogen, placement, rates, forms, and previous crop. 1994 Illinois Fertilizer Conference Proceedings. Jan. 24-26, 1994. Peoria, IL.
Teyker, R. H. 1992. Influence of environment and genotype on response to enhanced ammonium supply by corn. In Proceed. of Symposium. Effects of Enhanced Ammonium Diets on Growth and Yield of Wheat and Corn. Soil Sci. Soc. of Am., Foundation for Agronomy Research, Atlanta, GA.
