Illinois
Fertilizer Conference Proceedings
January 24-26, 1994
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R.J. Lambert, R.G. Hoeft, and R.H. Teyker1
The research presented developed from a greenhouse seedling study on different forms and rates of nitrogen (2). 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 presented to this conference in 1992 (1), showed supplemental-N placement underneath the corn row (0") produced increased grain yields (average 17 bu ac-1) compared to N placement (15") in center of a 30 inch row spacing. The previous crop on this field was corn in 1991 and yields were low so considerable N carry-over occurred. Good growing conditions in 1992 produced grain yields in the 150 to 170 bu ac-1 range.
Two fields studies were conducted in 1993 at two locations on the Agronomy
Plant Pathology farm of the University of Illinois at Urbana, IL. At location
1 the previous crop was corn in 1992 (LIC) and at location 2 the previous crop
was soybean (L2S). The objective of the two studies was to measure the response
of three corn hybrids to a factorial arrangement of supplemental-N, involving
placement (0" vs 15"), N-rates and N-forms.
The two experiments were planted on May 20 and 21, 1993. Soil type for both fields was a Flanagan silt loam, with a yield potential of 140 to 150 bu ac-1. For the L1C field the 1992 crop was corn which received 190 lbs ac-1 of supplemental-N and produced yields in 160 to 170 bu ac-1 range. For the L2S field the 1992 crop was soybean and no supplemental-N was applied. Soil tests of the L1C field had a pH of 6.4, and P1, and K values of 116 and 424 lb/acre, respectively. The L2S field had a pH of 6.2, and P1, and K values of 72 and 300 lb/acre, respectively. Supplemental-N was applied seven days prior to planting as anhydrous ammonium with and without the inhibitor. The inhibitor used was Dow XDE-474. The N was applied seven to eight inches below the soil surface. 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). A plot consisted of four rows spaced 30 inches apart, 17.5 feet in length and with four replications. The center two rows of a plot were harvested for grain yield. All plots were machine planted and harvested. Plots were overplanted and thinned to a plant density of 23,896 p.p.a. The three corn hybrids used were LH74 x LH51, LH119 x Oh545, and LHE136 x C103.
Before harvest a five ear sample from each plot in two replicates was harvested and the five ears used to estimate yield components for a plot. Yield components measured were weight grain plant-1, ear length, kernel weight, and kernels plant-1. Stalk lodging data was taken prior to harvest and averaged 1.4 and 1.5 percent for the two locations.
A factorial arrangement of treatments in a randomized complete block design
was used. Supplemental-N rates used were 60, 120, and 180 lbs ac-1. Control plots
for each hybrid, with no supplemental-N applied were used to measure residual
soil N. The L1C location had a range in grain yields for the three hybrids of
56 to 65 bu ac-1 indicating little carry-over N from the 1992 corn crop. The
L2S location had a range in grain yields for the three hybrids of 66 to 97 bu
ac-1 indicating a greater level of soil N was carried over from the previous
soybean crop.
The grain yields at the two locations were lower than expected with the average for LC1 being 102 bu ac-1 and L2S 115 bu ac-1. No difference was observed in the means for supplemental-N placement at the LlC location (0" = 101 vs 15" = 102 bu ac-1). A 7 bu difference was observed at L2S location for supplemental-N placement with a 0" placement yield of 119 bu ac-1 and 15" placement yield of 112 bu ac-1. A significant placement x N-rate interaction was observed at both locations. The grain yields at the 0" placement were always higher at the three N-rates compared to the 15" placement at both locations except for the 120 lb N-rate at the L1C location (Table 1) with the yield differences varying from 2 to 8 bu ac-1.
A significant placement x N-rate x hybrid interaction occurred at the two locations. The hybrids with highest yields and response to N-rates and placement were LH74 x LH51 and LH119 x Oh545. The LH74 x LH51 genotype had a 13 bu increase to N-rates at 0" placement at LlC and only a 5 bu increase to N-rates at 0" placement at L2S, however, the yields at the 60 and 120 lb N-rate were higher in the L2S environment (Table 1). The response of LH74 x LH51 at the 15" placement to N-rates was greater at the L1C vs L2S environments (30 bu vs 17 bu increases). A similar N-rate response at the 15" placement was observed for LH119 x Oh545 at the two locations (26 bu vs 22 bu Table 1). The highest yielding hybrid was LH119 x Oh545 at the 0" placement and N-rates at the L2S locations, with yields varying from 122 bu ac-1 at 60 lb N-rate to 136 bu ac' at the 180 lb N-rate (Table 1).
The average values for N-forms at the two locations were essentially equal with L2S having an average yield 111 bu ac-1 for both N and N + I and L1C having average yields of 102 bu for N and 101 bu for N + I. The LH119 x Oh545 hybrid was the only one to show consistent yield increases to N-form. The N + I form of N was consistently higher in grain yield at the two locations when compared at the three N-rates and two placements. For the 12 possible comparisons between the two N-forms at the three N-rates, two placements and two locations the LH119 x Oh545 hybrid had 11 comparisons where the N + I form of N had yield increases ranging from 2 to 22 bu ac-1 (data not shown).
Analysis of yield component data showed the grain yield differences were associated
with kernel number plant-1. The L1C location 0" placement produced 24 more
kernels plant-1 than the 15" placement. The 0" placement at the L2S
location produced 40 more kernels plant-1 than the 15" placement. For the
18 possible comparisons of 0" placement vs 15" placement at the two
locations for the three supplemental-N rates 14 comparisons had higher kernels
plant-1 at 0" placement vs the 15" placement or in 78% of the comparison
more kernels plant-1 were produced at the 0" placement, however this did
not always result in greater yields (data not shown).
A factorial experiment involving supplemental-N placement, rates, forms and
three hybrids was grown at two locations at Urbana, IL in 1993. A 7 bu ac-1
increase occurred for 0" placement vs 15" placement of N at the location
where soybean was the previous crop but no differences in yield were observed
where corn was the previous crop. Preliminary conclusions based on one years
data, indicate LH74 x LH51 showed a good response to N-rates at the two locations
and N placement. The LH119 x Oh545 hybrid had the highest grain yields at the
0" placement where the previous crop was soybean and produced the highest
grain yields at the two locations at the 60 and 1201b N-rates. Additional data
are needed to confirm these preliminary findings.
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.
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.
