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Yield Goal versus Delta Yield for Predicting Fertilizer Nitrogen Need in Corn

Dep. of Agron., 210 Waters Hall, Univ. of Missouri–Columbia, Columbia, MO 65211

View larger version (35K): [in a new window]   Fig. 1. The effectiveness of yield at the economically optimum N rate (EONR) rate as a predictor of EONR for corn. Data summarize 298 experiments of corn response to fertilizer N in five states.

View larger version (37K): [in a new window]   Fig. 2. The effectiveness of delta yield [grain yield at the economically optimum N rate (EONR) minus grain yield of the control] as a predictor of EONR. Data summarize 193 experiments of corn response to fertilizer N in five states where fertilizer N increased corn yield.

View larger version (28K): [in a new window]   Fig. 3. Correlation between economically optimum N rate (EONR) and N rate calculated as 24.1 kg N Mg-1 (1.2 lb N bu-1) x yield goal. The two approaches are equivalent at locations that fall on the 1:1 line. Data summarize 193 experiments of corn response to fertilizer N in five states where fertilizer N increased corn yield. Legend indicates whether manure was applied in the past 3 yr and the previous crop; alfalfa includes alfalfa 1 and/or 2 yr before corn.

View larger version (16K): [in a new window]   Fig. 4. The correlation of corn grain N concentration of the control with delta yield for 38 fertilizer N response experiments in Minnesota. All locations were responsive to fertilizer N.

View larger version (27K): [in a new window]   Fig. 5. Economically optimum vs. predicted fertilizer N rate. Predicted fertilizer N rate was predicted using a theoretically derived equation based on delta yield (Eq. [6]) and assumes 47% fertilizer N use efficiency. Data summarize 193 experiments of corn response to fertilizer N in five states where fertilizer N increased corn yield.