Supplemental Nitrogen Applications on Corn in Lower Mississippi River Delta Alluvial Soils

Abstract

Core Ideas Corn optimal N rate on two alluvial soils ranged from 200 to 265 kg N ha−1. Supplemental N applied at early silk increases corn grain yield on two alluvial soils. Relative chlorophyll readings did not consistently diagnose need for supplemental N. Nitrogen deficiency may occur late in the corn (Zea mays L.) growing season due to N fertilizer loss, particularly on poorly drained clay soils, or increased plant demand. Results from field trials conducted from 2006 to 2014 at the Northeast Research Station, St. Joseph, LA, were summarized to evaluate the influence of supplemental N (SN) on corn at early silk (R1). Four non‐irrigated and eight irrigated trials on Sharkey clay (Vertic Haplaquept) and six trials on the Commerce silt loam (Aeric Fluvaquent) were evaluated. Early season N (ESN) rates of a no‐N control plus 200, 235, 265, and 300 kg N ha−1 on Sharkey clay and 135, 170, 200, 235, and 265 kg N ha−1 on Commerce silt loam were applied after emergence. Additionally, a SN application of 65 kg N ha−1 was applied along with one of the ESN rates at R1. Grain yield was maximized at 200 to 265 kg N ha−1 on Sharkey clay and 200 kg N ha−1 on Commerce silt loam soil. Averaged across years, SN significantly increased grain yield of corn on irrigated Sharkey clay and non‐irrigated Commerce silt loam soils by 16 and 10%, respectively. The SN application at R1 may be effective if N is deficient; however, in many cases, there were no grain yield differences between the SN and the equivalent ESN rate. Relative chlorophyll reading was not reflective of the need for SN at R1, perhaps due to the significant changes on environmental factors post R1 until harvest.