Evaluating Tissue Tests to Improve Nitrogen Management in Furrow‐Irrigated Mid‐South Corn Production

Abstract

An ear‐leaf N of 30 g kg−1 differentiated between N‐adequate and N‐deficient corn plants at the R1 growth stage. The optimal corn stalk nitrate concentration ranged from 170 to 1000 mg nitrate N kg−1 at maturity. Nitrogen availability was excessive when stalk nitrate concentration values were >1000 mg nitrate N kg−1. The N rate needed for 95% relative grain yield was consistently near the N rate where nitrate accumulated in the stalk. The corn stalk nitrate test (CSNT) and ear‐leaf N concentration (ELNC) are used to determine the adequacy of corn (Zea mays L.) N management programs and is used most extensively in the Midwest and northeastern United States. Information on the utility of both the CSNT and ELNC for irrigated corn produced in the mid‐South is lacking. Twenty‐four N rate trials were conducted in Arkansas between 2013 and 2016 to evaluate the utility of the ELNC and CSNT in a furrow‐irrigated corn production system. An ELNC of 30 g kg−1 has been determined to differentiate between N‐adequate and N‐deficient corn plants at the R1 growth stage. The optimal CSNT concentration ranged from 170 to 1000 mg nitrate N kg−1 at maturity, indicating that adequate N was available to the corn crop to produce near‐maximum grain yield. The N rate needed to achieve 95% relative grain yield (RGY) was consistently identified near the N rate where nitrate N began to accumulate in the corn stalk. A CSNT values of <170 mg nitrate N kg−1 was found to represent the low category, suggesting that N was limiting corn grain yield, whereas N availability was found to exceed the amount needed to maximize grain yield when CSNT values were >1000 mg nitrate N kg−1. The ELNC and CSNT can be used to adequately determine the N status of corn produced within a furrow‐irrigated mid‐South corn production system.