Applicability of the Cornstalk Nitrate Test for Furrow-Irrigated Mid-South U.S. Corn Production.

The Corn Stalk Nitrate Test (CSNT) is a post-season nitrogen (N) management tool developed in the upper Midwest and used to determine if low/optimal/excessive N was applied to the corn (Zea mays L.) crop during the current year. Corn is a luxury consumer of N, with corn taking up more N than needed for maximal production with little evidence of lodging or yield loss. At maturity, corn plants receiving excess N will accumulate NO₃-N in the lower portion of the corn stalk. However, corn plants that received inadequate amounts of N will remobilize NO₃-N from the lower portion of the stalk and leaves to assist in grain-fill. Interpretation of CSNT results can help adjust the N recommendation for sequential corn crops and help fine-tune N management for a specific field over time. Due to the relatively small amount of land dedicated to corn production in Arkansas, little research has been conducted to evaluate the applicability of the CSNT. The objective of this study was to evaluate how applicable the CSNT is for furrow-irrigated corn production in Arkansas. Corn stalk nitrate samples and yield data were collected from corn verification fields throughout Arkansas in 2014 and 2015, where University of Arkansas best management practices were implemented. All locations achieved near maximum yields and were classified in either the Low or Optimal category based on NO₃-N concentration limits determined for the upper Midwest. Fields classified as Low had a narrow NO₃-N concentration range (<30 mg kg^-1). Whereas, large variability was identified in fields classified as Optimal, which had a fluctuation in NO₃-N concentration that ranged from 1 to 3900 mg kg^-1. With Arkansas having different management practices and N use efficiency compared to the upper Midwest, further research is needed to identify differences in the interpretation of stalk nitrate concentrations in Arkansas.