Cotton yield and lint quality responses to nitrogen rate and placement in the humid southeast

Abstract

AbstractProper N management in upland cotton (Gossypium hirsutum L.) is essential to optimize yields. Information on proper N application rate and placement method is needed for coarse‐textured soils of the humid Southeast. The objective of this study was to measure strip‐tilled cotton performance in response to five N rate and placement application methods. Five N rates (0, 45, 90, 135, and 180 kg N ha−1) and three placement methods {broadcast (urea + ammonium sulfate [AMS], surface banded (urea ammonium nitrate [UAN] + ammonium thiosulfate [ATS]), and injected (UAN + ATS) were evaluated from 2016 to 2018 at five sites in Virginia and one site in North Carolina. Petiole NO3–N, lint yield, lint percent turnout, and fiber quality parameters were measured. Nitrogen rate and placement had a significant effect on lint yield but only N rate affected petiole NO3–N concentration. Quadratic plateau analysis of relative yield found that 133, 128, and 180 kg N ha−1 were the optimum N rates for injected, surface‐banded, and broadcast systems with relative yields of 95, 90, and 94%, respectively. A critical petiole NO3–N concentration threshold of 5600 mg NO3–N kg−1 at early bloom was calculated to reach 92% relative yield. Neither rate nor placement had an effect on fiber quality parameters. This study shows that both surface banding and injecting between 128 and 133 kg N ha−1 can produce 90% or more relative yield for a modern cotton variety in the upper southeastern coastal plain of the United States.