Cotton Yield Responses to Fertilizer Nitrogen Rates in a Cotton‐Corn Rotation

Abstract

The amount of N fertilizer needed for optimal cotton (Gossypium hirsutum L.) yield in cotton‐corn (Zea mays L.) rotations should be established to enhance the agronomic, economic, and environmental sustainability of crop rotations in the mid‐southern United States. Nitrogen rates were evaluated in field studies from 1996 through 2001 on Commerce silt loam (SL) (fine‐silty, mixed, nonacid, thermic Aeric Fluvaquent) and on irrigated Gigger SL (fine‐silty, mixed, thermic Typic Fragiudalf) to determine cotton yield responses to residual and fertilizer N rates in 2‐yr rotation cycles with corn. The treatments included N rates of 0, 168, 224, and 280 kg ha−1 applied to corn, and N rates of 0, 28, 56, 84, 112, and 140 kg ha−1 applied to the following cotton crop. Effects of the corn N rate, fertilizer N rate, and their interaction on cotton yield were significant (P < 0.05) for both locations. Each 1 kg ha−1 increase in corn N rate decreased the lint yield response to fertilizer N rate 0.12% on Commerce SL and 0.09% on Gigger SL. Optimal fertilizer N rates for lint yield on Commerce SL were 112, 84, 84, and 56 kg ha−1 following corn N rates of 0, 168, 224, and 280 kg ha−1, respectively. Optimal N rates on Gigger SL were 84, 56, 56, and 56 kg ha−1 following corn N rates of 0, 168, 224, and 280 kg ha−1, respectively. Residual corn N influenced lint yield responses to fertilizer N rate and the N rates needed to achieve optimal yield in a cotton‐corn rotation.