Cotton yield responses to fertilizer Nitrogen rates in a cotton-corn rotation
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.