Long‐Term Tillage, Cover Crop, and Nitrogen Rate Effects on Cotton: Plant Growth and Yield Components

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Abstract
Cotton (Gossypium hirsutum L.) yield is influenced by tillage, cover crop, and N fertility, but the plant growth and yield component responses related to these yield responses have not been well defined. A field study was conducted from 1991 through 2001 on Gigger silt loam (fine‐silty, mixed, thermic Typic Fragidaulf) to determine the long‐term effects of tillage practices, cover crops, and N fertilization rates on cotton growth and yield components. Cotton was grown continuously without tillage (no‐till) or with surface tillage (surface till) following annual winter cover crops of wheat (Triticum aestivum L.), hairy vetch (Vicia villosa Roth), and volunteer winter vegetation in plots receiving fertilizer N rates of 0, 39, 78, 118, or 159 kg ha−1. Tillage practice, cover crop, and N rate significantly affected cotton plant height, main‐stem node number, number of nodes above white flower (NAWF), main‐stem internode length, lint fraction, percentage first harvest, individual boll weight, and boll number per square meter. Increases in lint yields were associated with increases in plant height (r = 0.73 to 0.95), node number (r = 0.71 to 0.83), internode length (r = 0.44 to 0.91), NAWF (r = 0.65 to 0.90), boll weight (r = 0.12 to 0.86), and boll number per square meter (r = 0.91 to 0.93). Lint fraction showed no association or, in some years, a negative association with lint yield (r = −0.12 to −0.70). No‐till management and optimal N rate improved the environment for plant growth, which enhanced several growth parameters and yield components that were associated with increases in yield.