Long-term tillage, cover crop, and nitrogen rate effects on cotton: yield and fiber properties

Loess soils of the Midsouth USA are easily eroded, contain little organic matter, and are drought susceptible. Conservation tillage and cover crops may increase cotton (Gossypium hirsutum L.) yields on these soils. A field study was conducted from 1995 through 2001 on Gigger silt loam (fine-silty, mixed, thermic Typic Fragiudalfs) to study effects of tillage, cover crops, and N rates on yield and fiber properties. Cotton was grown without tillage (no-till) and with surface tillage (surface till) following annual winter cover crops of wheat (Triticum aestivum L.), hairy vetch (Vicia villosa Roth), or volunteer winter vegetation (native) and with fertilizer N rates of 0, 39, 78, 118, or 159 kg ha(-1). Tillage, cover crop, and N rate affected cotton yield. The till x N rate, till x cover crop, and cover crop x N rate interactions were significant. Yields of cotton receiving zero fertilizer N were 28 to 49% higher under surface till than under no-till. In contrast, cotton receiving optimum N produced 5 to 11% higher yields with no-till than with surface till. Following native cover, 118 kg N ha(-1) optimized cotton lint yields under no-till (1249 kg ha(-1)) whereas only 78 kg N ha(-1) was necessary to optimize yields under surface till (1117 kg ha(-1)). Following wheat, 118 kg N ha(-1) optimized lint yields under both no-till (1246 kg ha(-1)) and surface till (1185 kg ha(-1)). Following hairy vetch, no fertilizer N was needed to optimize yields under no-till (1238 kg ha(-1)) and surface till (1160 kg ha(-1)). Tillage, cover crop, and N rate did not appreciably compromise or improve fiber quality. After 7 yr, lint yields did not decrease in systems employing no-till and cover crops, and combined with optimal fertilizer N, these conservation practices increased cotton yields.