CROP-ROTATION AND TILLAGE EFFECTS ON SOIL-WATER AND COTTON YIELD

The Texas Southern High Plains is a major cotton (Gossypium hirsutum L.) producing area where a monoculture of conventionally tilled continuous cotton is thought to be causing a downward trend in yields. A factorial experiment with split plot design evaluated the main and interactive effects of (i) cotton-wheat (Triticum aestivum L.)-fallow rotation vs. continuous cotton, (ii) no tillage vs. conventional tillage, and (iii) furrow diking vs. no diking on cotton yield and soil water. Effects were determined for both dryland and irrigated production. Of the main factors considered, the cotton-wheat rotation had the greatest positive effect on yield and also on soil water variables. Rotation increased dryland and irrigated lint yields 12.6 and 12.8%, respectively. No tillage significantly increased yields (6.9 and 5.5% for dryland and irrigated, respectively) and enhanced seasonal soil water status. Yield increase due to diking was not statistically significant (P > 0.05) under continuous cotton production or when wheat was rotated with cotton. The greatest cotton lint yield and soil water increases were obtained when no tillage was combined with the cotton-wheat rotation (20-25% increases). Percent yield increase was directly associated with improved soil water relations resulting from the crop ping and tillage treatments.