Runoff and soil loss by crop growth stage under three cotton tillage systems

ABSTRACT: Surface runoff and soil loss under natural rainfall were studied for cotton growth under three tillage systems on small plots in Alabama9s Tennessee Valley. Conventional tillage resulted in the highest soil loss, followed by reduced tillage with no cover crop and reduced tillage with a winter wheat cover crop. When the growing season was divided into two periods based on the last cultivation of the conventional tillage, more than 85% of total soil losses occurred in the first period for all treatments. Runoff during the seedbed stage was the highest for conventional tillage; reduced tillage with no cover crop produced the highest runoff in all other crop growth stages. High-intensity rainfall caused more runoff from both reduced tillage treatments than from the conventional tillage treatment. The 3-year average yields of seed cotton were 2,223, 2,123, and 2,076 kg/ha (1,980, 1,890, and 1,850 pounds/acre) for reduced-tillage-with-cover, reduced-tillage-without-cover, and conventional tillage treatments, respectively. Effect of tillage systems on seed cotton yield also varied with years. Conservation tillage systems showed no benefits over the conventional tillage system in yields under drought conditions. The reduced-tillage-with-cover treatment resulted in a severe yield reduction in 1987 after 2 consecutive years of drought before planting and during the critical growth period.