Influence of Weed Growth and Tillage Interval During Fallow on Water Storage, Soil Nitrates, and Yield

Abstract

AbstractIn an effort to minimize tillage operations and production costs five sweep tillage intervals were evaluated for 7 years during the two 11‐month fallow periods in a winter wheat (Triticum aestivum L. ‘Tascosa’)‐sorghum (Sorghum bicolor (L.) Moench) cropping sequence. The tillage intervals ranged from very short or once every 2 weeks to as long as 24 days after weed emergence. Their effect on soil water storage, soil NO3‐N level and crop yield were determined on Pullman clay loam in the Southern Great Plains.Delaying tillage for 17 and 24 days after weed emergence reduced available soil water in the top 120 cm of soil.Average NOa‐N content in the top 120 cm of soil decreased from over 185 kg/ha with sweep tillage at 2‐week intervals to 56 kg/ha when sweep tillage was delayed until 24 days after weed emergence.Average wheat yields were not reduced when sweep tillage was performed 17 days after weed emergence, however they were reduced when tillage was delayed until 24 days after weed emergence. Average sorghum yields were not reduced when tillage was delayed 10 days after weed emergence. Delaying tillage to 17 days after weed emergence cut sorghum yield. Most farmers till about 4 to 10 days after weed emergence. Delaying tillage as much as possible as indicated in this trial will eliminate on or two tillage operations in an 11‐month fallow period.