Conservation Tillage Effects on Infiltration and Irrigation Advance Times in Arizona Cotton

Field experiments were initiated in 2001 for a cotton-based conservation tillage project at sites in Marana, Coolidge, and Goodyear, Arizona. For the 2002 season, soil and water management assessments were made to evaluate surface irrigation performance under conservation tillage, following cover and grain crops. An additional site was added in the winter of 2002 at Maricopa, Arizona. Analyses included soil texture, infiltration rate, and water advancement. At Coolidge, conservation tillage plots had higher infiltration rates and longer advance times than the conventional plots in 2002 and 2003. At Marana, infiltration rates were initially higher for the Conservation plots but the rates converged at the end of four hours in 2002. In 2003, Conventional plots infiltrated about one inch more. Advance times for Marana showed water infiltration for Conventional wheel rows to be the fastest. At Goodyear, Conservation plots infiltrated more than Conventional plots during 2002. This also resulted in a slower advance time for the Conservation plots. In 2003, treatment effects were not comparable due to tillage by the grower. At Maricopa, Conservation plots infiltrated almost 2.2 inches more water than Conventional plots and water reached the end of the field three hours ahead of the fastest Conservation plot. Seasonal irrigation water applications to each treatment were relatively equal for all sites with the exception of Coolidge. Here, the long field combined with sandy soil made it difficult to adequately irrigate the Conservation plots. In 2002, an additional 21 inches of water was applied to the Conservation plots. In 2003, that amount was reduced to 12.5 inches. The yield data show a significant difference in 2002 only at Coolidge. There, Conservation plots yielded more than the Conventional ones. This may have been due to more water applied to the Conservation plots. In 2003, the opposite occurred with the Conventional plots yielding more than the Conservation plots. This could have been due to herbicide damage. At Maricopa, the Conventional plot also yielded more than the Conservation plot. Initial indications are that the conservation tillage does impact irrigation performance and may not be suitable for all locations depending on soil type and field layout