Cropping System Management: Irrigation, Tillage and Crop Rotation in a Semi-Arid Climate.

Semi-arid production regions like those in the Southern High Plains are challenged with maintaining crop production while utilizing deficit irrigation; however, enhancing soil quality and health will likely optimize inputs and maximize nutrient and water use efficiencies possibly making dryland farming more profitable.A field experiment was conducted to determine yield and in-season water productivity of cotton at three levels under conventional and reduced tillage in a rotation sequence of continuous cotton, wheat (terminated)-cotton and cotton following grain sorghum. Cotton was grown under two tillage systems--conventional and reduced (only cultivated to incorporate preseason herbicide applications), at three irrigation levels (low, base and high) and as a part of three crop rotations. The base irrigation level (2.5” of seasonal irrigation in 2014) met approximately 60% of crop water needs using ET scheduling. The other water levels were ±50% of the base amount (1.4” and 3.6”). All cotton was planted in areas of continuous cotton or in rotation with grain sorghum or a terminated wheat cover crop. Crop responses were evaluated by harvesting 4 rows x 60° pivot arc and determining turnout and fiber data from sub-samples from each treatment. Seasonal irrigation treatments were replicated three times. Cotton yields and seasonal irrigation water use efficiencies (WUE) from the three rotation sequences, two tillage systems, and three irrigation levels were calcualted. Generally, lint yields were lower for cotton produced under reduced tillage than those produced under conventional tillage. Cotton planted following a terminated wheat cover crop showed the greatest response to increased irrigation level. Overall, despite tillage, the 1.5 base level irrigation showed the highest yields except in the case of the S-C rotation under conventional tillage. These field tests provide management options that help maintain short-term grower productivity while providing valuable information to improve future water value.