Soil and Plant Water Evaporation from Strip‐Tilled Cotton: Measurement and Simulation

Abstract

Abstract It is estimated that 20% of cotton producers in the Texas High Plains use the strip tillage practice of planting cotton ( Gossypium hirsutum L.) in residues of chemically terminated winter wheat ( Triticum aestivum L.). The effect of the residue on water use partitioning between soil ( E s ) and crop ( E c ) evaporation has not been reported. This study tested the hypothesis that the cumulative evapotranspiration ( E t ), of crop ina strip tillage system and in conventional tillage are similar, and that the residue modifies the components of total E t by reducing E s and increasing E c . Winter wheat was planted in the fall of 1990 and was chemically terminated in the spring of 1991 in an Olton soil (fine, mixed, thermic Aridic Paleustoll) at Lubbock, TX. The plot was divided into a wheat‐stubble and a conventional treatment. Residue on half of the plot was left as stubble and residue on the other half was shredded and incorporated. Both plots were planted with cotton on 20 May 1991. Measurements included soil water and temperature profiles, soil evaporation, weather, and crop phenology and lint yield. Input values obtained from these data were used in the energy and water balance model (ENWATBAL) to calculate the daily and seasonal water lost to E s and E c for 100 d. Calculated daily E s varied <1 SD from measured values. Measured mean total E t were similar, i.e., 305 ± 20 mm for conventional and 304 ± 41 mm for cotton in the wheat stubble. Simulated E t was within 10% of the measured value. The ratio of total E c to E t was 0.50 in the conventional and 0.69 in the wheat stubble cotton. The more efficient use of E t in the wheat stubble increased lint yield by 35%. The E c water use efficiency was not modified by the wheat stubble and was 3.8 g lint kg −1 of transpired water. The modified version of ENWATBAL was adequate to calculate the daily and seasonal water use of a cotton crop in a terminated wheat stubble, and the results support our hypothesis. The E t water use efficiency was increased by the wheat residue without additional input of water.