Sod-Based Rotation, Conservation Tillage, and Water Use Efficiency.

Farmers in the southeast US have traditionally utilized a peanut (Arachis hypogaea L.) -cotton (Gossypium hirsutum) rotation with moldboard plow tillage; unfortunately, this management system contributes to disease and weed resistance, increased water loss by evaporation from the soil surface, and accelerated organic matter degradation.  To minimize these problems, researchers in the southeast US have proposed incorporating two years of a perennial grass into the traditional rotation and adopting conservation tillage practices into the management system.  This system, known as the sod-based rotation (SBR), typically consists of two years of bahiagrass (Paspalum notatum Flueggé) followed by peanut and then cotton managed with strip tillage.  While numerous studies have focused on the effects of this system on soil quality and crop yield, understanding the system’s influence on the water utilization of the crop is lacking.  To investigate this effect, peanut and cotton leaf samples were taken in late August and evaluated for chlorophyll content using a soil plant analysis development (SPAD) meter.  Typically SPAD values are positively correlated with water use efficiency (WUE); therefore, these values were used to estimate the (WUE) of the crops under each rotation (traditional and SBR) and tillage (moldboard plow and strip) system.  While rotation did not have an effect on SPAD values for each crop, tillage had a greater influence on SPAD values in cotton than in peanut.  Furthermore, the SPAD values were consistently higher in peanut than in cotton for all treatments.