Nitrate losses beneath an irrigated cotton field

Abstract

A field experiment was conducted for the purpose of analyzing the movement of water fronts and NO3-N leaching. A four-acre irrigated cotton field was divided into 12 sections with 2 plots in each. Each section represented a unit in an randomized complete block design, using two N treatments, two irrigation treatments and two samples sites. Cl⁻ and Br were used as conservative tracers to measure depth of water movement. At the conclusion of the growing season, twenty-four 10 ft. soil cores were removed from the field and analyzed for concentrations of NO3-N, Cl⁻ and Br⁻. Correlations existed between 15-bar water-holding capacity and chloride concentrations. The depth of the bromide front was significantly greater (p<5%) for the 70% irrigation efficiency than for the 90% efficiency. The concentration of nitrate-N below 5 feet was significantly lower for the 70% efficiency than for the 90% efficiency.