Agronomic Outcomes and Environmental Benefits of Sod Phase in Crop Rotations: I Nitrogen and Water Use Efficiency By Cotton.

This study evaluates the impact of sod phase in crop-rotation management under variable rain and irrigation water on potential leaching of nitrates by monitoring nitrate-N concentrations in soil solution. Nitrogen- and water-use efficiency of cotton (Gossypium hirsutom L.) was assessed by evaluating seasonal responses to climatic and managerial changes in systems with and without bahiagrass (Paspalum notatum Fluegge) as a sod phase in non-irrigated and irrigated rotations of peanut (Arachis hypogaea L.) and cotton with oat (Avena Sativa L.) as winter cover crop in both systems. The study was carried out at the University of Florida’s North Florida Research and Education Center in Quincy, Florida, USA on an Ultisol under conservation/strip tillage with both sod- and row-crop phases equally presented each year.

A trend of increased water use efficiency was observed in the rotation with sod phase. In dry years, the cotton in rotation with sod phase did not reach the stress level for initiating irrigation as often as cotton in the rotation without no sod phase. Without irrigation, cotton yields from the sod-based rotation were higher than the yields from conventional rotation.

The soil-solution volume and nitrate-N concentrations reflected crop-rotation management and years’ dry-wet period fluctuations. The N-concentrations of the soil solution from conventional rotation occasionally exceeded the US drinking water standard of 10 mg L^-1, while the concentrations from rotation with sod phase were below that level. Leaching of N tended to occur during wet periods of the year with annual losses of 22 kg ha^-1 N from conventional rotation versus 13 kg ha^-1 N lost from the one with sod phase.