Nitrogen (N) leaching from agricultural soils is a major concern in the southeastern USA. A winter cover crop following the summer crop rotation is essential for controlling N leaching and soil run-off, thereby improving sustainable development. Rotation of peanut (Arachis hypogea L.) and cotton (Gossypium hirsutum L.) with bahiagrass (Paspalum notatum) (i.e. sod-based rotation) can greatly improve soil health and increase crop yields and profitability. In the sod-based rotation, the winter cover crop is an important component. The objective of this study was to determine effects of summer crops, cotton and peanut, on growth and physiology of a subsequent oat (Avena sativa L.) cover crop in both a conventional (Peanut-Cotton-Cotton) and sod-based (Bahiagrass-Bahiagrass-Peanut-Cotton) rotations. Two rotations with an oat cover crop were established in 2000. In the 2006-07 and 2007-08 growing seasons, oat plant height, leaf chlorophyll and sap NO(3)-N concentrations, shoot biomass, and N uptake were determined. Our results showed that the previous summer crop in the two rotations significantly influenced oat growth and physiology. Oat grown in the sod-based rotation had greater biomass, leaf chlorophyll and NO(3)-N concentrations as compared with oat grown in the conventional rotation. At pre-heading stage, oat in the sod-based rotation had 44% greater biomass and 32% higher N uptake than oat in the conventional rotation; oat following peanut produced 40 to 49% more biomass and accumulated 27 to 66% more N than oat following cotton. Therefore, the sod-based rotation improved not only summer crops, but also the winter cover crop. Increased oat growth and N status from the sod-based rotation indicated greater soil quality and sustainability.
