The effects of rotation crops and their management on soil properties of Vertosols, cotton yield and profitability were monitored from 1993 to 2001 in 3 irrigated field trials in NSW (Warren in the Macquarie valley, and Merah North and Wee Waa in the lower Namoi valley), and 2 dryland trials in Queensland (Warra in the Darling Downs and Emerald in the Central Highlands).

Measurements taken in all trials were: soil physical and chemical properties to a depth of 0.6m in (e. g. soil organic matter, plastic limit, strength with a penetrometer, soil structure, exchangeable Ca, Mg, K and Na, pH, electrical conductivity). Profile water content to 1.2m, nutrient uptake, crop growth, cotton lint yield and fibre quality were also measured. Economic returns in irrigated sites were evaluated by comparing seasonal and cumulative gross margins. Commencing from the 2000-01 cotton season spatial and temporal deep drainage (with the chloride mass balance model) and nutrient leaching were measured at ACRI (cotton sown into standing wheat stubble), Wee Waa (wheat-cotton) and 3 rotations (continuous cotton, wheat-cotton and doIichos-cotton) at Merah North.