Management systems for cotton on permanent beds - Maximing the benefits of rotation crops.
The effects of rotation crops and their management on soil properties, and irrigated cotton productivity and profitability were evaluated from 1993 to 1996 in some typical cracking clays (V ertisols) of the Namoi and Macquarie valleys of New South Wales. The project consisted of 3 field experiments: (a) an experiment on tillage systems and rotations (intensive tillage or minimum tillage sown with continuous cotton, and minimum tillage sown with a cotton-wheat sequence which were imposed in 1985, on which three rotations: cowpea-cotton, continuous cotton and fallow-cotton were superimposed in 1993) located at the Australian Cotton Research Institute near Narrabri; (b) a rotation crop management experiment (wheat+l40 kg ha-1 N-cotton, unfertilized wheat-cotton, and winter grain legume-cotton sequences where the legume grain was either harvested or incorporated) located near Wee Waa; and ( c) a rotation crop management experiment [high input (99 kg N and 17 kg P ha-1, irrigated) wheat-cotton, low input (16 kg N and 17 kg P ha-1, rainfed) wheat-cotton, rainfed field pea-cotton, summer fallow-cotton, low input wheat-dolichos-cotton, low input wheat-dolichos +24 kg P & 73 kg K ha-1-cotton, and continuous cotton sequences] located near Warren. (The low input wheat-dolichos/P+K fertilizer-cotton sequence was replaced by a faba bean-cotton sequence in 1995). Soil properties which were monitored to a depth of 0.6 min every site included organic matter fractions, plastic limit, strength, shrinkage indices derived from shrinkage curves, exchangeable Ca, Mg, Kand Na, pH, nitrate-N and electrical conductivity. Profile water content and water extraction to 1.2 m, nutrient uptake, crop vegetative growth, cotton lint yield and fibre quality were also quantified. Economic rerorns were evaluated by comparing gross margins for rotation crop-cotton sequences.