This project continued the major study of waterlogging on heavy clay soils after furrow irrigation or heavy rainfall. The experiments concentrated on cotton, but some detailed work was also done on summer legumes to study detailed reasons for yield reduction daring waterlogging.

I. The optimum field slope for furrow irrigation was 1:1000 to 1:1500

2. The best yields were obtained from running siphons for 4h at each irrigation. Longer times of running siphons reduced yield, especially with slopes of 1:2000.

3. Foliar nitrogen fertilizer, applied prior to an irrigation which caused waterlogging, minimised the yield loss due to waterlogging, particularly with low to moderate soil N status.

4. Waterlogging-induced iron chlorosis has been found to limit crop growth of grain legumes and possibly cotton at some sites. Further research is needed on methods of identifying and reducing this effect.