This project has advanced the use of soil and tissue testing such that growers and advisors are now better able to optimise fertiliser use and have greater confidence in their management practices to provide sound nutrition for cotton crops. Adhering to these best management practices will improve the use-efficiency of fertilisers and reduce the potential for damage to the environment. The large quantities of macro-nutrients removed in seed cotton should be replaced to avoid depleting soil fertility.

Legume cropping can dramatically reduce the requirement for N fertilisers and substantially enhance soil quality. Legumes afford improved soil microbial biomass and reduced soil strength which enables better root growth and facilitates cultivation and tillage. Also, crops are better nourished due to improved availability of nutrients. Economic analyses have demonstrated higher gross margins from legume-based systems due to elevated cotton yields and the reduced requirement for N fertiliser.

By avoiding the overuse of N fertiliser, we can reduce greenhouse gas emissions via nitrous oxide. Further, atmospheric carbon dioxide can be sequestered and soil organic matter increased where tillage is minimised and permanent bed systems installed. Greater research effort is now being placed on the efficiency of N fertiliser use, and the regional extension officers are assisting this. This research offers the industry an opportunity to reduce N fertiliser use and greenhouse gas emissions, without reducing yield.

The results of this research are being extended to the cotton industry but have not been widely adopted by the industry. Further extension activity is planned and training for the extension team and industry on cotton nutrition and soil health issues.