This project will undertake research on both nitrogen (N) and phosphorus (P) and aims to increase understanding of the relationship between soil and fertiliser N & P supply, fertiliser placement, fertiliser timing, and irrigation strategy to achieve greater nitrogen use efficiency (NUE) and improved phosphorus soil nutrition. Optimising NUE can be complex as fertiliser type, application strategy and irrigation management can influence N availability to the plant and N loss to the environment under different farm practice scenarios. Under certain conditions, N losses to the atmosphere, deep subsoil and surface water can be substantial, leading to poor NUE.

In addition to applied fertilisers, N mineralised from soil organic matter is also a major source for cotton crops and is subject to the same loss pathways. In parallel, this project will undertake research into the dynamics of P uptake by cotton plants from both topsoil and subsoil, and the patterns of crop P accumulation, to better understand trends of long-term P supply throughout the soil profile. The research will investigate long term depletion rates of deep soil P reserves under different soil management strategies in irrigated farming systems. The findings will aid in the development of informed N and P management strategies to increase efficient and effective N and P use by Australian cotton growers.