CottonInfo's team of Regional Extension Officers (REOs) have a particular focus on helping growers to improve their nitrogen use efficiency.

As a result, the team have been conducting a series of on-farm trials across the cotton growing valleys, aimed at ground truthing the research around N use and its efficiency. Trials were conducted during the 2014-15 and 2015-16 seasons.

2014-15 trials

The aim of the 2014-15 season trials was to examine Nitrogen Fertiliser Use Efficiency, through the effect on yield of different rates of Nitrogen (N) fertiliser, as well as examining the fate of nitrogen fertiliser throughout the cotton crop season. Replicated trials were also carried out across all cotton growing regions by the CottonInfo REOs.

The findings from each valley can be downloaded below:

The results from these trials emphasis that there is not one optimum nitrogen fertiliser rate, and that further information is needed regarding the factors impacting both the availability and losses of nitrogen in the system, in order to more accurately apply the optimum economic and environmental rate.

For more information on the findings from each valley's trial, please contact the relevant CottonInfo REO.

2015-16 trials

Building on the 2014-15 trials, the aim of the 2015-16 trials was to look more closely at several of the nitrogen availability and loss factors. 

Traditionally, nitrogen availability has been determined by pre-season soil tests. This season, the team also conducted an in-season test to estimate the contribution of nitrogen mineralisation during the growing season. The Solvita mineralisation test was collected in partnership with the CRDC-funded Enhancing and Testing the Cotton Carbon Management Tool project run by the University of Queensland.

A second focus was to quantify nitrogen losses due to leaching during early irrigation events. The REOs used Nitrate Test-strips to measure the nitrate level in early irrigation events, to provide important information about the effectiveness of pre-season N fertiliser placement.

The trials also assessed the value of leaf and petiole testing to optimise in-crop fertiliser application, with variable rates above and below the recommended rates being applied.