Deep drainage and runoff, combined with poor nitrogen fertiliser practice, is resulting in significant nitrogen losses in early season irrigation. Currently 33% of growers are applying over 300kg N/ha, with research showing as little as 20% of this being taken up by the plants (Grace 2016). In an effort to keep the dialogue between researchers and growers active in the face of increasing nitrogen fertiliser costs and the industry need of responsible nitrogen management, CottonInfo established trials during the 2017/18 season quantify the runoff component of the nitrogen loss pathway and highlight the relationship between irrigation and nitrogen management.

Boosting the nitrogen use efficiency of cotton farms within Australia is a key objective of the Australian cotton industry. The movement of nitrogen with irrigation water has been anecdotally found by many growers with differences in crop growth and yields along the length of the field, from head ditch to tail drain. Nitrogen is also lost from the field through deep drainage and runoff totalling more than 10% of the applied N (MacDonald 2017). Both factors are influenced by irrigation management. Additionally, it has been highlighted through experiments in the Upper Namoi region by Baird (2016) that losses of 20 to 30 kg of pre-applied N can occur in the first irrigation alone. In the same study it was also found that irrigation intensity also affected Water Use Efficiency (WUE) and NUE.