Effect of application rate on nitrogen fertilizer recovery in an irrigated cotton cropping system

Irrigated cotton in Australia on heavy textured clay soils (Vertiol) is typically described as inefficient with respect to nitrogen, due largely to significant gaseous N losses through denitrification. We investigated the effect of different N rates (100N, 200N, 300N) on fertilizer recovery in furrow irrigated cotton. There was no significant effect of the different fertiliser rates on yield, with an average lint yield of 2,52 t ha-1 . Total fertiliser losses ranged from 28% to 49% of the fertiliser applied with the highest losses in the 300N treatment. The results demonstrate that N losses can significantly be reduced by avoiding excessive N application rates in irrigated cotton systems.

A field experiment was established in September 2017. The cotton was sown on the 18th October 2018 and 15N-labelled urea applied on the 9th November 2018. The experimental setup consisted of four N fertiliser treatments arranged in a randomised block design.