AN ASSESSMENT OF CONTROLLED RELEASE FERTILISER IN THE HERBERT CANE-GROWING REGION

LOSS OF NITROGEN from sugarcane fields is of serious environmental concern and also limits sugarcane production. Losses can be significant in high rainfall environments, where nitrogen is subject to surface runoff, leaching and denitrification. Large-scale field trials were established to compare the efficiency of controlled release (CR) nitrogen (N) (39-0-0 and 37-0-0) fertiliser against urea (46-0-0) in sugarcane crops grown in the Herbert valley. Rate response curves for CR N and urea were measured on clay and solodic soils. Fertiliser was applied and cane harvested using commercial equipment. Cane yield and CCS were measured in cane supplied to the mill. Controlled release N was significantly (P ≤ 0.05) more effective than urea 46-0-0 on both soil types. On the solodic soil, Agrocote® CR N was twice as efficient as urea-N; cane yield at 80 kg Agrocote®-N was equivalent to that achieved with 160 kg urea-N. On the same soil type, CR N significantly (P ≤ 0.05) increased cane yields by 10 t/ha above that achieved with 160 kg urea-N/ha, the maximum recommended N rate under Six Easy Steps. Compared to urea, Agrocote® increased (P ≤ 0.05) cane yield by an average of 4.8 t/ha on the clay soil. There were no significant yield responses to controlled release K. In the Herbert valley, controlled release was an effective tool to increase N-use efficiency and to manage risks associated with N-loss during heavy rainfall events. Controlled release fertilisers may reduce environmental losses and provide productivity gains in high rainfall environments.