FARMING SYSTEM CHANGES AND FERTILISER LOSS IN AN IRRIGATED SUGARCANE AREA-THE BURDEKIN

THIS paper reports on two changes to the 'normal' farming system in the Burdekin in which placement of fertiliser differs from common practice in plant cane. One placement method involves the surface application of a 'non-mobile' fertiliser mixture in bands beside the emerging plant, with reliance on subsequent irrigation to carry the fertiliser into the soil to the developing root system. The second placement method is associated with a change in the planting system to dual row into pre-mounded beds, with centre placement of fertiliser into the bed. This practice is currently growing in acceptance as growers move towards a controlled traffic farming system. Four rates of fertiliser were applied to ~3.75 ha strips in this investigation and run-off measured from each irrigation event and fertiliser rate. In both trials, the fertiliser in run-off was measured using programmable auto-sampling equipment and losses from the system, the method of loss and the implications for the downstream environment examined. Results of both investigations clearly show that under these practices fertiliser runoff losses were greater than those normally recorded. Results of the surface application of 'non-mobile' fertiliser indicated excessive losses of nutrients to receiving water bodies was likely from this practice as was a significant loss of fertiliser application efficiency. In the change to the dual-row mounded planting system, it was apparent that unexpected loss from the vertical band of applied fertiliser resulted, necessitating a rethink of the placement depth of the fertiliser in this system. These results are applicable to any irrigated sugarcane cropping system.