Evaluating alternative irrigation for a greener future

Abstract

The potential agronomic and environmental benefits of green cane harvesting and trash blanketing, the ongoing issues of nutrients and pesticides threatening the Great Barrier Reef, the rising ground water levels in the area, and water use efficiency issues, prompted the progressive MAFIA grower group to conceptualise a project to trial alternative irrigation systems and compare them with the conventional furrow irrigation system. A lateral move irrigation system was established on the Hesp property, in the Mulgrave farming area in the Burdekin, to irrigate sugarcane throughout a full 4 year crop cycle. This system was compared to conventional furrow and, on a nearby property, a drip irrigation system. The sites were extensively instrumented to measure parameters that would enable the water and nutrient balance to be monitored on the furrow and lateral move irrigated fields. Importantly, an intensive economic analysis was conducted to provide a guide to the economic evaluation of the three systems. Overall the results of the trial indicated that it was indeed possible to grow large sugarcane crops under the lateral move and drip irrigation systems, and that these crops could be subsequently harvested green. It was shown that the lateral move and drip systems also provided opportunity for improved water use efficiency over the furrow irrigation system and that the subsequent flow on benefits from this was reduced loss of nutrients via deep drainage and irrigation runoff. The economic evaluation, using actual inputs costs from the trial sites, show that the furrow and lateral move had similar operating costs which were significantly less than the drip system. However, it should be pointed out that this economic study looked at the adoption of a new irrigation system versus an existing furrow irrigation system. If the analysis was to examine a greenfield investment comparison, then the economic results could significantly change because of the extra capital investment required to establish a furrow irrigation system. In this analysis, environmental benefits resulting from improved water, nutrient and pesticide use are not accounted for in dollar terms, but if included would recognise the value of more efficient farming systems. While every effort was made to provide reliable information from this study, constraints associated with conducting the trial, within an existing “whole of farm” operation, meant that it should be considered more as a pilot study rather than a rigorous scientific trial. For this reason care should be taken in extrapolating the data from this study to other properties or areas where different circumstances and constraints could alter the perspective significantly.