Whole-Farm Economics of Long Fallowing in Semi-Arid Dryland Australian Wheat Production Systems.

As crop input costs, the prevalence of herbicide-resistant weeds and drought risk all continue to rise in semi-arid south-eastern Australia, regional dryland wheat producers require novel management practices to maintain profitability. The traditional practice of long fallowing – leaving a field out of production for an entire growing season – could reduce the cost of production whilst still maintaining total farm profit. During the 18-month long fallow period, crop weeds are controlled with non-selective herbicides and paddocks accumulate soil water and nitrogen, leading to lower production costs and higher average yield of the following crop relative to wheat grown in continuous sequence. Although long fallowing carries an opportunity cost associated with foregoing income from a field for an entire year, the economic benefits of the practice accrue at the whole-farm level. As the whole-farm economic impact of the practice has not yet been evaluated, the aim of this study was to compare total farm profitability of wheat-fallow rotations with continuous wheat and wheat-break crop sequences. APSIM (Agricultural Production Systems sIMulator) was used to simulate crop production over a 20-year (1997-2016) period on a hypothetical 4000 ha property in south-eastern Australia. Including a long fallow in the rotation decreased income variability and increased total farm profitability when wheat prices were low (<$AUD230/t) compared to continuous cropping scenarios. Continuous wheat production was more profitable at higher wheat prices, but profits continued to be more variable. Wheat grown on long fallow required less nitrogen fertiliser and achieved a higher average yield than wheat grown on wheat. Long fallow scenarios also benefited from reduced machinery depreciation, in-crop herbicide application and borrowing costs. This study shows that long fallow systems provide farmers with similar long-term profitability as continuous wheat production, whilst decreasing income variability and exposure to risk.