Crop area increases drive earlier and dry sowing in Western Australia: implications for farming systems

Abstract

Technologies such as minimum tillage and new herbicides have enabled the use of early and dry sowing in Western Australia (WA). Although there is a sowing date that maximises yield of individual fields, on-farm sowing dates are constrained by the availability of machinery and labour. It was hypothesised that farms with a larger crop area would begin sowing earlier and be more likely to dry sow than smaller farms because they would take longer to sow. Current sowing dates and the extent of dry sowing in WA were explored using multiple analytical approaches, such as analysis of farm records, survey data and historical weather records, and simulation modelling. Field records from seven farms showed that sowing date of the first cereal crop on-farm had advanced markedly in recent years. The timeline of this advanced cereal sowing date differed across sites but was prominent from 2010 for most sites. In a larger survey, conducted between 2011 and 2014, of 805 grain farms across all rainfall zones in the WA grain belt, the mean first crop sowing date was 29 April and half the farms used dry sowing. Farms with larger cropped areas tended to begin sowing crops earlier and were more likely to dry sow. Only 26% of small farms (<1000 ha crop) used dry sowing compared with 71% of large farms (>5000 ha crop). A larger proportion of lupin (34%) and canola (43%) was sown dry than wheat (16%) or barley (10%; P < 0.001). Simulation modelling demonstrated that the optimum time to begin sowing at the farm level was often well before the break of season (the first autumn rainfall of sufficient volume to ensure subsequent successful crop germination and establishment), but this was dependant on the size of the cropping program. Early and dry sowing will continue to expand, and research to understand how other agronomic management interacts with this change should be a priority. This may include cultivars with appropriate traits, such as longer duration to flowering, changes in weed management practices, management practices that accumulate soil moisture at sowing, interactions with water repellent soil and the interaction with dual purpose cropping.