Opportunities and constraints for managing within-field spatial variability in Western Australian grain production

Sensing, interpreting and acting upon within-field spatial variation in crop performance through precision agriculture (PA) techniques stands to benefit farmers economically and environmentally. The increases in crop gross margin required to offset the cost of purchasing and operating PA technology can be calculated to help growers make PA investment decisions. Economic modelling shows potential benefits of <$5/ha to $40/ha for variable rate management. This is supported by on-farm trials showing benefits of $29–63/ha for zone management in the northern sandplain of Western Australia. The full benefits of zone management can only be realised by developing methods for defining management zones that are consistent in performance, and accounting for crop nutrient requirements within zones by allowing for seasonal effects on yield potential. Various methods can be used to define zones of consistent performance in fields that can be targeted for variable rate fertiliser inputs. In many situations yield variation can be related to variation in soil plant-available water capacity. Predictive systems using geophysical information will enable inexpensive extrapolation of valuable point-based soil characterisation. Constraints to adoption by farmers include lack of training and technical support, equipment incompatibility, perceived riskiness of economic returns, and barriers to use of “hi tech” elements. Future research, development and extension should target a wider farmer audience who are aware of spatial variability but are not currently using PA technologies.