Understanding spatial variability in potato cropping to improve yield and production efficiency
This research project aimed to pioneer an understanding of the extent and causes of within-field spatial variation in Tasmanian potato yield using a range of new sensing technologies and provide a preliminary determination on the potential for variable-rate management responses to improve profitability. To achieve this goal, soil apparent electrical conductivity (ECa) and high resolution elevation data were used to first define the variation in soil and landscape resources over two growing seasons. Variation in crop production was estimated using in-season aerial reflectance measurements and then measured using a first generation on-harvester yield monitoring system. During the season, soil and crop physical and chemical properties were measured to groundtruth/calibrate the sensor-derived data. The project wasn’t without its technical issues, primarily related to the on-harvester yield monitoring system combined with logistical issues associated with the physical harvest operation and the contractual obligations around harvest timing for individual fields. However, the project successfully documented substantial within-field and between field variation in soil physical and chemical properties, elevation and crop yield. The average potato yield for the study fields was 64 t/ha, but within fields the yield was recorded to vary over three-fold (from 28 t/ha to 96 t/ha on average). The in-season aerial crop reflectance was shown to significantly correlate to soil physical variability when gathered early in the season and to variation in plant physical and chemical properties, as well as important soil nutrient properties and crop yield when gathered from week 14 onwards. During the project, collaborating farmers were provided with maps of variability and involved in discussing results and implications. A wider group of growers and advisors were updated on progress through an Industry meeting organised by Simplot Pty Ltd, two articles in Potatoes Australia and PA news, and a poster presentation at a Tasmanian PA Expo. The results have highlighted that at this early stage, the most appropriate option for exploring SSCM in potato production appears to be the pursuit of individual field-based decision rules within broad recommendations for gathering useful field-scale data and sampling/analytical operations. To this end a short set of general rules for instigating SSCM in potato production has been devised based initially on nutrient management with irrigation management as an option.