Size of the prize: The value of closing pasture yield gaps on heterogeneous soil types in a dairy farm in Canterbury, New Zealand

Identifying opportunities to further improve pasture production on high producing, irrigated Canterbury dairy farms is complex. An innovation systems approach was used to identify the factors contributing to variation in pasture production on a case study farm such as: soil characteristics, irrigation management, and grass grub populations. This paper focuses on the value proposition of managing soil zones to optimise pasture production. Using EM38 mapping, area under a single centre pivot irrigator were characterised into soil zones of ‘low’, ‘medium’ and ‘high’. Actual measurements of irrigation application and soil characteristics were modelled in APSIM to estimate the pasture production of ‘low’ and ‘medium’ soil zones under a constant irrigation regime, giving an annual difference of 2900 kg DM/ha between the zones. In a ‘typical irrigated Canterbury System 4 dairy farm’ modelled in FARMAX, with 20% ‘low’ and 80% ‘medium’ soil zones, increasing the pasture growth in the ‘low’ zone to that of the ‘medium’ zone gave an increase of 580 kg DM/ha. This produced an increase of 51 kg/ha of milk solids and increased the stocking rate by 0.2 cow/ha, which resulted in a profit increase of $298/ha/year. The value of this on a 255 ha farm would be $75,000 per annum, while at a regional scale, increasing the productivity of the 52,900 ha of ‘low’ zone soils on irrigated dairy farms in Canterbury would add around $14 M of profit. Taking a data-driven spatial management approach to understanding the drivers of variability in pasture production has potential to identify opportunities and their potential value even in high-performing systems.