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

Abstract

Identifying opportunities to improve pasture production on irrigated Canterbury dairy farms is complex. This paper focuses on managing soil zones to optimise pasture production. Using electromagnetic induction (EM38) mapping, the area under a single centre pivot irrigator was characterised into soil zones of ‘low’, ‘medium’ and ‘high’, according to moisture and texture. Actual measurements of irrigation and soil characteristics were used in the model APSIM to estimate pasture production in ‘low’ and ‘medium’ soils under constant irrigation, 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 pasture in the ‘low’ zone to that of the ‘medium’ zone gave an increase of 580 kg DM/ha. This produced 51 kg/ha more milksolids and increased stocking rate by 0.2 cow/ha, giving a profit increase of $298/ha/year. This improvement on a 255 ha farm was estimated at $75,000 per annum. On a regional scale, increasing productivity of 52,900 ha of ‘low’ zone soils on irrigated farms in Canterbury would contribute $14 M to the economy. Taking a spatial management approach to understand variability in pasture can identify opportunities and potential value.