North Otago soils: physical properties and nutrient requirements for economic production

Abstract

North Otago soils are all of sedimentary origin but range in topography from flat alluvial and terrace soils to hill soils. Most of the farmed soils are yellow-grey earths on the rolling downlands or plains. Yellow-grey earths on the downlands have dense subsoils that limit water movement during wet winters and rooting depth during dry summers. Plains soils have shallow depths to gravels limiting water holding capacity and making irrigation necessary for intensive pastoral production. The relationships between soil nutrient levels and pasture production has been shown to be of the diminishing returns type. Soil nutrient levels for near maximum pasture production on North Otago soils are Olsen P 20-25, sulphate-S 10-12, organic-S 15-20 and quick test K 5-8. At high stocking rates profitable responses in pasture and animal production can still be gained at higher Olsen P levels. The decision support nutrient model (OUTLOOKTM) has been developed to help farmers apply fertiliser at optimum rates for economic production. Keywords: economic production, North Otago, phosphorus, potassium, sedimentary soils, sulphur, yellow-grey earths