Dairy pasture responses to soil physical properties

Abstract

Relationships between relative seasonal pasture yields (total, spring, or summer/autumn) and soil physical properties were investigated. Dairy farm data were collected from trials over 7 years. There were few significant response relationships between total relative yield and each soil physical property at each soil depth, from 0 to 20 cm. Macroporosity (air-filled porosity; pores >30 μm), percentage of pores >300 μm, and total porosity at both 0–5 and 5–10 cm soil depths all had highly significant positive relationships with spring relative yield, with the best fit being for macroporosity. Summer/autumn relative yield had significant but negative relationships with macroporosity and the percentage of pores >300 μm at both 0–5 and 5–10 cm soil depths, and saturated hydraulic conductivity at 0–5 cm. Summation of yield data into seasonal totals gave more meaningful relationships with macroporosity, compared with summation over several individual yield harvests within a season. Macroporosity at 0–5 and 5–10 cm was the most useful indicator for predicting spring and summer/autumn pasture yields, but none of the physical measurements was a reliable indicator of total yield.