A survey of soil physical properties on sheep and dairy farms in southern New Zealand

The study compared soil macroporosity, bulk density, air permeability, and hydraulic conductivity on 97 sheep and 87 dairy farm sites surveyed in Southland and South Otago, New Zealand. Soil physical properties of 4 soil groups (15 soils) were investigated. Soils on sheep farms surveyed had significantly greater air permeability than soils on dairy farms, averaged over 0-15 cm. Soils on sheep farms had significantly greater saturated hydraulic conductivity (86 mm h(-1) and 26 mm h(-1)) than soils on dairy farms (32 mm h(-1) and 10 mm h(-1)), at 0-5 cm and 10-15 cm, respectively. Macroporosity decreased from 0-5 cm to 5-10 cm, at a significantly greater rate on dairy farms (by 3.6% v/v) than sheep farms (by 1.5% v/v). Bulk density increased between 0-5 cm and 5-10 cm by a greater amount for dairy farms (0.16 Mg-3) than for sheep farms (0.12 Mg m(-3)). Macroporosity on some Fragic Pallic Soils was considered limiting for plant growth, while Firm Brown Soils were regarded as well structured and most likely to resist treading damage.