The effect of irrigated land-use intensification on the topsoil physical properties of a pastoral silt loam

Abstract

In Canterbury, New Zealand, there has been a widespread conversion of dryland sheep grazing to more intensive irrigated dairying. We determined the effects of these land uses on soil physical properties, and water release characteristics, on adjacent sites: a centre-pivot sprinkler-irrigated dairy farm site, a dryland sheep site, and a non-grazed, non-irrigated control site. Despite the Pallic Soil being well drained, greater soil compaction occurred at the dairy site than at other sites, to at least 30 cm depth. The dairy site typically had significantly lower total porosity and macroporosity, and greater bulk density and volumetric water content, than the other sites. Available water capacity varied but was greater at the dairy site (0–30 cm) than at the sheep site and control site. Further research is required across more farms and soils to confirm these results in other conditions.