The influence of topography and pasture management on soil characteristics and herbage accumulation in hill pasture in the North Island of New Zealand

The aim of this study was to examine long-term effects of fertiliser and livestock management and micro-topographical variation on soil physical and chemical characteristics and herbage accumulation on a hill site in the southern North Island of New Zealand. Paddocks subjected to high fertility-high stocking rate (HH) and low fertility-low stocking rate (LL) treatments dating back to 1975 were used. Soil samples were taken from three slope categories (0-12(degree) low slope, LS; 13-25(degree) medium slope, MS; >25(degree) high slope, HS) from HH and LL and a range of soil chemical and physical features were assessed. Herbage accumulation (green matter and dead matter) was measured over 12 months on each microsite. Greater differences in soil and herbage features, such as unsaturated hydraulic conductivity (Kunsat), bulk density (BD), water holding capacity (VSM), soil compressibility (SC), total soil nitrogen (Total-N), Olsen-P and green dry matter accumulation (GDMA), were measured across slope categories than between management treatments, possibly because slope effects on soils would have operated over longer periods of time than the fertiliser-stocking rate contrasts. Increasing slope decreased GDMA on the site, as well as Total-N, Olsen-P, VSM and SC, but increased Kunsat, BD and soil rebound after compression (SR). Slope, VSM, Kunsat, SC, BD and Total-N were the soil variables with largest influence on differentiation between microsites. Olsen-P and SR were less important. Green dry matter accumulation was strongly influenced by slope, soil VSM and Kunsat, and to a lesser extent by soil Total-N and Olsen-P.