Soil inorganic nitrogen in spatially distinct areas within a commercial dairy farm in Canterbury, New Zealand

Abstract

For precision nitrogen (N) fertilisation of grazed dairy paddocks, soil N distribution needs to be quantified. It is expected that farm infrastructure will affect inorganic-N distribution due to its influence on cow grazing behaviour. Surface soil from four spatially distinct areas (main gate, water troughs, non irrigated and the remaining pasture) was analysed for soil ammonium-N (NH₄⁺-N) and nitrate-N (NO₃⁻ -N) from three paddocks (180 soil samples) on an irrigated commercial dairy farm in Canterbury, New Zealand. Variation between paddocks was higher for NO₃⁻ (P<0.001) than for NH₄⁺ (P=0.52). Differences between spatially distinct areas were detected for NH₄⁺ (P<0.001) but not for NO₃⁻(P=0.37), though there was variation in NO₃⁻ with distance from the gates and troughs. This study demonstrates methods for classifying spatially distinct areas of grazed pasture to quantify their influence on inorganic-N distribution. Further research is required to better understand variability.