Reducing nitrate leaching losses from a Taupo pumice soil using a nitrification inhibitor eco-n

Abstract

The decline in water quality in Lake Taupo has been attributed to nitrogen (N) leaching from surrounding land areas. Pastoral agriculture has been identified as a significant contributor to this N transfer to the lake through animal urine deposition. There is therefore an immediate need for new management options to reduce N losses. The objective of this study was to measure the effectiveness of using a nitrification inhibitor (eco-n) to reduce nitrate leaching losses from a pasture soil of the Taupo region. A 3-year study was conducted using 20 lysimeters on Landcorp's 'Waihora' sheep and beef farm, within 10 km of Lake Taupo. The results show that animal urine patches were the main source of nitrate leaching (>95% of the total annual loss) and that eco-n significantly (P<0.05) reduced nitrate leaching losses from urine treated lysimeters. When the lysimeter results were combined with a detailed GPS survey and GIS analysis of urine patch coverage of the farm it is concluded that eco-n reduced annual nitrate leaching losses by between 23 and 32%, with an average reduction of 27%. Thus eco-n represents a practical technology that pastoral farmers could adopt today, to assist them to meet new water quality standards in sensitive catchments near Lake Taupo and the upper Waikato River. Keywords: nitrate, urine patch, nitrification inhibitor, eco-n