New nitrogen mitigation technologies for evaluation in the Lake Taupo catchment

Planned implementation of a nitrogen (N) "cap" on land in the Lake Taupo catchment has led to the need for a range of N mitigation options for pastoral farmers to increase profitability while farming within the N cap. A multi-disciplinary research programme has focused on the potential of targeting different parts of the N cycle to increase N efficiency and reduce N leaching losses. A range of research areas have been examined which focussed on soil amendments, improved pasture plants, animal manipulation and farm system options with potential for reduced N leaching. The "best bets" of practical options from this research have been selected, in consultation with local farmers through the Taupo Lake Care group. These are being tested in a new farm grazing system trial with beef cattle in the Lake Taupo catchment. The treatments are; a control (beef heifers), high sugar ryegrass (to potentially increase N absorption by cattle and reduce N excretion in urine), strategic salt supplementation (to increase urine spread), animal DCD supplementation (to achieve delivery of DCD in urine thereby inhibiting nitrification and reducing nitrate leaching) and steers (to compare spread of urine with female cattle). This long-term trial commenced in April 2007 and will evaluate effects of these N mitigation options on pasture production, N cycling and N leaching. Keywords: DCD, grazing, Lake Taupo, mitigation, nitrogen leaching, salt