Implications of increased use of brought-in feeds on potential environmental effects of dairy farms in Waikato

Abstract

Abstract The effects of increased use of brought-in feeds were evaluated across 25 dairy farms in central Waikato. Farms were classified into low, medium and high feedinput categories based on 1200 kg DM/cow, covering a range typical of that in the main dairying regions of New Zealand. Average milksolids (MS)/ha was 1087 and 1900 kg in the low and high feed-input categories, but total land-use/tonne MS was the same when all off-farm land was accounted for. Average estimated on-farm nitrogen (N) leaching increased from 26 to 30 kg N/ha/year between the low and high feed-input categories, but off-farm leaching sources were equivalent to an increase of 20 and 84%, respectively. Greenhouse gas emissions/on-farm hectare were 61% higher on high feed-input farms, but the carbon footprint and N leaching per tonne MS were similar across feed-input categories. High feed-input farms used feed-pads and increased effluent area (66 versus 21% of farm) to increase nutrient efficiency. Mitigation analyses indicated that N leaching could be decreased by optimising effluent area, reducing N fertiliser rate and utilising low-N feeds. Keywords: nitrogen leaching, whole farm system, greenhouse gases, land use