Resource use efficiency and environmental emissions from an average Waikato dairy farm, and impacts of intensification using nitrogen fertiliser or maize silage

Abstract

A life cycle assessment (LCA) approach was used to estimate whole-system (dairy farm + grazing and forage land) resource use and environmental emissions for an averag e Waikato dairy farm enterprise. Effects of increased production from 850 to 1020 kg milksolids/ha using more nitrogen (N) fertiliser (+200 kg N/ha/yr) or forage (+2 t DM/ha/yr maize and oats silage) were also assessed. Fertiliser N increased production and economic efficiency, but decreased environmental efficiency through a predicted increase in N leaching and greenhouse gas (GHG) emissions. In contrast, using forage increased the use of land but increased milksolids/ha and with no loss in environmental ef ficiency (per kg milksolids). A preliminary compar ison of the average Waikato farm system and an example Swedish dairy farm system showed small dif ferences in environmental efficiency (GHG or N leaching/m3 milk) but much higher (5-fold) energy efficiency on the Waikato farm. This is important to maintain, particularly as farms intensify, if "food-miles" (energy use in transpor ting produce to markets) become a component of our "ecolabel" for supplying produce to overseas markets. Keywords: dairy farm, ef ficiency, environment, intensification, maize, nitrogen, resource use