A desktop evaluation of the environmental and economic performance of model dairy farming systems within four New Zealand catchments

Abstract

The environmental and economic performances of low, medium and high input dairy farming systems were evaluated for model farms within catchments in Waikato, Taranaki Canterbury and Southland. These four catchments, predominantly under dairy landuse, are part of a long term systems study of farm productivity and catchment-specific environmental issues. Within each catchment, environmental and economic performance indicators were derived for model farms by using the farm systems modelling tool UDDER and the OVERSEER™ nutrient budgeting programme. Our analyses indicated that high input systems, currently defined as farms within the top quartile of farm inputs, either as imported feed or fertiliser nitrogen (N), were often the least profitable, as defined by Earnings Before Interest and Tax (EBIT). These high-input systems consistently had the greatest environmental emissions of N and greenhouse gases, and the greatest energy consumption, on a per hectare and a per kg milksolids basis. The most profitable farm input system depended on payout and the catchment under study. Evaluation of the whole-farm system using these modelling tools demonstrated the relatively large contribution that stock wintering made to N emissions from farms within the two South Island catchments. Where reductions in N losses are sought, it would seem prudent to initially target mitigations at this part of the farm system. Keywords: dairy farming, environmental emissions, farm systems modelling, OVERSEER™ nutrient budgets, UDDER farm systems tool