Implications of Dairy Herd Size for Farm Material Transport, Plant Nutrient Management, and Water Quality

Abstract

Farm material transport to, from, and within dairy farms can create zones of plant nutrient depletion and accumulation that range in scale from local to international. The introduction, adoption, and use of fertilizers have resulted in substantial movement of plant nutrients to dairy farms. Fertilizers contributed to enhanced crop growth and frequently the correction of soil nutrient deficiencies. They also represented an opportunity to replace plant nutrients exported from a farm in crops so that it was possible for some farms to specialize in the production of crops. These exported crops often became imports for other farms that specialized in livestock. However, the nutrient-holding capacity of soil on any farm is limited, so the potential for additions to the stock of nutrients, especially of P and K, on a farm can be expected to decrease with time. After a period of net nutrient additions on a dairy farm, the quantity of nutrients that can be accommodated is controlled by the productivity of the animals, the management of the animal handling facilities, and the off-farm purchases of feeds and other materials for the animals. Field and biophysical-economic simulation studies have demonstrated that interactions between alternative management strategies and societal perspectives about water quality and the biological and economic performance of dairy farms may sometimes lead to unexpected outcomes.