The increase in demand for organic dairy products has prompted discussion on the environmental benefits of alternative farming practices. Agriculture, in general, has long been blamed for environmental degradation including high phosphorus (P) run-off from chemical fertilizers responsible for the pollution of streams and lakes, nitrous oxide emissions, and erosion. Researchers at the Organic Agriculture Centre of Canada and the University of Guelph have recently published the results of an extensive project examining the nutrient budgets on fifteen long-term organic dairy farms in Ontario.
Organic dairy production in Canada has increased about threefold from about 10 million litres of milk to 35 million litres in three years and demand continues to increase at about 20% per year. In Ontario, the number of certified organic dairy farms has increased from 13 to 46 from 1994 to 2003. The technical and economic character of Ontario organic dairy farms has been well documented but their sustainability with respect to nutrient status and nutrient use efficiency remains to be examined.
Net returns and economic performance can be improved in alternative dairy systems by reducing dependence on purchased inputs and improving nutrient use efficiency. Organic dairy farms often devote more of their land-base to pasture and hay production and less to cash crops and large grains than conventional farms. The livestock density on organic dairy farms is often lower than on conventional farms because of the focus on reducing feed import costs. On large conventional farms with high stocking density, large surpluses of nutrients are seen because more nutrients are brought onto the farm than are removed in the milk. As result, organic dairy farms are seeing lower surpluses of nutrients and due to ration balancing and cropping sequences, rather than farm or dairy herd size.
The objective of this research was to characterize farm-gate nutrient NPK budgets and nutrient use-efficiency on 15 long-term certified organic dairy farms in Ontario and to relate these to farm management characteristics and productivity.
The 15 farms studied were selected from across southern and eastern Ontario in 2003. In an initial farm survey, data was collected concerning farm size, livestock density, land-base usage patterns and nutrient imports and exports. All animals were accounted for and livestock density was calculated. Productivity, milk export quantities and average fat and protein contents were obtained from Dairy Farmers of Ontario milk statements. Whole farm mass nutrient balances were determined for each farm. Nutrient content of imported and exported feed, bedding, cash crops and seed was measured or estimated. All imports and exports to and from the farm were accounted for in the budget.
Whole farm budgets showed surpluses of 75.3 kg N per ha. The dominant N inputs were N fixation by legumes, atmospheric deposition and feed imports. Milk exports accounted for 75% of all N exports. Budgets showed small surpluses on nine farms and small deficits on six farms. Phosphorus inputs included mineral sources, feed and bedding while outputs of P were mainly in the milk. Potassium showed annual surpluses that were accounted for in feed and bedding. Milk accounted for the majority of K exports.
Currently, an intensive three-year project is being conducted on 10 low P organic dairy farms in Ontario and 4 transitional and organic Nova Scotian dairy farms to examine the effect of soil and forage quality on N fixation in legumes. The aim of this project is to track the quality of forage on low P soils, with minimal inputs, and measure the relationship to N fixation, as P can limit the amount of nitrogen fixed by legumes such as alfalfa and clover. The farmers involved in the project will receive detailed soil and forage quality tests as well as information on the amount of N being fixed in their fields.