Integrated Nutrient Management for Organic Dairying in Ontario

While the production characteristics and economic performance of organic dairy farms in Ontario has been documented, the efficiency of nutrient use on these farms is less well understood. Recent European research suggests organic dairying systems may be prone to phosphorus (P) deficiencies in the long term, and there is a need to evaluate whether such trends might be important on Canadian farms. The project commenced in 2003 on fifteen long term (>10y) organic dairy farms in Ontario.

Project objectives include:

1. To model whole farm nutrient (NPK) mass balances (imports-exports) on Ontario organic dairy farms and compare with conventional production systems.
2. To examine current status and historic trends in soil fertility on Ontario organic dairy farms and its relationship to farm nutrient balance and livestock nutrient management.
3. To characterize the distribution, form and dynamics of P in soil as affected by production system.
4. To evaluate local sources of phosphate rock, as alternative sources of soil P inputs.

Data from soil sampling of all farm fields, indicated soil test (0.5M NaHCO3) P levels were low to very low (<10ppm) on over 60% of all 225 farm fields tested. Annual farm nutrient (N, P, K) balances are being determined for each of 3 years. In year 1, average farm P surpluses (2.8 kg ha yr-1) were low.

Plot research trials were established at three farm sites to assess the ability of two Ontario (Carbonatite, Volcanaphos) and three imported phosphate rock (PR) sources (Calphos, Tennessee PR, and Pebbled PR) to supply P to a green manure (buckwheat) and following crop, when applied at 100, 400 and 800 kg P ha-1. PR materials contained from 1.4 to 16.8% total P, and little (<0.1%) extractable P. Over 7 weeks buckwheat growth in 2004, increased yields and P uptake was most evident for Calphos treated plots.

Additional research will examine mechanisms to improve solubility of un-acidulated PR materials in these alkaline soils.

Researchers
Derek Lynch, OACC, Dept. Plant and Animal Sciences, NSAC
Paul Voroney, Dept. of Land Resource Science, Univ. of Guelph
Ralph Martin, OACC, Dept. of Plant and Animal Sciences, NSAC
Alan Fredeen, Dept. of Plant and Animal Sciences, NSAC
Cory Roberts, Dept. of Land Resource Science, Univ. of Guelph (Graduate Student)
Dept. of Land Resource Science, Univ. of Guelph (Graduate Student)

Collaborators
Ontarbio Organic Farmers Co-operative Inc., Guelph, Ont.; Harmony Organic Dairy Products, Wellesley, Ont.; Ecological Farmers of Ontario, Wroxeter, Ont.

Funding Sources
New Directions Program of the Ontario Ministry of Agriculture and Food