Nutrient and Energy Flows on Organic and Transitional Farms in Ontario

Researchers
E. Ann Clark and Karen Maitland, Plant Agriculture, University of Guelph (Part of a larger project - Assessing Composting, Soil, Crop, And Livestock Management For Organic And Transitional Systems in Ontario, by Ralph Martin, Paul Voroney, and E. Ann Clark)

Abstract
Seventeen farm-crop combinations from six Ontario organic farms were monitored in 2003. The goal was to quantify nutrient and energy flow and soil, crop, and livestock management on farms differing in livestock and forage dependence. Farm infrastructure fell within the ranges typical of Ontario farms, including a landbase ranging from 41-243 ha. Capital cost of buildings ranged from $15-75,000, while equipment cost from $10,000 (horse-based) to $260,000 (mechanized). Yields were roughly 50, 70, 100, and 120% of provincial yields for soy, spelt (v. winter wheat), mixed grains, and hay. From an energy perspective, total labor for seedbed preparation, planting, weed control and harvesting averaged 2.8 hr/ha on mechanized vs. 7 to 40 hr/ha on horse-drawn farms. Number of field passes for seedbed preparation and weed control ranged from 1 to 5 (mean 3.5) per field. Most nutrients were supplied by composted manure, which was applied almost solely to soy and spelt for sale. Compost provided up to 148, 55, and 184 kg N, P, and K/ha respectively. Small grains grown primarily for on-farm feed tended to be unfertilized or were preceded by a forage plowdown or hay crop. Implied nutrient export averaged 41, 57, and 78 kg N/ha for spring grains, spelt, and soy, respectively. Comparable figures for P were 9, 14, and 9 kg/ha and for K were 13, 19, and 24 kg/ha, respectively. Soil organic matter, P, and K levels were consistent with healthy, well managed soils. Perennial forages were prominent on most farms, with N-fixing crops accounting for 60%, and living winter covers for 64% of reported 6-year rotations. However, the healthy soils and high yields found on the one stockless farm in the study disputed the premise that livestock, whether via manure or perennial forages in crop rotations, are essential for soil sustainability. Results will contribute to efforts underway at the Organic Agriculture Centre of Canada to model nutrient and energy flow on organic farms.