Book of Abstracts
11th IFOAM Scientific Conference
11-15 August 1996, Copenhagen, Denmark
Department of Animal Breeding and Genetics, Justus-Liebig University, Ludwigstr. 21, D-35390 Giessen, Germany
Organic and conventional dairying systems were compared using 5 pairs of farms under largely identical environmental conditions on a within-pair basis. It was the aim of the study to analyse nutrient and energy flows in the two systems, and to judge their ecological sustainability.
There were no significant differences in land use and in stocking rate, although the organic dairy farms grew more leguminous forage crops and had more forage crop land available per animal unit. However, this difference was not utilized advantageously, since the ecofarms did not feed more roughage, which, in addition, had a lower NEL- and CP-content, probably due to later harvesting and less nitrogen fertilization. The seasonally inadeqate nutrient supply on the organic farms led to a lower average milk production, although the rates of N-retention were similar. In both systems, only 72% of the theoretically possible milk yield was achieved. In general, the organically managed dairy herds were more healthy and incurred less veterinary expenditures.
At the farmgate, higher efficiencies of nutrient utilisation were recorded for N, P, and K on the organic farms. The high efficiency in phosphorus utilisation may, however, be due to a mining effect, since the soil phosphorus content was significantly lower in the organic system.
The nutrient flows were structurally different among the two systems: while the conventional farms had higher external inputs as well as a highernutrient export, the organic farms tended to operate more in closed cycles,albeit at a lower production level. Organic farms had a 47% lower energyconsumption at a 38% lower energy output, and were consequently 20% moreefficient in its use.
Many of the observed differences were less obvious than expected due to the marginal environmental conditions of the hill farming areas, which affected both systems, and wide ranges occurred within each system. However, the organic farms are operating more sustainably, although their resources are not always managed efficiently. An optimization of organic dairy farms in their feeding strategies as well as in their manure management appears of primary importance for future research.