Crop yields in organic and conventional production – studies from the Öjebyn project

In order to develop organic dairy production a system study called “The Öjebyn Project” was started in 1990. Öjebyn is a research station of The Swedish University of Agricultural Sciences in northern Sweden. There is 104 hectares of arable land; 58 hectares are grown organically and 46 hectares are grown conventionally. The feed produced on the farm was fed to around 50 dairy cows in each system. There has been a crop rotation of six years and a careful handling of farmyard manure and urine from the dairy cows. The crop yields have been recorded for twelve years as have the quality of each crop in terms of energy, protein and mineral content (P, K, Ca, and Mg). The difference in yield between the two systems has been changing over time. During the first three years there was a diminishing yield in the organic system, followed by a steady increase in yield. In the conventional system there was no such trend, on the contrary there was a tiny decreasing trend. Today’s conclusions about total crop yields from the systems would be quite opposite as if they were made six years ago. The organic system has throughout the study delivered crops with higher content of Ca, P and Mg but with a lower content of K. These differences in mineral concentrations affect the need of different mineral supply to the cows and at the end even the animal health.