Crop rotation and crop management effects on cereal yields in arable organic farming in Denmark

One of the main challenges in organic crop production is to ensure high and stable crop yields. In this study we used data from a 12 year old crop rotation experiment in Denmark to estimate the contribution of various management factors to yields of winter and spring cereals. The experiment included three factors in two replicates: 1) Grass-clover green manure crop (with and without), 2) catch crop (with and without), and 3) animal manure (with and without). Animal manure was the most important factor for increasing grain yield of cereal crops, but also grass-clover and catch crop contributed considerably to increasing yields. The grass-clover had a larger long-term effect on grain yields on the sandy loam soils than on the sandy soil. Yields were significantly reduced by weeds, and maintaing stable yields requires good weed control and prevention measures.