@inproceedings{orgprints7680,
           title = {Organic crop rotation experiments - short-term versus longer-term results},
          author = {Ilse A. Rasmussen and Margrethe Askegaard and J\orgen E. Olesen},
            year = {2006},
             url = {http://orgprints.org/7680/},
        abstract = {Danish experiments with cereal-based organic crop rotations have shown that the short-term results (the first course, up to four years after conversion) are different from those obtained in the longer-term (the second course, fifth to eighth year after conversion). Yield gain from use of manure increased from the first to the second course on a sandy soil, but decreased on loamier soils. Yield gain from leguminous catch crops increased from the first to the second course in a crop rotation without grass-clover. Some of these effects were caused by buffering effects of the grass-clover, other effects were caused by changes in soil fertility over time.}
}