Grass-clover and catch crops - How does grass-clover and catch crops affect crop performance and soil microbiology in unfertilised organic crop rotations?

In organic cropping systems, where commercial fertilisers not are used, the use of N2 fixing crops, such as grass-clover, is of crucial importance. Additionally, the use of catch crops will reduce the loss of nutrients from the soil and thereby maintain the nutritional status at a higher level leading to a sustainable crop production. The use N2 fixing crops and catch crops may also affect the microbial communities in the soil with consequences for the microbial biomass and activity. The objective of this study, which was a part of the DARCOF-project BIOMOD, was to investigate the influence of crop rotation, particularly the prehistory regarding plant residue amendment, on crop yields, soil respiration, N mineralisation, on emissions of the green house gas N2O and on the microbial biomass and activity. The study is described and discussed in more details in Vinther et al. (2003), and only an extended abstract is presented here