Crop cover improves the nitrogen status in vegetable crop rotations

Results from an organic vegetable rotation, and from a number of specific experiments with catch crops, shows that autumn crop cover strongly improves N availability for the succeeding crop. Though many different types of crop cover have been involved, from full year green manures, to short term catch crops and green manures and even white cabbage stubble allowed to continue growth after harvest, they have all had a similar effect on N dynamics in the field. With crops actively growing in the field until the late autumn, much less N is left in the soil, and the risk of leaching loss is strongly reduced. In the subsequent spring, mineralization of N from the crop residues leads to increased N availability for the succeeding crop. This main effect was found irrespectively of the type of crop cover, though the amount of N mineralized obviously varied depending of the type of crop cover.