Nitrogen catch crops may be cultivated after the harvest of a main crop. They take up nitrogen from soil. Consequently, less nitrogen leaches to groundwater, which then has a reduced nitrate concentration. The nitrogen uptake by catch crops strongly varies from one year to another, and one location to another. In this study, this variation is explained by using a simulation model and several experiments.
The available amount of nitrogen in soil, solar radiation and rainfall appear to strongly determine catch crop nitrogen uptake. Crop characteristics also affect uptake. Rooting depth is most determining when nitrogen availability is lower than the uptake capacity of the catch crop. When nitrogen availability is higher than the uptake capacity, the rate of expansion of radiation intercepting leaf area affects nitrogen uptake most strongly.
In autumn, winter or spring, catch crops are incorporated in soil. The next crop may then, after mineralization, utilize the nitrogen stored in the catch crop. Nitrogen availability to the next crop is at maximum when the crop is incorporated in January. This is, however, not always possible in practice. Changing the time of incorporation to late autumn or the end of winter has only a small effect on the nitrogen availability.
Thesis: Understanding the reduction of nitrogen leaching by catch crops