Fate of legume-derived nitrogen in monocultures and mixtures with cereals

Cropping grain legumes can cause benefits due to symbiotic nitrogen (N) fixation, but on a downside there are environmental risks like nitrogen losses especially after grain harvest. Until now, hardly any knowledge has been available on these effects of N derived from a preceding crop like spring peas (Pisum sativum L.) mixed with cereals or from winter peas. Therefore, field experiments were conducted in order to examine N mineralization and N preceding crop effect from six different winter pea genotypes (five regular-leaf-type peas and one semi-leafless pea) and one semi-leafless spring pea in three subsequent years (2003/04–2005/06) in pure and mixed stands with cereals on a silty loam, at the research farm of the University of Kassel, Germany. Immediately after grain harvest, total above-ground biomass was removed apart from the stubble, and a catch crop of either mustard and oil radish or mustard was sown, which was harvested in the first half of October.