In organic farming the cultivation of leguminous crops is one of the most important
sources of nitrogen (N). However, regarding the amount of N fixed, there are hardly
any published data for winter peas. Therefore, the N fixation of five regular leafed
winter peas types and one semi-leafless spring pea cultivar in single and mixed
cropping (with winter rye spring cereals respectively) was measured in four successive
growing seasons (2003/04 – 2006/07) at the experimental farm of the University of
Kassel and in two consecutive vegetation periods (2005/06 - 2006/07) at the
experimental farm of the University of Applied Science in Osnabrueck. The amount of
N fixed was calculated according to the extended difference method at the beginning
of flowering and at grain harvest.
N fixation was usually higher for winter peas than for spring pea. At the beginning of
flowering the amount of N fixed in pure stands was with a mean value of 92 kg ha-1 for
winter peas and 29 kg ha-1 for the spring pea higher than in mixture with a mean value
of 42 and 15 kg ha-1 respectively. At grain harvest the amount of N fixed for the spring
pea in pure stands was higher than in mixtures with a mean of 65 and 33 kg ha-1
respectively. On the other hand the N fixation for winter peas was usually comparable
in pure and mixed stands with a mean of 100 and 86 kg ha-1 respectively. This was a
consequence of the higher pea grain yield in mixture than in pure stands and of a
reduced biomass (leaves) loss in mixtures. Therefore, regular leaf winter peas can
contribute to the N supply of the crop rotation better than spring peas
