The effect of grasses grown for seed in mixture with legumes on the incidence of weeds and soil nitrogen content

Summary

This report was presented at the UK Organic Research 2002 Conference on behalf of the Colloquium of Organic Researchers (COR).
The incidence of weeds and the content of soil nitrogen were investigated in the first year of a field trial with organic grass seed production in which the grasses were grown with companion legumes. Two grass species, timothy (Phleum pratense L.) cv. Sobol and perennial ryegrass (Lolium perenne L.) cv. Baca, were tested together with three legumes: red clover (Trifolium pratense L.) cv. Start, white clover (Trifolium repens L.) cv. Vysocan and black medick (Medicago lupulina L.) cv. Ekola. The N-nutrition and control of weeds were provided by three “ecological” methods and a conventional one (bacterial nodules of legumes, mulch, organic manure and mineral fertilizer). Plots with red clover had the lowest number of weeds, those with black medick the highest. Perennial ryegrass was more competitive than timothy against weeds and the companion legume. Soil nitrogen was highest in plots with white clover and red clover. During the vegetative period the level of soil nitrogen increased in the combinations with red clover, stayed the same in combinations with white clover, but decreased in those with black medick and in control plots.