Yield of catch crops and spring barley as affected by time of undersowing

The possibility to reduce the influence of competition from undersown catch crops on spring barley by delaying the time of undersowing, without seriously affecting the autumn growth of the catch crop, was studied in six field experiments. Up to the harvest of barley, catch crops undersown in connection with the sowing of barley, when roots emerged from kernels, when the first leaf reached the top of the coleoptile and when the barley had three leaves fully developed, produced 588, 468, 250 and 50 kg above-ground biomass per ha, respectively, when 80 kg N ha(-1) was applied. The catch crops tested, Italian rye-grass, perennial rye-grass and red clover, produced 452, 291 and 273 kg ha(-1), respectively. The production of rye-grass was similar when 40 kg N ha(-1) was applied, but that of the red clover was about twice as large. The influence of the catch crops on the grain yield of barley varied among experiments and no general differences depending on catch crop or time of undersowing could be determined. Biomass production in the autumn was only affected by the amount of catch crop at the harvest of barley if the stand was very sparse or very dense. Italian rye-grass, perennial rye-grass and red clover increased their biomass during autumn with 1138, 981 and 1239 kg ha(-1), respectively.