Rye Grass as a Catch Crop in Spring Barley

The effect of rye grass catch crops in spring barley growing was tested on four Danish soils. Dry matter production of under sown late perennial rye grass was on average 800 kg, and of Italian rye grass 928 kg per ha. Nitrogen absorption in above ground catch crop plant material was respectively 15 and 16 kg N per ha. There was an increase of around 135% in dry matter production and around 170% in nitrogen absorption by adding 50 kg fertilizer nitrogen after harvest of the main barley crop. Italian rye grass sown after barley harvest gave 360 kg dry matter containing 8 kg N per ha. Spring sown rye grass reduced average soil nitrate by 7–8 kg N per ha in autumn and early winter. Autumn sown Italian rye grass reduced soil nitrate by 2 kg N per ha in early winter. In the following spring, the average effect of a rye grass catch crop was a reduction in soil nitrate of 4 kg N per ha. Spring sown perennial rye grass reduced average yield of the main barley crop by 149 kg and Italian rye grass by 442 kg grain per ha. There was no significant after-effect of rye grass catch crop in the succeeding barley crops.