Due to short post-harvest seasons, it is not always possible to grow worthy cover crops (CCs). This research aims to clarify the impact of undersown red clover (Trifolium pratense L., RC) and post-sown white mustard (Sinapis alba L., WM) management on their biomass, accumulated nitrogen (N), phosphorus (P), and potassium (K) content and the nutrient release to subsequent main crops. During the study period, RC mass yields varied from 220 to 6590 kg ha-1 DM and those of WM from 210 to 5119 kg ha-1 DM. WM shoot biomass increased with the increase in rainfall in August and the average daily temperature of the post-harvest period. CC productivity and efficiency were higher when growing short-season spring barley than winter wheat. In the warm and rainy post-harvest period, undersown WM after winter wheat increased the biomass by 34.1% compared to post-harvest sowing. The application of straw (+N) increased the accumulation of nutrients in WM biomass. The intensive fertilization of the main crop had a negative effect on RC yield and NPK accumulation. RC shoot biomass was characterized by a higher N content and WM by a higher P concentration. Well-developed CCs could reduce soil mineral nitrogen content by 28.5-58.8% compared to a plot without CCs. Nutrient transfer to spring barley was dependent on the N content of CC biomass and the carbon and nitrogen ratio (C:N < 20). We conclude that CC growth and efficiency were enhanced by the investigated measures, and in interaction with meteorological conditions.
Keywords: C:N; biomass NPK; clay loam; red clover; soil mineral N; white mustard.