Influence of soil tillage and long-term fertilization on the aggregate size distribution and seedbed roughness

Primary tillage and seedbed preparation are determining processes for the seedbed structure. In experiments on different sites the tillage effect and the long-term fertilization effect on the aggregate size distribution in the seedbed was analysed. Seedbeds with different roughness were prepared with different primary tillage implements (mouldboard plough, cultivator, short disc harrow) and various Power Take-Off (PTO)-speeds of the power harrow. An additional experiment analyses the long-term fertilization effects (unfertilized, mineral fertilizer, farmyard manure) on aggregate size distribution in the seedbed. The results show, that soil tillage and the long-term fertilization system influence the aggregate size in the seed bed in different manner. Soil tillage with cultivator loosened the soil more intensive than mouldboard plough. The loosening effect of the cultivator is strongly determined by the line distance and number/kind of the post tools. The increase of PTO-speed from 300 to 1000 1 min(-1) resulted in a finer seed bed. Long-term fertilized arable soil with farmyard manure had larger soil aggregates than un- and mineral fertilized soil.