PLOUGHLESS TILLAGE IN SWEDEN - RESULTS AND EXPERIENCES FROM 15 YEARS OF FIELD TRIALS

Results and experience from 140 field trials carried out during the period 1974-1988 are presented. The whole of Sweden was represented in the investigation, but the majority of sites were in the central and southern areas of the country. In the unploughed experimental plots, conventional autumn ploughing to 20-25 cm was compared with two or three stubble cultivations to approximately 10-12 cm depth. On average, use of ploughless tillage reduced yields of winter wheat, spring barley, winter and spring oilseed rape and sugarbeet and somewhat improved yields of oats and potatoes. The results from ploughless tillage were generally improved by the use of dual rear tractor wheels instead of single wheels, by the placement of artificial fertilizer instead of broadcasting and by the removal of straw. The incidence of annual weeds increased on average by 25% and stoloniferous weeds by 100%. The most suitable soils were peats, sandy loamy tills, silty loams or silty clay loams and heavy clays.