YIELD FORMATION IN CEREAL-RICH CROP ROTAT IONS AND MONOCULTURES IN ANEXTENSIVE AND INTENSIVE CROP-MANAGEMENT SYSTEM

In a long duration trial, conducted from 1979/80 to 1992 at TU-Munich' s research station in Roggenstein, the performance of monocultures of winter wheat, winter barley and winter rye, as well as numerous cereal -crop rotations were compared in an extensive and intensive crop-manag ement system. The results obtained can be summarized as follows. Over the course of 13 years, the influence of the immediately preceding cro p on the yield of the main crops was of much greater significance than the rotation as a whole. With winter wheat, no yield differences coul d be observed between monoculture and cereal crop rotation (if the rot ation did not include oats). Oats, rape, field bean, pea, potato and m aize as preceding crops, however, in crop management systems, led to, on average, an increase in yield of 13 dt/ha from the following wheat. Winter barley yields were not significantly different in monoculture, cereal crop rotations and crop rotations containing 66% cereals. Furt hermore, winter rye yields were the same in monocultures and cereal cr op rotations. With all cereals, intensification of fertilizing and che mical plant protection led to a considerable increase in yield, but di d nor diminish the effects of the preceding crop. Hence, even with the use of modern agronomical techniques it is impossible to compensate f or yield losses due to crop rotation.