Resource use at the cropping system level.

This paper illustrates the basic ideas of good crop rotations, adequate crop husbandry and high resource-use efficiencies and some relevant ecological approaches. The use of special crops to prevent the need of high inputs of crop protectants or to reduce losses of nutrients at the level of the cropping system deserves special attention in research. Examples are given for the ecological control of soil-borne fungi, parasitic weeds, nitrogen loss and other sustainable techniques to increase the resource-use efficiency at the cropping system level.