Long-term effects of primary cultivations on crop yields in a four-course rotation

Abstract

An experiment is described which investigated for a period of 12 years the effects of four methods of basic cultivation -ploughing, rotary cultivating, cultivating and discing -on crop yields in a four-course rotation of winter wheat, sugar beet, spring barley followed by either potatoes (on one half of each main plot) or ley (on the other). The cultivations were carried out at two different times and each crop was grown at two levels of fertilizer.The method of cultivation had no effect on the yield of barley when weeds were controlled by chemicals but, in the absence of such control, the three deeper working methods of cultivation gave higher yields than discing towards the end of the experiment. In the case of wheat, ploughing generally led to the highest yields and rotary cultivating led to higher yields than either cultivating or discing after the ley. Discing led to relatively low yields, particularly with cultural methods of weed control at the lower level of fertility.With the sugar-beet crop, yields of sugar were higher in all rotations after ploughing than after cultivating or discing, irrespective of the method of weed control and although yields after rotary cultivating were similar to those after ploughing in the second rotation they did not consistently exceed those after cultivating or discing in the other two rotations. With discing, in the absence of chemical weed control the yields were markedly reduced in the last rotation period. Ploughing also led to the highest yields of potatoes but there were no consistent differences between the other methods and an apparent trend to lower yields after discing in the absence of chemical methods of •weed control had not reached significance by the end of the experiment.It was concluded that ploughing was a more reliable method of seedbed preparation, not only with regard to consistency of performance under different conditions but also with regard to depth of working and extent of weed control.