ZERO AND CONVENTIONAL TRAFFIC SYSTEMS FOR POTATOES IN SCOTLAND, 1987-1989

Commercial potato production in the UK requires considerable traffic associated with primary and secondary cultivations and harvesting with consequent problems of topsoil compaction. The extent of these soil and crop effects were examined for a conventional traffic system and for an experimental zero traffic system which was developed from standard machines modified to have all wheels running on permanent wheeltracks at 2.8 m centres. Three rows of potatoes were grown between the wheel-tracks, the central row only being traffic-free, as the edge effects of the wheeltracks influenced the outer rows. Results for three seasons showed that the zero system gave mean increases of 14% and 18% in total and marketable potato yields, respectively, as a result of greater soil air-filled porosity in wet seasons and lower soil strength in dry seasons. During harvest, the conventional system produced 30% more soil clods and, after harvest, required a 70% greater draught force for cultivation. Commercial exploitation of the zero system will depend on the development of an economically viable, wide-track machine.