The importance of cover crops for protection of soil from water and aerial erosion, as well as leaching of nutrients from soil is emphasized. Use of green manures as a mechanical barrier against weeds, and beneficial effects of exudates of green manures on control of weeds, pests and diseases of vegetables are discussed. Recommendations are included for autumn and spring sowing of cover crops (e.g. rye, wheat, oat, barley, sorghum, vetch, rape and mustard), which are cut or desiccated in the spring and are left in the field as mulch. Negative effects of mulching are considered, i.e. a decrease of soil temperature in the spring resulting in a slower growth rate and later ripening of tomato. It is also stated that yield of some vegetables, including tomato, can be lower in the no-tillage cultivation compared with traditional cultivation. However, the dry matter content is higher in tomato grown with no-tillage. Field trials were conducted in Lublin, Poland, to study the effect of cover crops, such as rye, white and red clover, and field pea on health of tomato. Data are tabulated on fungi isolated from soil under tomato grown with rye and field pea as mulch crops compared with the traditional cultivation system during 1998-2000. The results showed that use of cover crops resulted in a good control of plant pathogens, especially Fusarium oxysporum f.sp. lycopersici, and an increase in the number of antagonistic fungi, e.g. Trichoderma spp. It is concluded that use of cover crops allows decrease of the number of mechanical cultivations, as well as decrease of the use of fertilizers, fungicides, insecticides and herbicides.
