Effect of hairy vetch (Vicia villosa Roth.) and vetch-rye (Secale cereale L.) biculture cover crops and plastic mulching in high tunnel vegetable production under organic management

ABSTRACT Effects of cover crops on soil physical and chemical properties and yield of the following cash-crops were evaluated in an organic system in a high tunnel. The sequence of crops in the two-year study was: vetch or vetch-rye followed by zucchini (Cucurbita pepo) and then lettuce (Lactuca sativa L) in 2016 and celery (Apium graveolens L.) in 2017. In the plots with cover crops, two mulches (black and transparent polyethylene (PE) film) were used to cover the soil at the end of the first season during the winter period. The differences in the biomass between vetch grown on its own and the vetch-rye mixture were not significant, but the total amount of N accumulated in the biomass of the vetch (252 kg N ha−1) was greater than that of the vetch-rye mixture (174 kg N ha−1). The use of cover crops improved soil properties in the first season (2016), including water stable aggregate index and soil organic matter. In the second season (2017), the use of cover crops combined with PE mulching had a beneficial effect on soil the pH, the water-stable aggregate index, and the availability of Ca, Mg, B and Fe. Covering the soil with black PE mulch during the winter (in both the vetch and the vetch-rye treatments), increased celery yield, compared with the transparent PE mulch and the untreated soil. The use of black PE mulch in the vetch treatment and transparent PE mulch in the vetch-rye treatment reduced soil organic carbon.