Biomass production, weed suppression, nitrogen and phosphorus uptake in white oat (Avena sativaL.) and grazing vetch (Vicia dasycarpaL.) cover crop bicultures under an irrigated no-till system

Cultivation of a multipurpose cover crop is of interest to Eastern Cape farmers experiencing soil infertility and weed pressures. The objective of the study was to investigate effects of oat–vetch bicultures on biomass production, weed suppression, and nitrogen (N) and phosphorus (P) uptake. The study was conducted between 2009 and 2010. Treatments included 90% oat + 10% vetch, 70% oat + 30% vetch, 50% oat + 50% vetch, 100% vetch, 100% oat and a weedy fallow as control. Bicultured cover crops had significantly (p < 0.05) higher biomass compared to sole vetch in both seasons but reduced biomass compared to sole oat only in 2010. Weed suppression increased with an increase in biomass. Weedy fallow had the least weed suppression (p < 0.05) at all sampling times, whereas sole oat provided the best early weed control compared to the rest of treatments. Nitrogen uptake by sole vetch was comparable to 50% oat + 50% vetch and 70% oat + 30% vetch. Phosphorus uptake differed only in the 2010 season and 90% oat + 10% vetch, 70% oat + 30% vetch and sole vetch had the best uptake. Weedy fallow had the least N and P uptake during the two seasons. Bicultures can be used for improved biomass, weed suppression, and N and P uptake with potential of alleviating soil degradation effects in the Eastern Cape province.