Corn Yield Response Under Winter Cover Crops: An Updated Meta-Analysis.

Past research has highlighted the contribution of winter cover crops (WCC) to promoting sustainable cropping systems without reducing crop productivity. However, cover crops have also been reported to penalize subsequent row crop yields, which in part may prevent widespread acceptance of the practice among farmers. Our objective is to investigate the overall corn (Zea mays L.) yield response to WCC through a quantitative summary of peer reviewed research. We updated a previous meta-analysis by including seventeen studies published during the 2004-2015 period, resulting in 70 additional observations, and incorporating management information of the cover crop system utilized in different regions across the US and Canada. The logarithm of the response ratio, defined as corn yields following WCC relative to yields after no cover crop (NCC), were used for comparison among studies and assesment of cover crop performance. Preliminary results show neutral to positive contribution of WCC to corn yields. Grass species neither increase nor decrease corn yields whereas legumes, or mixtures, increase yields by four to six per cent respectively. Neutral responses of grass WCC exhibit small variability due to a large number of studies included in the sample. In turn, positive responses of legume and mixture WCC are associated with larger variability due to the small number of studies for these groups. WCC seem to favor or maintain corn yields, and may promote sustainability with minimal conflict to crop productivity.