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

The benefits that cover crops bring to row crop production have been widely investigated, as they relate to reducing erosion, promoting soil health, or reducing invasive weeds; all factors that directly or indirectly influence crop yields. However, cover crops have also been reported to penalize subsequent row crop yields, which in 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 thirty new studies published during the 2004-2015 period, resulting in 100 additional observations, and incorporating management information of the cover crop system utilized in different regions across the US and Canada. We included W CC species, killing dates, nitrogen fertilization rates, region, soi l texture, and WCC biomass accumulation, as possible moderators of cornyield response to WCC. The logarithm of the response ratio, defined as corn yields following WCC relative to yields after no cover crop (NCC) was used for comparison among studies and assessment of cover crop performance. . Our results show neutral to positive contribution of WCC to corn yields. Grass species neither increased nor decreased corn yields whereas legumes, or mixtures, increased yields by 24% respectively. Neutral responses of grass WCC exhibited 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 smaller number of studies for these groups. WCC seem to favor or maintain corn yields without reducing corn productivity.