COS 142-5 - Global synthesis of cover cropping impacts on cash crop yield: A meta-analysis

Background/Question/Methods

The growing number of research perceived those sustainable agricultural practices like cover crops benefit the agroecosystem resilience under a more variable climate. However, there is an ongoing debate on cover crop impacts on crop yields. Some studies reported reduced yield in short term and others reported a long-range yield increase with healthier soil properties. To address this uncertainty, the objective of this research is to quantitatively evaluate how the impacts of cover crop on crop yields vary under different cover crop species, subsequent cash crop types, edaphic variables, and land management. To this end, we collected field-based crop yield data at a global scale and conducted a meta-analysis. Around 3000 primary articles are collected from the Web of Science from 1985 to 2021. We denoted the natural logarithm-transformed response ratio (lnR) as effect size and used bootstrapped iteration in R to conduct an unweighted meta-analysis. If the estimated 95% confidence interval (CI) is larger than zero, it means cover crop positively impacts the crop yield and vice versa. When the estimated CI range overlaps zero, no statistically significant difference is considered between cover crop and non-cover crop treatments.

Results/Conclusions

The preliminary results showed that the 95% CI of lnR ranged from -0.0161 to 0.0353, overlapping with zero. Such results indicated that cover crops did not impact cash crop yield overall. However, legume cover crops and mixed cover crops had a positive impact to yield, though only with a minor lnR increase. The impact of cover crop on yield is not different between different cash crop species such as corn and soybean. Land management affected the cover crop’s impacts on yield. For example, crop yield under tillage management was found slightly higher than no cover crop. While cover crop combined with no-tillage was reported no impact to yield. Our results indicate that the introduction of cover cropping will not reduce cash crop yields. In some cases, cover crops combing with specific cash crop species and other land management practices could result in a slight increase in crop yield.