Cover Crop Selection Influences Yield

Maize growth responses to soil microbes and soil properties after fertilization with different green manures
Applied Microbiology and Technology 2016
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Are you cover cropping over the winter?  According to a group of researchers in China, the type of cover crop is going to influence both your microbial diversity and your yield.  Four types of green manure (a cover crop that gets tilled into the soil) were used in the experiment, Common Vetch, Milk Vetch, Vicia Villosa, and Radish.  A soil plot with no cover crop was used as the control.  The cover crops were seeded in the fall (October), tilled under the following May, corn was seeded right after, and then the corn was grown through the summer and harvested the following September.  Upon harvest, the researchers collected soil from each of the treatments, then analyzed it for microbial content.  They also collected ears of corn from the treatments and assessed yield characteristics. 
       The researchers found that Milk Vetch significantly outperformed the control and radish groups in yield, plant height, and cob weight.  If fact, corn yield was increased by 31.3% as compared to the control.   The Vicia and Common Vetch had slightly higher yields than the Radish and control group.  The Radishes did not increase yield (explained by the fact the other treatments were legumes, which fix nitrogen, radish does not).   On the microbial end of things, there were variations in types of microbes present in the different treatments.  Several groups of bacteria were identified, though the most interesting finding was that the Milk Vetch showed a significantly higher amount of Acidobacteria, while the control had a higher amount of Proteobacteria.   Acidobacteria are known to have disease fighting qualities which could have contributed to the increased growth.  The Proteobacteria group contains disease causing organisms, as well as microbes that could potentially compete with crops for nitrogen. 
        The scientists also found that soil pH was lowered by the cover crops as compared to the control group.  There was also an increase in the soil's organic matter content in all treatments.  The Milk Vetch soil had significantly higher available Nitrogen and Phosphorus than both the control and Radish treatment. These factors would contribute to increased yield.   The other treatments did show increases, though the results were varied and not always significant.  This study teaches us that specific cover crops have influence on crop yields due to their influence on microbial and physical soil characteristics. 

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