Rye Cover Crop Effects on Biologically Active Pools of Soil Organic Matter at Different Topographic Positions.

Introducing rye cover crop to conventional cropping systems enhances soil carbon sequestration, alleviate nitrogen leaching and improve overall soil health for sustainable agricultural production and productivity. Although most benefits of rye cover crop are too subtle to be quantified in short term studies, biologically active pools of soil organic matter (SOM) such as particulate organic matter (POM) and short term mineralizable carbon are sensitive indicators of soil quality changes induced by management systems such as cover crop. Despite economic and environmental benefits of cover crop depend on many factors; variation in field topography can affect actual benefits of cover crop within a cropping system. The objective of this study was to evaluate the effects of rye cover crop on biologically active pools of SOM at different topographic positions. Soybean-maize rotation system experiments with and without rye cover crops were established on field with diverse topographic positions namely summit, slope and depression in 2011 at Kellogg Biological Station (KBS) and Mason Research Field of Michigan State University. Soil samples were collected two months after killing of rye cover crop to assess POM and short term mineralizable carbon. The concentration of POM was significantly higher at depression of KBS in 2014, whereas there was no significant difference among topographic positions at Mason. Rye cover crop treatment increased POM concentration at summit position of KBS, and at slope and summit positions of Mason (P<0.05). Overall, the concentration of POM showed increasing trends over years at Mason, whereas the results at KBS were inconsistent. Short term mineralizable carbon was significantly higher at depressions in both 2013 and 2014 at KBS, but significant differences were not observed among topographic positions at Mason. Similarly, the effect of rye cover crop was not significantly different on short mineralizable carbon at all locations and growing seasons. The preliminary results of the present study revealed that the contribution of rye cover crop to biologically active pools of SOM depends on topographic positions, cover crop performance, time of killing rye cover crop and soil sampling.