Long-term Cover Crop Use and Soil Health Study

Matt Ruark Lab, UW-Madison and UW-Extension Soil Science


  • Determine the effect of continuously using cover crops for 4 or 5 years on soil health, measured as potentially mineralized nitrogen (PMN) and permanganate oxidizable carbon (POXC).
  • The study site was a continuous corn silage system with fall manure application and no further N added. Treatments included rye as a cover (chemically terminated) or a forage (harvested) crop and no cover crop
  • We measure PMN from soils collected throughout the growing season. The PMN was then compared to the plant N uptake and yield to evaluate seasonal soil N supply.


  • There were no statistical differences in PMN among cover crop treatments at any time point in the 2015 season.
  • PMN for both the no cover crop and rye forage treatments decreased over the growing season, while the PMN for rye cover did not.
  • In 2015, there was a reduction in plant N uptake from no cover to rye as cover treatment and even less in te rye as forage treatment
  • In 2016 the corn in the no cover treatment took up twice as much nitrogen as corn in the rye as forage treatment. Thus rye as a cover or as a forage decreased N uptake and corn yield.
  • Together, this suggests that the plants are taking up different amounts of N and that some factor other than N availability that is causing differences in plant N uptake.
  • There were no statistical differences in POXC among cover crop treatments at any time point in the 2015 or 2016 season.


Figure 1:Rye as a cover plot (left) and rye as a forage crop (right) in June        Figure 2: Rye as a cover plot (left) and no cover plot (right) in June

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