Cover cropping is an ecological management practice that provides a variety of
ecosystem functions to farms, such as increasing soil organic matter content and improving
nutrient retention. Background soil fertility due to unique management legacies is expected to
influence the productivity of cover crops and subsequently mediate their effects on ecosystem
functions related to nutrient retention. We used a long-term experiment at Michigan State
University’s Kellogg Biological Station to test the legacy effects of four distinct management
systems (ranging from conventional to certified organic) on the production and function of
crimson clover and cereal rye cover crops grown alone and in mixture, with a focus on the
potential to reduce nitrate leaching. Cover crops were planted following winter wheat harvest in
the summer of 2019 and corn was planted in all treatments the following spring after cover crop
termination. We applied bromide as a conservative tracer of water and anion flow in the soil
profile to assess management legacy and cover crop treatment effects on potential anion
leaching.
We found that via changes to soil fertility, management legacies influenced cover crop
productivity and species composition in mixture: in the legacies with lower soil fertility, crimson
clover was more competitive than rye and dominated the mixture. Legacies with higher soil
fertility—which were those with a history of ecological nutrient management—had higher
average cover crop biomass (mean = 3357 kg ha-1
) and a higher percent recovery of bromide
(mean = 33.28%), an estimate of soil anion retention. Further, percent recovery of bromide was
positively correlated with cover crop biomass (r
2
=.17) and the free particulate organic matter
fraction (r
2
=.29), indicating that the effect of management legacy on cover crop function is
mediated by cover crop production and background soil fertility. This experiment reveals complex interactions between soil fertility, cover crop growth, and nutrient leaching potential
that depend on soil conditions resulting from specific management regimes.Master of ScienceSchool for Environment and SustainabilityUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/167297/1/Marta_Plumhoff_Thesis.pd