Fall cover cropping can increase arbuscular mycorrhizae in soils supporting intensive agricultural production

Intensive agricultural practices, such as tillage, monocropping, seasonal fallow periods, and inorganic nutrient application have been shown to reduce arbuscular mycorrrhizal fungi (AMF) populations and thus may reduce benefits frequently provided to crops by AMF, such as nutrient acquisition, disease resistance and drought tolerance. We have evaluated the ability of different cover crops to elevate the native mycorrhizal inoculum potential of soils under soil-climatic conditions typical of the upper Midwest U.S. production agricultural region. We measured the number of soil AMF propagules at three sites in the late fall following cover crops that were seeded into summer-harvested small grains within a no-till rotation. At all three sites, soil AMF propagule numbers were generally low (<= 1 propagule g(-1)). Fall cover crops significantly increased the mycorrhizal inoculum potential of the soils. Forage oats (Avena sativa (L) Hausskn.), by itself or in mixtures, was most effective at both sites where it was planted. At the third site, a cover crop mixture doubled the inoculum potential of these soils. The effect of cover crop treatments on AMF propagules was corroborated at one site over two seasons by measuring AMF biomass with the neutral lipid fatty acid mycorrhizal biomarker, C16:1cis11. Identification of AMP-promoting cover crops for inclusion in diversified, no till cropping rotations in the upper Midwest U.S. will provide opportunity for reduced inorganic nutrient application with economic and environmental benefit. Published by Elsevier B.V.