Submitted to: Applied Soil Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/15/2011
Publication Date: 1/31/2012
Citation: Lehman, R.M., Taheri, W.I., Osborne, S.L., Buyer, J.S., Douds, D.D. 2012. Fall cover cropping can increase arbuscular mycorrhizae in soils supporting intensive agricultural production. Applied Soil Ecology. 61:300-304. doi:10.1016/j.apsoil.2011.11.008.
Interpretive Summary: Fall cover crops reduce seasonal fallow and may present many other benefits to agricultural producers in terms of reducing erosion, retaining nutrients, etc. Fall cover crops also provide a host for obligate mutualistic arbuscular mycorrhizal fungi (AMF) that may provide many benefits such as increased nutrient bioavailability, pest and pathogen resistance, and drought tolerance to the following cash crop. AMF numbers are very low in intensively cultivated lands. We studied the ability of specific fall cover crops to increase AMF numbers in several cropping systems in South Dakota. We found that some cover crops, particularly forage oats and mixtures containing forage oats, significantly elevated AMF numbers. Based on proven benefits of AMF, increasing AMF numbers by fall cover cropping with oats or cover crop mixtures should deliver economic and environmental benefits to production agricultural systems.
Technical Abstract: 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 mycorrhizal inoculum potential of soils within production agricultural conditions typical of the upper Midwest U.S. 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, AMF propagule numbers were generally low (= 1 propagule per gram soil). 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 the AMF biomass with the neutral lipid fatty acid mycorrhizal biomarker, C16:1cis11. Identification of specific cover crops that promote AMF 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.