Theses and Dissertations at Montana State University (MSU)
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Item Long term multispecies cover crops in semi-arid Montana: soil response and aboveground biomass(Montana State University - Bozeman, College of Agriculture, 2020) D'Agati, Kristen Mary; Chairperson, Graduate Committee: Catherine A. Zabinski; Perry Miller (co-chair); Perry R. Miller, Clain A. Jones and Catherine Zabinski were co-authors of the article, 'Soil biological effects of herbicide-terminated multi-species cover crop mixes, in semi-arid Montana' which is contained within this thesis.; Catherine Zabinski, Clain A. Jones and Perry R. Miller were co-authors of the article, 'Aboveground biomass quality and quantity of long-term multispecies cover crop mixes, in the semi-arid Montana' which is contained within this thesis.; Maryse Bourgault, Perry R. Miller, Clain A. Jones and Catherine Zabinski were co-authors of the article, 'Soil biological response to spraying, grazing, or haying of long-term multispecies cover crops in semi-arid Montana' which is contained within this thesis.Low and variable annual precipitation (250-350 mm) make management strategies that conserve soil moisture imperative for wheat producers in semi-arid Montana. A wheat-fallow rotation was historically the most common dryland cropping system in semi-arid Montana, due to its ability to conserve soil water; however, summer fallow has negative environmental impacts (Campbell et al., 1991). There is interest to incorporate cover crops into a rotation as a partial replacement for summer fallow to enhance soil quality. An eight-yr study explored the effect of cover crops on biological soil properties through aboveground biomass inputs of four plant functional groups: brassica (BC), fibrous root (FR), tap root (TR), and nitrogen fixers (NF) grown as two-species mixes, six-species mixes (three functional groups), a full eight-species mix, and two controls--chemical fallow and sole pea. Cover crops grew for about 60 days, were terminated with glyphosate, then soil samples were taken nine months after termination at wheat seeding. The only difference in biological parameters based on functional group was that mycorrhizal colonization in wheat was higher following FR than BC at one site. Potentially mineralizable nitrogen (PMN) was 1.6-1.7 times higher and microbial biomass was 1.4 times higher in soils from cover crop treatments relative to fallow at one of two sites. PMN was 1.2-1.3 times higher in soils from six-species mixes than two-species mixes at both sites, and six-species mixes produced 1.4 times more biomass at one site. Nitrogen fixers had the lowest C:N ratio of the functional groups at both sites, while FR had the highest at one site. In a second study of cover crop termination, cover crops were grown about 90 days and terminated with one of three strategies: chemically, grazing, or haying. Soils were sampled nine months after termination at the time of wheat seeding. Few enzyme differences and no PMN differences or meaningful patterns were discovered among termination strategies. Minimal differences in biological parameters, even when shoot biomass was removed, may mean grazing or haying could improve net revenue without detracting from soil health. In semi-arid annual systems, water limitations may be the main concern with growing cover crops.Item Mycofumigation with Muscodor albus : effects on Verticillium wilt and black dot root rot of potato, effects on Glomus intraradices and ectomycorrhizal fungi, and M. albus proliferation in soil(Montana State University - Bozeman, College of Agriculture, 2008) Grimme, Eva; Chairperson, Graduate Committee: Barry J. Jacobsen.Muscodor albus Worapong, Strobel & Hess, isolate CZ-620 (MA) is an endophytic fungus that produces volatile organic compounds (VOCs) and non-volatile antimicrobial compounds. The use of these VOCs to inhibit or kill a wide range of microorganisms is termed mycofumigation. This dissertation focuses on parameters of MA mycofumigation including: production and bioactivity of previously un-described water-soluble antimicrobial compounds produced by MA; distribution of antimicrobial compounds from a MA point source in three soil types as measured by effects on Verticillium dahliae and Colletotrichum coccodes; control of V. dahliae and C. coccodes on potato; the ability of MA to colonize soil; and the effects of mycofumigation on ectomycorrhizal fungi (EMF) in vitro and on the colonization of onion roots by the arbuscular mycorrhizal (AM) fungus Glomus intraradices. The bioactivity of water-soluble compounds produced in potato dextrose broth was significantly increased as measured in growth reduction of C. coccodes, V. dahliae, and Rhizoctonia solani. No reduction was observed for Aphanomyces cochlioides and Pythium ultimum. Antimicrobial compounds from a MA colonized barley point source reduced V. dahliae and C. coccodes populations in soils by 60-100% at distances up to 9 cm from the inoculation source depending on soil type. Mortality rate ranging from 70-100% was observed within a 3 cm radius from the inoculation source. In both field and greenhouse trials, MA colonized barley formulation reduced Verticillium wilt and black dot root rot severity and reduced populations of both pathogens in potato tissue as measured by real-time quantitative PCR and serial dilution. Planting directly into mycofumigated soil previously infested with V. dahliae or C. coccodes resulted in equal control of the pathogens when compared to a one-week mycofumigation period prior to planting. After six weeks of incubation MA did not colonize sterile soil further than 0.5 cm away from a MA inoculation point. In vitro experiments showed that most of the tested EMF were inhibited in the presence of MA VOCs, but were able to resume growth when removed from VOCs. Incorporating MA into soil had no negative but supportive effect on onion root colonization by the AM fungus G. intraradices.