Post-termination Effects of Cover Crop Monocultures and Mixtures on Soil Inorganic Nitrogen and Microbial Communities on Two Organic Farms in Illinois

Abstract

Cover crops can continue to affect agricultural systems even after they have been terminated by influencing nitrogen dynamics and by altering soil microbial communities. These post-termination effects can influence soil fertility, weed pressure, and the dynamics of potential plant pathogens in the narrow window of time between cover crop termination and cash crop emergence. We evaluated the post-termination effects of 12 different spring-sown cover crop mixtures and monocultures on soil nitrogen and microbial communities on two different organic farms in Central Illinois (on Lawson silt loam soil) and Northern Illinois (on Virgil silt loam soil). In comparison to control plots with no cover crops, all cover crop treatments significantly reduced soil nitrate levels but increased the potentially mineralizable nitrogen pool following termination. Nitrate levels of cover crop plots approached those of controls after 2 and 4 weeks, respectively, but potentially mineralizable nitrogen levels in cover plots remained elevated for at least 4 weeks following termination. Monocultures of Brassica cover crops showed the greatest decrease in soil nitrate, while Brassicas and unplanted control plots containing high biomass of weeds showed the greatest increase in potentially mineralizable nitrogen in comparison to plant-free control plots. In contrast to their effect on soil nitrogen, cover crops had very limited impact on the composition of soil microbial communities. Overall microbial community composition varied across sites and years, and only soil fungi significantly responded to cover cropping treatments. Nevertheless, we found that some highly correlated groups of soil microbes showed significant responses to soil nitrate and to high plant biomass. Key members of these correlated groups included ammonia-oxidizing organisms and saprotrophic fungi. Our results suggest that cover crops may reduce the potential for springtime nitrogen leaching losses by retaining nitrogen in the soil organic pool, and they may also have impacts on the soil microbial community that are particularly relevant for nitrogen cycling and decomposition of plant residues.

Effect of no-till followed by crop diversification on the soil microbiome in a boreal short cereal rotation

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Biostimulant Effects of Chaetomium globosum and Minimedusa polyspora Culture Filtrates on Cichorium intybus Plant: Growth Performance and Metabolomic Traits

“…Le Clair, a filamentous anamorphic species belonging to the Basidiomycota phylum. M. polyspora has been widely isolated in agricultural soils worldwide and found to be overrepresented in the tilled soil (Klaubauf et al, 2010 ; Panelli et al, 2017 ; Lucadamo, 2018 ; Longley et al, 2020 ; Větrovský et al, 2020 ; Orrù et al, 2021 ). This species presents several traits such as rapid growth, low requirement of nitrogen, ability to concentrate important biogenic macroelements (N, P, S, K, and Ca) and translocate nutrients, metabolic plasticity, and the production of antibiotic and antifungal compounds (triene compounds), which make it an efficient pioneer colonizer (Beale and Pitt, 1995 ; Pinzari et al, 2014 ).…”

Soil carbon and nitrogen dynamics under conservation agriculture components for direct seeded rice-green gram system

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