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ARS Home » Plains Area » Fort Collins, Colorado » Center for Agricultural Resources Research » Soil Management and Sugarbeet Research » Research » Publications at this Location » Publication #343366

Research Project: Management Practices for Long Term Productivity of Great Plains Agriculture

Location: Soil Management and Sugarbeet Research

Title: Interactions of stover and nitrogen management on soil microbial community and labile carbon under irrigated no-till corn

Author
item Stewart, Catherine
item Roosendaal, Damaris
item Manter, Daniel
item Delgado, Jorge
item Del Grosso, Stephen - Steve

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/2/2018
Publication Date: 2/8/2018
Citation: Stewart, C.E., Roosendaal, D.L., Manter, D.K., Delgado, J.A., Del Grosso, S.J. 2018. Interactions of stover and nitrogen management on soil microbial community and labile carbon under irrigated no-till corn. Soil Science Society of America Journal. doi:10.2136/sssaj2017.07.0229.

Interpretive Summary: How long-term residue removal impacts the soil microbial community and labile soil carbon pools in irrigated, no-tillage continuous corn systems is unknown. We measured the effects of partial stover retention (PR) compared to full stover retention (FR) on labile soil C pools, soil microbial biomass, and community composition under three N fertilization treatments after 7 yr. Soil microbial biomass (PLFA-C) was 40% and 42% lower under PR, compared to FR, for the 0 and 60 kg N ha-1 treatments, respectively, reflecting lower soil C contents under PR. Residue treatments did not significantly alter microbial community composition. Labile C was on average 11% greater under PR, primarily deeper than 7.5cm, suggesting greater root inputs and slower decomposition. Residue retention and N fertilizer promote microbial biomass by enhancing rhizodeposition and reducing decomposition, but overall soil C reductions with residue removal will lower microbial populations and consequently nutrient cycling rates.

Technical Abstract: Irrigated soils appear to be particularly susceptible to SOC decomposition and residue removal will likely exacerbate this effect by reducing C inputs, increasing soil temperature, and potentially stimulating microbial biomass. However, little is known about the long-term impacts on the soil microbial community and how they interact with labile soil C pools in irrigated, no-tillage continuous corn systems. We measured the effects of partial stover retention (PR) compared to full stover retention (FR) on labile soil C pools, soil microbial biomass, and community composition under three N fertilization treatments after 7 yr. Soil microbial biomass (PLFA-C) was 40% and 42% lower under PR, compared to FR, for the 0 and 60 kg N ha-1 treatments, respectively, reflecting lower soil C contents under PR. At the highest N rate, 202 kg N ha-1, microbial biomass did not differ between the PR and FR treatments. Residue treatments did not significantly alter microbial community composition. Microbial communities under no or low N were separated by gram-negative, AMF, and saprotrophic fungal biomarkers reflecting fresh plant-derived C input, while higher N rates separated along actinomycetes and gram-positive biomarkers. POM-C was on average 11% greater and POM C:N ratio was 31% greater under PR, primarily deeper than 7.5cm, suggesting greater root inputs and slower decomposition. Residue retention and N fertilizer promote microbial biomass by enhancing rhizodeposition and reducing decomposition, but overall soil C reductions with residue removal will lower microbial populations and consequently nutrient cycling rates.