Linking C and N Cycling to Microbial Community Function in Cover Crop Systems

Project Overview

Project Type: Graduate Student
Funds awarded in 2006: $9,995.00
Projected End Date: 12/31/2008
Region: Western
State: California
Graduate Student:

Annual Reports


  • Agronomic: corn


  • Crop Production: cover crops, nutrient cycling, organic fertilizers
  • Education and Training: demonstration, display
  • Production Systems: agroecosystems
  • Soil Management: green manures, organic matter, soil analysis, nutrient mineralization

    Proposal abstract:

    Cover crops have emerged as a crop management strategy with potential to achieve agricultural sustainability, maintain environmental quality, and secure grower profitability. Comparing the impacts of cover crop root carbon (C) exudation on nitrogen (N) processing by the microbial community within soil microenvironments of rhizosphere versus bulk soil will shed light on the specific underpinnings of short-term N stabilization versus losses due to C-inputs to long-term conventional and alternative cropping systems. The global research objective of this proposal is to elucidate how cover crop C-input controls short- and long-term N cycling through regulating microbial community function within soil microenvironments, across a gradient of nutrient management systems. My proposed approach is novel because it combines 13C-stable isotope techniques, physical soil fractionation, and quantitative functional gene assays (amoA and nosZ genes) to reveal the role of microorganisms in C and N cycling within different cover crop agroecosystems. The global outreach objective of this proposal is to present a synthesis of biophysical data and economic analyses at field days and grower workshops sponsored by the University of California, Cooperative Extension. This study directly addresses the project goals of WSARE in that the results will provide a better understanding of soil organic matter dynamics and nutrient cycling in cover crop systems to develop sustainable crop management strategies and to incite greater grower regard for cover cropping as a profitable and environmentally sound farming practice.

    Project objectives from proposal:

    The specific research objectives of this project are to: 1) identify and quantify the microbial communities (e.g., nitrifying and denitrifying populations) associated with overall C stabilization and N cycling within soil microenvironments during the cover crop and subsequent maize growing season, 2) link microbial-mediated turnover and stabilization of C with soil microenvironment formation, and 3) evaluate the impact of long-term agroecosystem management on short- and long-term C and N flows through the microbial community and soil microenvironments. Characterizing the nitrifier and denitrifier communities across a gradient of long-term cropping systems will address the WSARE goals of maintaining and improving soil and water quality as well as evaluating biodiversity at the farm-scale. Illuminating the potential role of cover crops as N replacements fosters the WSARE mission to reduce the use of toxic fertilizer materials in agricultural production.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.