Improving Soil Health and Microbial Activity through Zone Tillage and Innovative Cover Cropping Strategies

Project Overview

Project Type: Graduate Student
Funds awarded in 2014: $9,995.00
Projected End Date: 12/31/2015
Grant Recipient: University of Minnesota
Region: North Central
State: Minnesota
Graduate Student:
Faculty Advisor:
Dr. Julie Grossman
University of Minnesota

Annual Reports


  • Vegetables: eggplant


  • Crop Production: conservation tillage
  • Education and Training: demonstration, workshop
  • Natural Resources/Environment: biodiversity, soil stabilization
  • Soil Management: green manures, nutrient mineralization, organic matter, soil analysis, soil microbiology, soil quality/health


    We evaluated three cover crops (winter rye + hairy vetch, oat + field pea, and medium red clover) in zone tilled organic yellow crookneck squash production for biomass and N content at early and late termination dates.  We also measured soil quality  in crop rows and between rows using potentially mineralizable N (PMN), soil inorganic N, and permanganate oxidizable C (POXC).  Squash yield did not vary by cover crop treatments.  Cover crops left between crop rows to fully mature did gain biomass and N content.  In 2016, PMN detected in-row mineralization of winter rye + hairy vetch residues at the mid-season sampling when inorganic N increased.  Interestingly, POXC was affected only slightly by treatments, likely due to the assay’s sensitivity to soil organic matter stabilization rather than nutrient cycling.  Results echo the role that residue C/N plays in soil N cycling.  Moreover, the extended growing period for cover crops between crop rows in the first several weeks of crop growth appeared to boost soil fertility while having no negative effect on crop yield.


    Soil quality is described by Doran & Parkin (1994) as the degree to which soil functions within an ecosystem to sustain biological productivity and plant and animal health, while maintaining long-term environmental benefits.  Improving soil quality and biological activity is important in organic cropping systems where crop nutrition is provided via transformation of organic amendments into plant available, inorganic nutrients by soil microbes.  As such, the National Organic Program strongly encourages the use of cover crops, diversified crop rotations, and reduced tillage practices (Agriculture, 2007).  Soil quality is achieved in part through continued ground cover, often accomplished with the use of cover crops and by leaving cover crop residue on the soil surface.  In turn, the use of zone tillage has been proposed as a way to incorporate cover crop residue only where crops will be planted and to maintain living cover crops between rows to prevent N mineralization where it is liable to leaching (Brainard et al., 2013; Williams et al., 2016).  This approach has great potential in Northern climates ,where winter annual legumes rarely reach maturity by vegetable planting, which makes it difficult for growers to gain as much N from legumes as is fully possible (Zhang et al., 2013).  Maintaining ground cover between rows with these cover crops until flowering may increase N input and other ecosystem services.

    Project objectives:

    The goal of our study was to investigate the effect of zone tillage, allowing for extended cover crop growth in vegetable systems, on cover crop N contributions, soil quality, and yield of certified organic yellow crookneck squash (Cucurbita pepo).  Specifically, our objectives were to 1) assess the effect of extended cover crop growth on organic matter and N contributions, 2) compare the effect of zone till management on in-row soils where immature cover crop residue was incorporated via tillage to between-row soils where soil is undisturbed and roots are present, and 3) determine how squash yields were affected by cover crop contributions to soil quality.

    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.