Effect of Cover and Green Manure Crops on Soil Health, Plant Health and Tuber Yield in Organic Sweet Potato Production

Project Overview

Project Type: Graduate Student
Funds awarded in 2016: $11,956.00
Projected End Date: 10/31/2017
Grant Recipient: University of Missouri
Region: North Central
State: Missouri
Graduate Student:
Faculty Advisor:
Dr. Xi Xiong
University of Missouri


  • Vegetables: sweet potatoes


  • Crop Production: cover crops
  • Education and Training: demonstration, extension, farmer to farmer, on-farm/ranch research
  • Production Systems: general crop production
  • Soil Management: green manures, soil quality/health
  • Sustainable Communities: sustainability measures

    Proposal abstract:

    Organic sweet potato growers are challenged by sustainable soil management, which impacts the occurrence of soilborne disease, weed competition, and other pest issues that consequently reduce the tuber yield and/or quality. Being organic, their options are limited for pest control, especially fungal disease that affects the roots and/or tubers. The proposed research aims to develop a strategy of using cover and/or green manure crops and evaluate their effects on soil health, plant health, as well as disease and weed suppression. The proposed experiment will be conducted at a Certified Organic producer’s field based in central Missouri. A field experiment with a split-plot design will assess the effect of rapeseed and cereal rye, both as cover or green manure crop over a two-year period. Both species exhibit fungicidal/herbicidal effects. Soil volumetric water content will be monitored monthly, and water-stable aggregates, which represent the soil-water relationship, will be determined three times a year. Soil samples will also be collected for soil organic matter, pH, nutrients, and phospholipid fatty acid (PLFA) analysis three times per year to observe changes in soil properties over the course of the study. The PLFA will assess soil microbes, including various groups of fungi and bacteria, for their diversity and density. This will give indication of the soil fertility, nutritional status and microbial diversity throughout the study. Evaluations will also include weed species coverage, disease occurrence (Fusarium root and stem rot), and sweet potato yield. This will result in increased knowledge on how best cover crops can be used sustainably in organic sweet potato production to manage the soil as well as weed and disease problems. The expected outcome is the development of a strategy for improving soil health and sustainability that enhances suppression of soilborne pathogens and weed species in organic sweet potato production. The project will also be evaluated by monthly interviews with the farmer involved in this project, and a couple of surveys which sample the farming community and the general public for their opinions and acceptance towards this project.

    Project objectives from proposal:

    The proposed research will result in an increased knowledge and understanding of:

    • the effect of cover and/or green manure crops on soil water status and soil properties
    • soil health which will be determined by measuring soil microbial population/activity, and specific beneficial bacteria or fungi, for weed and disease suppression;
    • The effect of cover and/or green manure crops on sweet potato quality and yield, and consequently, the economic benefits.

    Specifically, the learning outcomes include increased awareness for both farmers and agriculture professionals on the use of cover crops in the crop production systems, also enhanced skills and motivation to adopt the practice. Additionally, the motivation to farmers to adopt the principles in their production systems.

    The action outcomes will be the implementation resulting in farmers adopting the practice resulting in improved soil health and plant health, incorporation of the principles by agriculture professionals, stimulation of further research in this area and the incorporation of the research results in extension publications and field guides. Additionally, the farmers will incur reduced losses in organic sweet potato production hence increased productivity, increased yields, increased market opportunities due to better quality produce and eventually improved economic well being for the farmers. This will also result in partnerships with various stakeholders who could even support cover crop research. This will eventually result in the sustainable use of resources hence improved environmental stewardship and 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.