A System Approach for Improved Integration of Green Manure in Commercial Vegetable Production Systems

Project Overview

Project Type: Research and Education
Funds awarded in 2002: $171,800.00
Projected End Date: 12/31/2005
Region: Southern
State: Florida
Principal Investigator:
Johannes Scholberg
Agronomy Department, University of Florida

Annual Reports


  • Vegetables: cucurbits, peppers, sweet corn, tomatoes


  • Crop Production: conservation tillage
  • Education and Training: decision support system, demonstration, farmer to farmer, on-farm/ranch research
  • Pest Management: mulching - vegetative
  • Production Systems: agroecosystems, holistic management, integrated crop and livestock systems
  • Soil Management: green manures, organic matter, soil analysis, nutrient mineralization


    We determined the benefits of green manures to increase yields and/or to reduce N-fertilizer rates at Tifton (S-GA), Citra (N-FLA), and Boynton Beach (S-FLA). Sunn hemp performed well at all three locations and it accumulated 120-160 kg N/ha. However, most of this N was lost within 2 wks so it should be followed by a commercial crop or by crimson clover (Tifton) or a rye/vetch mix (Citra). Use of green manures reduced crop N requirements by 25-50%, increased potential yields and cost-benefit ratio of a CSA operation. They also increased soil quality while suppressing weeds, lesion and ring nematodes.

    Project objectives:

    Vegetable cropping systems have experienced some of the highest levels of diversity loss. We designed innovative cover crop-based vegetable production systems specific to the southeastern US by combining a selection of summer and winter legumes with minimum tillage practices. Our main objective was to complement existing information on improved use of cover crops as a nitrogen source for commercial vegetable production systems and to integrate this information in web-based nutrient management and information tools for organic amendments. In order to achieve this objective we aimed to strengthen regional collaborative efforts between scientists and participants from the Univ. of Florida, Florida A&M Univ., the Univ. of Georgia, farm-based research organizations, and regional growers groups. Our overall goal was to develop a regional group of scientists and innovative farmers who are committed to develop sustainable production practices and guidelines for both conventional and organic farmers.

    Short-term objectives:

    A1) Determine which (combination of) cover crop(s) when used with minimum tillage will result in optimal nitrogen supply to subsequent vegetable crops;

    A2) Assess the amount of supplemental N fertilizer required for optimal yields for cover crop based production systems and compare their yields with conventional systems;

    A3) Determine nitrogen uptake efficiencies and N leaching for cover crop-based cropping systems in comparison with conventional vegetable cropping systems; and

    A4) Develop a regional research and outreach program for improved integration of cover crops in commercial vegetable systems in close collaboration with local growers.

    Long-term objective:

    B1) Evaluate the long-term effects of included treatment combinations on soil quality, crop disease levels and abundance and diversity of weed, arthropod and nematode populations;

    B2) Improve the exchange and integration of information on the use of cover crops in
    commercial production systems in the SE region;

    B3) Development of web-based nutrient management systems that will allow producers to make more efficient use of organic nutrient sources such as cover crops; and

    B4) Use of the Decision Support System for Agrotechnology Transfer (DSSAT) model for risk assessment (environmental and economical) of above cropping systems for a number of farming systems and locations throughout the southeastern US.

    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.