Perennial legumes as a sustainable source of soil organic matter in Southeastern organic farming systems

Project Overview

Project Type: Research and Education
Funds awarded in 2006: $190,000.00
Projected End Date: 12/31/2008
Region: Southern
State: Georgia
Principal Investigator:
Carl Jordan
University of Georgia

Annual Reports


  • Agronomic: potatoes
  • Vegetables: sweet potatoes, beans, broccoli, cabbages, eggplant, garlic, greens (leafy), onions, peas (culinary), peppers, sweet corn, tomatoes
  • Additional Plants: herbs, ornamentals


  • Crop Production: agroforestry, nutrient cycling, organic fertilizers
  • Education and Training: extension, networking, on-farm/ranch research, participatory research
  • Natural Resources/Environment: hedgerows, hedges - woody
  • Soil Management: green manures, organic matter


    The contribution of perennial leguminous shrubs in an alley cropping system to soil carbon and nutrients was measured in 36 experimental plots. Soils in plots with leguminous shrubs had approximately 100 % more carbon and 90% more nitrogen than in plots without the shrubs. Pot experiments in which the shrub was labeled with stable isotopes showed that root sloughing was the source of the increased carbon and nitrogen. An economic analysis of three different cash crops in an organic alley cropping system showed that only chili peppers Capsicum annum were economically profitable, because of their relatively high market value.

    Tables, figures or graphs mentioned in this report are on file in the Southern SARE office.
    Contact Sue Blum at 770-229-3350 or for a hard copy.

    Project objectives:

    Research Objectives

    To compare crop yield, soil organic matter, and soil properties of an alley cropping system plus winter cover crops and composts with a more conventional organic farming system that uses composts plus winter cover crops but no perennial leguminous shrubs..

    To measure the time and effort needed to manage the two systems.

    To determine whether pruning of above ground biomass of a perennial legume causes an increase in root sloughing, and if so, to quantify the contribution of root sloughing to soil organic matter and nitrogen.

    Outreach and Educational Objectives:

    To develop an outreach component that will disseminate research results, establish on-farm trials, conduct workshops and internships, and provide feedback to researchers;

    To continue, expand, and integrate the Agroecology Lab's current educational program for undergraduates and graduate students into the outreach program.

    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.