Effects of Organic Amendments on Soil Humic Substances Content and Physiological Properties of Water-Stressed Zea mays and Glycine max

Project Overview

Project Type: Graduate Student
Funds awarded in 2004: $9,793.00
Projected End Date: 12/31/2005
Grant Recipient: Virginia Tech
Region: Southern
State: Virginia
Graduate Student:
Major Professor:
Greg Evanylo
Virginia Tech

Annual Reports


  • Agronomic: corn, rye, soybeans


  • Crop Production: biological inoculants, municipal wastes, nutrient cycling, organic fertilizers, tissue analysis
  • Education and Training: demonstration, extension
  • Production Systems: general crop production
  • Soil Management: organic matter, soil analysis, soil quality/health

    Proposal abstract:

    Water stress is the most critical environmental factor limiting crop production in the Piedmont soil physiographic province of the southeastern United States due to high evapotranspiration and low plant available water. Plants have evolved an antioxidant defense system in order to ameliorate this oxidative stress. Direct application of humic substances has increased antioxidant activity, chlorophyll content, photosynthetic efficiency, and overall drought resistance of many crops. The use of organic amendments may enhance plant antioxidant activity during stress via the presence of humic substances found in these compounds. Little research has been conducted linking the effects of organic amendments and increased soil humic substances content to enhanced antioxidant activity during water stress and improved yield quality (e.g. seed density, starch, protein, oil, and fiber content). It is important to quantify such plant physiological benefits in order to provide further evidence of the value of organic amendments and to promote their usage on moisture deficient Piedmont soils. Since 1999, commercial inorganic fertilizer, poultry litter, and various combinations of composts have been applied to a Fauquier silty clay loam (fine, mixed, mesic Ultic Hapludalf) at the Northern Piedmont Agricultural Research and Extension Center in Orange, Virginia. We will quantify soil pH, soil nutrient, organic matter, humic and fulvic acid content; plant available moisture; leaf water potential, photochemical efficiency, and antioxidant activity; and seed density, starch, protein, oil, and fiber content of Zea mays and Glycine max during the typically droughty Piedmont summers. We hypothesize that organically-amended soils will contain higher humic substances content, increase plant antioxidant enzyme activity, and improve crop yield and seed quality of water-stressed Zea mays and Glycine max more than inorganically fertilized soils.

    Project objectives from proposal:

    To compare the effects of inorganic fertilizer, poultry litter, and two composts on soil properties (pH, nutrient concentrations, bulk density, moisture release curves and plant available moisture, organic matter, and humic and fulvic acid content) and plant properties (leaf water potential; photochemical efficiency; superoxide dismutase, ascorbate peroxidase, and catalase activities; malondialdehyde concentration; 1000 g seed weight, seed density, starch, oil, protein, and fiber content of Zea mays and Glycine max).

    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.