Allelopathic effects of small grain cover crops on cotton plant growth and yields

Project Overview

Project Type: Graduate Student
Funds awarded in 2007: $10,000.00
Projected End Date: 12/31/2009
Grant Recipient: Texas Tech University
Region: Southern
State: Texas
Graduate Student:
Major Professor:
Dr. Vivien Allen
Texas Tech University

Annual Reports


  • Agronomic: cotton, rye, wheat
  • Animals: bovine


  • Crop Production: conservation tillage
  • Education and Training: demonstration, farmer to farmer
  • Farm Business Management: budgets/cost and returns
  • Pest Management: allelopathy, biological control, cultural control, mulches - killed
  • Production Systems: agroecosystems
  • Soil Management: green manures, soil analysis, soil quality/health

    Proposal abstract:

    Cotton (Gossypium hirsutum L.) is an important crop in the Texas High Plains, grown largely with irrigation. A 9-yr crop-livestock, integrated system showed a 25% decrease in water use and decreased fertilizer inputs but variable effects on cotton yield and profitability compared with a monoculture cotton system (Allen et al., 2005; Allen et al., 2007). Prior to planting cotton in the integrated system, rye was used as a cover crop aimed to reduce soil erosion, increase soil fertility and was harvested by grazing steers. Small grain cover crops include rye, wheat and triticale are also known to produce allelopathic chemicals. Reberg-Horton et al. (2005) reported that phytotoxicity found in rye tissue was correlated with 2,4-dihydroxy-1, 4-(2H)benzoxazine-3-one (DIBOA) and the concentrations of DIBOA in rye tissue differed due to harvest date and rye cultivar. Marcias et al., (2005) reported that DIBOA was transformed primarily into 2-benzoxazolinone (BOA) in soil. The previous research in the integrated system indicates that small grains abate the following cotton yield in the rotation. Hou's (2005, unpublished data) work showed the steers grazing before planting cotton increased cotton lint yield by about 400kg/ha compared with take the rye as hay. The study on the difference between soil moisture, fertility, pathogens and cover crop density could not explain the difference. Thus, our hypothesis is that allelopathic chemicals present in rye can explain the observed effects on growth suppression of rye and cotton and that grazing by steers at least partially alleviates this effect.

    Project objectives from proposal:

    The overall objective is to identify the cause of small grain cover crop suppression on growth of rye and cotton and to alleviate this suppression through grazing management and/or selection of small grain species and varieties that minimize this effect. Specific Objectives: 1. To investigate whether BOA is present in soils when rye and wheat have been grown in alternate rotation for 9 yr and whether past grazing affects concentrations. 2. To determine whether DIBOA is present in Maton rye and to investigate effects of grazing vs hay on concentrations in aerial plant parts. 3. To investigate differences in concentrations of DIBOA in Lockett wheat and four varieties of rye and the effects of these forages as cover crops on subsequent establishment, growth, and yield of cotton. 4. To determine the biological activity of rye and rye extracts on germination and initial root elongation of cotton. 5. To determine effects of grazing vs no grazing on growth of rye and the following crop of no-till planted cotton.

    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.