Allelopathic effects of small grain cover crops on cotton plant growth and yields
In west Texas, no-till planting cotton into rye or wheat cover crops reduced growth and lint yield of cotton compared with no cover crop. Production of allelopathic compounds, a known phenomenon in small grains, was suspected. Known allelopathic compounds from rye were detected in soil [2-benzoxazolinone (BOA)] and plant material [2,4-dihydroxy-1,4-benxozaxin-3-one (DIBOA)] in greenhouse and field experiments. Field and greenhouse trials verified cotton plant suppression by these small grain residues and by direct application of alleopathic chemicals. Grazing the cover crop by cattle may help alleviate these negative effects. Cover crops have environmental benefits but negative effects need further investigation.
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.
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 residues on germination and initial growth of cotton.
5. To determine effects of grazing vs no grazing on growth of rye and the following crop of no-till planted cotton.