permaculture

[Lawrence London <lfljvenaura@gmail.com>]

Allelopathic Effects Of Rye (Secale Cereale L.) And Their Implications For
Weed Management - A Review - Sent using Google Toolbar

http://www.colostate.edu/Depts/Entomology/courses/en570/papers_1998/pester.htm

"Abstract

Allelopathy offers potential for selective biological weed management
through the production and release of allelochemicals from leaves, flowers,
seeds, stems, and roots of living or decomposing plant materials (Weston,
1996). Under appropriate conditions, allelochemicals may be released in
quantities suppressive to developing weed seedlings. Allelopathy is strongly
coupled with inherent stresses of the crop environment, including insects
and disease, temperature extremes, nutrient and moisture variables,
radiation, and herbicides (Einhellig, 1996). These stress conditions often
enhance allelochemical production, thus increasing the potential for
allelopathic interference. Rye is an example of a plant which provides
excellent weed suppression through both allelopathic and competitive
mechanisms. Rye residues maintained on the soil surface release
2,4-dihydroxy-1,4(2H)-benzoxazin-3-one (DIBOA) and a breakdown product
2(3H)-benzoxazalinone (BOA) (Barnes and Putnam, 1987) both of which are
strongly inhibitory to germination and seedling growth of several dicot- and
monocotyledenous plant species. Further, microbially produced transformation
products of BOA demonstrate several fold increases in phytotoxic levels
(Chase et al., 1991a; Gagliardo and Chilton, 1992). Hence a variety of
natural products contribute to the herbicidal activity of rye residues.
Several studies have demonstrated the allelopathic characteristics of rye
residues and root exudates containing DIBOA and BOA. For example,
experiments have shown marked reductions in germination and growth of
several problem agronomic weeds including barnyardgrass (Echinochloa
crusgalli L.), common lambsquarters (Chenopodium album L.), common ragweed
(Ambrosia artemisiifolia L.), green foxtail [Setaria viridis (L.) Beauv.],
and redroot pigweed (Amaranthus retroflexus L.) (Putnam and DeFrank, 1983;
Shilling et al., 1985). Researchers are optimistic the results of these and
future studies will provide the necessary information to develop alternative
weed management strategies and cropping systems to enhance the
sustainability of agriculture."