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Effects of fertility on biomass, phytotoxicity, and allelochemical content of cereal rye

Mwaja, V.N., Masiunas, J.B., Weston, L.A.
Journal of chemical ecology 1995 v.21 no.1 pp. 81-96
Secale cereale, intercropping, Vicia villosa, soil fertility, allelopathy, allelochemicals, plant competition, Lepidium sativum, Echinochloa crus-galli, weed control, chemical constituents of plants, continuous cropping, root shoot ratio, biomass production
Studies were conducted to evaluate biomass production, tissue phytotoxicity, and allelochemical content of rye (Secale cereale L.) shoots grown in three fertility regimes (low, medium or high) in the greenhouse. Wheeler rye or a polyculture of rye and hairy vetch (Vicia villosa Roth) grown with high fertility produced the greatest biomass (78.7 and 82.7 g), with the lowest root-to-shoot ratio (0.22 and 0.43) produced in the high-fertility treatments. The polyculture treatment grown with low fertility had a greater proportion of hairy vetch (18%) than when grown with high fertility (6%). Rye shoot residue phototoxicity was affected by fertility regime. Radicle elongation of cress (Lepidium sativum L.) and barnyardgrass [Enchinochloa crus-galli (L.) Beauv.] was inhibited by rye shoot residues in a modified Parker bioassay. Rye shoot residue grown with low fertility was less inhibitory to cress radicle elongation than rye residue from the medium- or high-fertility regimes. Extracts of dried rye shoots grown with high fertility were less inhibitory than extracts from other fertility regimes. The concentrations of ether extracts of rye causing 50% inhibition (I50) of cress radicle elongation were between 125 and 276 micrograms/ml for greenhouse-grown and 60 and 138 micrograms/ml for the field-grown rye shoots. The major phytotoxic compounds in the rye shoot extracts were identified as DIBOA and BOA. The concentration of DIBOA in the greenhouse-grown rye shoots ranged between 128 and 423 micrograms/g while BOA concentration ranged between 2.5 and 31 micrograms/g. DIBOA and BOA levels were lowest in the shoots grown with high fertility. Correlations between the shoot biomass, DIBOA and BOA concentration, and cress barnyardgrass radicle length were significant.