Published online by Cambridge University Press: 12 June 2017
The allelopathic potentials of Hope white lupine (Lupinus albus L.) herbage and herbage extracts were evaluated. The emergence and growth of cotton (Gossypium hirsutum L. ‘Deltapine 45A’), soybean [Glycine max (L.) Merr. ‘Lee 68′], and six weed species under greenhouse conditions were measured after seeding directly into a moist, silt loam soil into which dry Hope lupine herbage, collected at second bloom, had been incorporated at rates from 500 to 8000 ppm (dry herbage/dry soil, w/w). At the lower rates, incorporated Hope white lupine stimulated the emergence of large crabgrass [Digitaria sanguinalis (L.) Scop.]; at the higher rates, cotton emergence was inhibited. Cotton and soybean fresh weights were stimulated at incorporation rates up to 2000 ppm, but were inhibited at higher concentrations. The growth of johnsongrass [Sorghum halepense (L.) Pers.] and large crabgrass was stimulated at most incorporation rates. Stimulated plants were chlorotic and had longer internodes. Emergence and growth of other species tested were not significantly affected by incorporated Hope white lupine. Equivalent concentrations of Hope white lupine herbage extracts were about 17 times more inhibitory to germination of cress (Lepidium sativum L. ‘Curlycress’) seed than to growth of sorghum [Sorghum bicolor (L.) Moench ‘AKS 663′] coleoptiles or radicles. The inhibitory principle extracted from Hope white lupine herbage was non-volatile, heat insensitive, and significantly less active in soil. Fractionation of a herbage extract suggested that neither the alkaloid nor phenolic acid content could account for herbage phytotoxicity in soil.