Germination, Growth, and Ecology of Sicklepod'

Germination, growth. and potential phytotoxicity of sickle- pod (Cassia obtusifolia L.) were studied. Seed germination occurred in the tenmperature range from 18 to 36 C, but rapid seedling growth occurred only between 30 and 36 C. Seed dormancy caused by a waxy coat resulted in only 15% germination in soil over a 12-month perio(l. A 1:15 (g/ml) water extract of sicklepod tops inhibited ger- mination of cotton (Gossypiuml hirsutirn L.) and oat (Avena sativa L.) seedl. Incorporation of sicklepod residues in soil reduced germina- tion of cotton seed but increased persistence of sericea (Lespedeza cauneata (Dumont) G. Don.) and crimson clover (Trifolium incar- tnatunttt L.) because damping-off was almost eliminated. There was evidence in nutrient cultures that sicklepod released a phytotoxic residuie from its roots, reducing growth of cotton but having no effect on soybeans (Glycine max (L.) Merr.). Sicklepod grew well in soils ranging from pH 3.2 to 7.9. Sicklepod response to N, P, and K levels was similar to cotton and higher than that of soybeans.