Allelopathic effect of sweetpotato (Ipomoea batatas) cultivars on certain weed and vegetable species

Abstract

A glasshouse study was conducted to determine the allelopathic potential of sweetpotato (Ipomoea batatas (L.) Lam.) cultivars Bosbok, Brandal and Koedoe. Nine indicator plants, three weeds: yellow nutsedge (Cyperus esculentus L.), purple nutsedge (Cyperus rotundus L.) and common pigweed (Amaranthus hybridus L.), and seven crop species: carrot (Daucus carota L. cv. Kaapse Mark), tomato (Lycopersicon esculentum Mill. cv. Heinz 1370), cucumber (Cucumis sativus L. cv. Special Rust Resistant), radish (Raphanus sativus L. cv. White Icicle), onion (Allium cepa L. cv. Pyramid), lettuce (Lactuca sativa L. cv. Great Lakes).and oats (Avena sativa L. cv. SWK 001) were grown in soil from field plots previously cropped with these sweetpotato cultivars. The three cultivars were grown on separate plots. Soil from adjacent uncropped and weed-free fallow plots served as a control. Yellow nutsedge plants grown from tubers in soil from sweetpotato cv. Brondal field plots accumulated significantly less dry matter than plants grown in soil from cv. Bosbok, cv. Koedoe or fallow plots. It is suggested that substances inhibitory to yellow nutsedge growth were present in soil subsequent to growing Brondal sweetpotato. Compared with growth in soil from fallow plots, growth of the other test species was not inhibited in soil previously cropped with sweetpotato. In fact, the growth of carrot, cucumber, lettuce, oats, onion and tomato plants tended to be stimulated in some soils.