a1 Malaysian Agricultural Research and Development Institute (MARDI), Jalan Kebun, Kelang, Selangor, Malaysia
In two field experiments, sweet potato showed symptoms of lime deficiency, and consequently produced extremely low DM, at the natural pH of local peat (3.5–3.7). Liming to increase pH remarkably increased tuber and vine dry matter to pH 5.5 and harvest index to pH 3.8, but higher pH values decreased dry matter and harvest index. Tuber and vine yields generally decreased with continuous monocropping, probably because of increasing infestation with weevils (Cylas formicarius) and other pests, and depletion of available nutrients.
(Accepted July 20 1981)
p1 Present address: Department of Agriculture, University of Queensland, St Lucia, Brisbane, Australia 4067;
p2 Present address: Geography Department, University of Malaya, Kuala Lumpur, Malaysia.