RESPONSE OF COMMON BEANS (PHASEOLUS-VULGARIS L) TO P AND N FERTILIZERS IN FIELD TRIALS

Two field experiments were conducted in a volcanic soil to study the response of common bean (Phaseolus vulgaris L.) to applications of triple superphosphate (P) (60 kg P2O5/ha) ad urea (N) (20 kg/ha). The fertilizers were applied either singly or together (1) by broadcasting, (2) by evenly spreading them in the rows (conventional method), (3) as a concentrated band at seed level (concentrated method), or 4) by different combinations of the above. The control treatment was not fertilized. The experimental design consisted of completely randomized, triplicated blocks. The crop was harvested at maturity and the grain yields were measured. When applied singly, P significantly (p less-than-or-equal-to 5 %) increased grain yields only when used in concentrated form or in the conventional way. The response of plants to N fertilizer was low; in fact, N placed singly by the concentrated method actually lowered yields. Applying the fertilizers together by broadcasting did not markedly change the yields. The highest yield increases were obtained when P was applied in concentrated form and N was applied either conventionally or in concentrated form.