Germination and seedling development of some crops and vegetables as influenced by sweetpotato and taro residues

摘要

Sweetpotato and taro are widely planted rootcrops that have been found to possess allelopathic principles. In this study the effect of their allelopathic nature on seed germination, seedling development and initial growth of mungbean, cowpea, corn, upland rice, pepper and toma to was determined using plant residue extract and residue itself. The germination of all the test seeds was markedly reduced by the residue extract of sweetpotato, taro and sweetpotato + taro extract combined. The effect of the same extracts, however, on the germination coefficient or cumulative germination of the same seeds differed. Germination coefficient was significantly reduced by all the extracts in cowpea and tomato. In mungbean and upland rice, taro and sweetpotato + taro extracts brought about marked reduction but not sweetpotato. In corn and pepper the ex tract from either sweetpotato or taro and their combination did no t have any notable effect at all on germination coefficient. On the other hand, the vigor index or the overall performance of par ticular seeds during the process of germination and emergence were notably reduced by the residue extracts of sweetpotato and taro whether they were applied alone or in blend. Sweetpotato and taro residues incorporated into a soil germinating medium regardless of whether alone or in combination did not bring about marked effect on the germination of the test seeds. The germination coefficients, however, was generally reduced by theresidues although the trend of remarkable effect of a particular residue was not consistent from one seed-species to another. All the residues depressed very highly the vigor index of all the test seeds. The plant height, number of first order lateralroots and total root length of mungbean and corn seedlings was also eminently inhibited by the sweet-potato and taro residues.