Possible Utilization of Water Hyacinth (Eichhornia crassipes (Mart.)Solms), an Aquatic Weed, as Green Manure in Vegetables Cropping Systems

摘要

In previous studies using 15N-labeling techniques, the authors observed the release of N from water hyacinth (Eichhornia crassipes (Mart.) Solms) (WH) residues incorporated into a soil-rice cropping system, and suggested the utilization of WH residues as green manure (GM) in agricultural farmland especially in tropical and subtropical regions (WIDJAJANTO et al. 2001). In the present study, attempts were made to analyze clarify the effect of the application of WH residues on vegetable cropping systems. In this experiment, several kinds of crops such as lettuce (Laduca sativa), spinach (Spinacia oleracea), Chinese cabbage (Brasska rapa var. pervades), radish (Raphanus sativus), okra {Abelmoschus esculentus), green soybean (Giycine max Mem), and corn (Zea mays L.) were examined at different levels of added WH residues. A certain increase in yield was obtained, though the optimum rate of the applied residues varied among the crops. The results indicated that it might be possible to utilize of WH residues as GM through incorporation into vegetable cropping systems in tropical and subtropical regions. In this experiment, it was found that a higher application of WH as GM can be recommended for radish, okra, green soybean and corn which showed a stronger response in terms of vegetative growth.