Abstract
Effects on the growth and yield of rice, when using no agricultural chemichals. In a 4 year period, 1991-1994, community structures of arthropods and weeds were examined in a rice paddy, producing the following results.
1. During the investigation period, rice yield in the paddy field using no agricultural chemichals produce 75% less than a field which did. Although only slightly observed, in this period, rice plant damage by insects and disease in the paddy field without chemicals was very sever, especially Monochoria vaginalis Presl. From these facts, it was considered that the disease in yield of this field was due to resultant competition with weeds.
2. Decreased number of aquatic arthropods: seedshrimps, waterfleas, mosquito larvae and Dragon-Fly Nymphs, in floods waters using pesticides application.
3. Parasitism rate of rice-planthopper insects in the paddy field with agricultural chemichals was lower than that of the paddy field without chemichals.
