2023 Volume 68 Pages 41-50
In Mindanao, Republic of the Philippines of which rice grain yield per unit area is particularly low among those of Asian countries, we tried to identify the problems of tropical rice cultivation through growing the fixed-type indica rice variety RC240 in 24 hectares (hereafter, ha) of farmersʼ paddy fi elds and investigated the effects of the soil-microbial flora activator Takeo-Tanisaka Solution (hereafter, TT Solution) on tropical rice cultivation (Experiment 1). Experimental results showed that the low grain yield of rice cultivation in Mindanao was caused chiefly by severe damages from diseases, insect pests and rodents, natural disasters such as floods and droughts, and inadequate fi eld facilities such as irrigation systems, and the application of TT Solution and the reduced use of chemical fertilizers not only increased grain yield markedly but also lessened damages from diseases, insect pests and drought. It was also indicated that fungicides should not be used, though the use of minimal insecticide was allowed. Subsequently, to validate the results in Experiment 1, we participated in a rice cultivation contest competing only in grain yield, which was organized by Agusan Branch of the Philippine Rice Research Institute, for three consecutive cropping seasons (Experiment 2). In the contest, we did not use chemical fertilizers and fungicides, but used TT Solution and the minimum necessary insecticide. Also, grass and bushes that were spreading around the experimental paddy fi eld (1,995 m2) were constantly and thoroughly mowed, because they were considered convenient breeding places for insect pests, rodents, and pathogenic fungi. In addition, water management in the experimental fi eld was meticulously performed. As a result, despite using the fixed-type rice variety RC240 not having as high yield potential as hybrid varieties, we achieved higher grain yields than any other participating teams (major bio-chemical companies), all of which used their self-developed hybrid varieties, fertilizers, and agricultural chemicals, in all three seasons. The average grain yield 7.22 t/ha over the three seasons we achieved were 2.4 to 2.9 and 1.9 to 2.0 times higher than the average of RC240 in Agusan region and that of all varieties in Republic of the Philippines, respectively. Further, the application of TT Solution and our field water management completely suppressed the occurrences of soil cracking, surface soil separation, and diseases. It was therefore concluded that the application of TT Solution and the fi eld management adopted in the contest would be an effective way to increase grain yield and to realize and promote ʻlow input sustainable agricultureʼ in the tropics.
