ECOLOGICAL STUDIES ON GROWTH AND NUTIRTIONAL DYNAMICS OF CROPS AND PLANTS GROWN IN PADDY FIELDS AND NATURAL SUBMERGED COMMUNITY.

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Rice seedlings were transplanted in the 1/5000a Wagner's pots with only top soils sampled from natural submerged community of rivers and ponds and paddy fields under Nature, Organic and conventional farming system. There was significant positive correlation between rice straw weight in the pots and the biomass of natural plants and rice plants at harvesting. Significant highly positive correlation could be seen in case of no-tillage paddy fields and natural submerged community. Pot experiment seems to be effective on judging soil productivity.Soil profile in ponds for irrigation had more than 30cm softened top soil with fine soil particle and was quite different from soil profile in the riverside where softened top soil having 5cm.Nitrogen mineralization from the top soils of natural submerged community was quite more than those in paddy fields under Nature Farming. Soil C/N ratio of natural submerged community was from 10 to 13 and were less than about 20 in compost.Regeneration of 3-5cm softened top soil in the paddy field like natural submerged community brought no weed and better rice harvest. Tillage and puddling of around 3cm of paddy fields under dry condition in winter stimulated the formation of 3-5cm softened top soil.Root system formation of reed, bulrush, mat rush and rice plants grown under submerged condition were also observed. Present status and future prospects of sustainable agriculture in Japan was reviewed historically.