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

在自然、有机和常规耕作制度下，只取河流、池塘和稻田自然淹没群落的表层土壤，在1/5000a Wagner’s盆栽中定植水稻幼苗。盆内秸秆重量与天然植株和收获时水稻植株生物量呈极显著正相关。免耕稻田与自然淹没群落呈极显著的高度正相关。盆栽试验似乎是判断土壤生产力的有效方法。灌溉塘土壤剖面软化表层土30cm以上，土壤颗粒细，与河滨土壤剖面软化表层土5cm有较大差异。天然淹没群落表层土壤氮矿化程度明显高于水田。天然淹没群落土壤C/N比值在10 ~ 13之间，堆肥土壤C/N小于20左右。稻田3 ~ 5cm软化表层土更新后，如天然淹没群落，无杂草，水稻收获较好。在冬季干燥条件下，对约3cm的水田进行耕作和水坑处理，可形成3-5cm的软化表层土。对芦苇、芦苇、芦苇和水稻在淹水条件下的根系形成情况也进行了观察。对日本可持续农业发展的现状和前景进行了历史回顾。

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.