Project study on Material Cycle in Paddy Field Biotope

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In order to preserve healthy paddy field ecosystem, it is important to estimate diffusive flux of chemical substance in irrigation water such as pesticide and fertilizer that flows into paddy field. The transport phenomenon of dissolved pesticide and fertilizer in irrigation water was characterized as diffusive and dynamic phase in the paddy field.The behavior of irrigation water near by the inlet of the modeled paddy field was observed such that the irrigated water flowed into paddy field with a whirl-motion with increasing its size as it move into the paddy field. Water flow formed the two zones of high speed flow and very slow speed flow. The former the solute in the irrigation water moves by the advection the latter by the diffusion. It was indicated that it had to be evaluated by appropriate places and appropriate quantities of the samplings, etc., when diffusive conditions of the pesticide in paddy field, etc. were investigated.Dr.Watanabe studied pesticide fate and transport in … More paddy field and its application for the good agricultural practices such as irrigation and drainage controls for the paddy rice production. As the result, Automatic irrigation system with high drainage gate that can store the paddy water and prevent runoff during the significant rainfall event can be recommended as the best management practice. Also, usual flow through irrigation or continuous irrigation-drainage scheme having significant amount of pesticide 'runoff from paddy field is not recommended for preserving aquatic ecosystem and paddy field biotope. Simulation model of PCPE-1 was intended to use in this case however the result underestimated the observation. Hence. this system has the necessity of the improvement.Dr.Okazaki measured Cd balance of the Honmachi university experimental paddy fleld Considering adsorbed cadmium in the rice was 6mg/ha/year, etc., the inflow of Cd from the Honmachi paddy field estimated to be 5mg/ha/year, and its ninoff with 10mg/ha/year. This indicated that the attention was needed for the Cd Japanese regulation.Dr.Toyoda carried out the field investigation of the feed rice plant under the condition of fertilization and non-fertilization of the nitrogen fertilizer in the Honmachi university experimental paddy field. As the result of estimated nitrogen budget, the quantity of 248kgN/ha in the fertilization treatment and 118kgN/ha in the non-fertilization treatment was stored into the ripe plant from paddy field soil.Dr.Hrasawa compared with direct seeding and transplantation cultivation practice, and examined for the dry weight production and nitrogen accumulation.The result showed that there were more biomass in direct seeding, because the leaf received a great amount of solar radiation d***ing the growing period, and that the environmental condition of other influencing organism during the growing period for direct seeding practice is some what different from that of the transplantation cultivation.Dr.Fukushima showed that the considerable deference in plant community in terraced paddy field and in Yachida. Observed plant community had 348 kinds in the terraced paddy field, on the other hand, there were 309 types in Yachida. There was the hydorphyte conmmunity in Yachida to locate valley part in geographical feature. However, in order to locate the highland using rain water, the kind of plant community in terraced paddy field was different. It is considered that the different ecology was observed depending on the landform. Less