Project study on Material Cycle in Paddy Field Biotope

为了保护健康的稻田生态系统，估算流入稻田的农药、化肥等化学物质在灌溉水中的扩散通量具有重要意义。灌溉水中溶解的农药和化肥在稻田中的运移现象具有扩散和动态的特点，通过观察模型稻田入水口附近灌溉水的运动规律，发现灌溉水进入稻田时呈漩涡运动，并随着灌水量的增大而增大。水流形成了高速流动和极慢速流动两个区域。前者灌溉水中的溶质通过平流运动，后者通过扩散运动。指出，在研究农药在稻田等地的扩散情况时，必须通过适当的地点和适当的采样量等方法进行评估。渡边博士研究了农药在…中的去向和迁移更多的水田及其应用的良好农业措施，如灌溉和排水控制的水稻生产。因此，在重大降雨事件时，推荐采用具有高排水闸门的自动灌溉系统来储存稻水和防止径流。此外，对于水田中农药径流量较大的常规灌溉或连续灌排方案，也不建议用于保护水生生态系统和稻田生物栖息地。PCPE-1的模拟模型本打算在这种情况下使用，但结果低估了观察结果。因此。本系统有改进的必要性。冈崎博士对本町大学实验稻田的Cd平衡进行了测量，考虑到稻米中吸附的镉为6 mg/ha/年等，本町稻田Cd的流入估算为5 mg/ha/年，其下限为10 mg/ha/年。丰田章男博士在本町大学试验稻田进行了施氮和不施氮肥条件下饲用水稻植株的田间调查。作为氮素收支估算的结果，施肥处理和不施肥处理的氮素产量分别为248kgN/ha和118kgN/ha。Hrasawa博士将其与直播和移栽栽培进行了比较，并对其干物质生产和氮素积累进行了测定。结果表明，直播的生物量较多，这是因为在生长期叶片受到了大量的太阳辐射，其他影响生物在直播期间的环境条件与移栽栽培有所不同。Fukushima博士指出，梯田和八田的植物群落有很大的差异。所观察到的水田植物群落有348种，而在八田则有309种。在地理特征上，八田有水生植物群落，定位于谷地部分。然而，为了定位利用雨水的高地，梯田水田的植物群落类型是不同的。人们认为，不同的地貌所观察到的生态是不同的。较少

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