Study on estimating and reducing of nitrate leaching in farmland on sand dune

为防止沙丘农业区地下水的硝酸盐污染，对鸟取县东部沙丘地区大葱产区地下水硝酸盐淋失状况及控制硝酸盐淋失的施肥法进行了研究。1)鸟取县东部沙丘农业区大部分井的地下水NO3-N浓度在10mgN/L以上，尤以大葱产区为最。2)利用整体蒸渗仪测定了葱栽培沙地土壤中硝态氮的淋失量。培养初期出现大量硝态氮淋失，根系生长不充分，渗滤液中硝态氮浓度达100mgN/L。CONTR…不能减少栽培初期硝酸盐淋失。更多的有机释放肥料有效。但是，当基肥的施用量推迟到开始根际扩张时，硝态氮的淋失有效地减少了。3)研制了一种能够记录根区较低入渗量并随时间变化的盐分浓度变化的装置。利用该装置研究了大葱种植沙地土壤中硝态氮浓度随时间的变化规律，建立了利用传感器了解土壤中溶质运移趋势、利用超临界流体分析仪测量土壤渗滤液水量和水质的监测系统。4)大葱沙地土壤性质在水平方向上呈现出不同的分布特征，其空间相关性与土壤中的CEC等养分含量有关。5)研制了新型土壤改良剂--水滑石和植物炭化改良剂，并通过盆栽试验验证了其对沙丘土壤硝态氮淋失的抑制效果。适量的施肥量促进作物生长，抑制硝态氮的淋失。特别是植物炭化材料，大大提高了沙丘土壤的养分和持水能力，综合考虑植物根系生长发育的限量配施是最有效的硝态氮淋失减量方法。较少

Status of nitrate leaching in scallion production filed located in the east part of Tottori sand dune and fertilizer placement method that controlled nitrate leaching was examined to prevent the nitrate pollution of underground water in the dune agricultural zone.1)NO3-N concentration of underground water of most of wells in dune agricultural zone in east part of Tottori Prefecture had 10mgN/L or more and was especially in uptrend in scallion production area. The quality of groundwater, which stay on clay layer located at depth of 10m, changed by the precipitation in short time, and its composition was similar to the soil solution.2)NO3-N leaching from scallion cultivation dune farmland was measured by a monolith lysimeter. A large amount of NO3-N leaching was occurred in the first stage of cultivation with an insufficient growth of the root, and NO3-N concentration of the leachate reached 100mgN/L.. Nitrate leaching at the first stage of cultivation was not able to be reduced by contr … More olled-release fertilizers effectively. However, when the base fertilizer application was delayed until starting root expansion, the nitrate leaching was effectively reduced.3)Device (SCFS) that was able to record the amount of lower infiltration from the root zone and a change with the lapse of time of the salt concentration was developed. A change with the lapse of time of NO3-N concentration that leached from scallion cultivation sandy field was clarified by this device.The monitoring system, which can make clear solute transport tendency in soil with sensor and measure water volume and quality of leachate by SCFS, was constructed.4)The soil property of the scallion production dune filed showed various distributions horizontally, and the spatial dependence was shown in properties to be related to nutrients holding such as CEC. Soil properties seemed to influence growth, quality, and the amount of scallion.5)New soil amendments, hydrotalcite and plant charred materials, were created, and the effect of the NO3-N leaching reduction in the sand dune soil was verified by the pot test. The materials application of the proper quantity promoted the growth of crops, and controlled the NO3-N leaching.. Especially, the plant charred materials have greatly improved the nutrients and water holding capacity of sand dune soil.It was concluded that the limited part fertilizer application that took growth and the development of the plant root into consideration was the most effective NO3-N leaching reduction method. Less