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

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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