Effects of Improvement of Agricultural Infrastructure on Runoff Loads from Lotus Paddy Fields

IIO Wataru, YOSHIDA Shigeki, KITAMURA Tatsumi, MATSUMOTO Shunichi, KURODA Hisao

doi:10.2965/jswe.42.171

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Other Title

ハス田群からの水質汚濁物質流出負荷量に対する基盤整備の影響
ハスデングンカラノスイシツオダクブッシツリュウシュツフカリョウニタイスルキバンセイビノエイキョウ

Published: 2019

DOI

10.2965/jswe.42.171

Publisher: Japan Society on Water Environment

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<p>Ibaraki Prefecture produces the largest volume of lotus root in Japan. The Teno area in Tsuchiura City (Ibaraki Prefecture) is the first to develop an infrastructure consisting of a concrete levee and to separate irrigation and drainage canals in Japanese lotus paddy fields. This was carried out over the period from 1995 through 2015. In this study, we studied the changes in runoff loads from lotus paddy fields due to the improvement of agricultural infrastructure in this area. Runoff loads of suspended solids (SS) , chemical oxygen demand (COD) and total nitrogen (TN) were the largest in March and April. This result is attributed to the manuring using basal fertilization and calcium cyanamid in this period. On the other hand, the runoff load of total phosphorus (TP) was maximum in July and August. As a cause, the elution of phosphate-phosphorus from lotus paddy soils and bottom sediments in drainage canals under lowered dissolved oxygen concentrations can be considered. Furthermore, annual balanced losses of COD, TN, and TP from lotus paddy fields were increased compared with those before the improvement of agricultural infrastructure. The separation of irrigation and drainage canals decreased soil sedimentation, which resulted in increases in losses of COD, TN, and TP from lotus paddy fields.</p>

Journal

Journal of Japan Society on Water Environment

Journal of Japan Society on Water Environment 42 (4), 171-176, 2019

Japan Society on Water Environment

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