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Exposure risk assessment and evaluation of the best management practice for controlling pesticide runoff from paddy fields. Part 1: Paddy watershed monitoring
Author(s) -
Vu Son Hong,
Ishihara Satoru,
Watanabe Hirozumi
Publication year - 2006
Publication title -
pest management science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.296
H-Index - 125
eISSN - 1526-4998
pISSN - 1526-498X
DOI - 10.1002/ps.1295
Subject(s) - environmental science , surface runoff , paddy field , hydrology (agriculture) , irrigation , pesticide application , pesticide , surface water , drainage , water balance , watershed , drainage basin , water resource management , agronomy , environmental engineering , ecology , geography , geotechnical engineering , cartography , machine learning , computer science , biology , engineering
Rice pesticide concentrations in surface water along with hydrological balance and water management conditions were investigated in a paddy watershed of about 100 ha at the Sakura river basin in Tsukuba, Japan, for 3 years from April 2002. Monitoring on different hydrological scales ranging from a paddy plot up to a watershed determined the importance of water management associated with rainfall events and the cyclic irrigation for reducing pesticide discharge into aquatic environments. Surface drainage significantly increased as a response to rainfall events greater than about 1.5 cm day −1 . A total of 16 herbicides were detected in the stream water and their peak concentrations mostly occurred from early to mid‐May following the pesticide application period. Two water management factors influencing the pesticide runoff from paddy fields were defined: excess water storage capacity (EWSC) and water holding period (WHP). Uncertainty analyses of pesticide discharge from a paddy plot for dymron (daimuron) and imazosulfuron (IMS) were performed using Monte Carlo simulation (MCS) with prescribed probability of rainfall and water management practice from observations over a period of 3 years. Application of an intermittent irrigation scheme with shallow water depth practice and high drainage gate to maintain the EWSC > 2 cm and increasing WHP from the current Japanese Agricultural Chemicals Regulation law of 3–4 days to at least 10 days were recommended for reducing the pesticide runoff from paddy fields in a monsoon region such as in Japan. The combination of good water management in field plots and small‐scale water cycling is the best management practice for controlling pesticide discharge from paddy watersheds. Copyright © 2006 Society of Chemical Industry