Influence of water management and fertilizer application on 137Cs and 133Cs uptake in paddy rice fields

Publication date: June 2016
Source:Journal of Environmental Radioactivity, Volume 157
Author(s): Shokichi Wakabayashi, Sumio Itoh, Nobuharu Kihou, Hisaya Matsunami, Mayumi Hachinohe, Shioka Hamamatsu, Shigeru Takahashi
Cesium-137 derived from the Tokyo Electric Power Company's Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident contaminated large areas of agricultural land in Eastern Japan. Previous studies before the accident have indicated that flooding enhances radiocesium uptake in rice fields. We investigated the influence of water management in combination with fertilizers on ¹³⁷Cs concentrations in rice plants at two fields in southern Ibaraki Prefecture. Stable Cs (¹³³Cs) in the plants was also determined as an analogue for predicting ¹³⁷Cs behavior after long-term aging of soil ¹³⁷Cs. The experimental periods comprised 3 y starting from 2012 in one field, and 2 y from 2013 in another field. These fields were divided into three water management sections: a long-flooding section without midsummer drainage, and medial-flooding, and short-flooding sections with one- or two-week midsummer drainage and earlier end of flooding than the long-flooding section. Six or four types of fertilizer subsections (most differing only in potassium application) were nested in each water management section. Generally, the long-flooding treatment led to higher ¹³⁷Cs and ¹³³Cs concentrations in both straw and brown rice than medial- and short-flooding treatments, although there were some notable exceptions in the first experimental year at each site. Effects of differing potassium fertilizer treatments were cumulative; the effects on ¹³⁷Cs and ¹³³Cs concentrations in rice plants were not obvious in 2012 and 2013, but in 2014, these concentrations were highest where potassium fertilizer had been absent and lowest where basal dressings of K had been tripled. The relationship between ¹³⁷Cs and ¹³³Cs in rice plants was not correlative in the first experimental year at each site, but correlation became evident in the subsequent year(s). This study demonstrates a novel finding that omitting midsummer drainage and/or delaying drainage during the grain-filling period enhances uptake of both ¹³⁷Cs and ¹³³Cs.



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