Changes in exchangeable potassium concentration, and related chemical properties, of paddy soils in Fukushima Prefecture treated to reduce radiocesium uptake
2019
Nakayama, H. (Fukushima agricultural technology center (Japan)) | Sato, S. | Suzuki, Y. | Nemoto, F.
Following the 2011 accident at the Tokyo Electric Power Fukushima Daiichi Nuclear Power Station, large amounts of potassium fertilizer were applied to paddy soils to reduce the uptake of radiocesium by rice. The Fukushima Prefectural Government recommended that extra potassium fertilizer be applied before planting with the goal of increasing the soil exchangeable K content (ExK) to above 250 mg K2O /kg soil. After collecting ExK data for paddy fields in Fukushima Prefecture in 2011 (n = 863), 2014 (n = 730), and 2017 (n = 577), we divided Fukushima Prefecture into 13 regions and investigated the changes in ExK from 2011 onward in these different regions. In addition, we investigated soil chemical properties related to the increase in ExK. In regions where rice with high concentrations of radiocesium was harvested in 2011, supplemental potassium fertilizer (250 kg /ha /year)was applied, resulting in an increase in ExK by 313 mg K2O /kg soil during the period from 2011 to 2014. In 2017, 81% of all sampling sites had ExK greater than 250 mg K2O /kg soil. Simple linear regression analysis identified effective CEC (ECEC) and EK (K equivalent/ECEC) as soil chemical properties correlated with the magnitude of ExK increase from 2011 to 2014 in all 13 regions. CEC, however, was not correlated with the magnitude of ExK increase. The coefficient of determination (R**2) for the linear model of the relationship between magnitude of ExK increase from 2011 to 2017 and the quantity of additional K fertilizer applied was 0.41. The goodness of fit of the model was improved (R**2 = 0.52) by multiplying the quantity of additional potassium fertilizer by the reciprocal of EK, suggesting that EK (or ECEC, which is used to calculate EK) may serve as an indicator of ExK maintenance.
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