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Sediment that has deposited after the flood generated by the 2019 typhoon (referred to as Flood Sediment, FS) was collected along two rivers in eastern Fukushima Prefecture, Japan to determine the total and exchangeable radiocesium ($^{137}\mathrm{Cs}$), and acid-extractable potassium (K) contents. Then, these FS parameters were compared with those of decontaminated soils (DS) in nearby agricultural fields to discuss the potential transfer risk of $^{137}\mathrm{Cs}$ from rivers to nearby remediated soils. While FS had about four times higher total $^{137}\mathrm{Cs}$ content, it showed a three-times lower exchangeable $^{137}\mathrm{Cs}$ content than DS. Furthermore, acid-extractable K referred to as non-exchangeable K (Nex-K) content was high enough to restrict $^{137}\mathrm{Cs}$ transfer from soil to crops for both FS and DS. From these comparisons, we concluded that deposition of FS onto DS may not increase the transfer of $^{137}\mathrm{Cs}$ from soil to crops.

The Fukushima nuclear accident in March 2011 generated a 3000 km$^{2}$ plume of soils heavily contaminated with $^{137}$Cs. Decontamination was completed early in 2019. Typhoon Hagibis was the first extreme event that occurred in the region after decontamination. Its impact on sediment sources and sediment $^{137}$Cs contamination was investigated through the application of a sediment fingerprinting procedure using spectrocolorimetry and geochemical properties. Sediment deposits ($n=24$) were collected in the Mano and Niida River catchments after the 2019 typhoons, and their signature was compared to that of potential sources (e.g., cropland, forests, and subsurface; $n=57$). Results demonstrate the dominance of cropland as the main source of sediment (mean: 54%) followed by forests (41%) with much lower contributions of subsurface material (5%). Overall, $^{137}$Cs concentrations in sediment were on average 84%–93% lower than the levels recorded after the accident in 2011, which demonstrates the effectiveness of cropland decontamination.

To investigate how the long-term application of inorganic fertilizer and organic amendments affects the turnover rates of organic matter in physico-chemically fractionated components in paddy soils and how their rates are related to their amounts, we studied the effect of variable management of inorganic fertilizer and organic amendments for > 50 years on the ∆14C values of accumulated soil organic carbon (SOC) in fractionated components of 5 soil samples from three paddy fields. SOC was fractionated into four components based on their physico-chemical properties: (1) light fraction (LF) derived from plant residues, (2) heavy fraction (HF) containing stable aggregates, (3) oxidizable fraction (OxF) and (4) non-oxidizable fraction (NOxF) forming organo-mineral complexes with fine-textured minerals. The ∆14C values were determined by accelerator mass spectrometry using graphitized samples. The ∆14C values of SOC in NOxF (from −305‰ to − 90.5‰) were much lower than those of HF (from −123‰ to − 3.7‰) and OxF (from −215‰ to 21.0‰). Lowest values for NOxF suggested slowest turnover rates as expected, and higher and comparable values for OxF and HF implied much faster turnover rates of SOC in OxF compared with upland soils. This could be one of the characteristics of SOC dynamics in paddy soils, probably reflecting repeated puddling of plow layer soils. ∆14C values in all the fractions increased in response to the application of inorganic fertilizer and organic amendments, suggesting faster turnover rate. Soils with clayey and weathered characteristics had the lowest ∆14C values, or slowest turnover rates among the study fields. The relationship between the ∆14C value and the amount of accumulated C for HF, OxF and NOxF indicated that the more the SOC accumulated, the faster the turnover rate of the SOC was, regardless of the fractions, and the relationship of the HF was considerably different from those of OxF and NOxF. In conclusion, these results can be the basis for understanding the C dynamics and for improving soil fertility status and soil C sequestration in paddy soils. [ABSTRACT FROM AUTHOR]

To investigate how the long-term application of inorganic fertilizer and organic amendments affects the accumulation of organic matter in physico-chemically fractionated components in paddy soils and how the accumulation is determined by soil properties and anthropogenic carbon input, we studied the effect of variable management of inorganic fertilizer and organic amendments for > 50 years on the amounts of accumulated soil organic carbon (SOC) in fractionated components in three paddy fields. SOC was fractionated into four components based on their physical and chemical properties: (1) light fraction (LF) derived from plant residues, (2) heavy fraction (HF) containing stable aggregates, (3) oxidizable fraction (OxF) and (4) non-oxidizable fraction (NOxF) forming organo-mineral complexes with fine-textured minerals. On average, the amount and percentage of accumulated C in the four fractions were as follows: OxF (6.63 gC kg−1soil, 46%) > NOxF (5.32, 35) > LF (1.68, 12) > HF (1.12, 7.2), suggesting about 80% of SOC was in fine, stable fractions. The amount of accumulated C in all fractions increased slightly with the application of inorganic fertilizer, while it increased considerably with the use of organic amendments. In addition, the application of fertilizers and amendments raised the proportion of C content in LF and HF, which are labile and related to soil fertility. Stepwise multiple regression analysis using two principal component analysis scores of soil properties and anthropogenic C input further revealed that the labile fractions (LF and HF) were more strongly determined by the management of fertilizers and amendments, while the stable fractions (OxF and NOxF) were more strongly determined by soil-specific properties, mainly the amorphous nature of the soil. These results indicate that the use of certain amounts of organic amendments would be recommended to carry out rational management to improve soil fertility and C sequestration in paddy fields, with the application of amorphous minerals as an additional option. [ABSTRACT FROM AUTHOR]

It is a general problem in geoscience to estimate the time-series of velocity and temperature fields for a fluid based on limited observations, such as the flow velocity at the fluid surface and/or a temperature snapshot after flow. In this study, an adjoint-based data assimilation method (also known as 4-D variational data assimilation) was used to reconstruct the thermal convection in a highly viscous fluid (e.g. Earth's mantle) to investigate which observations constrain the thermal convection and how accurately the convection can be reconstructed for different wavelengths. The data assimilated to the adjoint-based model were generated synthetically from forward models with convecting cells of different length-scales. Based on the surface velocity and temperature snapshot, our simulations successfully reconstructed thermal convection over 50 Myr in the case that the wavelength of the convective cells is sufficiently large. We obtained two main results from this parametric study. (1) When we only considered instantaneous thermal structure fitting in the cost function, the convection reconstruction tended to fail. However, there are some cases where the laminar thermal convection can be reconstructed by assimilating only the velocity along the fluid surface. (2) There is a limit to the reconstruction of thermal convection in the case that the convecting cells are small (∼1000 km for a 50 Myr reconstruction). We propose that (1) is related to the balance of forces due to the thermal buoyancy and viscous stress around the thermal anomalies and (2) is related to how information is preserved (i.e. how the previous thermal structure is maintained in the observable state throughout the convection process). The results enable the use of geological records to estimate time-series of velocity and temperature in Earth's deep interior, even though the records may only contain information from shallow parts of Earth. [ABSTRACT FROM AUTHOR]

To investigate the interactive effects of parent material and topography as soil forming factors, we examined the distribution of soil materials in an alluvial plain, where two types of surface geology were situated upstream and different parent materials supplied accordingly. We hypothesized that these two types of parent material make it possible to trace alluvial processes by analyzing their spatial distribution based on soil physicochemical properties. We collected 101 soil samples from the alluvial plain and nine soil samples from two types of unmixed upstream areas, i.e., granite and mélange. Particle size distributions and total concentrations of 32 elements were analyzed for spatial variabilities. Elemental composition of unmixed upstream samples and isarithmic maps of elemental composition of the soils in the alluvial plain based on geostatistical analysis revealed that gravel, coarse sand and total Na, Al, K, Ca, and Mn concentrations were higher at the southern part close to granite rock areas, whereas silt+clay content and total C, N, Mg, Ti, and Fe concentrations were higher at the northern part close to the mélange area, suggesting strong influence from parent material. In contrast, fine sand content and total P and Si concentrations showed west-east trends, suggesting topography effects reflecting particle size selection. Directional semivariograms suggest coarse sand and silt+clay content, as well as total C, N, Na, Mg, Al, K, Ca, Ti, and Mn concentrations were more strongly affected by parent material, whereas gravel and fine sand and total P concentration were more strongly affected by topography. Accordingly, the combination of elemental composition analysis and geostatistics revealed that the contribution of parent material and topography to total elemental contents in paddy surface soils in the alluvial plain varied among elements. In conclusion, evaluation of the interactive effects of parent material and topography on spatial variability of soil material characteristics enabled better understanding of soil formation processes and their potential fertility. [ABSTRACT FROM AUTHOR]

To prove the hypothesis that paddy rice utilizes soil nonexchangeable potassium (neK) and causes associated structural changes in clay minerals, K status and clay mineralogy of 22 surface soils from three paddy fields under long‐term fertilizer management for 51–93 years were investigated. Soil neK content was determined as the difference between 1 mol L−1 hot HNO3 extractable K and 1 mol L−1 ammonium acetate exchangeable K. Clay mineralogy was identified by X‐ray diffraction (XRD). The radiocesium interception potential (RIP), an index of frayed edge sites in the interlayer sites of 2:1 type clay minerals, was also determined. The neK contents under the ‐K and NPK treatments were considerably lower than those under the unfertilized treatment in all the fields, indicating the exploitation of soil neK by rice. XRD analysis of the clay samples revealed 7% shift from the 1.0 peak to 1.4 nm one under the ‐K treatment compared with the unfertilized one, and the amounts of neK were negatively correlated with those of RIP (p <.01), suggesting the expansion of interlayer spaces of the 2:1 type phyllosilicates such as mica due to the release of neK. In addition, the neK content positively correlated with K balance of the long‐term experiments (p <.05). The differences of neK between unfertilized K and ‐K treatments corresponded to 22–157 kg K ha−1, or 0.42–1.68 kg K ha−1 year−1. In conclusion, utilization of considerable amount of soil neK under K depleted conditions should be considered to establish sustainable K management for paddy rice. [ABSTRACT FROM AUTHOR]

After our coauthors described the first remote‐access parathyroidectomy (RAP) series in 2000, several other approaches were developed. No systematic review has been performed to classify and evaluate RAP techniques. We performed a literature search using PubMed and Cochrane Library (CENTRAL). A total of 71 studies met our inclusion/exclusion criteria. RAP can be categorized into five approaches: (1) endoscopic and robotic axillary, (2) anterior chest, (3) transoral, (4) retroauricular, and (5) a combination of these approaches. The limited data in the literature suggest that the cure rates and safety of RAP are in no way inferior to those of open parathyroidectomy. Each approach has its advantages and disadvantages, and the recommendations for the selection of each approach are listed. The selection of approach methods might depend on the surgeon's experience and familiarity and the patient's preference and disease status. [ABSTRACT FROM AUTHOR]

Over 50 years of the Green Revolution since the 1960s, the global population has increased by 2.5 times, cereal production by 3.3 times and the use of N, P and K fertilisers by 9.4, 4.2 and 4.3 times, respectively. Information is still limited, however, on the influence of these impacts on the fertility status of agricultural soils. Here we investigated the influence of the Green Revolution on 142 paddy soils in three tropical Asian countries, that is, Thailand, the Philippines and Malaysia, during the given period by repeated soil sampling in the 1960s and 2010s at or near the same locations. We revealed that the phytoavailablility indices of three macronutrients – N, P and K, that is, available P, exchangeable K and total N, showed 743% (p < 0.01), 12% and 1% increase on average, respectively, while total C showed 9% decline. Comprehensive investigation of overall fertility status by factor analysis using 11 soil parameters suggested that only the factor scores associated with 'available P status' increased drastically in all the three countries (p < 0.01) whereas those associated with 'organic matter and N contents' and 'inherent potentiality' did not exhibit any consistent changes among the countries. In conclusion, intensive soil/fertiliser management systems under the Green Revolution have successfully improved the nutrient status, especially P status, of paddy soils with slight decrease of soil organic matter over the last 50 years, while a large amount of nutrients applied, especially N and K, has been released from soil to the outer environments. Conversion to a high‐efficiency system of external nutrient inputs with organic matter‐conserving strategies is, therefore, urgently required to secure sustainable food production while restoring the environment during the coming decades. Highlights: Paddy soils from 142 locations in three tropical Asian countries were repeatedly surveyed in the 1960s and 2010s.Available P increased by 8.4 times, that of exchangeable K and total N showed 12% and 1% increase, while organic matter level showed 9% decline.Factor analysis indicated significant increase of the factor scores for those associated with 'available P status'.A high‐efficiency system with organic matter‐conserving strategies is to be established for both sustainable food production and restoration of the environment. [ABSTRACT FROM AUTHOR]

This study presents a forward model to quantify the P‐wave velocity (VP), S‐wave velocity (VS), and electrical conductivity (σ) of the solid‐liquid mixtures for a given set of pressure, temperature, lithology, liquid phase (aqueous fluid or melt), liquid fraction, and geometrical parameters in relation to the aspect ratio and connectivity of the liquid phase. This is based on previous experimental and theoretical studies on seismic velocity and electrical conductivity of solid rocks and liquid phases. A total of 78 lithologies, an aqueous fluid with NaCl (∼0–10 wt.%), and mafic to felsic melt appropriate for the crust and the uppermost mantle conditions were described in terms of VP, VS, and σ, as per previous experimental measurements and molecular dynamics simulation. This forward model is provided as a Windows executable program, and generates synthetic VP, VS, and σ, referring to the seismic velocities and electrical conductivity observed in the northeast Japan arc. After generation of the synthetic VP, VS, and σ, the original lithology and liquid parameters (phase, fraction, aspect ratio, and connectivity) were searched by implementing the grid search algorithm to map the misfit over the broad parameter space. The mapping shows the presence of a global misfit minimum around the optimized solution and the possibility of resolving the lithology and the liquid phase parameters based on the observed VP, VS, and σ by using the forward model presented in this study. Plain Language Summary: Liquid phases such as aqueous fluid and magma present within the solid Earth play crucial roles in various geodynamic processes including earthquake and volcanic eruption, as well as in the evolution of our planet. This study aims to improve the subsurface imaging of the potentially variable types of liquid phase and solid rock, based on the near‐surface observations concerning seismic velocity and electrical conductivity of the Earth's interior. We constructed a quantitative model to predict the physical properties of liquids and rocks. Then we used the model to perform "inversion," which estimates the physical properties of liquid and rock based on the observed seismic velocity and electrical conductivity. The inversion test using synthetic data shows the utility of our model. Key Points: A forward model is presented to quantify seismic velocity and electrical conductivity of solid‐liquid mixtures in crust‐uppermost mantleThe input parameters include pressure, temperature, lithology, liquid phase composition and fraction, and solid‐liquid geometryFor a given set of seismic velocity and electrical conductivity, the optimal parameter values can be found by inversion [ABSTRACT FROM AUTHOR]

The Green Revolution (GR) made a major contribution to increasing the rice yield in the Philippines from 1.3 t ha−1 in 1966 to 4.0 t ha−1 in 2018, but the changes in paddy soil fertility that occurred during this 50-year period remain unknown. We collected 37 soil samples from the plow layers of paddy fields in Luzon, Leyte, Panay, and Mindanao in the Philippines in 2016 and 2017 (the '2010s') and compared their fertility-related soil properties with published data for soil samples collected from the same or nearby sampling sites in 1969 (the '1960s'). Paddy soils in the Philippines had relatively high exchangeable calcium (Ca) and magnesium (Mg) content, cation exchange capacity (CEC), available silicon (Si) content, and total carbon (C) and nitrogen (N) content, reflecting their indigenous pedological background. We found that the 2010s soils had a lower available N content, particularly in wetter regions, despite the high input of N fertilizers, whereas the available phosphorus (P) showed a six-fold increase from the 1960s to the 2010s. The total potassium (K) content had significantly decreased during this period, possibly due to the mining effect of intensive farming with K-deficient fertilization. The 2010s soils contained a greater silt content and higher proportion of smectite in the clay fraction, which may have been transported from upstream via irrigation water. The increase in smectite corresponded with a significant increase in the cation exchange capacity, despite the organic C and clay contents tending to decrease, and these increases in smectite and soil pH may have contributed to the increase in the available fraction of Si that had not been applied as fertilizers. These findings demonstrate that paddy soil fertility in the Philippines changed in many ways over this 50-year period, largely owing to the direct impact of GR implementation in paddy fields but also potentially due to offsite effects from upland fields. The environmental impact of the nutrient loss and soil organic matter degradation behind the fertility improvement should be assessed holistically for the sustainable development of rice paddy ecosystems. (337 words) [ABSTRACT FROM AUTHOR]

Artificial radionuclides including radiocesium (134 Cs and 137 Cs) and radiosilver (110mAg) were released into the environment following the Fukushima Dai-ichi nuclear power plant accident in March 2011. These particle-bound substances deposited on soils of north-eastern Japan, located predominantly within a ∼3000 km2 radioactive fallout plume and drained by several coastal rivers to the Pacific Ocean. The current dataset (Evrard et al., 2021), which can be accessed at 10.1594/PANGAEA.928594, compiles gamma-emitting artificial radionuclide activities measured in 782 sediment samples collected from 27 to 71 locations across catchments draining ∼6450 km2 during 16 fieldwork campaigns. These campaigns were conducted in Japan between November 2011 and November 2020 in river catchments draining the main radioactive plume. This database may be useful to evaluate and anticipate the post-accidental redistribution of radionuclides in the environment and for the spatial validation of models simulating the transfer of radiocesium across continental landscapes. [ABSTRACT FROM AUTHOR]

Remote‐access total endoscopic thyroidectomy (TET) is a recently established approach that can avoid producing scars in the neck. There are no clear surgical indications for TET for benign nodules or for malignant tumors at present. We report a successful TET in a 50‐year‐old Japanese woman with follicular lymphoma of the thyroid gland after an open neck biopsy. She had been referred to us with a neck tumor noted 2 months earlier. Because of adhesion, we performed a combined resection of the thyroid and partial right sternohyoid muscle. To the best of our knowledge, there is no other report of a TET performed after open neck surgery. Our patient's case demonstrates that (a) the cosmetic outcome of TET is clearly superior to that of conventional open neck surgery, and (b) a TET can be suitable even for reoperation if carefully selected. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the current soil properties in lowland paddy fields in Peninsular Malaysia and to assess the long-term changes in the soil fertility status during 50 years after the Green Revolution. Forty paddy fields were selected close to the study sites surveyed in 1965 and grouped based on six physiographic environments: the brackish swamp (including acid sulfate soils), the brackish alluvium, the freshwater swampand the riverine alluvium in the west coast, and the riverine alluvium and the beach ridges interspersed with swales in the east coast. Soil samples from the depth of 0–15 cm were analyzed for the physicochemical properties. Despite similar fertilizer application rates over Peninsular Malaysia, several differences were found in the current soil properties between different physiographic environments, such as 1) higher levels of clay fraction, 1.4 nm minerals, CEC, exchangeable bases and available Si as well as Mg- and Na-rich status in the brackish environments, 2) higher levels of available N in the riverine alluvium environment in the east coast , and 3) the excessive P accumulation in the acid sulfate soils. The long-term changes well appeared in the dramatic increase of P availability and the alleviation of soil acidity. In addition, the composition of exchangeable bases changed toward Ca-rich and Mg-low status. Large reduction in soil organic matter was found in the swamp environments while those in the riverine alluvium environment in the east coast were increased. It could be concluded that despite the successful increase in rice yield after the Green Revolution, the long-term changes in the paddy soil fertility showed positive and negative aspects depending on physiographic environments. Appropriate fertilizer application schemes taking into account different soil characteristics in different physiographic environments should be required to achieve both efficient, sustainable rice production and environmental conservation. [ABSTRACT FROM AUTHOR]

Understanding of the long-term soil fertility trends is the basis for rational and sustainable management of the soil resources in agricultural fields. In tropical Asia, the Green Revolution initiated in the late 1960s contributed to a drastic increase in both food production and human population. Among the tropical Asian countries, Thailand is known as a rice-exporting country, but the country's rice yield is still relatively low. Therefore, this research aimed to investigate the effect of the Green Revolution on the changes in paddy soil fertility status in Thailand over the last 50 years. In total, 65 surface soil samples were collected in 2015 and 2016 from paddy fields in the northeast, north, central plain, and Bangkok Plain of Thailand. To compare the fertility-related data of the samples with those of soils collected from 1964 to 1972, the sampling sites in the 2010s were placed at or near the same locations of the original sites. Over the last 50 years, the mean pH, total C, total N, available N, available P, and exchangeable K values increased significantly (p < 0.01). In particular, the available P content dramatically increased from 3.19 to 42.8 mg kg–1, reflecting the rapid increase in fertilizer application. Contrarily, the mean exchangeable Mg and clay content values decreased significantly (p < 0.05). Regionally, the total C and total N contents of the soils in the northeast were significantly lower than those in the other regions (p < 0.05), and the available P, exchangeable K, and available Si contents were often evaluated as deficient, reflecting the very sandy texture of the soils. In conclusion, the fertility status of the paddy soil in Thailand has improved considerably over the last 50 years, and the increase in total C suggests the potential of paddy soil for C sequestration, even in the tropics. These trends should be considered to achieve more sustainable food production and environmental conservation in Thailand. [ABSTRACT FROM AUTHOR]

To evaluate the effects of type of micaceous mineral and degree of weathering on the ability to adsorb and desorb radiocaesium (RCs) ions, various levels of weathering were induced (K‐depletion) in three types of micaceous minerals: biotite, muscovite and illite. The ability to adsorb RCs was represented by RCs interception potential (RIP) and a desorption ratio was determined by the amount of 137Cs desorbed from the minerals by 1 M ammonium acetate (137Cs desorption ratio). The RIP values were in the order of illite > biotite > muscovite. The RIP values for biotite gradually increased with the release of up to ~50% of the K+ from interlayer sites but then decreased with the further release of K+, up to ~100%, which was associated with the formation of a fully expanded interlayer: vermiculite. The change from increasing to decreasing RIP due to the weathering of the biotite strongly indicated that the selective adsorption sites for RCs are not located in an expanded interlayer but in intermediate sites between non‐expanded and expanded interlayers: frayed edge sites (FES). In contrast, for both the muscovite and illite, the RIP only increased. The 137Cs desorption ratio, <7% for all the samples, tended to decrease with increasing degrees of weathering and did not differ greatly by mineral type. These results contribute to a more accurate prediction of the risk of RCs transfer from soils to crops and the understanding of the weathering processes of micaceous minerals in soils. Highlights: Radiocaesium adsorption and desorption was investigated for gradually K‐removed biotite, muscovite and illite.Vermiculitization of biotite via K removal firstly increased then decreased the frayed edge sites (FES).Adsorption was influenced by di/trioctahedral character and charge localization, and desorption by degree of weathering.These results lead to better understanding of the weathering processes of micaceous minerals and fate of RCs in soils. [ABSTRACT FROM AUTHOR]

Early definitive diagnosis of necrotizing enterocolitis (NEC) based on Bell's staging criteria is difficult because there are few observable changes on abdominal imaging and blood chemistry tests at the onset of the disease. To investigate whether prostaglandin E-2 major urinary metabolite (PGE-MUM) can be a useful surrogate marker reflecting the disease state and severity of NEC in infants. Infants were enrolled in this study between January 2014 and December 2016. NEC diagnosis was based on Bell's staging criteria > Stage II or necrotic bowel observed at surgery. After diagnosis, PGE-MUM level was measured and compared with that of the other disease and healthy infant groups. Median PGE-MUM value was highest in the NEC group (576 [65–3672] μg/g•Cre/BSA × 1000), followed by the other disease group (94 [57–296] μg/g•Cre/BSA × 1000) and the healthy infant group (19 [10–44] μg/g•Cre/BSA × 1000) (sensitivity: 92.3%, specificity: 81.5%, accuracy: 85.0%; p < 0.01). PGE-MUM level correlated with improved status of NEC, length of necrotic intestine, and Bell's staging criteria. PGE-MUM level may be a useful surrogate biomarker reflecting the disease state of NEC. The method of urine sample collection is also advantageous, being noninvasive for infants. This is the first study reporting PGE-MUM level in NEC. Study of diagnostic test. LEVEL II. [ABSTRACT FROM AUTHOR]

To examine the exchangeability of 137Cs and K in soils of agricultural fields after decontamination, 173 soil samples were collected in 2016 from the plowed layer (0–15 cm depth) of decontaminated agricultural fields in Tomioka town, Fukushima prefecture, Japan. We investigated total 137Cs, exchangeable 137Cs, exchangeable K, and nonexchangeable K content for these soils. The total 137Cs content in soils was, on average, 1,200 Bq kg−1 (value range: 20–4,400 Bq kg−1), which was an 80% decrease from the values determined before the decontamination. This result indicated that the decontamination process considerably reduced the total 137Cs content in the plowed layer. The exchangeable K content in soils was on average 172 mg kg−1 (value range: 27.9 – 743 mg kg−1). More than 80% of soils showed the exchangeable K content lower than the recommended threshold value for paddy soils needed in order to reduce the 137Cs transfer from soil to plant (i.e. 200 mg kg−1). The nonexchangeable K content showed a wide range of values (value range: 98.8–1,280 mg kg−1) and no significant correlation with the exchangeable K content. Because nonexchangeable K is released more slowly but is comparable to exchangeable K as a reservoir of phytoavailable K, more frequent K application is recommended for soils with lower contents of both exchangeable and nonexchangeable K. The total 137Cs content in soils showed a significant positive correlation with the exchangeable K content in soils (p < 0.01), which means that decontamination efforts intended to reduce the total 137Cs content in soils might also lead to a reduction in the exchangeable K content. In conclusion, the application of K fertilizer is strongly recommended in the decontaminated agricultural fields because the decontamination causes a considerable decrease in exchangeable K content along with a reduction in total 137Cs content. [ABSTRACT FROM AUTHOR]