Ichiro Taniyama

Background levels of trace and ultra-trace elements in soils of Japan

Abstract Five hundred and fourteen soil samples collected from 78 sites in Japan were analyzed for their contents of trace and ultra-trace elements. We estimated the background levels (natural abundance) of 57 elements in soils. The concentration ranges were so wide that the ratios of the highest values to the lowest values were more than 100 for all the elements, with the exception of Be, Ga, Mo, Ag, In, Sn, and Ba. While the concentrations of the first transition elements (21Sc to 30Zn in atomic numbers) were higher than the concentration of the other elements, those of lighter (3Li and 4Be) and heavier elements tended to decrease, with an increase or decrease of atomic numbers, with the apparent exception of Pb, Th, and U. Concentrations of elements with even atomic numbers were, in most of the cases, higher than the concentrations of both adjacent elements with odd atomic numbers. Frequency distribution of most of the elements was strongly positively skewed. Markedly positive correlation coefficients (r>0.9) were observed among the elements within the same group in the Periodic Table in many combinations. The dendrogram obtained by cluster analysis showed that the occurrence and distribution of the elements in soils were mostly controlled by the chemical properties of each element, rather than by the nature and properties of individual soil samples. The total contents of the elements in soils were strongly dependent on the chemical composition of the parent rocks from which respective soils were derived.

Modified rothamsted carbon model for andosols and its validation: changing humus decomposition rate constant with pyrophosphate-extractable Al

Abstract We modified the Rothamsted carbon model (RothC) to adopt it to Andosols. We changed the decomposition rate constant of the humus (HUM) pool because the presence of Al-humus complexes in Andosols gives HUM strong stability. In addition, the inert organic matter (IOM) pool was set at zero, because the soil did not contain carbon when it was formed from fresh volcanic ash. H(f) was defined as the factor required to divide the decomposition rate constant of the HUM pool so that the modelled soil organic carbon (SOC) level matched the measured level. H(f) was calculated for 32 Japanese Andosols, and the relationships between H(f) and soil properties such as contents of acid-oxalate-extractable Al, Fe, and Si (Mo, Feo, and Sio) or pyrophosphate-extractable Al (Alp) were analysed. The equation H(f) =1.20 + 2,50Alp(% ), (r 2 = 0.518) was selected to divide the decomposition rate constant of HUM. The modified model was tested for four long-term experimental data sets on Andosols under various climatic conditions, soil textures, and management techniques from north to south across Japan. We obtained considerably improved fits between the contents of modelled and measured SOC by using the modified RothC instead of the original model. Use of this modified model may contribute to the improvement of the performance of existing SOC2 models in modelling Andosols. It can be used for estimating CO2 emission from soils, as well as for planning suitable organic matter management in Japanese Andosols.

Testing the suitability of the Rothamsted Carbon model for long-term experiments on Japanese non-volcanic upland soils

Abstract We evaluated the suitability of the Rothamsted Carbon (RothC) model for long-term experiments on Japanese non-volcanic upland soils using 6 long-term experimental data sets: 2 Brown Lowland Soils, 2 Yellow Soils, 1 Gray Lowland Soil, and 1 Brown Forest Soil. The predicted changes in the content of soil carbon with time were very close to the observed values in almost all the treatments at all the 6 sites. These 6 sites were distributed from North to South across Japan and included a variety of climatic conditions, soil textures, and land management practices. We therefore concluded that the RothC model adequately simulated changes in the soil carbon content with time in Japanese non-volcanic upland soils.

Contamination of agricultural products and soils with radiocesium derived from the accident at TEPCO Fukushima Daiichi Nuclear Power Station: monitoring, case studies and countermeasures

ABSTRACT Five years have passed since the accident at Tokyo Electric Power Company Fukushima Daiichi Nuclear Power Station that was triggered by the Great East Japan Earthquake on 11 March 2011. Severe damage to agriculture and the environment is still of great concern in Japanese society. We review the contamination status of agricultural products and soils, decontamination efforts and countermeasures to reduce radiocesium concentration in soil and crops, as well as the responses of Japanese ministries. Since rice is an important staple food for Japanese, the impact of radiocesium on rice (Oryza sativa L.) and paddy fields has been extensively investigated since the accident, and, therefore, issues concerning rice receive considerable attention in this review.

Changes in Topographical Features and Soil Properties after Exclosure Combined with Sand‐Fixing Measures in Horqin Sandy Land, Northern China

In a field experiment we evaluated the effects of exclosure and sand-fixing measures on land restoration of shifting sand dunes in a semi-arid, sandy grassland located in Northern China. We fenced an area of about 2.1 ha, enclosing 2 shifting sand dunes—one large and the other small. In 1996, on each dune we applied 2 sand-fixing measures developed in China—burying wheat straw in a checkered pattern (Sc) and planting seedlings of a sand-fixing shrub, Artemisia halodendron (Ar). Changes in the topographical features and soil properties were then monitored for 6 years. The effectiveness of the sand-fixing measures was assessed by monitoring the topographical features and soil properties. Sand dune fixation took 1 year, and a biological soil crust with high contents of soil organic carbon and fine particles (clay+silt) was formed within 3 years. These results are consistent with those reported in previous studies, confirming that such crusts reduce wind erodibility. The effectiveness of exclosure alone, without the other measures, was also implied, especially for the small dune, based on the changes in the topographical features and soil properties outside the exclosure, where a “no-grazing” policy had been implemented from 2000. The rate of soil restoration was higher on the small dune than on the large dune. This was due to the differences in the initial soil conditions caused by the topographical features, suggesting that the capacity of a site to reverse desertification by itself depends on the dune size. Sc was slightly more effective than Ar, presumably because Ar inhibited the invasion of other plant species, whereas Sc allowed invasion of various species. Although the soil properties in the very thin surface crust were restored, the restoration of the soil properties in deeper layers was not significant even after 6 years. It would take a longer time (e.g., 10 to 20 years) for the restoration of the soil properties in deeper layers to sustain more intensive land use in this region.

Significance of mass flow in nitrate-nitrogen supply to plant roots

Abstract Young corn plants (Zea mays L.) were grown in pots with Nishinosato loamy sand by moisturing with Ca(NO3)2 solution at different concentrations, in order to check the effect of the NO3-N concentration of the soil solution on the plant growth without quantitative limita tion of NO3-N supply. Eight treatments were established according to the NO3 concentration supplied. The dry weights of the plants increased with increase in the NO3-N concentration for moisturing and reached a maximum at 12.9 me per liter NO3-N in the supplied solution (treatment No. 4). NACP (the amount of N absorbed by the plants divided by the amount of H2O transpired in a given period, converted to me per liter) coincided with the NO3-N concentration of the rhizosphere soil solution at around 20 me per liter, where transport of NO3-N to the plant roots was limited in mass flow. The minimum NO3-N concentration of the rhizosphere soil solution to give a maximum yield was found in No. 4. The values were 115 and 9.3 me per liter i...

Spatial prediction of radioactive Cs concentration in agricultural soil in eastern Japan

Abstract As a result of the accident at the Fukushima Dai-ichi Nuclear Power Station (FDNPS) operated by the Tokyo Electric Power Company, radioactive cesium (Cs) was released into the surrounding environment. To determine the extent of decontamination required in agriculture fields and to consider management options, we surveyed and measured soil Cs concentrations in 3461 agricultural fields, and used these data to construct a distribution map of radioactive Cs concentration in agricultural soil in eastern Japan. Soil Cs concentration was positively correlated with radiation dose (r2 = 0.89, n = 2199). This linear correlation was affected to some extent by soil surface condition, soil group and land use type. Linear regression analysis was conducted by land surface condition, soil type and land use type. We constructed a soil Cs concentration map by regression and by a regression-kriging (RK) method that combines regression equations with ordinary kriging of the regression residuals. Prediction accuracy of the RK was higher than that of the regression; we therefore adopted the RK. Total radioactive Cs concentration in soil was highest in the 20-km evacuation zone surrounding FDNPS, and tended to be higher to the northwest of FDNPS than in other directions. About 5900 ha of paddy fields and 3000 ha of upland fields in Fukushima Prefecture were above contamination level 2 (> 5000 Bq kg−1), and were mostly distributed in the evacuation zone.

Factors controlling organic amendment application rate and long-term change in application rate in Japanese paddy field using longitudinal questionnaire survey dataset (the Basic Soil Environment Monitoring Project, Stationary Monitoring, 1979–1998)

Using data from a longitudinal survey (the Basic Soil Environment Monitoring Project, Stationary Monitoring, 1979–1998, launched by the Ministry of Agriculture, Forestry and Fisheries of Japan), it was found that livestock possession, soil type, utilization form of paddy fields and full-/part-time status of farmers were important factors controlling application rates of organic amendments (OA) in Japanese paddy fields. When data points were categorized in terms of these four factors, application rate of livestock waste compost (LWC) on the basis of fresh weight (FW) varied remarkably. Application rates of LWC decreased during the survey period, whereas rice straw residue (RSR) application rates increased. The smallest LWC application rate (average 0.3 ± 0.2 Mg FW ha−1 for the period between 1994 and 1998) was found among rice (Oryza sativa L.) single-cropping, poorly drained lowland paddy soils (PDLPS) including Histosols, with full-time farmers possessing no livestock. Even among rice single-cropping, the application rate was clearly larger (average 10.6 ± 0.5 Mg FW ha−1 for the period between 1979 and 1983) for non-poorly drained lowland paddy soils (non-PDLPS), with full-time farmers possessing livestock. Much greater than this was the LWC application rate for converted paddy fields (average 29.9 ± 4.3 Mg FW ha−1 for the period between 1989–1993), non-PDLPS, with full-time farmers possessing livestock. Accordingly, this study emphasizes the importance of categorizing data points at least in terms of soil type, utilization form of paddy fields, livestock possession and part- or full-time farming status when constructing an inventory, exploring changes in OA application rate, and making policy.

Changes in concentrations of 131I, 134Cs and 137Cs in leafy vegetables, soil and precipitation in Tsukuba city, Ibaraki, Japan, in the first 4 months after the Fukushima Daiichi nuclear power plant accident

Abstract Concentrations of 131I: iodine-131, 134Cs: cesium-134 and 137Cs: cesium-137 in leafy vegetables, soil and precipitation after the Fukushima Daiichi nuclear power plant accident were investigated at Tsukuba city, approximately 170 km from the nuclear power plant. The first precipitation after the accident was on March 21–23, 2011, and contained an amount of radionuclides. The concentration of 131I in leafy vegetables, particularly spinach (Spinacia oleracea L.), was significantly increased because of dry deposition of the first radioactive plume. The concentrations of 131I, 134Cs and 137Cs in soil were significantly increased by the first precipitation on March 21–23; however, the contribution of precipitation to the concentrations of 131I, 134Cs and 137Cs in leafy vegetables was smaller than that in soil. Changes in the concentrations of 131I, 134Cs and 137Cs differed between spinach and komatsuna (Japanese mustard; Brassica campestris var. peruviridis).