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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]

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]

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 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]

Abstract: Although it is well known that phytoavailability of radiocaesium is gradually lost after its deposition on the ground by fixation to soil minerals, the decreasing rates during early period after the deposition is not yet quantitatively evaluated. In this study, stable Cs was added to 5 types of soil, including Andosols, a sand-dune regosol and a smectic lowland soil, in a laboratory soil incubation experiment to assess the aging effect of radiocaesium. Aliquots of a soil sample were put into pots and incubated in an artificial climate chamber. Orchardgrass or red clover was cultivated for 28 d in soil pots containing one of the allophanic Andosol samples seven times during about 1200 d using new pots for each cultivation. The soil-to-plant transfer factors of Cs declined exponentially until about 100 d and were almost constant thereafter. The extractabilities of Cs by water and 1 M NH4OAc solution from this allophanic Andosol soil sample also decreased with time and their decreasing patterns were similar to that of the transfer factor. The temporal changes of extractabilities of Cs in other soil samples were also examined 6 times during about 600 d. Rate of decline for the extracted yield of the added Cs by 1 M NH4OAc varied widely among all the soil types. Two allophanic Andosol samples showed relatively higher extractabilities in comparison with the other soils throughout the incubation experiment, which may be attributable to the lower contribution of Cs specific sorption sites to total cation exchange capacity of the allophonic Andosol soil samples. [Copyright &y& Elsevier]

The concentration of radiocesium ( 134 Cs and 137 Cs) in agricultural fields around Fukushima Dai-ichi Nuclear Power Plant (FDNPP) was elevated after the accident in March 2011. Evaluation of soil properties that influence phytoavailability of radiocesium is important for optimal soil management to minimize radiocesium transfer to crops. In this study, soybean grain and soil samples (0–15 cm) were collected from 46 locations in Fukushima Prefecture in 2011, and 137 Cs concentrations were measured. 137 Cs concentration ranges were 11–329 Bq kg −1 -dry in soybean grain samples, and 0.29–2.49 kBq kg −1 -dry in soil samples. The radiocesium interception potential (RIP) values in the soil samples ranged from 0.30 to 8.61 mol kg −1 . RIP negatively correlated with total carbon content and oxalate-extractable Si and Al + 1/2 Fe in the soils, suggesting that soils rich in organic matter and poorly crystalline clays tended to have lower RIP in this region. The soil-to-plant transfer factor for 137 Cs, analyzed in relation with various soil characteristics, varied by two orders of magnitude and was significantly negatively correlated with RIP and exchangeable K concentration in soil. The results show that RIP is useful for evaluating the efficiency of radiocesium transfer from soil to plants in this region. [ABSTRACT FROM AUTHOR]