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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]

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]

Land use intensity in the Cameroon plateaus, where Ferralsols and the associated highly weathered soils are dominant, has been steadily increasing, so that soil fertility status and its controlling factors on these plateaus should be elucidated to establish long-term land management strategies. Although it is known that Ferralsols have small, but variable CEC values, it has not been fully determined which clay components are the main source of CEC clay in Ferralsols. Here, soils in three Cameroon plateau regions of different altitude (the lower South Cameroon (SC) Plateau with an altitude of 300–600 m, SC L ; the upper SC Plateau with an altitude of 600–900 m, SC H ; and the Adamawa Plateau with an altitude above 900 m, ADM) were collected, and their physicochemical and mineralogical properties were investigated. The relative abundance of illitic minerals, which are a minor but the most promising source of CEC clay in Ferralsols, was determined by using three indicators: the relative abundances of 1.0 nm-thick structures as represented by XRD peak intensity (XRD 1.0 nm ), structural K in illitic minerals as represented by clay-K content, and the quantity of intermediate interlayer sites between illite and vermiculite structures (i.e., frayed edge sites) as represented by the radiocesium interception potential (RIP). The relative abundances of two low-activity clay components, kaolinite and gibbsite, were determined by differential thermal analysis, and the degree of Al-substitution in goethite was determined by differential x-ray diffraction analysis. All three quantitative indicators for illitic minerals decreased along the altitude gradient, SC L > SC H > ADM, and were positively correlated with CEC clay . While kaolinite also showed a decreasing trend at higher altitude, it did not show any significant correlation with CEC clay . In contrast to the decrease in these Si-bearing minerals, gibbsite and Al-substituted goethite increased along the same altitude gradient. These associative changes strongly indicate that illitic minerals were the clay component largely controlling CEC clay and that de-silication or aluminization may proceed at higher altitude or on stable surfaces with older formation ages in the Cameroon plateau regions. Thus, mineralogical properties well explained the distribution of Ferralsols; they were marginal in the SC L region, while those with relatively high CEC clay were dominant in the SC H region and those with lower CEC clay were dominant in the ADM region. [ABSTRACT FROM AUTHOR]