• Volume 57,Issue 5,2020 Table of Contents
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    • >Development Strategy of Soil Science
    • Status Quo of and Strategic Thinking for the Development of Soil Science in China in the New Era

      2020, 57(5):1051-1059. DOI: 10.11766/trxb202006240330

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      Abstract:Soil science plays an important strategic role in ensuring sustainable development of the agriculture and the construction of ecological civilization in China. This paper briefly reviews the status quo and development trend of soil science research at home and abroad, analyzes national strategic needs and key scientific issues of the research on soil science in the future, and collates priority aspects and key strategic directions of the soil science of China over the next 5-10 years, such as earth’s critical zone process and evolution of soil functions, theories and technologies for improvement of farmland soil health and quality, regional soil mixed pollution processes and green remediation, soil biological process and function, in an attempt to further promote leaping development of the soil science in China.

    • Progress and Perspective of Studies on Soils in Space and Time

      2020, 57(5):1060-1070. DOI: 10.11766/trxb202004270199

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      Abstract:Soils evolve in space and time and soil changes are coupled with the changes in climate and environment, rock weathering and biogeochemical cycling. A better understanding and accurate quantification of soil spatio-temporal variation not only act as a basic research task of soil science but also are prerequisite for scientifically evaluating and reasonably maintaining soil functions. The main objective of this study was to review the recent studies on spatio-temporal soil variation. Dozens of latest related publications were reviewed, of which the topics included soil formation and evolution, soil morphology, soil survey, soil classification, digital soil mapping and soil degradation. It is anticipated that main scientific issues may include the simulation of coupling processes between soil and environment within the framework of earth surface system, precise modeling of the soil-landscape, and the data fusion and assimilation of multisource soil information. Based on the analysis, future priority areas of soils in space and time studies may include the soil formation and evolution driven by Critical Zone processes, digital soil mapping at various scales, the principle and technology for soil information acquisition based on multi-sensors, a complete and detailed national even global soil inventory and its sharing platform, and the processes of regional soil resource degradation and the recovery of soil functions.

    • Some key research fields of Chinese soil physics in the new era: Progresses and perspectives

      2020, 57(5):1071-1087. DOI: 10.11766/trxb202002280077

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      Abstract:In the recent 20 years, soil physics in China has developed fast, and contributed the papers published in high-reputed international journals from 5% up to 30%. These researches mainly focus on soil hydrological processes and scaling transform, soil physical quality and sustainable agriculture, water-heat-salt transport and ecological regulation, contaminants transport and numeric modeling. This paper reviewed the state of the art of these four fields, and pointed out knowledge gaps and future perspectives. These developments result not only from national demands, applications of new technology and methodology, but also from the integration and convergence of multi-disciplines. Although soil physics in China has made a great achievement, she faces the shortage of original researches and the weakness of instrument development. One the other hand, she has many opportunities to develop further as solving the requirements from food security and ecological environment security.

    • The Frontier and Perspectives of Soil Chemistry in the New Era

      2020, 57(5):1088-1104. DOI: 10.11766/trxb202003080103

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      Abstract:Soil chemistry is an important and fundamental branch of soil science. On the basis of providing a historical overview of the progress of soil chemistry, this review exclusively summarized the most striking achievements in four innovative topics of soil chemistry and followed by analyzing the future research opportunities in soil chemistry with particularly emphasizing multidisciplinary coordination. The study of soil chemistry originated from observing the ability of soils to exchange ions and evolved to the direction of soil electrochemistry, rhizosphere/soil chemistry, interfacial processes of soil minerals, organic matters, and microorganisms that have been gradually led by China. Being the center of the community of this new era, China has particularly made an immense breakthrough in intercrossing soil chemistry with microbiology, geochemistry, mineralogy, and environmental chemistry. Moreover, the innovation of in-situ, real-time, and high-resolved analytical techniques including synchrotron radiation-based spectroscopy, microfluidic modulation spectroscopy, high-resolution microscopy, and spectroelectrochemistry, has remarkably advanced the progress of soil chemistry. There are three key aspects determining the destiny of soil chemistry in the coming decade: 1) explore the soil chemistry mechanism in the matter cycles and energy exchange in the Earth surface system, to achieve an original breakthrough from “0 to 1” in soil chemistry; 2) on the basis of the Earth surface theory, the exploration of the mechanisms of biogeochemical cycles and energy exchange in the complex system is likely by the coupling of multi-interfaces, elements, and processes, and a breakthrough toward originality in soil chemistry can be expected; 3) finally and also importantly, future research in soil chemistry should be built upon the national needs and priorities for constructing ecological civilization, battling for soil pollution and global change.

    • The Strategies for Development of the Subdiscipline of Soil Biology for the 14th Five-Year Plan

      2020, 57(5):1105-1116. DOI: 10.11766/trxb202006150298

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      Abstract:Soil organisms are the essential part of biodiversity on the Earth. Soil organisms could drive soil organic matter decomposition, nutrients cycling, pollutants transformation and degradation, and the emission and consumption of greenhouse gases, which is important for global food security, environmental protection, and climate change response. The discipline of soil biology is to study soil biodiversity and distribution, soil biological processes and functions, and the regulation and application of soil organisms. Since the 21st century, the breakthrough of molecular biological technologies and the widely application of ecology theories have greatly advanced the development of soil biological study. This article reviewed the development history of soil biology, introduced the recent progress of soil biology in details, proposed the development trend of soil biology in terms of theory and application, and further figured out the future development direction of soil biology. With the multidisciplinary integration and the advances in technology, soil biology enters a new period of development. Soil biological studies have obtained great achievements especially in soil biological resources digging, time-spatial distribution patterns, ecosystem services functions and the regulation of biology, which will be beneficial to the soil health, plant health, and the health of human being and our planet.

    • Study on soil erosion and conservation in the past 10 years: Progress and prospects

      2020, 57(5):1117-1127. DOI: 10.11766/trxb202002240070

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      Abstract:Under the background of ecological civilization, soil erosion and conservation face new opportunities and challenges nowadays. We employed a bibliometric analysis on the research of soil erosion and conservation in the past ten years. The results summarized the research tendency and hotspots, and presented China's main achievements and international status in this field. Considering social needs, we pointed out the main existing problems for scientific researches on soil erosion and conservation. Then, we identified the front scientific issues, including the coupling mechanisms of hydrology and soil erosion, the soil erosion process and modeling, the soil erosion evolution and its catastrophic mechanism under global change, the mutual feedback between socio-economy and soil erosion, the soil conservation for ecological function improvement, and the new technologies and methods for soil erosion research.

    • Discussion on the Strategies for Development of the Subdiscipline of Soil Fertility and Soil Nutrient Cycling for the 14th Five-Year Plan

      2020, 57(5):1128-1136. DOI: 10.11766/trxb201912050657

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      Abstract:Soil fertility and soil nutrient cycling is more like an applied discipline in the soil science, with a long history and a huge volume of literature accumulation. It plays an important role in assessing and exploiting the soil resources, enhancing crop production and nutrient use efficiency, and reducing environmental loads of non-point source of pollutants from croplands. During the 14th five-year-plan period, it is essential to strengthen researches on processes, rates, products, and influencing factors of the nutrient transformation in the soil, the basis of soil fertility and soil nutrient cycling. In view of the fact that the agriculture is developing towards a two-pole structure, that is, the cropping of staple crops, such as rice, wheat, and maize, declining in intensity, and the facilitated farming, such as plastic film-sheds and greenhouses, rapidly expanding in area in China, and in response to the calls of the nation for reduction of the environmental loads of non-point source pollutants and maintenance of safety of the eco-environment, it is crucial to intensify researches on the following topics in the sub-discipline of soil fertility and soil nutrient cycling, during the 14th five-year-plan period. i.e. 1) impacts of turning intensive cropping into fallow and crop rotation on soil fertility, and principles, pathways and methods of the practice maintaining and improving soil fertility; 2) principles, pathways and methods of scientific management of rapidly restoration of soil fertility, maintenance of soil health, and effectively utilization of soil nutrients under a highly intensive cropping system; and 3) basic scientific issues, like how to harmonize the relationships between soil, crops and environment, how to bring soil fertility into full play and how to efficiently utilize soil nutrients.

    • Research Progresses and Prospects on Soil Pollution and Remediation in China

      2020, 57(5):1137-1142. DOI: 10.11766/trxb202004190179

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      Abstract:Soil pollution and remediation is an important branch of soil science, which plays a key role in promoting control and remediation of soil pollution and ensuring the national soil environmental security and ecological civilization construction in China. This paper briefly states soil pollution status in China, introduces the research status and development trend in soil pollution and remediation at home and abroad, points out some problems in the research and development of soil pollution prevention and control in China, and puts forward the countermeasures and suggestions on general strategies and main directions of the future research and development in soil pollution and remediation in China.

    • Frontier Trends and Development Strategies of Soil Quality and Food Safety in the 14th Five-Year Plan

      2020, 57(5):1143-1154. DOI: 10.11766/trxb202003110110

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      Abstract:The comprehensive evaluation and improvement of soil quality are closely linked with food security and human health. As an important component of the development strategy of soil science during the 14th Five-Year Plan, the subdiscipline about the soil quality and food security is making contribution to govern and improve the quality of cultivated soil, which will cope with the food security crisis. The results of bibliometric analysis show that although China has started late in the research of this subdiscipline compared with the developed countries, it is accelerating upward and even has the tendency to surpass all of the other countries in recent years. With the erupting of the climate and environmental pollution issues, the international research hotpots of this subdiscipline are mainly focused on the environmental monitoring, soil utilization, fertilization management, remediation of pollution (heavy metal(loid), antibiotic, organic pesticide, and pathogenic microorganism) and sustainable development. Meanwhile, this subdiscipline takes the soil quality, soil pollution, and food security as the key research directions. Combined with the fields of geomatics, environmental science, applied mathematics, and medicine to form new prior interdisciplines, this subdiscipline can utilize their advanced theories and techniques of isotope tracer, biogeochemical cycling, molecular biology, and health risk model to solve some key scientific problems in the soil quality monitoring under regional scale, quality management of soil nutrients, human health risk assessment, migration and transformation of pollutants in soil-crop systems, and immobilization and remediation of soil pollution in the future.

    • >Research Articles
    • Spatial and temporal characteristics of rill development on slopes of waste dump of mine under different vegetation restoration measures

      2020, 57(5):1155-1165. DOI: 10.11766/trxb201904240128

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      Abstract:【Objective】Slopes of coal mine dump are characterized by severity of soil erosion, diversity of erosion type and complexity of erosion processes. The law of soil erosion on the slopes is different from that on slopes of original landform in mining areas. In order to explore effects of revegetation controlling soil erosion on slopes of coal mine dumps, survey of a dumping site was carried out in the Yongli Coal Mining of Zhungeer Banner, Inner Mongolia. 【Method】The survey, using the quadrat survey procedure, covered a bare slope as CK, and slopes revegetated in the pattern of Salix cheilophila+ Hippophae rhamnoides Linn. And Astragalus adsurgens Pall (SHA) or Salix heilophila and Astragalusadsurgens Pall (SA), for a different time period of 1a, 3a or 5a, in an attempt to explore spatial and temporal effects of the revegetation on rill development on the slopes. 【Result】Results show: (1) on all the slopes, the rills varied in the range of 4-8 cm in width and in the range of 2-4 cm in depth in the first year, on the slopes of CK, SHA and SH did in the range of 4-8 cm, 8-12 cm and 4-8 cm in width, respectively, and all in the range of 4-6 cm in depth in the third year, and on the slopes of CK and SHA, they did in the range of 8-12 cm in width and in the range of 4-6 cm and 8-14 cm in depth respectively; (2) Over the five years, the rills on Slopes CK, SHA and SA varied in the range of 7.57-11.35 cm, 7.58-13.31 cm and 5.57-6.14 cm, respectively, in mean width, in the range of 3.38-6.23 cm, 4.19-10.34 cm, and 2.59-4.24 cm, respectively in mean depth, and in the range of 1.52-5.25 m?m-2, 1.42-1.68 m?m-2 and 1.88-2.25 m?m-2, respectively, in density; (3) For the first year, the rills in all the slopes increased with length of the slope in ratio of width and depth quite sharply, but with the time going on, they showed a decreasing trend in the ratio, while they varied in an increasing trend in rill density and rill erosion amount with length of the slope; and (4) Compared with CK, SHA and SA decreased the slope rill erosion modulus by 25.0% and 25.86%, respectively, showing little erosion controlling effect in the first year, but they did by 61.73% and 35.31% respectively, showing significantly enhanced erosion controlling effect.【Conclusion】SHA and SA come to be effective only in the third year and on. The rills on Slopes SHA and SA varied in the range of 8 -12 cm and 4-8 cm, respectively, in width and in a range of 4-6 cm and 2-6 cm, respectively, in depth, which indicates SA is more effective in controlling development of rills, in terms of width and depth of rills. And the rills on Slopes SHA and SA varied in the range of 1.42-1.68 m?m-2 and 1.88-2.25 m ?m-2, respectively, in density, which suggests that SHA is more effective in terms of number of rills per unit area. Both of the effects become more significant with increasing distance from the top of the slope. Erosion modulus was 1.15% lower in SHA than in SA in in the first year, and then came up to 1.55 kg?m-2?a-1 and 2.62 kg?m-2?a-1, respectively, in the two, suggesting that SHA is more effective in controlling erosion. All the findings in this survey may serve as a scientific basis and theoretical guidance for rational revegetation of mine dump slopes.

    • Erosion of Slopes of Lou Soil Stacks Different in Gravel Content

      2020, 57(5):1166-1176. DOI: 10.11766/trxb201905220129

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      Abstract:【Objective】 During the processes of production and construction in Guanzhong Region, a large number of stacks of Lou soil were formed. Gravel in the stack is an important factor affecting soil erosion on stack slopes in characteristic. Therefore, this study was designed to explore impacts of gravel concentration on runoff and sediment yielding processes on slopes of Lou soil stacks different in gravel content.【Method】In this paper, artificial rainfalls were simulated indoor, different in intensity (1.0 mm?min-1, 1.5 mm?min-1, 2.0 mm?min-1 and 2.5 mm?min-1), to explore their effects on runoff and sediment yield on slopes of Lou soil stacks different in gravel content (0, 10%, 20% and 30%). The experiment had test plots set up, 5 m×1 m×0.6 m in area and 25° in slope gradient. The nozzles of the artificial rainfall simulator were 18 m high over the slopes, spraying water evenly (more than 80% in evenness). Rainfall intensity were calibrated before the start of each test to ensure that the deviation of the actual rainfall intensity in the test was kept less than 5% of the designed rain intensity for the test. During the test, flow velocity of the runoff on the slope was measured with the dyeing method, width of the flow with a steel ruler, duration of runoff and sediment collection recorded with a stopwatch, and quantity of the samples weighed on an electronic scale. 【Result】 Results show: (1) runoff lasted the longest on the Lou soil slope 10% in gravel content under rainfall 1.0 mm?min-1 in intensity, and the shortest under rainfall lower than 1.0 mm?min-1 in intensity; (2) mean flow velocity of runoff increased with rising rainfall intensity on all the gravel-containing slopes regardless of gravel content. The flow velocity on the slope 10% in gravel content was the highest under rainfalls 1.0 and 2.5 mm?min-1 in intensity, and 15.3%~21.2% and 13.6%~14.1% lower than that on the slope under rainfall 1.5 and 2.0 mm?min-1 in intensity, respectively; (3) sediment content in runoff dropped drastically during the initial period (0~6 min) of each rainfall, regardless of rainfall intensity on all the gravel-containing slopes, and 6 min later, it gradually leveled off under the rainfalls 1.0 and 1.5 mm?min-1 in intensity, and fluctuated sharply under the rainfalls 2.0 and 2.5 mm?min-1 in intensity. During this period gravels dominated the process of sediment yield; (4) the amount of erosion per rainfall event showed a significant power function relationship with rainfall intensity, and decreased by 22.4%~42.6%, 8.2%~66.3%, 2.2%~56.5% and 45.0%~68.3%, on the gravel containing slopes under rainfall 1.0 mm.min-1, 1.5 mm.min-1, 2.0 mm.min-1 and 2.5 mm.min-1 in intensity, respectively as compared with that on the pure soil slope. 【Conclusion】This study may serve as a theoretical basis for establishment of a model for research on water erosion on slopes of soil stacks in the Guanzhong Region .

    • Study on Environmental Magnetic Characteristics of Loess in Har Keren Desert, Israel

      2020, 57(5):1177-1185. DOI: 10.11766/trxb201906240232

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      Abstract:[Objective] Aeolian loess, widely distributed over the world, is a good carrier for studying paleoclimate change. However, mechanisms of their recording climate change vary as their geographical environments from region to regions. The loess region in the south of Israel borders, a subtropical desert. To explore mechanisms of loess magnetic characteristics responding to the environment of this region, a field survey was conducted in the loess area on the fringe of the Negev Desert to investigate systems environmental magnetism and particle size composition. [Method] This study had soil samples collected from the area and analyzed for types, contents and particle sizes of magnetic domain particles therein by means of the room temperature and high temperature magnetic methods. Through analysis of particle size composition of the samples, transport process and deposition characteristics of loess were determined. [Result] Results show that the magnetic minerals in the HK profile consisted mainly of clastic magnetite and maghemite, quite low in content. The Dearing plot of the sample shows that the magnetic domain particles in the magnetic minerals were quite coarse and mainly of coarse single domain (SD) and multi-domain(MD). Analysis of particle size composition shows that particles in the HK profile varied in size, tended to be coarse, declining from the bottom to the top in the profile, with frequency distribution curve appearing to be of positive skewness and were hard to be fractionated, exhibiting the feature of a mixture of multiple transport modes, which was somewhat different from that of a typical aeolian loess. [Conclusion] (1) Both the room-temperature magnetic parameters and high-temperature thermomagnetic curve of the HK profile show that the magnetic minerals in the HK (Har Keren) profile samples consist mainly of clastic magnetite and maghemite, quite low in content, quite coarse in particle size, and dominated with coarse SD and MD, which reflects that they are clastic magnetic minerals coming from the source area. The loess in the profile is quite similar to that in the arid region of Northwest China in magnetic characteristics. (2) The room-temperature magnetic parameters of the HK profile, as a whole, vary within a quite narrow range and ascend somewhat only in the sub-surface layer, which may be attributed to the impact of the modern soil forming process. And (3) median particle size of the HK profile displays a trend of declining from the bottom to the top, and the particles tend to coarse on the whole. Its frequency distribution curve appears to be of positive skewness and the particles are hard to be fractionated. Besides, in the bottom of the profile mixed are gravel debris layers. All of the above reflect that the process of near-source-wind-driven transport and deposition has been subjected to the fluvial effect of flows.

    • Latitudinal Variation Characteristics of Soil Color in Different Spatial Extents and Their Climatic Significance

      2020, 57(5):1186-1196. DOI: 10.11766/trxb201905040180

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      Abstract:[Objective] This study was intended to explore spatial variation of soil color parameters and reliability of the parameter being used as an alternative indicator of climate change. [Method] In this study, color analysis of the soils developed under different climatic conditions was carried out. The soil profiles studied in this paper were scattered in the range geographically from 23.79°N to 64.72°N, and from 38.52°E to 148.45°W, striding across the low latitude, mid-latitude and high latitude. Among the total of 32 soil profiles, 9 had data derived from the literature and the remaining 23 sections were collected from Fujian, the Ganzi Tibetan Autonomous Prefecture in the West Sichuan Plateau, Siberian of Russia, and Alaska of the USA. The soil profiles were distributed one each in Zhao'an, Yunxiao, Changtai, Hui'an, Putian, Fuqing, Zhangping, Quanzhou, Changting, Ninghua, Lianjiang, Minqing, Shaxian, Mingxi, Ningde, Taining, Jian'ou, Zhenghe, Songxi, Wuyishan, the Ganzi Tibetan Autonomous Prefecture, Siberian of Russia, and central Alaska. As the soil profiles were distributed extensively in such a huge region, they divesified greatly in soil type, and developed separately in a huge variety of climatic conditions, including humid subtropical climate, temperate continental climate and Qinghai-Tibet Plateau climate, etc., which differed sharply in annual mean precipitation and annual mean temperature. [Result] Results show: (1) on a small spatial scale, soil color parameters are complex in variation and not so significantly related to climate, while on a large spatial scale, soil color parameters exhibit a certain trend of varying with latitude. Redness (a*) of the soils declines with increasing latitude, while yellowness (b*) does a fitting curve with latitude quite similar to a parabola with an upward opening. The ratio of yellowness to redness (b*/a*) increases approximate linearly with increasing latitude;(2) Color parameters of the soil profiles are more or less related to climatic factors (annual mean precipitation and annual mean temperature); the coorelation coefficient of b*/a* with annual mean temperature is the highest. The coorelation coefficient of a* with annual mean precipitation is slightly higher than that of b*/a*, but a* is more likely to be affected by other factors. [Conclusion] Therefore, the soil chroma parameter b*/a* is quite sensitive to spatial variation of soil color, so is a suitable indicator of climate changes.

    • Fractal Characteristics of Particle Composition for Soils Developed from Different Parent Materials

      2020, 57(5):1197-1205. DOI: 10.11766/trxb201904280012

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      Abstract:【Objective】 To explore the influence of different parent materials on the heterogeneity of soil particle size distribution and soil structure, 【Method】laser particle size analysis and fractal techniques were used to investigate particle composition with its fractal characteristics of soils developed from alluvium, granite residues, quaternary clay and neritic deposit. 【Result】The results showed that: 1) a wider range of particle size distribution, higher content of coarse particles but less heterogeneity was observed for soils developed from granite residues and neritic deposit, while higher concentration of fine particles within a range of 2~200 μm and higher heterogeneity for soils developed from alluvium and quaternary clay. 2) according to the D values, the influence of parent materials on the heterogeneity of particle composition varied with pedogenic layers. The heterogeneity of particle size distribution declined from A to C layer for soils developed from alluvium and granite, however, an opposite trend was observed for soils developed from neritic deposit, and less significant difference in different pedogenic layers for soils developed from quaternary clay. In addition, the type of parent materials had less influence on the range of particle size distribution among pedogenic layers in accordance with the results of D0. 3) the degree of heterogeneity and particle size range were significantly determined by soil pH, CEC, free oxides, vermiculite and kaolinite in soils developed from different parent materials (P < 0.05).【Conclusion】The above results showed that the parent materials had a significant effect on soil particle size distribution and its fractal characteristics.

    • Problem Diagnosis and Geographic Optimization for Fertilization of Wheat in Henan Province Based on Spatial Analysis

      2020, 57(5):1206-1218. DOI: 10.11766/trxb201906250273

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      Abstract:【Objective】Variable rate fertilizing is an important way to improve fertilization economic efficiency and reduce adverse environmental effect. The objective of this paper is to make a diagnosis of the fertilization of wheat in Henan in an attempt to find out problems and to optimize application rates of NPK fertilizers in line with geographical change of wheat potential yield and soil properties.. Henan Province is a major wheat cultivation area of China, contributing 25% of the total wheat production of the country.【Method】Funded by the formula fertilization project of the Ministry of Agriculture of China, the province launched extensively Three-Zone Comparison Experiments (TCE) during the years of 2007—2009. TCE had experimental sites set up all over the province. Each site was designed to have three adjoining plots, randomly selected and laid out for wheat cultivation under CK (no fertilization), CF (local farmer customary fertilization) and RF (fertilization recommended by local agricultural experts), separately. In this paper, data were collected from a total of 2277 TCE sites in 82 counties for comparison analysis. Before seeding of wheat, a soil sample was collected from the cultivated-layer of each plot, and then the samples from the three adjoining plots were mixed into one as soil sample of the site for analysis of OM, pH, total N, Olsen-P and readily available K. Wheat yield, NPK application rates of each plot and soil properties and accumulated sunshine hour, accumulated precipitation, accumulated evaporation, accumulated temperature above 0°C and that above 10 °C of each TCE site, during the wheat growth period were all recorded separately for comprehensive analysis following the steps below. 1) mapping wheat yield, N, P, K application rate, contents of total N, available P and readily available K in soil with the aid of kriging interpolation, and comparing the maps to identify problems in application of N, P and K fertilizers in this area; 2) adopting the Random Forest(RF)method to assess relative contribution of soil properties of the cultivated soil layer, fertilization rate and geographical variation of soil type and climate to variation of wheat yield; and 3) superimposing the wheat potential yield map, soil total N map, soil available P map and soil readily available K map acquired in the research and referring to the research on soil nutrient sufficiency standard and recommendation of NPK application rates for targeted wheat yield to optimize fertilization recommendation geographically in line with the principles of “yield-targeted fertilization” and “soil-oriented fertilization” for the province. 【Result】Results show that the customary application rates of N and P tended generally to be higher, while that of K to be lower in some areas. However, most of the fertilization recommendations failed to reduce the rates of N and P. but generally raise the rate of K application. The two fertilization schemes, customary and recommended, are found to share a common problem, i.e. N, P, and K application rates mismatched targeted wheat yield and soil fertility in spatial distribution. Random forest analysis shows that geographic variations of soil, type and climate were the dominant factors of the spatial variation of wheat yield, and fertilization followed the next and soil nutrients the last in effect, while variations of geographical factors and fertilization were the ones determining spatial variation of wheat yield increment, which had nothing to do with soil nutrients. High fertilization rates were the major reason explaining the weak relationship between soil nutrient status and wheat yield.【Conclusion】On the background of high nutrient and water supply, physical geographical distributions of soil type and climate now are the key factors determining spatial variation of wheat yield at a provincial scale. Owing to the hardness of breaking through the obstacle of soil type and the limitation of climate conditions, it is almost infeasible to alter the rule of spatial distribution significantly within next few years. Based on the spatial variations of potential wheat yield and soil nutrient level, the recommended N, P2O5 and K2O application rate should be in the range of 120~210 kg·hm-2, 45~105 kg·hm-2 and 45~120 kg·hm-2, respectively. It is estimated that geographic optimization may save N, P and K fertilizer by 14.2%, 40.0% and 39.5% over the fertilization schemes recommended by local experts and by 20.9%, 41.1% and 17.5% over the customary application rate of the local farmers.

    • Effects of Soil Amelioration Measures Mitigating Soil Salinity and Improving Crop P Uptake in Coastal Area of North Jiangsu

      2020, 57(5):1219-1229. DOI: 10.11766/trxb201908210284

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      Abstract:【Objective】In the coastal areas of North Jiangsu exist enormous tracts of mudflat, which are important land reserves for exploitation in China. However, the existence of high soil salinity in the mudflat, once turned into farmland, not only reduces soil phosphorus availability, but also seriously restrains productivity of the farmland and phosphorus utilization efficiency. Biochar, humic acid and gypsum are considered to have good effects in ameliorating and utilizing the soil. Therefore, the objective of this study is to investigate effects of the use of these soil amendments on soil salinity-alkalinity and crop uptake and utilization of phosphorous in the soil.【Method】 For that end, a field microplot experiment was carried out in the fields of light saline soil (D) and moderate saline soil (Z), and an indoor pot experiment using the soils from the two fields. The experiments were designed to have five treatments for each of the two soils and three replicates for each treatment. The five treatments included (1) application of N only (CK); (2) conventional fertilizer (P); (3) conventional fertilizer + biochar (PC); (4) conventional fertilizer + humic acid (PH); (5) conventional fertilizer + gypsum (PG). The experiment initiated in 2017 under a crop rotation system of Barley-maize. Soil samples were collected from the 0~20 cm and 20~40 cm soil layers of each treatment once at each crop growing stage for analysis of effects of the amendments on soil salt content, soil pH and soil sodium adsorption ratio (SAR) and phosphorus absorption. 【Result】Results show that soil salt content in the coastal area of Jiangsu varied with the season markedly, that is, salt accumulating in spring, salt leaching in summer, soil uprising in autumn and salt stabilizing in winter. The soil salt controlling effects of the management measures were more significant in the 0~20 cm soil layer than in the 20~40 cm soil layer, especially Treatment PG. Treatment PG reduced the salt content in the 0~20 cm soil layer by 31.06% and 40.60% and soil pH by 0.67 and 0.51 in the soils light and moderate in soil salinity, respectively. Compared with CK, all the amendment treatments were lower in SAR and Na+ content in the 0~20 cm soil layer, which indicates obvious improvement in soil structure. In terms of decrease in SAR, treatments displayed an order of PG > PH > PC with the soil light in salinity and an order of PG > PC > PH with the soil moderate in salinity. All the amendment treatments promoted P uptake and yield of barley and maize in the soil light in salinity, while only Treatments PC and PG did in the soil moderate in salinity. After two rounds of rotation, in the soil light in salinity, Treatments PC, PH and PG were found to have increased the cumulative phosphate utilization rate by 4.9 times, 3.5 times and 1.8 times that of CK, respectively, while in the soil moderate in salinity only Treatment PC and PG showed similar effects. 【Conclusion】The saline soil in the coastal area of North Jiangsu varied with the season in soil salt content. The amendment of biochar, humic acid or gypsum can effectively promote removal of soil salt and alkali, thus improving the soil structure. Among all the amendments tested, gypsum is the best in decreasing soil salt content, pH and sodium adsorption ratio. All the amendments significantly promote crop P uptake, and hence increase cumulative phosphorus utilization rate and crop yield in the soil light in salinity. Humic acid shows a better effect in the soil light in salinity than in the soil moderate in salinity.

    • Does Amendment of Montmorillonite Promote Humification of White Alfalfa

      2020, 57(5):1230-1239. DOI: 10.11766/trxb201903060110

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      Abstract:【Objective】 Humic substances (HS), the main component of soil organic matter, are kind of macromolecular compounds, specific and multi-phased in property, formed during humification. However, in the past two decades, doubts have been arising about rationality of the disassociation process of HS. Currently, the research has shifted its focus from on chemical properties of HS to on identification of processes and mechanisms related to HS renewal and stabilization. Plant residues and microbial biomass are the main parent materials for the formation of humic substances, meanwhile, clay minerals, as an important part of the soil, also play an important role in the process. However, still little is known about any specific effects of clay minerals on formation of HS. Some scholars have used microbial pure culture methods to study formation of HS, but because of the absence of clay minerals, the formation of HS studied does not represent that in soil. Therefore, more efforts should be done to further elucidate in detail the complex interactions between HS and the surface of minerals, as well as the role of soil microbes as a participant. In order to explore effects of montmorillonite on humification process, white alfalfa, an angiosperm, was used in an incubation experiment with montmorillonite and microbe-soil extract as control conditions. 【Method】 In this experiment, there were three treatments, i.e. Treatment A, white alfalfa with montmorillonite and soil extract added; Treatment AnM, white alfalfa with soil extract added only; and Treatment AnI, only white alfalfa. Effects of the treatments and duration of the incuabtion on composition of humus-like substances and structure of humic-like acids(HLA)formed as incubation product of white alfalfa were studied. Water-soluble substances(WSS), fulvic-like acid(FLA), humic-like acid(HLA) and humin-like(HLu)were extracted with the modified humus composition method. HLA samples were extracted with the method recommended by the International Humic Substances Society (IHSS) for analysis of structure of HA with the elemental composition- infrared spectroscopy. 【Result】 Results show that the amendment of montmorillonite promoted decomposition of TOC and accumulation of simple structured HLA. After 90 days of incubation, H/C in Treatment A increased from 1.38 to 1.61, after 180 days from 1.39 to 1.53, and after 360 days from 1.36 to 1.48. The sharp increase in H/C in the early stage in Treatment A made the structure of HLA simple. However, with the incubation going on, the increase in H/C gradually dulled in trend. Its ratio of 2920/1640 in the infrared spectrum tended to be in consistence with that in elemental composition. At the end of the incubation, HLA, regardless of treatments, developed eventually quite close to the O/C and H/C of soil HA in value. Among the treatments, the HLA in Treatment (AnM) was the closest to real soil HA in complexity, indicating that montmorillonite cannot help HLA turn into soil HA. 【Conclusion】 Overall, montmorillonite amendment may promote decomposition of TOC and formation of HLA, and accelerate humification process of white alfalfa; however, it does not enhance the aromatization of HLA in degree and the structure of HLA in complexity as speculated or reported in the literature. Instead, it simplifies the structure of HLA, which is still quite different from real soil HA.

    • Effects of Na+, Ca2+ and Na+-Ca2+ Mixture on the Stability of Humic Acid Colloids

      2020, 57(5):1240-1248. DOI: 10.11766/trxb201906050252

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      Abstract:【Objective】In this study on humic acid in soil, the technique of light scattering was adopted to compare effects of three different electrolytes common in soil, i.e. Na+, Ca2+ and Na+-Ca2+mixture, on agglomeration kinetics of humic acid colloids relative to concentration of the electrolyte and elucidate effects of interface behaviors of ions different in valence and complementary ions on humic acid dispersion stability and agglomerate structure. 【Method】The technique of dynamic light scattering was used to monitor effective hydrodynamic diameters of humic acid agglomerates, which were found increasing with time in all the three electrolytes, regardless of concentration. Based on the time-dependent changes in agglomerate diameter, total mean agglomeration rate, critical agglomeration concentration and activation energy were calcuated, and agglomeration mechanism analyzed. Fractal dimension of humic acid agglomerates 60 d after agglomaeration was determined. 【Result】Resuls show: (1) agglomeration of humic acid colloids was quite similar in all the electrolytes: effective hydrodynamic diameter of humic acid agglomerates linearly increased with time in electrolytes low in concentrations and followed a power law in those high in concentration. The effects of Na+ and Ca2+ on agglomeration of humic acid colloids in the experiment were much higher than those of the ions different in valence as is described in the Schulze-Hardy law; (2) in the electrolyte of Na+-Ca2+ mixture, Ca2+ ions dominated agglomeration process, and agglomeration process in the electrolyte of Ca2+ differed from that in the electrolyte of Na+-Ca2+ and the sharper the lower the concentration; (3) in the electrolyte of Na+-Ca2+ mixture, Na+, as complementary ion in the electrolyte of Na+-Ca2+ mixture, had certain complementary effects on critical coagulation concentration, inter-particle activation energy and agglomerate structure, especially the last; and (4) the humic acid agglomerates in the electrolyte of Na+-Ca2+ mixture was quite compact in structure, varying between those in the electrolytes of Na+ and Ca2+. It is, therefore, feasible to control compactness of the agglomerates in structure in the electrolyte by adjusting ion composition of the electrolyte. 【Conclusion】 The agglomeration of humic acid colloids induced by Ca2+ depends not only on compression of the surface electric double layer on the counter ions, which reduces electrostatic repulsion and causes agglomeration, but also on polarization of Ca2+ in the strong electric field that induces and contributes to formation of covalent and bridge bonds between Ca2+ and oxygen-containing functional groups on the surface of humic acid. In addition, the competitive adsorptions of Na+ and Ca2+ on the surface of humic acid inhibits agglomeration of Ca2+, thus forming agglomerate moderate in compactness. All these findings may provide some new ideas and theories for exploring colloidal interface reaction and mechanism for agglomeration of soil colloids.

    • Effects of Soil Warming and Nitrogen Addition on Soil Dissolved Organic Matter of Cunninghamia lanceolata Plantations in Subtropical China

      2020, 57(5):1249-1258. DOI: 10.11766/trxb201904160078

      Abstract (1640) HTML (818) PDF 1.23 M (1560) Comment (0) Favorites

      Abstract:【Objective】 As affected by anthropogenic activities, such as greenhouse agriculture that emits greenhouse gases, the global mean surface temperature rose by about 0.85 °C over the period of 1880—2012; and nitrogen deposition in China increased significantly by 0.41 kg•hm-2 with each passing year over the period from 1980 to 2010. In the context of global warming, soil dissolved organic matter (DOM) attracts more and more attention due to its important role affecting global carbon and nitrogen balance, which is of great significance to the ecological environment. This study aims to investigate effects of soil warming and nitrogen addition on content and structure of soil DOM in the soil of Cunninghamia lanceolata plantations in subtropical China. 【Method】 In 2014—2015, a mesocosm field experiment was carried out in a Cunninghamia lanceolata plantations in subtropical China. The experiment was designed to have six treatments, that is, (1) CT (no warming and 0 kg•hm -2•a-1); (2) W (+5 ℃, 0 kg•hm -2•a-1); (3) HN (no warming and 80 kg•hm -2•a-1); (4) LN (no warming and 40 kg•hm-2•a-1); (5) WHN (+5 ℃ and 80 kg•hm -2•a-1); and (6) WLN, (+5 ℃ and 40 kg•hm-2•a-1). Soil samples were collected in January 2015 (dry season) and April 2015 (rainy season), separately for analysis of DOM. 【Result】Results show that soil warming increased the content of DOM, but decreased its aromaticity index and humification index, which might be attributed to the effect of high temperature promoting conversion of SOM (soil organic matter) into DOM. The impact of nitrogen addition on DOM structure showed a seasonal pattern. In the dry season, addition of nitrogen increased both the content and aromaticity index of DOM, while in the rainy season, it increased the content of DOM, but reduced its aromaticity and humification index significantly. Under the joint effect of high temperature and nitrogen addition, the DOM peaked in content and got simpler in structure. Besides the direct impacts of temperature and nitrogen content, soil moisture and pH were also key factors cotrolling DOM dynamics as revealed by RDA (redundancy analysis). 【Conclusion】Based on the findings of the experiment, it could be concluded that 1) Both warming and application of nitrogen affect soil pH, thus making it easier for SOM to convert into DOM. Since the dissolution of organic matter in soil solution is mostly endothermic, warming accelerates the dissolution of plant residues and SOM into DOM; while nitrogen addition can also increase soil DOM content by promoting plant growth. 2)The effects of warming and nitrogen addition on soil DOM show a strong seasonal pattern, indicating that the influences of future global warming and nitrogen deposition will vary with environment conditions from region to region. Hence, more experiments should be done to further explore impacts of warming, nitrogen addition and their interaction on soil DOM, and some other environmenatl variables should be taken into account to attain a more profound comprehension of carbon and nitrogen cycling under a changing global climate.

    • Composition Characteristics of Organic Carbon Pool in Upland Red Soil under Long-term Application of Straw and Pig Manure

      2020, 57(5):1259-1269. DOI: 10.11766/trxb201905130190

      Abstract (1660) HTML (969) PDF 581.74 K (1754) Comment (0) Favorites

      Abstract:【Objective】 This study aimed (i) to investigate processes and mechanisms of long-term application of crop straw and pig manure affecting content and fractionation of organic carbon pools in upland red soil; (ii) to analyze effect and adaptability of the RothC model simulating changes in organic carbon in upland red soil; and (iii) to provide reference data for management of organic carbon and sustainable development of agriculture in upland red soil. 【Method】 Soil samples were collected from the topsoil layer (0 ~ 20 cm) of a upland of red soil, where out laid were the four treatments, that is, CK (chemical fertilizer), PS (peanut straw), RS (rice straw) and PM (pig manure), in the National Agro-Ecosystem Observation and Research Station in Yingtan, Jiangxi Province of China. Organic cabon in the soil samples was extracted and sorted into five fractions, i.e. particulate organic carbon (POC), organic carbon in sand and stable aggregates (SAOC), dissolved organic carbon (DOC), labile organic carbon (LOC), and inert organic carbon (rSOC), with the modified Zimmermanns’ method. Based on the RothC model, the above-listed fractions of soil carbon were further sorted separately into five subfractions, i.e. organic carbon in readily-decomposable plant residue (DPM), organic carbon in hardly-decomposable plant residue (RPM), microbial biomass carbon (BIO), organic carbon in humus (HUM) and inert organic carbon (IOM). Content and proportion of each fraction and subfraction was determined for analysis of effects of the long-term fertilization relative to treatment. And relationships of each carbon fraction or subfraction with soil iron-aluminum oxides and input of extraneous carbon were analyzed and discussed. 【Result】 Results show that in terms of content and proportion, the fractions of organic carbon in the upland red soil exhibited an order of SAOC > rSOC > LOC > POC > DOC and HUM > IOM > RPM > BIO > DPM. Compared with CK, Treatment PM was 17.0% , 86.7% and 86.7% higher in SOC, DPM and RPM, respectively, and Treatment PS was 94.4% higher in both DPM and RPM. However, the three fertilized treatments did not have much impact on content and proportion of the fractions of BIO, HUM and IOM. The correlation analysis shows that the fraction of rSOC(IOM) was negatively related to free aluminum oxides in the soil, but positively with amorphous - iron oxides in content; that POC was ultra-significantly and positively related to DPM and RPM; that SAOC was significantly and positively related to BIO and HUM; and that rSOC(IOM) was ultra-significantly and negatively related to LOC. 【Conclusion】 Long-term fertilization significantly increases soil organic carbon in red soil upland, but the effect varies with fertilization practice. However, the increasing trend levels off after 26 years of fertilization, thus, in the RothC model, the effects of amendament of organic manure to chemical fertilization on BIO, HUM and IOM appear to be quite insignificant. In the soils applied with PS, RS or PM, organic carbon is dominated with SAOC (63 ~ 2 000 μm) and rSOC (0.45 μm ~ 63 μm) in HUM and IOM. Long-term chemical fertilization amended with PS or PM brings a large volume of carbon into the soil and significantly increases the proportions of DPM and PRM, while amendament of RS can significantly promote transformation of organic carbon from DPM and PRM into BIO and HUM, thus improving soil quality of the farmlands. Long-term fertilization high in organic carbon input and high soil free - aluminum oxides content both accelerate sequestration of inert organic carbon by soil microorganisms.

    • Formation of Soil Aggregates and Distribution of Soil Nutrients in Rhizosphere of Salt-tolerant Trees in Coastal Polder Reclamation

      2020, 57(5):1270-1279. DOI: 10.11766/trxb201908240243

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      Abstract:【Objective】This study is oriented to explore effects of salt-tolerant trees different in species ameliorating coastal saline-alkali soils for screening trees suitable for establishment of shelterbelts and ecological greening in coastal areas.【Method】Three different species of trees, i.e. Tamarix chinensis (salt-secreting arbor), Rhaphiolepis umbellata (salt-rejecting shrub), and Ulmus pumila (salt-rejecting arbor) were planted in a tract of mudflat of saline-alkali soil in the Songbu Polder on the coast of Wenzhou. Two years after the trees were established, soil samples were collected from the rhizospheres of the trees for analysis of particle size distribution of soil aggregates and key physicochemical properties of the aggregates by particle size, including soil organic carbon (SOC), dithionite-citrate-bicarbonate-extractable Fe (hydro)oxides (DCB-Fe), total nitrogen (TN), alkali-hydrolyzable nitrogen (AN), available phosphorus (AP), and readily available potassium (AK).【Result】Compared with the soil in the bare-land (CK), the soil in the rhizosphere of T. chinensis, R. umbellata, and U. pumila was 0.14, 0.43 and 0.39 lower in pH and 80%, 70% and 72% lower in electrical conductivity (EC), respectively. The soil particle size of CK was <0.053 mm, while soil aggregates were formed in the rhizosphere of the trees with the content of soil micro-aggregates (0.25-0.053 mm) being 5.0%-5.9%, and the content of macro-aggregates (2-0.25 mm) being much lower, accounting for less than 1% of the total of soil aggregates. The content of SOC increased significantly in the rhizosphere soils, but the content of DCB-Fe decreased significantly (P<0.05), especially in micro-aggregates, which suggests that soil aggregation was coupled with Fe removal and C accumulation. Soil nutrients, including TN, AN and AP were elevated in content within the rhizospheres of all three species. The content of TN (1.20 g·kg-1) and AN (42.6 mg·kg-1) in the rhizosphere soil of U. pumila was 15.4% and 23.8%, respectively, higher than those in CK. The content of AN (85.8 mg·kg-1) in micro-aggregates was the highest among the aggregate fractions in the rhizosphere of U. pumila . Interestingly, much higher AP contents in silt-clay aggregates (16.4-19.0 mg·kg-1) than those in micro-aggregates (10.4-11.4 mg·kg-1) were detected in the T. chinensis and R. umbellata plantations, whereas no difference was observed in U. pumila rhizosphere soil (P>0.05). After establishment of the trees, AK decreased significantly or by 4.5%-11.5% in rhizosphere soils as compared that in CK (P<0.05). For all the rhizosphere soils, the content of AK varied in the range of 115.0-216.3 mg·kg-1 in micro-aggregates, which was significantly lower than those in silt-clay aggregates (303.0-342.0 mg·kg-1).【Conclusion】 Cultivations of the salt-tolerant trees can ameliorate saline-alkali soils by reducing salinity and improving soil structure and soil fertility. T. chinensis, R. umbellata, and U. pumila could all be used as effective pioneer trees for mudflat reclamation projects. Among these species, U. pumila appeared to be the most effective thanks to its high capability of carbon and nitrogen enrichment in the rhizosphere soil.

    • Bibliometric-based Analysis of Advances in Researches on Fusarium Wilt Disease

      2020, 57(5):1280-1291. DOI: 10.11766/trxb201909090479

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      Abstract:【Objectives】 Fusarium wilt, caused by Fusarium oxysporum, is a kind of fungal disease highly destructive to crops. A review was prepared of advances and hot spots in the research on through citation analysis.【Method】In order to ensure that the review is objective and scientific, literature analysis was performed based on the data collected and retrieved by "Fusarium wilt" as the subject word from the core collection of the database of ISI Web of Science of the period of 1985 ~ 2019. A total of 4972 relevant papers were obtained finally by April 1, 2019. All the retrieved documents were downloaded in the format of "full record and quoted references" and "plain text", and renamed to download-fw.txt format, for easy recognition by CiteSpace for further analysis. Then, the CiteSpace visualization software was used for citation analysis by cooperation, co-occurrence, co-citation, research hotspot and frontier trend. 【Result】Statistical analysis of volume of the publications shows that the United States, China and India ranked the top three in this field. Analysis of betweenness central indicators shows that the Netherlands, the United States and India were the top three in importance of literature, while China was among the top 10s with a positive upward trend. Further analysis by institution shows that the United States Department of Agriculture, the University of Cordoba, the French National Agricultural Research Institute, the University of Utrecht, etc. were outstanding ones in this field; Domestic research institutions, represented by the Nanjing Agricultural University, actively carried out relevant researches and contributed a huge number of publications addressing the issue “Fusarium wilt is widely distributed and complex crop disease” in the fields of plant science, agronomy and agricultural economics.【Conclusion】 Further citation analysis shows that “induction”, “genetic diversity” and “pathogenicity” are important hot spots in the recent ten years, and literature co-citation clustering analysis shows that “Bacillus amyloliquefaciens”, “systemic resistance”, and “non-pathogenic Fusarium oxysporum” were the research frontiers in this field. With the research on Fusarium wilt going on in-depth, it is speculated that the future research will go on keeping focus on microbial control and prevention, breeding of disease resistant crop varieties, and interaction of root - pathogen - beneficial microbes and its mechanism, and moreover, the adoption of the multiple omics technology will sure help understand the pathogenesis of Fusarium wilt and provide a theoretical basis and technical support for fundamental studies on and prevention of Fusarium wilt.

    • Effects of Rhizobia and Arbuscular Mycorrhizal Fungi on Nodulation, Yield and Quality of Medicago Sativa

      2020, 57(5):1292-1298. DOI: 10.11766/trxb201907030439

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      Abstract:【Objective】It is beneficial to explore effects of Sinorhizobium medicae (SM) and arbuscular mycorrhizal fungi (AMF) on alfalfa (Medicago sativa) growing in acid soils, to extrapolating the forage crop and promoting development of animal husbandry in Southwest China, so a micro field experiment was carried out.【Method】The experiment was designed to have 4 inoculation treatments, i.e. CK (blank control); SM (inoculation of SM); AMF (inoculation of AMF); and SM+AMF (inoculation of both SM and AMF) and carried out to study effects of the inoculations on nodulation, nutrient uptake, yield and quality of the alfalfa growing in an acid yellow soil, typical and representative of the studied region in Southwest China.【Result】Results show that the alfalfa in Treatment SM+AMF had more nodules, though smaller in size, a higher mycorrhizal infection rate, more rhizobacteria and mycorrhizal fungi infection sites on root surface, higher N fixation efficiency and a higher P absorption capacity than those in the other three treatments. Besides, the crop was also higher than the others in yield, contents of crude protein, crude fat and ashes, and accumulations of N, P, Ca and Mg in shoots, exhibiting significant synergy of the two inoculants. Compared with CK,both SM and AMF promoted plant growth, increased forage yield, and improved forage quality, but no significant difference between the two in these effects. In addition, the crop in Treatment SM was higher than that in CK in N content and accumulation of N, P and K in shoots, and higher than Treatment AMF in whole plant N accumulation. AMF stimulated the activities of nitrate reductase and roots, thus improving NO3-assimilation and nutrient uptake, which explains why the plant in Treatment AMF was higher than that in Treatment SM in P, K, Ca, and Mg content and accumulation in shoots. 【Conclusion】Both AMF and SM can promote uptake of N, P, and K by alfalfa and improve yield and quality of the forage to a varying extent. Therefore, inoculation of SM or AMF, particularly of both, is beneficial to cultivation of alfalfa in acid soils in Southwest China.

    • Selenium Distribution in Surface Soil Layer of Karst Area of Guangxi and Its Affecting Factors: A case study of Wuming County

      2020, 57(5):1299-1310. DOI: 10.11766/trxb201909120327

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      Abstract:【Objective】China is a country deficient in selenium (Se), because the soils in most of its provinces and regions or about 72% of its total land are under Se stress to a varying extent. However, during the soil survey completed recently, Guangxi was found to have a large tract or continuous patches of soil rich in Se, or so far the largest tract in the country. In that region, the soils in Karst areas were apparently higher in Se content than those in non-Karst areas. It is hypothesized that the tract of Se-rich soils benefit jointly from their soil forming parent rock, soil composition and unique Se enrichment mechanism. In order to validate this hypothesis, a comprehensive study was conducted. In this study, a total of 15480 topsoil samples, 452 subsoil samples and 200 rock samples were collected in Wuming County, South Guangxi, where exist large tracts of karst landform for analysis of soil physico-chemical properties, and contents of calcium oxide (CaO), potassium oxide (K2O), sodium oxide (Na2O), magnesium oxide (MgO), silicon dioxide (SiO2), aluminum oxide (Al2O3), Total iron (TFe2O3), selenium (Se), manganese (Mn), titanium (Ti), soil organic carbon (SOC) and pH.【Method】Spatial contrast, scattergraph and multivariate statistic methods were adopted to analyze sources of Se containing materials in the soil and impacts of soil forming parent rock, weathering processes, soil composition, pH and soil organic carbon (SOC) on soil Se, collate the affecting factors in sequence of priority. And furthermore, discussions were held on main causes of the formation of the Se highly-enriched soils in the key Karst areas of Guangxi. 【Result】Results show that the concentration of Se in the topsoil of the study area varies in the range of 0.07~9.04 mg•kg-1 and its background value is 0.87 mg•kg-1, which is 4.36 times that of the country. Soil Se demonstrates a good spatial coupled relationship with the stratum and is strongly and positive related to soil Se in the subsoil layer, which suggests that soil Se in the topsoil comes from underlying soil layers; scattergraph indicates that soil Se was affected by weathering intensity (CIA), Al2O3, TFe2O3, SiO2, SOC, pH, CaO, K2O, Na2O and MgO. Multivariate fitting with linear regression equation and equation error testing reveal that CIA, clay minerals (Al2O3), and Fe-bearing minerals played leading roles in secondary enrichment of Se, while SOC, K-bearing minerals, Na-bearing minerals, Mg-bearing minerals followed in the function, and pH, Ca-bearing and Mn-bearing minerals did in the last with very weak effects. 【Conclusion】Based on the findings about sources of Se and relationships between Se enrichment affecting factors, it is concluded that weathering processes dominates Se enrichment in the soils in Karst areas, while the high contents of clay minerals and Fe-bearing minerals in the soil play leading roles in sorption of Se, which may be the main reason why high Se enrichment occurs in the Karst area of Guangxi where limestone is lower in Se content than the average rock in China.

    • >Research Notes
    • Survey of Cambosol Series in Hebei Province

      2020, 57(5):1311-1318. DOI: 10.11766/trxb201907270213

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      Abstract:In order to explore characteristics of cambisols as a series in Hebei Province, data of the series, containing 61 types of cambisols, were cited from the “Hebei Volume - Soil Series of China” published by the Science Press in 2017 for collation and analysis of morphological features of the soil profiles, basic soil physico-chemical properties, classification information, and agricultural performances. Results show: (1) cambisols were found almost everywhere in the province and the largest in distribution area; (2) the 61 types of cambisols could be sorted into 3 soil suborders,8 soil groups,15 soil subgroups and 52 soil families; (3) the cambisols varied quite significantly in profile morphology and soil physico-chemical properties; and (4) the cambisols were generally quite low in fertility and widerly agricultural production performance, and varied in productivity, high, middle or low in yield. At present,the division of obvious transitions between soil families and soil series for cambisols in Hebei is not conducive to guiding agricultural production. It is suggested that proper amendments should be made to the methods or criteria for division of soil families and soil series.

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