• Volume 57,Issue 4,2020 Table of Contents
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    • >Insights and Perspectives
    • Soil Health and Agriculture Green Development: Opportunities and Challenges

      2020, 57(4):783-796. DOI: 10.11766/trxb202002220064

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      Abstract:Agriculture green development (AGD) is the future for modern agriculture, and soil health is the cornerstone of AGD. This article summarized the connotation, research progress and trend of soil health in domestic and overseas. By summarizing the main management strategies for healthy soil cultivation, this paper puts forward novel ideas and approaches for promoting soil health, and discusses the challenges and opportunities for soil health engineering. The cores for the promotion of healthy soils are: eliminating the limiting factors of soils; increasing the content of soil organic carbon and nutrient use efficiency; exploiting the biological potentials; promoting synergistic interactions between above-ground and below-ground. The aim of soil health engineering is to synergize the production and other ecosystem services delivered by soils by optimizing the internal regulatory processes whilst minimizing the external inputs. The cultivation of healthy soil needs holistic engineering, which requires comprehensive integration of whole industry chain in the nexus of external input, crop production, products-processing, and waste recycling. Meanwhile, cross-disciplinary innovation, government-farmer-research-extension institute collaboration, and policy support and incentive systems are crucial for realizing soil health towards AGD.

    • >Reviews and Comments
    • Evolution of Research on Soil Erosion at Home and Abroad in the Past 30 Years--Based on Bibliometric Analysis

      2020, 57(4):797-810. DOI: 10.11766/trxb201906030237

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      Abstract:The use of visualized bibliometric analysis helps evaluate objectively advancement of the research on soil erosion, which in turn promotes knowledge about frontiers of the research at home and abroad, thus pushing the research fast forwards in China. With the aid of the CiteSpace software, bibliometric analysis was performed of the data cited from the Web of Science and CNKI(China National Knowledge Infrastructure)for history of the advancement of the researches on soil erosion, both at home and abroad in the recent three decades. For the convenience of analysis, the time period set for the study was divided into three phases (1992—2000, 2001—2009 and 2010—2018). It was found that the researches on soil erosion the world over focused firstly on relationship between soil erosion and land productivity and its evaluation methods and then turned towards interactions between climate change and soil erosion, accurate estimation of soil erosion, as well as large scale macroscopic research on soil erosion during the phase of 1992—2000. As the research in the country was getting more and more policy-oriented, the phase of 2001—2009 witnessed foci of the research being shifted to laws of soil and water conservation and economic benefits-pivoted soil erosion control, and gradually towards ecological construction and sustainable development as the core issues and application of GIS and remote-sensing to the researches in this field. In the last phase of 2010—2018, eyes of the researcher focused on RUSLE and other models, especially for relationship of soil erosion with land use, slope and some other influencing factors. Finally, based on comparison between the three phases in focus and frontier of the soil erosion researches at home and abroad, the paper put forth directions for future researches on soil erosion in China.

    • >Research Articles
    • Effect of Returning Chopped and Pelletized Straw at A High Rate Enhancing Soil Organic Carbon in Subsoil of Farmlands of Black Soil

      2020, 57(4):811-823. DOI: 10.11766/trxb201907150244

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      Abstract:【Objective】To solve the problems of soil organic carbon deficiency in the subsoil layer and the yield of crop straw being too large in volume to make full use of in farmlands of black soil in Northeast China, a long-term (2015—2018) field experiment was carried out. 【Method】The field experiment was designed to have three treatments, i.e. CK (no straw returned), FS (returning of chopped straw) and KL (returning of pelletized straw), and three straw returning rates, i.e. Rate 1 (15 t•hm-2), Rate 2 (45 t•hm-2, 3 times as high as Rate 1) and 3 (75 t•hm-2, 5 times as high as Rate 1). The straw was deeply incorporated into the subsoil layer. Soil samples were collected from all the plots separately each year for analysis of soil organic carbon content, organic carbon structure and soil nutrient ratio in an attempt to find out a way to turn waste into treasure and hence to promote sustainable development of black soil. 【Result】Results show: 1. Organic carbon content in the subsoil of the treatment plots varied in the range of 2%-20%(1 a), 5%-27%(2 a) and 1%-18%(3 a). The effect of straw returning raising organic carbon content in the subsoil was significant and improved with increasing returning rate and the effect of the treatments the highest in returning rate were the most significant and particularly in the second year, which indicates that organic carbon accumulation occurred mainly in the second year. Two-way variance analysis shows that straw returning rate was an important factor affecting soil organic carbon; 2. Nuclear magnetic resonance test shows that at the end of the experiment, the organic carbon in Treatment FS5 was found the highest in aliphaticity, while that in Treatment KL5 the highest in aromaticity, indicating that chopped straw is more likely to promote formation of organic carbon of alkyl carbon chain, while pelletized straw is to promote formation of organic carbon of aromatic hydrocarbon type; 3. In Treatments FS5 and KL5, soil C/N and C/P ratios increased by >10%, and C/K ratio did by >20%. The effect in Treatments KL was short and instant, while that in Treatments FS was long and slow. 【Conclusion】In a conclusion, deep incorporation of processed straw at a high rate can significantly increase organic carbon in the subsoil layer and help keep soil carbon in balance with nitrogen, phosphorus and potassium. It is, therefore, a feasible way to build up the black soil in thickness and fertility and to solve the difficult problem of straw returning in Northeast China.

    • Effects of Reclamation/Cultivation on Soil Quality of Saline-alkali Soils in the Yellow River Delta

      2020, 57(4):824-833. DOI: 10.11766/trxb201905050105

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      Abstract:【Objective】Soil reclamation/cultivation will sure affect soil environment of the saline-alkali soils involved and cause changes in soil quality. Therefore, it is necessary to explore or characterize changes in soil quality of the saline-alkali soils different in year of cultivation for reasonable utilization of saline-alkali soil resources.【Method】In this study, soil samples were collected, separately, from the topsoil (0~20cm) and subsoil (20~40cm) layers of farmlands, under the same wheat/maize crop rotation system, but different in year of cultivation (< 5 a, 10 ~ 15 a, 20 ~ 25 a, 30 ~ 35 a and 50 ~ 60 a), in the saline-alkali soil region of the Yellow River Delta. The samples were analyzed from the aspects of soil physics, chemistry and biology, for bulk density, organic matter, total nitrogen, available phosphorus, readily available potassium, total salt, pH, sucrase and alkaline phosphatase, a total of nine soil quality indicators. On such a basis, principal component analysis was performed, SQI (Soil quality index) calculated and variation of soil quality in the farmland with years of cultivation evaluated quantitatively. 【Result】Results show that soil quality improved with cultivation going on. Compared with virgin wasteland, the farmlands cultivated for < 5 a, 10 ~ 15 a, 20 ~ 25 a, 30 ~ 35 a, and 50 ~ 60 a were 36.97% ~ 161.49% and 164.44% ~ 444.40% higher in SQI of the 0 ~ 20 cm and 20 ~ 40 cm soil layers, respectively. SQI varied in increasing rate from period to period. Compared with the virgin wasteland, the farmland increased by 36.70% and 164.44% in SQI, respectively, in the 0 ~ 20 cm and 20 ~ 40 cm soil layers during the initial period of the cultivation (<5 a) and by 38.27% and 18.18% during the period of 10 ~ 15a of cultivation; by 10.37% and 39.35% during the period of 20 ~ 25 a of cultivation as compared with that during the period of 10 ~ 15 a; by 24.42% and 24.79% during the period of 30 ~ 35 a of cultivation as compared with that during the period of 20 ~ 25 a of cultivation; and by 0.74% and 0.17% during the period of 50 ~ 60 a of cultivation as compared with that during the period of 30 ~ 35 a of cultivation. And SQI began leveling off after 30 ~ 35 a of cultivation. The 0 ~ 20 cm soil layer was 65.69%, 93.85%, 53.53%, 53.08% and 86.95% in SQI than the 20 ~ 40 cm soil layer, respectively, in the farmland cultivated for <5 a, 10 ~ 15 a, 20 ~ 25 a, 30 ~ 35 a and 50 ~ 60 a.【Conclusion】All the findings in this study demonstrate that crop cultivation improves soil quality, and the effect varies with the cultivation going on. It is, therefore, advisable to conduct comprehensive scoring based on principle component analysis so as to objectively and efficiently evaluate soil quality of farmlands different in year of cultivation.

    • Spatial Differentiation of Soil Selenium in Hilly Regions of South China and Its Influencing Factors: A Case Study in Fengcheng City

      2020, 57(4):834-843. DOI: 10.11766/trxb201904280083

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      Abstract:In Jiangxi Province, Fengcheng City is a typical area rich in soil selenium. Based on the data of the 699 soil samples collected from the surface layer (0-20 cm) of farmlands in Fengcheng City in 2015—2016, geostatistical analysis, correlation analysis and geographic detectors were applied to systematically analyze spatial differentiation of soil selenium in distribution and its influencing factors. The research was done in an attempt to provide certain valuable reference for conservation of soil selenium and the production function of the selenium-rich land. Results show that soil selenium contents of Fengcheng City ranged from 0.13 to 0.69 mg∙kg-1 with coefficient of variation being 27.27% or moderate in level and averaged 0.33 mg∙kg-1, about 1.14 times as high as the soil selenium background value (0.29 mg∙kg-1) of the country. Semi-variogram function analysis shows that the range of soil selenium was 12.86 km and quite large for spatial autocorrelation, and that its nugget effect value was 44.30%, which indicates that spatial variation of soil selenium was mainly affected by structural factors. In the spatial distribution, hot spot areas (area where high values concentrate) were distributed mainly in the west of Quangang Town, the southeast of Dongjia Town, the center of the Shangzhuang Neighborhood, the southwest of Shangtang Town, the northwest of Qujiang Town, the center and south of Luoshi Town and the southwest of Xiushi Town. Arsenic, copper, mercury, potassium oxide, calcium oxide, pH, soil parent material and elevation are factors affecting spatial variability of the soil selenium but vary in extent (P <0.05). Arsenic is the highest in the effect, explaining 29% of the variability, and plays an important role in the enrichment and migration of selenium in the topsoil of Fengcheng City.

    • Spatial Variability of Soil Nitrogen, Phosphorus and Potassium Availability in Coal Mining Subsidence Slopes

      2020, 57(4):844-854. DOI: 10.11766/trxb201906140170

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      Abstract:【Objective】In the central and northeastern parts of China (excluding the eastern part of Inner Mongolia Autonomous Region), coal mining has caused extensive land subsidence, thus leading to land damage and soil degradation, which in turn seriously affects grain production, and intensifies conflicts between people and land. The aim of this study was to explore mechanisms for soil nutrients, for instance, nitrogen (N), phosphorus (P) and potassium (K), migrating and transforming in coal mining subsidence slopes, and to provide certain scientific basis for comprehensive management of eco-environment in the mining areas. 【Method】The cultivated land and forest land in a coal mining subsidence, low in phreatic water level and typical of Jiulishan mining region in Jiaozuo City, Henan Province, China, were selected as object of the study. Soil samples were collected from soil layers (0-10 cm, 10-20 cm, 20-30 cm, 30-40 cm and 40~50 cm) of soil profiles distributed in different slope positions (center, bottom, middle, top and control) and lands different in land use for analysis of total contents and availabilities of N, P and K, and further for spatial variability of the indices. 【Result】It was found that in terms of nutrient spatial variability on the slope, the three soil nutrients followed an order of available P (118%) > available N (69%) > total N (41%) > available K (27%) > total P (19%) > total K (4%). Compared with the cultivated land, the forest land lowered significantly (P<0.001) in soil total P and available P, but ascended significantly (P<0.001) in soil available K. Along the subsidence slope, availabilities of soil N and K in the cultivated land was the highest at the depressed in the bottom of the slope, while that of soil P in cracky areas at the top of the slope. However, in the forest land on the slope, availabilities of soil N, P and K were the highest in the depressed zone at the bottom of the slope, and the lowest in the middle slope zone. The high spatial variability of soil nutrient availability therein could be explained by the following; 1) loss of dissolved organic N and available K from cultivated soils with surface runoff; 2) cracks enhancing soil redox potential in the farmland, thus promoting release of soil P; 3) translocation of available K with vertical leaching in the depressed zone at the bottom of the slope. 【Conclusion】Therefore, it is suggested that the land in such coal mining subsidence, low in phreatic water level, should be reclaimed in light of the rules of migration and transformation of soil nutrients and soil water relative to position along the subsidence slope. The cracky area on the top of the slope, the middle slope and the depressed at the bottom of the slope should be reclaimed into high-yield cultivated land or vegetable gardens, shrubbery and economic forest or orchard, respectively, so as to realize sustainable soil management and the goal of cost-minimizing input in land reclamation of coal mining subsidence.

    • Application of Le Bissonnais Method to Study Soil Aggregate Stability in Red Soils under Different Types of Vegetation

      2020, 57(4):855-866. DOI: 10.11766/trxb201905090099

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      Abstract:【Objective】Revegetation can improve stability of soil aggregates, whih are one of the key factors affecting soil quality and soil erosion resistance. In order to explore differences in aggregate stability in soils under different types of revegetation, and main mechanisms of aggregate destruction in red soil, a field experiment was carried out in the red soil region of South China. 【Method】Based on a long-term field experiment, which consisted of four plots under different typs of vegetation (Zoysia matrella, Vetiveria zizanioides, Indigofera amblyantha, and Amorpha fruticosa ) planted 5 years ago for revegetation, this experiment was oriented to explore soil aggregate stability in different soil layers (0~10 cm, 10~20 cm and 20~30 cm), with the Le Bissonnais (LB) method, including three treatments, i.e. fast wetting (FW), wet stirring (WS), and slow wetting (SW), and mechanisms of soil aggregate decomposition (dispersing, mechanical disturbing and clay swelling). 【Result】Results show: 1) the plots under Zoysia matrella and Vetiveria zizanioides were higher in organic matter content, porosity, owing to their better developed root systems, than the other two in different soil layers compared with Indigofera amblyantha and Amorpha fruticosa. The difference between the four platns was especially significant in the section of fine roots (diameter less than 2 mm), which made up the majority of the root system, accounting for 99.53%~99.81%, 98.83%~99.39%, 95.56%~98.99%, and 86.26%~94.85% in the plots under Zoysia matrella, Vetiveria zizanioides, Indigofera amblyantha, and Amorpha fruticosa, respectively; 2) in terms of mean weighted diameter (MWD) and percentage of >0.25 mm aggregates in the soils after three aggregate destructive tests, the four plots exhibited an order of Zoysia matrella > Vetiveria zizanioides > Indigofera amblyantha > Amorpha fruticosa, which suggests that the soil aggregates in the plots under herbs (Zoysia matrella and Vetiveria zizanioides) were higher in stability than the plots under shrubs (Indigofera amblyantha and Amorpha fruticosa ). It is therefore assumed that type of vegetation has a significant impact on soil aggregate stability; 3) organic matter, bulk density, sand content and root parameters all had significant influences on soil aggregate stability, especially fine roots with diameter ranging from 0.5 to 2 mm, which is key to soil aggregate stability; and 4) in terms of percentage of >0.25 mm aggregates in the plots subjected to destructive tests, an order of FW < WS < SW was observed in the plots of Zoysia matrella and Amorpha fruticosa, and one of FW < SW < WS in the plots of Vetiveria zizanioides and Indigofera amblyantha. The percentages of >0.25 mm aggregates varied in the range of 50.45%~79.59% in the four plots subjected to FW test, lower than that in the plots subjected to WS or SW tests. The MWD of soil aggregates ranged from 1.21 mm to 1.83 mm in the soils subjected to WS test and from 1.81 mm to 2.36 mm in the soils subjected to SW test, indicating the aggregates in the soils were stable ones, while it ranged from 0.39 mm to 1.21 mm in the soil subjected to FW test, much lower than that in the former two, indicating that the aggregates were unstable ones. Therefore it could be assumed that FW is the most destructive to soil aggregates and that dispersion is the primary mechanism of soil aggregate decomposition. 【Conclusion】Herbs are more effective than shrubs in improving soil structure stability, and FW test is a better method to evaluate soil aggregate stability in this region. All the findings in this experiment may serve as reference for researches on soil aggregate stability and choices of plant species selection for revegetation in this region.

    • Estimation of Soil Electrical Conductivity Based on Spectral Index and Machine Learning Algorithm

      2020, 57(4):867-877. DOI: 10.11766/trxb201902190024

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      Abstract:【Objective】Soil salinity is an important indicator for evaluation of soil salinization in arid regions. It is of great practical significance to grasp real-time information about salinization to disaster prevention, ecology stabilization and harmonization of human-land relationship in this area. 【Method】A total of 400 soil samples were collected from the Weigan River-Kucha River Delta Oasis in the Xinjiang Uygur Autonomous Region of China in October 2017, and prepared, separately, with distlled water into suspensions, 5:1 in ratio, from which soil extracts were obtained for analysis of electrical conductivity (EC) and VIS-NIR (visible-near infrared) spectral reflectances in the laboratory. Based on the obtained data and the Monte Carlo cross validation (MCCV), 364 samples were determined to be valid. After the raw spectrum reflectances (R) were pre-processed with differential, absorbance (Abs), continuum removal (CR) and three others, 21 spectal indices were selected and established. Then based on the 21 optimal spectral indices, EC was assessed using the back propagation neural network (BPNN), support vector machine (SVM), and extreme learning machine (ELM), compared to the partial least squares regression (PLSR), and validated with its root mean square error (RMSE), determination coefficient (R2) and ratio of performance to interquartile range (RPIQ). 【Result】Results show: the 21 optimal spectral indices based on R and its pretreated data are R_NDSI(R2006, R2257), R_DSI(R1882, R2010), R_RSI(R2006, R2257), R_FD_NDSI(R1376, R2142), R_FD_DSI(R1376, R2142), R_FD_RSI(R1913, R2142), R_SD_NDSI(R416, R2470), R_SD_DSI(R894, R1373), R_SD_RSI(R689, R2355), ABS_NDSI(R2005, R2168), ABS_DSI(R2006, R2257), ABS_RSI(R2006, R2168), ABS_FD_NDSI(R876, R2490), ABS_FD_DSI(R1376, R2123), ABS_FD_RSI(R1913, R2142), ABS_SD_NDSI(R1081, R1725), ABS_SD_DSI(R858, R1374), ABS_SD_RSI(R709, R2355), CR_NDSI(R2119, R2261), CR_DSI(R2119, R2261), and CR_RSI(R2119, R2261), among which R_FD-RSI (R1913, R2142) is the optimal (r= 0.649) one. Compared with the PLSR, the machine learning algorithm (MLA) could significantly improve accuracy of the model, with the R2 increased by 34.55%. Among the three models using the machine learning algorithm, ELM was the best (R2 = 0.884, RMSE = 3.071 mS?cm-1, RPIQ = 2.535). 【Conclusion】In this study, different spectral pretreatment methods were used to obtain 21 optimal spectral indices. In constructing the spectral indices in this study, besides considering the remote sensing mechanism, it is advisable to explore in depth more implicit information. Compared with the traditional linear model, the MLA-based soil EC estimation model is obviously higher in accuracy. All the findings in this study may serve as a scientific reference for quantitative estimation of soil salinity in arid regions.

    • Effect of Customized Organic Manure Improving Mineralization and Nitrification of Soil N in Yellow Soil of Guizhou

      2020, 57(4):878-886. DOI: 10.11766/trxb201905310087

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      Abstract:【Objective】Soil nitrogen is an important factor in producing quality tobacco leaves. About 2/3 of the nitrogen absorbed by tobacco during its whole growth period is in the form of mineralized nitrogen. So, nitrification ratio of the nitrogen in tobacco planting soil is the key to the production of high quality tobacco. Rational application of organic manure can regulate mineralization of soil N of all forms. The aim of the study is to determine a reasonable rate for application of specialized organic manure in yellow soil in Guizhou, and to improve nitrification rate in the tobacco planting soil so as to improve quality of tobacco leaves. 【Method】In this study, samples of the yellow soil collected from Guizhou were used in an incubation test with the Stanford long-term aerobic and intermittent leaching incubation method. The test was designed to have 4 treatments, i.e. CK(0 kg•hm-2), 1F (750 kg•hm-2), 2F (1500 kg•hm-2) and 3F (2250 kg•hm-2) in terms of application rate of customized organic manure, to simulate the process of soil nitrogen mineralization. And during the incubation test, a portion of each sample in each treatment was rinsed on D0, D5, D15, D30, D45 and D60, separately, for determination of nitrification ratio. Compared with common organic manure, the specialized organic manure was higher in concentration of available nitrogen, reaching up to 41.3%.【Result】Results show that the content of mineral nitrogen, regardless of form, increased with the incubation going on during the incubation period. Mineralization was dominated by nitrate nitrogen at the early stage. After 5 days of incubation, NH4+ -N turned up in dominancy. With the incubation going on, nitrate nitrogen was being mineralized. After D5, the nitrification rate of soil nitrogen in the yellow soil dropped below 10%. The proportion of nitrate nitrogen in the release of soil N was seriously lower in the late growth period. The total amount of NO3--N the soil could supply during the prime growing season of the plant reached only up to 66.89 mg•kg-1, which was far from enough to meet the demand of the crop for nitrogen throughout the growing season. Once the customized organic manure was applied, soil nitrogen mineralization showed a trend of “fast first and then slow”. So soil nitrogen mineralization was high during the initial period, and then the release of mineral nitrogen reduced and levelled off at the late stage, which is in consistence with the rule of nitrogen absorption by tobacco for its growth. The application of customized organic manure increased the content of soil readily available nitrogen through mineralization significantly or even by 420.1%, the content of NO3--N by 276.6%,and nitrification ratio 8.1% to 50.4%. In Treatment 3F (2250 kg•hm-2), soil nitrification rate ranged from 43.69% to 51.22%, which was the most conducive to quality of the tobacco. It was found that NO3--N content and total available nitrogen mineralization capacity of the organic manure increased with rising organic manure application rate. 【Conclusion】Application of the specialized organic manure at a high rate increases nitrogen supply capacity of the soil, promotes mineralization of NO3--N and improves nitrification rate. Especially when the application rate reaches up to 2 250 kg•hm-2 as is in Treatment 3F, nitrification rate in the soil increases during the tobacco growing period, which is conducive to improvement of quality of the tobacco. In the tobacco growing season, application of the specialized organic manure can ensure stable release of available nitrogen and improve the nitrification rate, which is the most suitable condition for growth of tobacco plants. In conclusion, application of 2 250 kg•hm-2 of the organic manure is the most suitable rate for tobacco cultivation in the yellow soil area of Guizhou.

    • Cations Exchange and Its Effect on Acid Buffering Capacity of Acid Purple Soil

      2020, 57(4):887-897. DOI: 10.11766/trxb201905050146

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      Abstract:【Objective】Purple soil is a key soil resource for development of the agriculture Southwest China. A proportion of the purple soil has been somewhat acidified. A better understanding of the composition of exchangeable cations in acid purple soil and its influence on subsequent acidification processes of the soil is conducive to potential acidification risk assessment of the soil. 【Method】In this study, a total of 38 acid purple soil samples were collected from Hechuan District, Chongqing Municipality for analysis of physico-chemical properties and determination of acid buffering capacity. Acidification degree of the purple soil samples was evaluated based on their respective pH values and content of exchangeable acidity. Comparison between the samples of purple soils and some zonal soils (Alfisol, Ultisol, and Oxisol) was performed in content of exchangeable bases and cation exchangeable capacity (CEC). And then, contributions of minerals to base cations and CEC were discussed in detail. In the end, effects of exchangeable cations on acid buffering capacity of the purple soils were analyzed.【Result】Some of the soil samples, about 65%, show that the purple soil was acidified seriously with soil pH being < 5.5. Fortunately, the portion of acidified purple soil was still quite high in content of exchangeable base cations and cation exchange capacity (CEC), with Ca2+ being the highest in content ((13.3±5.27) cmol·kg-1), and K+, Na2+ and Mg2+ being (0.267±0.190), (0.196±0.116), and (3.91±1.15) cmol·kg-1, respectively. The average content of exchangeable base cations was 11.8 times as high as the content of exchangeable acidity, even though the highest content of soil exchangeable acidity in the purple soil reached up to 6.40 cmol·kg-1. Compared to the acid soils developed in the subtropical and tropical regions of China, the acid purple soil was significantly higher in CEC than Untisol and Oxisol. The content of exchangeable Ca2+ and Mg2+ in the purple soil was 5.9 and 3.9 times as high as that in Ultisol. In terms of soil minerals, the purple soil was dominated with quartz, mica, K-feldspar, albite, montmorillonite, illite, kaolinite and hematite. The abundant clay minerals, especially montmorillonite, increased the amount of surface negative charge of the purple soil and, correspondingly, enhanced adsorptive ability of the purple soil for base cations. And intensified weathering of the soil replenished the soil with base cations, thus stabilizing soil pH. Further analyze of content of organic matter in the purple soil shows that the purple soil was much lower than Alfisol, Ultisol, and Oxisol in content of organic matter. As a consequence, the minerals in the soil were the main contributors of surface charges in the purple soil. Acid buffering capacity of the purple soil varied in the range of 3.18- 25.6 mmol·kg-1·pH-1, and was significantly and positively related to exchangeable bases and CEC in the soil, which means a high content of base cations and CEC helps enhance soil acid buffering capacity, thus retarding acidification of the purple soil.【Conclusion】Though the purple soil in some areas is quite serious in acidification, as affected by its soil forming parent materials and weathering degree of the soil, the soil has an abundance of base cations, which help retard the process of soil acidification. These are the characteristics of soil acidification of the purple soil relative to the acid soils in other areas.

    • Influence of Mn-doping on Structure and FT-IR Properties of Crystalline Iron Oxides

      2020, 57(4):898-907. DOI: 10.11766/trxb201901110021

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      Abstract:【Objective】 Manganese (Mn) doping may affect iron oxide in structure and property, and then influence its performance in adsorption, catalysis and so on, especially its utilization in soils and environment. However, it is still little known about the detailed influence of Mn2+ doping in microstructure owing to complex hydrogen bonding and similar chemical bonding of the iron oxide crystallines. 【Method】 In this study, samples of crystalline iron oxides (CIO) and samples of Mn2+ doped CIO different in molar ratio (R) (CIO-Mnx, x=0.1, 0.2, 0.3 and 0.5, separately) were prepared out of goethite and hematite. Influences of Mn2+ doping on iron oxide in crystal structure and morphology were analyzed with the aid of XRD and TEM. Peak fitting was performed of the two wave number ranges, high (3 000-3 700 cm-1) and low (450-750 cm-1) of the FT-IR graphs of the samples, and changes in hydroxyl functional group and crystalline chemical bonding of Mn2+-doped CIO were analyzed. 【Results】 Results show that Mn2+-doping just inhibited the formation of CIO, such as goethite and hematite, when R was less than 0.3, but promoted the formation of Mn-doped magnetite, some goethite and no visible hematite, when R was 0.5. In the CIO samples existed four types of hydroxyls, that is free hydroxyls, adsorbed hydrohydroxyls, surface associated hydroxyls and structural hydroxyls. With R rising from 0.1 to 0.3, relative content of the first two types decreased, while the latters increased. Adsorption peaks of the free hydroxyls and structural hydroxyls red shifted with Mn2+ doped, but those of adsored hydrohydroxyls decreased and those of surface associated hydroxyls behaved on the contrary when R increased from 0.1 to 0.3. When R was 0.5, structural hydroxyls almost disappeared, relative content of the surface associate hydroxyls varied between that of CIO and that of CIO-Mnx, and wavenumber of the adsorption band of surface associated hydroxyls was close to that of the CIO sample. Intensity and shape of the adsorption peaks of crystal structure Fe-O around 455 cm-1 and 619 cm-1 were related to the morphology of goethite, and those of the adsorption peaks around 478 cm-1 and 560 cm-1 were to the crystallinity of hematite. Intensity and wavenumber of the adsorption peak of hematite at 560 cm-1 decreased when R increased from 0.1 to 0.3, and adsorption peaks at 478 cm-1 disappeared with Mn2+ doped. When the R was 0.5, adsorption peaks almost disappeared at 543 cm-1, widened and intensified at 474 cm-1 and 593 cm-1, and remained the same as that of CIO at 619 cm-1. According to analysis, the vacant sites for cations in the structure of hematite in CIO-Mnx samples might get coupled with Mn2+ to form adsorption peaks around 567~589 cm-1, of which intensity increased with rising R. In CIO-Mn0.5 samples, Mn-doped magnetite formed with Mn2+ replacing Fe2+, thus forming a lattice vibrated Mn-O adsorption band around 593 cm-1. 【Conclusion】 According to the results of the study for CIO and CIO-Mnx, a spot of Mn2+ inhibited the crystallization of CIO, which increased the varieties of hydroxy on the surface of CIO-Mnx and changed the composition of hydroxyl in the samples. That the Mn2+ replaced the Fe3+adsorbed at vacancies in CIO caused a strong absorption around 567~589 cm-1 in IR spectra. But the mass of Mn2+doping could change the CIO from goethite and hematite to Mn-doped magnetite, which appeared the different FT-IR characterizations of hydroxyl and crystalline structure.

    • Distribution and Composition of Microplastics in Sediments in the Estuaries of the Ganjiang River Leading into Lake Poyang

      2020, 57(4):908-916. DOI: 10.11766/trxb201901080016

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      Abstract:【Objective】Microplastics contamination is an aggravating environmental problem threatening the marine ecosystem, where it has spread globally even to the remotest habitats. Extremely small in particle size (<5 mm), microplastics have been found in high density in waters and sediments, and are interacting with organisms and the environment in a variety of ways. Microplastics in the environment have the characteristics of being extremely small in particle size, hydrophobic, and capable of carrying persistent organic pollutants (pops). A wide range of marine organisms have been found to have ingested microplastics by mistake as food, thus leading to loss of nutritional value of diet, physical damage and exposure to pathogens. In addition, microplastics are ready to adsorb toxic hydrophobic organic contaminants, which arouses the question of what risk of chemical exposure aquatic biota faces from microplastic-associated contaminants. Moreover, the presence of marine microplastics in seafood could pose a threat to food safety for mankind. 【Method】The Nanji National Nature Reserve, and the estuaries of the northern branch, the mid branch as well as the southern branch of the Ganjiang River were selected as objects of this study. Sediment samples were collected from 12 sampling sites for isolation of microplastics therein by flotation separation, and exploration of distribution and composition of the microplastics in the sediment. Data were analyzed with one-way ANOVA. 【Result】Results show that in terms of microplastics abundance in the sediment, the four regions appeared to follow an order of the mid branch > the southern branch > Nanji > the northern branch, varying in the range of 1 452±221 ind•kg-1, 1 285±69 ind•kg-1, 102±65 ind•kg-1 and 11±6 ind•kg-1, respectively. Microplastics abundance in the sediment varied with water regime of the regions, exhibiting an order of dry season > normal season > rainy season. The microplastics in the sediment were dominated with foam, and then fiber in of Naji, mainly with fibre in the northern branch, and mainly with fragments in the middle and southern branches, accounting for more than half of the total amount of microplastics. Microplastics in the sediment were mostly 2~3 mm in particle size, and some 3~4 mm in Nanji and mostly < 1 mm in the branches, which making up more than half of the total microplastics. The microplastics in the Ganjiang River varied in particle size and displayed an order of <1 mm > 1~2 mm > 2~3 mm > 3~4 mm > 4~5 mm in particle size composition. The larger in particle size, the smaller in proportion. The microplastics differed greatly with type in surface morphology and roughness. Fragment microplastics were various in color and shape, with rough surface and obvious signs of wear. Fiber microplastics were smooth, linear and mostly blue in surface. Foaming microplastics were mostly white, light in texture and various in shape. Film microplastics were smooth, soft and irregular. There was great variability in composition of microplastics with type. The microplastics in the Ganjiang River were composed mainly of polyethylene and polypropylene. 【Conclusion】 Microplastics abundance is closely related to human activities, and the microplastics in the Ganjiang come mainly from the decomposition of daily plastics supplies and packaging, such as fertilizer and cement bags. Overall, all the findings in tthis study provide strong evidence of the high levels of microplastics pollution in the Poyang Lake, and suggest that more attention should be paid to monitoring microplastics pollution of the Poyang Lake.

    • Effects of Nutrient Management on Soil Fertility and Tea Quality in Anxi Tea Plantation

      2020, 57(4):917-927. DOI: 10.11766/trxb201904300148

      Abstract (1501) HTML (863) PDF 2.64 M (1734) Comment (0) Favorites

      Abstract:【Objective】Tea is the most important non-alcoholic beverage crop in the world. To meet increasing demand of the market, tea production is intensified through nutrient management. Anxi County in China is one of the main regions producing famous oolong tea—Tieguanyin, where lagging nutrient management is the bottleneck of tea production. This study aims to provide a scientific basis for nutrient management in Anxi tea plantations, through comprehensive analysis of effects of nutrient management modes on plantation soil fertility and tea leaf quality. 【Method】 In 2015, tea and soil samples were collected from 50 representative tea plantations in the ten major tea production towns of Anxi County, including 150 fresh tea leaf samples, 50 surface soil samples (0-20 cm) and 46 profile soil samples (top: 0-20, mid: 20-40, sub: 40-60 cm). The soil samples were air-dried and ground for determination of soil pH, organic matter (OM), alkali nitrogen (AN), available phosphorus (AP) and available potassium (AK), the five indices set as soil fertility parameters in this study, and the tea leaf samples were analyzed on UPLC-MS (ultra-high performance liquid chromatography coupled with triple quadruple mass spectrometry) for determination of contents of nine main tea-quality-related secondary metabolites. By N fertilization rate, the 50 tea plantations were tentatively divided into three groups: low, moderate and excess. 【Result】 Based on the division, restricted principal axis analysis shows that nutrient management significantly explained 34.4% of the overall differences in topsoil fertility between the tea plantations (P<0.001), which further confirmed that the classification by N fertilization rate could represent the comprehensive level of nutrient management of a tea garden. The tea plantations of the moderate group significantly differed from those of the low and excess groups in soil fertility in the top and mid soil layers, but did not so obviously in the sub soil layer. Nutrient management had the most significant effect on AP among the five soil fertility indices in the topsoil, which was followed by AK, AN and OM, and excess fertilization resulted in severe soil acidification. Further analysis shows that nutrient management significantly affected tea quality and explained 7.48% of the differences in the comprehensive tea quality between the groups (P<0.001). The tea leaves from the plantations of the moderate group were the high in content of secondary metabolites, and so the best in tea quality. 【Conclusion】 On the whole, nutrient management does not only affect soil fertility in the tea plantations in Anxi, but also influence quality of the Tieguanyin produced therein. Either excess or less fertilization is not suitable for production of high quality tea leaves. A proper N fertilizer application rate for high-quality tea production in Anxi tea region is recommended to be 200-400 kg·hm-2·a-1.

    • Effect of Boron Application on seed yield and quality of Direct Sown Winter Rapeseed ( Brassica napus L.) in Red Soil Region

      2020, 57(4):928-936. DOI: 10.11766/trxb201905280207

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      Abstract:【Objective】The red soil region, known as a prominent rapeseed growing area in China, normally coincides with low soil pH and light texture, and hence susceptibility of leaching loss of available boron, thus resulting in boron deficiency in the soil . Rapeseed, being a high boron demanding crop, is very sensitive to boron (B) deficiency. With rapid development of the society and changes in structure of the rural labor, direct sowing of rapeseed is developing and expanding in scale and area rapidly. However, almost nothing has been done on effects of direct sowing on sensitivity of the rapeseed to boron deficiency and their mechanisms. therefore large-scaled field experiments was laid and carried out in this region in an attempt to explore effects of boron fertilizer application on yield, seed quality and economic benefits of the crop and then to provide a reasonable guidance for B management in the production of rapeseed in the red region. 【Method】During the 2017—2018 growing season, seven field experiments designed to have four treatments each in B application rate: (1) B0 (without boron fertilizer); (2) B4.5 (4.5 kg boron fertilizer hm-2); (3) B9.0 (9.0 kg boron fertilizer hm-2); (4) B13.5 (13.5 kg boron fertilizer hm-2 ), were carried out in Jiangxi, Hunan, South Hubei and North Guangxi. The boron fertilizer used is a specialized slow release boron fertilizer pelletized the size of a seed and containing 10% of B. The boron fertilizer was mixed with seeds and sown together (6 kg·hm-2). 【Result】Boron application significantly increased rapeseed yield at all the experimental sites, and the increment decreased with rising soil available boron content, and peaked in Treatment B9.0, which was1 021 kg·hm-2 or 110.6 % higher in yield and 4 938 yuan·hm-2 higher in economic profit than Treatment B0 . However, the application of boron fertilizer at a higher rate did not have much effect on yield or biomass of the crop. A similar pattern, but lower in magnitude, was observed with shoot biomass. It was also found that boron application significantly improved economic indices of the crop, such as harvest intensity, number of grains per pod, number of pods per plant, and contents of oil, oleic acid and linoleic acid of the seed, except for the indices of thousand grain weight and protein content in the seeds. So it is quite obvious that boron application increases oil yield and improves quality of the harvest of the direct seeding crop. Boron application increased boron content in all the parts of the plant at the manuring stage, especially in pod shell and stem. Boron accumulation in the stem, pod shell and seed could reach up to 79.5%, 244.2% and 125.6% in the treatments applied with boron than in the treatment applied with no boron. Treatment B9.0 was the highest in seed yield, but its boron fertilizer recovery rate was only 9.4%, which suggests that utilization efficiency of the applied boron fertilizer was still very low and a large proportion of lost via leaching and surface runoff owing to low soil pH and light texture. 【Conclusion】As the soil in the red soil region is very low in soil available boron content, boron application shows a significant yield increasing effect on direct sown rapeseed Boron application increases seed yield by increasing its per-plant productivity and harvest density of direct sown rapeseed, which is more sensitive to boron deficiency than transplanted rapeseed. Boron application also improves quality of the seeds and increases contents of oil, oleic acid and linoleic acid. Though the practice of boron application is still quite low in apparent utilization efficiency, it does promote boron adsorption and accumulation of the direct sown rapeseed crops. Considering seed yield and quality, economic profit and boron fertilizer utilization efficiency in all, the boron application rate of 9.0 kg·hm-2 is recommended as the optimal practice of boron fertilization in the red soil region.

    • Temporal Variation of Soil Organic C and Nutrients in High Yield Paddy Soils of Yujiang County in the Past 40 Years

      2020, 57(4):937-942. DOI: 10.11766/trxb201904180202

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      Abstract:【Objective】Soil organic carbon and nutrients are important indicators of soil fertility. The study on rules of the temporal variation of soil fertility is of important theoretical guiding significance to improving soil fertility and maintaining sustainable development of the agriculture. 【Method】Based on the data of the Second National Soil Survey in 1980 and the soil sampling in 2002, soil samples (0-15 cm) were collected from three soil layers (0-10, 10-20 and 20-40 cm) at the same 26 sampling sites in paddy fields of Yujiang County in 2017 for analysis of soil organic carbon, nutrients, pH and CEC, and comparison was performed for rules of the variation of soil fertility in the past 40 years. 【Result】 The contents of organic carbon, total nitrogen, available phosphorus and available potassium in the upper surface paddy soil (0-10 cm) in Yujiang County was (27.3±1.3) g·kg-1, (2.9±0.2) g·kg-1, (40.5±3.8) mg·kg-1 and (148±7.9) mg·kg-1, respectively. Compared with the data in 1980, organic carbon and soil nutrients have significantly improved; especially organic carbon, total nitrogen and available potassium in the 0-10 cm soil layer of the paddy fields have increased by 35%, 40% and 34%, respectively, in the past 15 years since 2002. The available phosphorus content in the 0-10 cm soil layer did not change much, while it did increase by 56% in the 10-20 cm soil layer. Compared with the data obtained in 2002, pH in the 0-10 cm, 10-20 cm and 20-40 cm soil layers decreased significantly, while CEC did reversely.【Conclusion】Long-term paddy cultivation applied with chemical fertilizer significantly increased soil organic carbon, nutrients and CEC, but decreased soil pH, especially in the past 15 years.

    • Effects of Chinese Fir Litter and its Biochar Addition on Mineralization of Native Soil Organic Carbon

      2020, 57(4):943-953. DOI: 10.11766/trxb201906040226

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      Abstract:【Objective】 Understanding of how soil organic carbon (SOC) mineralization in response to management practice and environment change is crucial for mitigating greenhouse gases emission and minimizing the impacts of forest ecosystems on climate. However, there is little information available about relationship of SOC mineralization with quantity of extraneous carbon. In this experiment, effects of addition of Chinese fir litter and its biochar (BC), on native SOC mineralization were investigated to provide certain scientific basis for building up soil fertility in Chinese fir plantations and utilizing biomass resources efficiently in subtropical China. 【Method】 In this study, soil samples (0-20 cm topsoil layer) were collected from the Cunninghamia lanceolata plantation at the Wanmulin Nature Reserve of Fujian Province. 13C-labeled litter (Chinese fir) and its biochar (pyrolysed at 350°C) were used as two different types of extraneous carbon (an easily decomposable carbon and a relatively stable carbon) in the indoor incubation experiment. The experiment consisted of 11 treatments, i.e. S (soil without any addition), SL1 (soil added with 10 g·kg-1 litter), SL2 (soil added with 20 g·kg-1 litter), SL3 (soil added with 30 g·kg-1 litter), SL4 (soil added with 40 g·kg-1 litter), SL5 (soil added with 50 g·kg-1 litter), SB1 (soil added with 10 g·kg-1 BC), SB2 (soil added with 20 g·kg-1 BC), SB3 (soil added with 30 g·kg-1 BC), SB4 (soil added with 40 g·kg-1 BC) and SB5 (soil added with 50 g·kg-1 BC). The carbon derived from different sources was distinguished with the 13C isotope technique. The soil samples were incubated at 25°C with water holding capacity kept at 60% for 28 days. 【Result】Results show that the addition of either litter or BC significantly increased the cumulative amount of CO2, and the effect of the litter treatments was more obvious than that of their corresponding BC treatments. Cumulative CO2 derived from added litter or BC and native SOC increased with increasing quantity of the extraneous carbon. After 28 days of incubation, 5.71%-13.68% of the litter carbon (LR-C) was decomposed, whereas only 0.34%-0.50% of the biochar carbon (BC-C) was, and 6.42-13.58 times and 2.06-3.94 times as much of the native SOC in the litter and BC treatments, respectively, as that in Treatment S was decomposed. Regression analysis shows that there was a significant linear relationship between native SOC decomposition rate and quantity of the extraneous carbon added (P<0.01). LR-C decomposition rate was positively related to addition rate of the extraneous carbon, while BC-C decomposition rate displayed a significant parabolic relationship (P<0.05) and peaked when the addition rate was 10 g·kg-1 (Treatment SB1). 【Conclusion】 Addition of litter and BC accelerated mineralization of native SOC and the effect increased with addition rates. Compared with decomposition of litter, that of BC was less affected by microbial activity due to its lower bioavailability and higher stability in the tested soil during the short incubation period. Therefore, it may be a management practice more conducive to enhancing soil carbon sequestration of the plantations in this region, to return biochar into the soil.

    • Effects of Litter Carbon, Nitrogen and Enzyme Activity in Soil under Chinese Fir

      2020, 57(4):954-962. DOI: 10.11766/trxb201808060408

      Abstract (1825) HTML (658) PDF 559.34 K (1837) Comment (0) Favorites

      Abstract:【Objective】Climate change triggers variation of soil net primary productivity, which are likely to affect litter input to forest soil. Litter is an important source of nutrients for plants and soil microorganisms in forest ecosystems and may also alter stocks and cycling of soil carbon (C) and nitrogen (N). However, so far little has been found in the literature about responses of soil C and N to litter input in subtropical forests. This study aims to understand how soil C and N respond to increased litter input in a Chinses fir plantation in South China, caused by climate change. 【Method】In this study, a four-year field experiment, designed to have two plot, Plot A with litter kept on the soil and Plot B with litter removed, was carried out in a Chinese fir plantation in South China. Soil samples were collected from the plots at the end of the experiment and analyzed for soil C and N and their isotopes (δ13C, δ15N), enzyme activity microbial biomass C and N (MBC, MBN), as well as N-acquiring enzymes. 【Result】Results show that Plot A significantly increased activity of soil N-acquiring enzyme activity (β-N-acetylglucosaminidase) and hence accelerated decomposition of soil organic matter. Therefore it was found that litter triggered decline of soil ammonium, nitrate N and DON, but barely affected soil MBC and MBN, which is probably because litter intensified the competition of microbes with plants for soil N, so soil microbe released more N-acquiring enzyme to meet their demand for N. In Plot A phenol oxidase and peroxidase increased in activity,while in Plot B they decreased in activity, which indicates that soil microbes tend to decompose Chinese fir litter rather than soil organic matter as energy to acquire N. In Plot A soil organic C and dissolvable organic C did not vary much, which indicates that litter does not have much impact on carbon in the soil. Litter did not have much impact on soil δ13C either, but did, by significantly increasing soil δ15N. Soil δ15N is an indicator of openness of soil N system. The higher the soil δ15N, the more open the soil N system, the more likely the occurrence of N loss, which indicates that litter accelerates soil N mineralization and loss. Besides, it was also found that in Plot B β-glucosidase and cellulolytic enzyme declined in activity, which indicates that litter removal may downregulate soil C recycling rate. 【Conclusion】Based on the findings of the experiment, it could be concluded that 1) litter significantly affects soil N, but not soil C, which indicates that soil N is more sensitive to changes in litter input than soil C; 2) Litter may alter the soil microbial environment of the Chinese fir plantation and enhance root growth and N uptake of the plant, thus leading to intensified competition between soil microbes and plants for soil N and decline of soil N in content; 3) As Chinese fir litter is high in C/N, soil microbes need to excrete more soil phenol oxidase and peroxidase activity to decompose fresh litter for energy to compete for soil N. Therefore, climate changes cause variation of litter production in Chinese fir forest, which in turn produces different impacts on recycling of soil C and N, thus disturbing balance of soil C and N in subtropical coniferous forests.

    • Responses of Soil Organic Carbon Dynamics and Microbial Community Structure to Organic Nitrogen Fertilization in the Temperate Needle-broadleaved Mixed Forest

      2020, 57(4):963-974. DOI: 10.11766/trxb201908130350

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      Abstract:【Objective】Carbon (C) and nitrogen (N) cycles in terrestrial ecosystems are closely coupled and reflect the flow of energy and nutrients, respectively. Elevated atmospheric N deposition increases, decreases, or does not affect vegetation and soil C storages across ecosystems and studies. Moreover, the efficiency of C sequestration caused by N amendment varies widely. There is a great uncertainty in the response direction and the magnitude of C sequestration. Soil organic carbon (SOC) transformation and C storage dynamics in forest ecosystems are specific to the increase in atmospheric N deposition, depending on soil initial N status, type, rate, and duration of N fertilization. In the past decades, related research mainly focused on the effect of inorganic N deposition. It is still unclear how organic N deposition affects the SOC and its components in the temperate needle-broadleaved mixed forest. There is few research exploring microbiological mechanism responsible for the change of SOC under N enrichment. The objectives of this research were: (1) to investigate whether multiple levels of N addition significantly changes the C concentrations of bulk soil and different physical fractions, microbial biomass and community structure, as well as general soil properties; (2) to estimate the N critical loads for the alteration of soil C and N concentrations in the temperate needle-broadleaved forest; and (3) to explore the potential linkages between changes in SOC concentration and microbial community abundance. 【Method】In this paper, the in-situ urea fertilization experiment with four levels (0, 40, 80, and 120 kg•hm-2•a-1,N) was set up in the Changbaishan temperate coniferous and broad-leaved mixed forest. After fertilization for three years, soil samples in 0—10 cm mineral layer were collected to determine the soil C and N concentrations, percentage of soil aggregates and SOC content of different particle sizes. The relative abundance and community structure of soil microorganisms were determined using phospholipid fatty acid (PLFA) technique. The relationships between changes in SOC content and changes in microbial community were explored. 【Result】The results showed that three years of N fertilization significantly increased the contents of NO3--N, DON, and TN in soils, and soil acidification was significant. Although N fertilization did not significantly increase SOC content in the surface soil, it significantly increased the contents of labile SOC fractions (particulate organic C and aggregate associated organic C) by 27.5% to 96.3%, resulting in the accumulation of SOC fractions. The critical load of N deposition is estimated as 80 kg•hm-2•a-1. The change in SOC content (ΔSOC) was positively correlated with the change in aggregate associated organic C and particulate organic C. Except for aerobic bacterial abundance, N fertilization did not change the abundance of microbial groups, but significantly changed the structure of microbial community, G+/G- ratio increased while aerobic/anaerobic ratio decreased. There was a significant correlation between labile SOC content, soil aggregates and microbial PLFA abundance, suggesting a close relationship between microbial community structure and SOC accumulation and stability. 【Conclusion】The above results indicate that organic N enrichment tends to promote the formation of soil aggregates in the temperate needle-broadleaved mixed forests, produce anaerobic microenvironment, change microbial community structure, and thereby lead to soil carbon accumulation. Our results suggest that atmospheric N deposition rate below the threshold could lead to a slow accumulation of SOC in the temperate mixed forest over the short term.

    • Community Structure of Burkholderiales and Its Diversity in Typical Maize Rhizosphere Soil

      2020, 57(4):975-985. DOI: 10.11766/trxb201901040008

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      Abstract:【Objective】Under the class β-proteobacteria, Burkholderiales is a kind of Gram-negative bacteria, characterized physiologically as strict aerobic, facultative anaerobic and obligate anaerobic chemoheterotrophic types, and composed mainly of Burkholaceae, Oxalobacteriaceae, Alcaligenaceae, and Comamonadaceae in taxonomy. In rhizospheric environment, Burkholderiales is an important group of pro-growth bacteria that can promote growth and development of plants. It can not only promote plant growth by producing phytohormones, but also improve the environment in which plants grow via nitrogen fixation, nodulation and phosphorus solubilization. Studies, so far accomplished, have demonstrated that soil physicochemical properties, soil pH, soil type and fertilization can affect the community structure and composition of Burkholderiales, but failed to address variation of the effects with soil type and its potential relationship with crop yield.【Method】In this study, 16S rRNA high-throughput sequencing of Burkholderiales was performed with a pair of specific primers. Based on the findings, responses of Burkholderiales to nitrogen, phosphorus and potassium fertilization (N, P and K) in community structure and of the maize crops in three different types of agricultural soils (phaeozem, cambisol and acrisol) in shoot biomass and yield were investigated.【Result】Results show that application of chemical fertilizer did not affect much richness and diversity of the Burkholderiales in the three types of soil, as compared to the unfertilized plot. Moreover, three taxa of bacteria, i.e. Oxalobacteraceae, Comammonadaceae, and Burkholderiaceae, were detected at the family level of Burkholderiales. And Oxalobacteraceae was the dominant group. In addition, fertilization markedly increased relative abundance of the Burkholderia (mainly Burkholderia spp.) and Massilia (mainly Massiliaspp. and Massilia sp. WG5) in the cambisol low in organic matter (P<0.01), while it significantly increased relative abundance of the Herbaspirillum (mainly Herbaspirillum sp. ZM319), but decreased that of the Noviherbaspirillum (mainly Noviherbaspirillum spp.) (P<0.01) in acidic acrisol. However, it did not affect much the relative abundance of all detected groups of Burkholderiales in the phaeozem high in soil organic matter and nutrient. Pearson correlation analysis and canonical correspondence analysis (CCA) indicates that nutrient (such as AP and AK) content and soil pH are the main factors affecting the community composition and structure of these bacteria (Burkholderia, Massilia, Herbaspirillum and Noviherbaspirillum). Furthermore, linear regression analysis and Mantel test shows that only the relative abundance of Massilia is significantly correlated with the shoot biomass and yield of maize (P<0.05). All these statistical analyses demonstrate that changes in community structure of Massilia may affect shoot biomass and yield of the crop. 【Conclusion】 This study indicates that although chemical fertilization is the main cause of the increase in shoot biomass and yield of maize, changes in community structure of rhizosphere microbes, such as Burkholderiales, may also be potential biological factors affecting shoot biomass and yield of maize.

    • AMF Diversity Analysis of Lichen and Moss Biocrusts in Shapotou Region

      2020, 57(4):986-994. DOI: 10.11766/trxb201904190054

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      Abstract:【Objective】Arbuscular mycorrhizal fungi (AMF) are one of the most widely distributed plant symbiotic fungi in nature. They can form symbiont with cryptogam in biological soil crust (BSC), which is of great significance to the restoration and succession of desert vegetation. However, there are few studies on AMF community structure and diversity in different BSCs types, which limited the understanding of the roles of AMF community in the development of BSCs and its contribution to desert ecosystems. So, will the changes of BSC type affect the community characteristics of AMF complexes in desert ecosystems? 【Method】 In view of the problems mentioned above, this study was based on enclosed revegetation sites in the southeast fridge of the Tengger Desert located at the Shapotou Desert Research &Experiment Station, with the lichen and moss crusts and their underlying soils as the research object. We used high-throughput sequencing technologies studied the AMF community structure composition and diversity of lichen, moss crusts and their underlying soils, and to determine whether different BSCs types will cause differences in AMF community characteristics. 【Result】 The following results were obtained. AMF community richness and diversity index of the underlying soils of moss crusts were the largest and the underlying soils of lichen crusts were the smallest. The AMF community diversity of the underlying soils of moss crusts is significantly different from other groups. The richness and diversity of AMF community of underlying soils were higher than crusts layers, and moss crusts was higher than lichen cursts. The AMF in the lichen and moss crusts and their underlying soils consisted by Glomeromycetes, Glomeromycota. At the genus level,one unclassified species (g_unclassified_c_Glomeromycetes, 6.69%-99.99%) and Glomus (19.55%-47.18%), Paraglomus (0.01%-20.91%), Scutellospora (13.37%) and Gigaspora (7.72%) were the dominant species, and the species that could be classified into Diversisporaceae (g_unclassified_f_Diversisporaceae, 4.13%) were quite limited in percentage. The species of AMF community in the lichen crusts and their underlying soils were exactly the same in composition, but their relative abundance was different. Compared with lichen crusts and their underlying soils, only the species of Glomeromycetes and Glomus were found in the moss crusts, and the species of Paraglomus could not be found. Except for species that appeared in the other samples, there were also found an unclassified Diversisporaceae species and Paraglomus, Scutellospora, Gigaspora in the underlying soils of moss crusts. The species of the unclassified Glomeromycota and Glomus were coexisted in all samples, but the relative abundance was different, which indicates that they belonged to the dominant fungi in the BSCs of this area. The species of Glomus were found in the underlying soils of lichen and moss crusts, and the difference between them was not significant, but there were significant differences with lichen and moss crusts, which suggested that Paraglomus may be the plant symbiotic fungi in the surrounding environment. 【Conclusion】 With the development of BSCs, the diversity of AMF community increased, and the succession of BSC and diversity of AMF communities can promote each other.

    • Effects of Complex Anti-Fungal Agents Biocontrolling Fusarium Wilt on Banana and Its Microbiological Mechanism

      2020, 57(4):995-1007. DOI: 10.11766/trxb201904180111

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      Abstract:【Objective】Worldwidely, banana production is severely hindered by banana Fusarium wilt, a devastating soil-borne disease caused by Fusarium oxysporum f. sp. cubense (Foc). With no widely adopted effective methods available to control or prevent the disease, it causes serious economic losses every year. In this study, complex biocontrol fungal agents were introduced and effects of their application preventing banana Fusarium wilt and potential mechanisms were explored, in an attempt to provide certain references for controlling disease on the large field scale. 【Method】 A pot experiment, lasting for 2 seasons were conducted and designed to have three groups of pots, namely, CK (no controlling agent applied), NFP (NFP for application of a complex anti-fungal agent prepared by combining non-pathogenic Fusarium oxysporum.sp and Paecilomyces.sp in 1:1 ratio), and NFPT (application of a complex anti-fungal agents prepared by combining non-pathogenic Fusarium oxysporum sp., Paecilomyce sp. and Trichoderma sp. in 9:9:4 ratio) for comparison between the pots for effects of the applications controlling banana Fusarium wilt and effects on soil microbial diversity. The Illumina Miseq high-throughput sequencing platform was used to analyze bacterial 16SrRNA gene and fungal ITS regions, the real-time fluorescence quantification PCR (RT-qPCR) was to determine number of pathogens in the soil. 【Result】Applications of the complex fungal agents (NFP and NFPT) have good effects of controlling banana Fusarium wilt disease, with control efficiency being 43% and 48%, respectively, and improve richness and diversity of bacteria and fungi. Principal coordinate analysis (PCoA) based on Bray-curtis distance matrix shows that significant differences in composition of the bacterial and fungal communities exist between the pots applied with the complex fungal agents and the pots in CK. The first principal component (PC1) explains 29.45% and 43.14% of the variability in the bacterial and fungal communities, respectively, and differs sharply between the treatment pots and the CK pots in composition of the overall bacterial and fungal communities. The microbes (non-pathogenic Fusarium oxysporum sp., Paecilomyce sp. and Trichoderma sp.) introduced into the soil are found quite limited in survivability in this study, and their abundance has only a marginal direct effect on the number of F. oxysporum and disease severity of the Fusarium wilt disease. However, they suppress the disease by altering composition of the soil microbiome. In particular, application of the complex fungal agents (NFP and NFPT) increases relative abundances of the beneficial indigenous microbial groups, such asMarmoricola, Nocardioides, Nonomuraea, norank_c__Acidobacteria, DS-100 and norank_f__Blastocatellaceae__Subgroup_4. Their relative abundances are good indicators of the disease suppression effect and may play a keystone role in the process of the complex fungal agents suppressing banana Fusarium wilt disease. 【Conclusion】 In a word, application of the complex fungal agents (NFP and NFPT) significantly reduces the banana Fusarium wilt disease severity index. All the findings presented above show that relative abundance of the introduced non-pathogenic Fusarium oxysporum sp., Paecilomyce sp. and Trichoderma sp. has only a marginal effect on F. oxysporum. In contrast, the changes in abundance and community structures of the bacteria and fungi after application of the agents are the key factors suppressing the disease. Application of the agents stimulates the potential beneficial indigenous microbial groups that are significantly and negatively related to banana Fusarium wilt disease severity index. Thus, the effect of the complex fungal agents suppressing the disease seemed to be a joint one of the actual antagonism of the introduced microbes with the pathogens and their promoting growth of beneficial indigenous microbial groups.

    • Energy Metabolism of Community Dominated by Proteobacteria Methanotroph in Anoxic Environment of Wetland

      2020, 57(4):1008-1016. DOI: 10.11766/trxb201904040135

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      Abstract:【Objective】 Methanotrophs, using methane as carbon and energy sources for growth, play an important role in keeping balance of global methane in balance and controlling greenhouse effects. The process of bio-oxidation of methane spans over different redox niches. Recent researches demonstrate that methanotrophs. Belonging to the phylum of Proteobacteria have the potential of methane metabolism in anoxic niches of wetland, however so far little has been reported on mechanisms of their energy metabolism. This study was to explore mechanism of the energy metabolism of the Proteobacteria dominated methanotrophs in anoxic niches from three aspects.【Method】Bioelectrochemical techniques were used to explore potential of extracellular electron transfer of the methanotrophs. In exploring for potential electrons of the methanotrophs, the reaction system, when aerobic, was designed to have two potential electron acceptors, i.e. oxgyen and ferrihydrite and when anoxic, only one, i.e. ferrihydrite to study energy metabolism of the methanotrophs in anoxic conditions. Mineralogy analysis of the ferrihydrite in the system was performed to determine reduction dynamics of the mineral and structure of its secondary mineral. And analyses of community composition of the methanotrophs before and after reduction of the ferrihydrite were conduction to determine changes in the community.【Result】Results show that the methanotroph groups were able to transfer directly or indirectly extracellular electrons. Once oxygen was used up, the methanotrophs could keep on their energy metabolism by making use of ferrihydrite as electron acceptor. In the anoxic condition, the methane-oxidizing bacteria could reduce the iron mineral 50 times as fast as the ANME (Anaerobic methanotrophic archaea) anoxic methanotrophic archaea, and the secondary mineral were tentatively found to be vivianite via SEM (Scanning electron microscope), EDS (Energy disperse spectroscopy) and XRD (X-ray diffraction) analysis. Based on the principal component analysis of the methanotroph groups, the microbial community varied in composition relative to mode of energy metabolism. Comparison of the methanotroph groups at the phylum level found that in the hyperoxic systems, γ-Proteobacteria in reduced ferrihydrite increased up to 56% in relative abundance, and Methylococcales became the only one species of methanotroph in phylum, while in the anoxic systems, γ-Proteobacteria decreased down to 6% in relative abundance, but α-Proteobacteria increased up to 31%. 【Conclusion】In the anoxic systems, methanotrophic bacteria (γ-Proteobacteria) and non-methanotrophic bacteria worked together driving iron reduction. This study has revealed the process of energy metabolism of the Proteobacteria dominated methanotroph groups, and developed the theory of methane oxidation driven by NC10 bacteria and ANME archaea in anoxic environment, and hence provide certain theoretic support to future studies on bio-control of methane prodction.

    • Four Species of Herbs in Karst Areas and Their Adaptabilities to the Karst Matrices

      2020, 57(4):1017-1031. DOI: 10.11766/trxb201907170370

      Abstract (1266) HTML (675) PDF 2.92 M (1547) Comment (0) Favorites

      Abstract:【Objective】 This paper is aimed to find out priority of plants in adaptability to karst matrices.【Method】Four native species of plants, Cynodon dactylon, Miscanthus sinensis, Trifolium repens and Festuca elata in the karst areas were selected for test in a pot experiment with pots packed with different matrices, separately.【Result】Results show that the karst habitat diversifies in plant growing matrix. Physico-chemical properties of the matrices as a whole improved with plants growing on and on, except for decrease in total potassium content. The plants were the highest in germination rate and survival rate in the pots of limestone soil, < 1mm sand and < 1mm sand + limestone soil and the lowest in the pots of limestone debris and limestone debris + litter, while among the four species of plants, Trifolium repens and Cynodon dactylon was the highest in germination rate and survival rate, respectively. With the plants growing on and on, the plants were higher in plant number, plant height and coverage in the pots of limestone soil, < 1mm sand, < 1mm sand + litter and lower in the pots of limestone debris and limestone debris + litter; and the plants in all the pots increased in coverage, and only Cynodon dactylon increased in number. The plants in the pots of limestone soil, < 1mm sand, litter, and < 1mm sand + litter were the highest, and the lowest in the pots of limestone debris, and limestone debris + litter in biomass, while among the plants, Cynodon dactylon and Trifolium repens were high and Miscanthus sinensis and Festuca elata were low. The plants were high in total chlorophyll in the pots of < 1mm sand, limestone soil, limestone soil + 1mm-5mm sand and < 1mm sand+ 1mm-5mm sand + limestone debris + limestone soil, and low in the pots of limestone debris, while among the plants, Trifolium repens and Cynodon dactylon were higher and Miscanthus sinensis and Festuca elata lower, and Miscanthus sinensis and Cynodon dactylon were higher in δ13C than Trifolium repens and Festuca elata. The value of δ13C in the plant is related not only to species of the plant, but also to the matrix it grew in.【Conclusion】To sum up, the plants in karst areas can grow not only in limestone soil, but also in other matrices. The four species of plants in this experiment are highly adaptable to the matrices of limestone soil, < 1mm sand, < 1mm sand + litter and limestone soil + 1mm-5mm sand, fairly adaptable to 1mm-5mm sand, litter, <1mm sand + 1mm-5mm sand + limestone debris + litter, limestone soil + 1mm-5mm sand + litter, <1mm sand + limestone soil + litter and 1mm-5mm sand + litter, and barely adaptable to limestone debris and limestone debris + litter, and Cynodon dactylon and Miscanthus sinensis are more adaptable than Trifolium repens, and Festuca elata. Therefore, Cynodon dactylon and Miscanthus sinensis can be selected preferentially as pioneer plant for ecological restoration in karst areas. The extension from studies on the single soil matrix to studies on plant growing matrices of karst areas helps broadens the research theory and perspective, which is of great significance to ecological vegetation restoration in karst areas.

    • >Communications and Comments
    • Evolution process of setting of Pale-Type in US soil Taxonomy

      2020, 57(4):1032-1039. DOI: 10.11766/trxb201910300222

      Abstract (981) HTML (980) PDF 449.17 K (2170) Comment (0) Favorites

      Abstract:At the beginning of its development, the Chinese Soil Taxonomy referenced the US Soil taxonomy, citing no a few concepts and names therefrom. The comparison between the two systems found that in the latter existed a Pale-type, which was translated into a name that coincided with the name of a soil type in the former, but differed in connotation. The Pale-type in the US Soil Taxonomy encompasses great groups and subgroups of soils, and its detailed retrieval conditions show that it is a more specific category that has no similar soil type in the Chinese Soil Taxonomy. In the US Soil Taxonomy, Pale-type is used to classify soils high in development degree and old in age. Through comparing and analyzing two editions of the US Soil Taxonomy and several editions of the Keys to Soil Taxonomy, this paper briefly introduces the origin of the setting of Pale-type and the revision course of its retrieval condition and retrieval sequence. At present, many pedologists have proposed to revise the Chinese Soil Taxonomy. On such a basis this paper is going to expound how the evolution process of the Pale-type setting enlighted the development of the Chinese soil taxonomy, with a view to providing suggestions for revision of the Chinese Soil Taxonomy.

    • >Research Notes
    • Effects of Slow-release Fertilizers on Growth and Nutrient Uptake and Utilization of Canola Grown on Purple Soil

      2020, 57(4):1040-1050. DOI: 10.11766/trxb201910140229

      Abstract (1207) HTML (497) PDF 670.03 K (1513) Comment (0) Favorites

      Abstract:A fertilization field experiment on Brassica napus L., Sanxiayou 5 in cultivar was conducted. The experiment aimed to study effects of special slow-release fertilizer and conventional fertilizer on biomass and nutrients (nitrogen, phosphorus and potassium) uptake and utilization of canola, and nutrient accumulation in soil. The field fertilization experiment on canola (Sanxiayou 5) was designed to have six fertilization treatments, i.e. F0 (no fertilizers), Fc (conventional fertilizer), F375 (special slow-release fertilizer at 375 kg·hm-2), F525 (special slow-release fertilizer at 525 kg·hm-2), F675 (special slow-release fertilizer at 675 kg·hm-2) and F825 (special slow-release fertilizer at 825 kg·hm-2). Results show that application of slow-release fertilizer improved yield and effective number of pods per plant of canola, exhibiting an order of Treatment F675 > Treatment F825 > Treatment F375 in the effect. Compared with Treatment Fc, Treatment F675, Treatment F825 and Treatment F375 increased yield of the crop by 43.54%, 36.82% and 13.88%, respectively. Besides, the application reduced N nutrient loss rate from 78.30% (in Treatment Fc) to 53.97%(in Treatment F375) -73.66% (in Treatment F825), and P nutrient loss rate from 56.65% (in Treatment Fc) to 20.53% (in Treatment F375) - 46.13% (in Treatment F825). Total N, total P and total K in the rhizosphere soil applied with slow-release special fertilizers increased from 0.651 0 g·kg-1, 0.404 4 g·kg-1 and 20.74 g·kg-1 (in Treatment Fc) to 0.661 7-0.691 4g·kg-1, 0.407 2-0.496 0 g·kg-1 and 28.96-29.50 g·kg-1. Fertilization could significantly increase biomass of the crop, and application of special formulated slow-release fertilizer could not only improve fertilizer utilization rate, but also have less impacts on nutrient contents in the rhizosphere soil. Taking into account sustainable development of the agriculture, it is advisable to use the special slow-release fertilizer in practical production.

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