• Volume 54,Issue 6,2017 Table of Contents
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    • >Reviews and Comments
    • A Review of Researches on Biochar Adsorbing Organic Contaminants and its Mechanism

      2017, 54(6):1313-1325. DOI: 10.11766/trxb201704060004

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      Abstract:Biochar is a kind of porous and carbon-rich material prepared out of waste biomass through pyrolyzation anaerobically or aerobically. Thanks to its high adsorption capacity, handy resources, low preparation cost and environment-friendliness, biochar has aroused more and more attention among the academic circles. Knowledge about mechanism and rules of biochar adsorbing organic contaminants is crucial to proper evaluation of its environmental behaviors and application value. This article reviewed with emphasis reports available on mechanisms of biochar adsorbing organic pollutants, such as partition, surface adsorption, pore interception, etc. Generally speaking, biochar prepared at low temperature adsorbs non-polar organics mainly via partitioning. This non-competitive adsorption mechanism can be used to explain the process of biochar adsorbing pollutant high in concentration.Surface adsorption is a kind of competitive sorption mechanism. Organic contaminants caught on the effective sites on the surface of biochar are adsorbed via electrostatic interaction or hydrogen bonding,ionic bonding,π-electron donor-acceptor (π-π EDA), etc. Pore interception is another microscopic mechanism of biochar adsorbing organic pollutants.Partitioning and adsorption of organic pollutants inside the pores is also an important portion of the biochar adsorption capacity. Both polar and/or non-polar organic contaminants can be sorbed on biochar via pore interception.In fact, the mechanisms of biochar adsorbing organic compounds are various with one dominated and additional other mechanisms also occurred.In addition, this paper analyzed and summarized influencing factors of mechanisms of biochar adsorbing organic contaminants.Physico-chemical properties of biocharincluding high specific area, well-developed porosity, rich polar functional groups and stable aromatic structure are essential to determine the application value of this super-sorbent.Only biochar with properties matchable to organic contaminants in polarity, aromaticity, molecular size can be used to bring their adsorption capacity into full play. Sorption environment such as pH, medium and co-existing ions is also an important factor affecting adsorption effect of biochar. All account for the complex process of biochar adsorbing organic compounds. However,the researches reported in the literature are found to have some problems. For example, some of them remained on the stage of laboratory and little is reported in the literature on using experimental methods to probe mechanisms of biochar adsorbing organic compounds. At the end, the article brought forth solutions to the existing problems and described prospects of the application of biochar in remediation of organic polluted soils in future.

    • >Insights and Perspectives
    • Role of Microbial Assimilation of Soil NO3- in Reducing Soil NO3- Concentration

      2017, 54(6):1326-1331. DOI: 10.11766/trxb201706010145

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      Abstract:NO3- accumulation in the soil would trigger N losses through runoff, leaching and N2O emission. It is, therefore, of particular importance to take appropriate nitrogen (N) management strategies to reduce soil NO3- accumulation, and hence to enhance N use efficiency and reduce N losses to the environment. Application of nitrification inhibitor (NI) has been demonstrated to be effective in reducing soil NO3- concentration, NO3- leaching and N2O emission, and simultaneously increasing crop yield. However, there is an indisputable fact that NI application increases ammonia (NH3) emission and causes NI contamination. As a matter of fact, soil NO3- concentration varies with NO3- generation (nitrification) and consumption (assimilation) rates in aerobic conditions. Under the influence of the viewpoint that soil microbes prefer NH4 -N for their growth, it is commonly held that soil microbes rarely use NO3- in farmlands. Consequently, the study on processes of soil microbial NO3- assimilation has been neglected to a certain extent. The process of soil microbial NO3- assimilation is found to be unique in advantage. It turns NO3- into microbial biomass N for temporary storage before mineralization to be available to crops for a longer season or crops in the following season. There is no doubt that soil microbial NO3- immobilization is stimulated by specific extraneous C input, which deserves more attention in future studies concerning how to reduce soil NO3- accumulation. Further studies should primarily focus on the following several aspects: (1) to elucidate mechanism of the microbe driving NO3- assimilation under elevated C availability, (2) to explore how to control microbial assimilation and remineralization of NO3- to match soil N supply with crop N demand and reduce N losses, and (3) to explore how to avoid stimulating denitrification and associated N losses while enhancing microbial NO3- assimilation under the condition of sufficient C supply.

    • >Research Articles
    • Responses of Microbial Biomass Carbon and Nitrogen to Erosion and Deposition in Black Soil Thin in Depth

      2017, 54(6):1332-1344. DOI: 10.11766/trxb201703080015

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      Abstract:Abstract 【Objective】Soil erosion is a serious problem, causing soil and nutrient losses and altering physical, chemical and biological properties of the soil. Numerous reports have been published on effects of soil erosion on soil physicochemical properties. However, little has been done on quantitative analysis of how soil erosion and deposition affect soil microbial biomass in the black soil region of China. Soil microbial biomass is a sensitive indicator of changes in the environment, compared with soil organic matter. The study on impacts of soil erosion and deposition on soil microbial biomass is expected to be able to provide certain important basis for scientific evaluation of the environmental effects of soil erosion. Therefore, the study was oriented to investigate response of soil microbial biomass carbon and nitrogen to soil erosion and deposition, by analyzing soil microbial biomass carbon, microbial biomass nitrogen and erosion rate of the soils at different locations (the upper stream, middle stream and downstream reaches) in the valley and different positions (the upper, middle, and lower slope position) on a slope. 【Method】The Binzhou River Valley, a typical region of black soil thin in soil layer in Northeast China, was taken as the research area. Contents of microbial biomass carbon and microbial biomass nitrogen in the soils of the sampling sites different in slope position and location in the valley were measured using the chloroform fumigation extraction method and erosion rates of the soils estimated using the 137Cs tracer method. 【Result】Results show significant differences exist between the soils in spatial distribution of soil microbial biomass, and negative relationships of the spatial distributions of soil microbial biomass carbon and microbial biomass nitrogen with that of soil erosion and deposition. On the watershed scale, soil erosion rate declined drastically from the upper stream down to the middle stream and the lower stream, while both soil microbial biomass carbon and microbial biomass nitrogen exhibited a reverse trend, being significantly higher in the downstream than in the upper stream and middle stream. The content of soil microbial biomass carbon was 26.9% and 17.4% lower, respectively, in the upper stream and the middle stream than in the downstream, and the content of soil microbial biomass nitrogen 22.9% and 18.1% lower. On the slope scale, soil erosion rate descended significantly from the middle slope position to the upper slope position and to the lower slope position; but both soil microbial biomass carbon and microbial biomass nitrogen acted reversely, too, beingsignificantly higher at the lower slope than at the middle slope. The content of soil microbial biomass carbon was 13.8% and 20.2%, respectively,lower at the upper slope and the middle slope than at the lower slope, and the content of soil microbial biomass nitrogen 10.0% and 19.5% lower. Regression analysis shows that the contents of soil microbial biomass and nutrient decreased linearly with increasing soil erosion rate. Microbial biomass carbon, microbial biomass nitrogen, organic matter and total nitrogen in the soil were negatively related with soil erosion rate at an extremely significant level (p <0.01), respectively. 【Conclusion】Obviously soil erosion has some profound impacts on spatial distributions of the microbial biomasscarbon and microbial biomass nitrogen in the soil. The removal and redistribution of soil nutrients caused by the processes of soil erosion and deposition is the main reason why spatial distribution of soil microbial biomass differ between erosion and deposition areas.

    • Characterization of Runoff and Sediment Yield in Farmlands on Loess Slopes Based on R/S and Wavelet Analysis

      2017, 54(6):1345-1356. DOI: 10.11766/trxb201704190031

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      Abstract:【Objective】On the Loess Plateau of China, water erosion in slope farmlands is the major type of soil erosion. Knowledge about changes in runoff and sediment yield therein will sure contribute to understanding nature of the erosion on a microscopic scale. The objective of this study was to investigate temporal variation of runoff and sediment yield on microrelief like farmland on loess slope under rainfall. An in-lab experiment was designed to have slopes, 5°, 10°, 15°, 20°, and 25° in gradient, and four commonly adopted tillage patterns (flat slope, artificial digging plowing, artificial backhoe plowing, contour tillage) paired in combination. 【Method】For the in-laboratory experiment, a steel trough (2.0 m long, 1.0 m wide and 1.0 m deep ) filled with soil was set up with slope gradient adjustable in the range of 0~30°. Rainfall was simulated with downward sprinklers, 18 m high above the ground, which allows all the artificial raindrops to reach targeted terminal velocity and size of raindrops in natural rainfall and to distribute like a natural rainfall. Each artificial rainfall event lasted 90 minutes. Samples of runoff were collected every two minutes after the initiation of runoff for. fractal-theory-based rescaled range analysis (R/S) to predict trend of the variation of temporal sequence of runoff and sediment and for Morlet wavelet analysis to identify principal cycles of the variation of each runoff and sediment yield sequence.【Result】Results show that Hurst index of the runoff sequence lies in the section between 0.567 and 0.798, while that of the sediment sequence in the section between 0.632 and 0.861, both being higher than 0.5, displaying a long-range positive correlation between the two. Hence the temporal sequence of runoff and sediment yield on loess slope farmlands in future will remain the same as that in the past. In addition, the volume of runoff and sediment yield displayed a positive and negative logarithmic relationship, respectively, with duration of rainfall, expressed by the equation of S=a+ bln t (R2>0.5, a and b are constants). Generally, runoff peaked in volume 28 to 29 minutes after its initiation on the slope farmlands regardless of tillage pattern, while, sediment yield might have a long cycle of over 30 minutes in sequence on slope farmlands under certain tillage, indicating that the sediment yield on these slope farmlands might vary periodically every 30 minutes, which, however, needs to be validated by more detailed data of a longer time sequence.【Conclusion】All the findings in the study demonstrate that it is reliable to use R/S analysis combined with Morlet wavelet analysis in predicting temporal variation of runoff and sediment yield. This study also enriches the theory of run-off and sediment transfer, and lays a foundation for in-depth understanding of the runoff and sediment, which is of great significance to further researches on relationship between soil erosion and time sequence on a microtopographic scale.

    • Study on Runoff and Sediment Reducing Effects of Erosion Control Measures on Slopes of Slag Dumps with Simulated Rainfall

      2017, 54(6):1357-1368. DOI: 10.11766/trxb201705270151

      Abstract (2052) HTML (0) PDF 1.47 M (2460) Comment (0) Favorites

      Abstract:【Objective】The ecological and environmental problems caused by mining, especially coal mining, have aroused worldwide concerns and attention. It is, therefore, essential to explore rapid and effective ways to rehabilitate the ecological systems in the mining areas. 【Method】Outdoor simulation of rainfall events was conducted with rainfall intensity controlled at 1.0 mm min-1-1Agropyron was formerly planted in the farmlands around the mining and transplanted on the slopes and the fish-scale pits dug temporarily. The rainfall simulator was a trough-type artificial simulator. When the nozzle is 3m above the ground, the raindrops may reach the end point speed. Plots of the artificial slopes were 3m×1 each in area and 35° in slope gradient. Before the start of the experiment, rainfall was calibrated in intensity until it reached 85% or higher in uniformity coefficient. During the rainfall events, runoff flow velocity was measured with the dye tracing method. During the first 3 minutes of rainfall, samples of runoff and sediment were gathered every minute, and after that once every 3 minutes. Sediment samples were oven-dried for weighing. 【Result】(1) Runoff leveled off in rate in 6minutes after the initiation of runoff on all the three types of slopes, regardless of type of control measure. The erosion rate on the slope of gangue tended to fluctuate, while declining and the trend was more obvious than those on the protected slopes. (2) Planting grass reduced runoff by 42.91%~51.21%, 26.28%~55.20% and 10.33% and sediment by 97.54%~97.95%, 41.87%~42.26% and7.80%, respectively, on earthy slopes, rocky slopes and slopes of gangue, while digging fish-scale pits did by 51.89%~72.72%, 22.37%~42.92% and 21.32% and by 98.41%~99.30%, 94.90%~91.84% and 39.50%, respectively. (3) On earthy slopes, digging fish-scale pits was 8.98%~21.51% and 0.46%~1.76%, respectively, higher in runoff and sediment reduction rate than planting grass, while on rocky slopesand slopes of gangue, planting grass was 3.91%~12.28% and 0.28%~3.06% higher and 10.99% and 31.70% higher, respectively. (4) On all the three types of slopes without protection measures taken, linear relationships (R2 = 0.775,p<0.01; R2 = 0.649,p<0.01; R2=0.450,p<0.05) were found between erosion rate and runoff rate, but they were weakened or fading out altered when the protection measures were taken. 【Conclusion】All findings in this study may serve as scientific basis in guiding ecological restoration of slopes of gangue in the mining area.

    • The Study of Lime Soil Reaction Intensity Estimates Based on CaCO3 Content and pH

      2017, 54(6):1369-1376. DOI: 10.11766/trxb201705110109

      Abstract (2069) HTML (0) PDF 1.12 M (3251) Comment (0) Favorites

      Abstract:【Objective】Soil CaCO3 content and pH are two common indices in routine soil analysis, while lime reaction, pH and content of carbonate equivalents are the three important diagnostic indices in the Chinese Soil Taxonomy. However, generally, the determination of soil pH and CaCO3 content needs to be done with the help of experimental instruments in lab, which is rather costly and time consuming; Actually, intensity of lime reaction can be measured in field with titration of 1:3 dilute hydrochloric acid, which is simple, quick and cheap. Moreover, content of CaCO3, pH and intensity of lime reaction are somewhat interrelated. Therefore, if a model of quantitative relationships between soil CaCO3 content, pH and lime reaction intensity can be built up for a specific area, it will no doubt save or spare the time and money needed for determination of soil pH and CaCO3 content in lab, and it will help make tentative determination in the field of what type of calcareous soil in the Chinese Soil Taxonomy. The purpose of this paper is to try to establish such a model.【Method】Correlation analysis and regression analysis were performed of the data of the 110 typical soil profiles investigated during the provincial soil survey of Shanxi Province, including lime reaction intensities determined in the field, and soil pHs, calcium carbonate contents and ESPs (Exchangeable Sodium Percentage) measured in lab of the soil samples from their 426 genetic horizons, for relationship between calcium carbonate content and soil pH, and statistical analysis was for relationships of lime reaction intensity with soil pH and calcium carbonate content.【Result】Results show that in the soil developed from loess parent material in North China with pH <9, content of calcium carbonate is an important factor affecting soil pH, and the optimal relationship between the two fitted with regression accords with an exponential curve, while pH >9 , no significant relationship was observed between the two, but lime reaction intensity could be used as indicator, reflecting to a certain extent or semi-quantitatively a range of pH or content of CaCO3, rather than a precise value. Moreover, from the viewpoint of soil genesis, the content of CaCO3 is of great significance to the study of soil morphology. So if soil pH or CaCO3 is required to define accurately the position of a soil in the Chinese soil Taxonomy (for instance to define whether or not the soil solum is acidic, or has a calcic horizon / calcification, etc.), it is advisable to recommend the use of the more accurate data obtained in lab. In non-alkaline (pH<9.0) soils derived from loess parent material in North China that have foam reaction in the field, soil pH lingers basically in the ranger 8.51±0.49, no matter whether foam reaction intensity or CaCO3 content is high or low. Soil acidity in such a range has little restraint on crop growth. Therefore, if it is considered whether crop growth would be affected from the angle of soil pH or CaCO3 content only, there is no need to have any lab tests to determine accurate pH or CaCO3 content.【Conclusion】It is feasible to realize semi-quantitative estimation of soil CaCO3 content and pH in soils derived from loess parent material in North China by field testing of lime reaction intensity.

    • Relationship between Soil Salinization and Groundwater Characteristics in the Yellow River Delta

      2017, 54(6):1377-1385. DOI: 10.11766/trxb201701160401

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      Abstract:【Objective】Soil salinization is one of the most important environmental problems that restrict the ecological system and the sustainable development of agriculture in the Yellow River delta. Composed mainly of silt and fine sand the soil is stronger in capillary water action, turning groundwater into the main factor affecting migration, accumulation and release of salt in soil body. To study relationships between soil salinity and groundwater will sure be of important theoretical value and practical significance to amelioration of the saline alkali soil and control of secondary salinization of the soil in the Yellow River Delta. 【Method】In order to study the relationship between salt accumulation in topsoil and groundwater characteristics and to monitor in-situ variation of soil salt content and groundwater table in the Yellow River Delta, four sections were laid out and a total of 20 wells set up by taking into full consideration factors like hydrogeological features, soil salinization status, topography, land use and human activities. Groundwater tables in the wells were measured, and water samples from the wells and topsoil (0~15cm) samples in the locations of the wells were collected in February, May, August and November, 2013 for analysis of salt content and characteristics of the groundwater. Groundwater tables were measured, and samples of the groundwater and topsoil (0~15 cm) were collected from the wells and the fields near the wells, separately, in February, May, August, and November 2013, for analysis of soil salt content and characteristics of the groundwater. Grey correlation analysis of the obtained data was performed to quantitatively analyze relationships of groundwater table with EC, pH, and ion content (Ca2+, Mg2+, K+, Na+, CO32−, HCO3, Cl- and SO42−) of the water relative to season. 【Result】Results show that soil salt varied in the range of 3.90~6.31 g kg-1 in content, in the topsoils and of 2.54~3.44 g kg-1 in the subsoil both belonging to the category of medium or higher in salinization degree; Groundwater tables were all rather high, fluctuating in the range of 1.16~1.71 m; and the anion in the groundwater was dominated with Cl-1, while the cation with Na+, accounting in total for 65% of the total of ions. Correlation analysis shows that the relationships of the groundwater characteristics with salt content in the topsoil varied from index characteristics and with time as well. On the whole, salt accumulation in the surface soil was closely related to EC, Na+ and Cl- in the groundwater, but not so to pH, CO32−and HCO3. 【Conclusion】To control and manage soil salinization in the Yellow River Delta, it is essential to intensify control of EC, Na+ and Cl- in the groundwater of the region.

    • Variation of Soil Salinity in Plow Layer of Farmlands under Long-term Mulched Drip Irrigation in Arid Region

      2017, 54(6):1386-1394. DOI: 10.11766/trxb201704270601

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      Abstract:【Objective】In Xinjiang, an arid region, water scarcity has promoted extensive use of drip irrigation under plastic film mulch in agricultural production as an effective water-saving technique in this region. However, Xinjiang is also a region where soil salinization is common. With the extensive replacement of conventional irrigation with drip irrigation, the benefit of the former washing salts off the soil disappeared. Moreover, the irrigation water in this region is quite high in mineralization and ready to supply the soil with salt. So, although the effect of drip irrigation saving water and increasing yield is quite obvious, long-term adoption of the technique may lead to salt accumulation in the soil, thus lowering soil quality. This paper is oriented to explore impacts of 15-year long-term drip irrigation on soil salinity or soil salt content of the field in an attempt to provide certain scientific basis for management of soil salt under mulched drip irrigation in this region. 【Method】A tract of farmland, around 224 km2 in area was delineated in Regiment 147, Division Eight of the Xinjiang Production and Construction Corp, in the Manas River Basin, North Xinjiang for the study. The data of salt contents and soil available nutrient contents in the plow layer accumulated during the years from 1996 to 2010 of the tract of farmland were analyzed statistically with the aid of GIS technology to characterize variation of soil salt in the plow layer and relationship between soil salt and other soil indices in the plow layer relative to irrigation history. 【Result】Results show: (1) soil salt content in the plow layer decreased from 3.13 g kg-1 to 3.00 g kg up>-1 or by 4.2% in the first 3 years of drip irrigation, but it rose back up to 4.81 g kg-1 or 53.7% at the end of the study; (2) after 15 years of drip irrigation, soil salt content in the plow layer of the study region increased significantly, varying mainly in the range of 4 ~ 10 g kg up>-1, and a large proportion of the plow layer soil could be sorted as moderately or heavily salinized soil; and (3) long-term mulched drip irrigation in the arid region led to redistribution of soil salt in the plow layer, approaching to normal distribution in the scope of the regiment as a whole. 【Conclusion】Under the condition of the study, long-term mulched drip irrigation has led to salt accumulation in the plow layer, because the water used in drip irrigation carries some salt, which may serve as supplement to soil salinity. It is, therefore, recommended to flood the field to wash soil salt off every two or three years in areas under long-term mulched drip irrigation, and to build up soil fertility and soil organic matter content, which may play a positive role in controlling soil salt accumulation due to drip irrigation in this region.

    • Preliminary Study on Effect of Straw Mulching and Incorporation on Water and Salt Movement in Salinized Soil

      2017, 54(6):1395-1403. DOI: 10.11766/trxb201705020061

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      Abstract:【Objective】Soil salinization is the major cause of reduction of agricultural production in Dongying of Shandong Province, China, where shallow groundwater table, high evaporation and low precipitation cause soil salt to move upwards and accumulate on the surface soil of farmlands, so that yields of the crops therein are often quite low. In the study, an indoor simulation experiment was carried out using soil columns to explore effect of the farming practice of simultaneous straw mulching and straw incorporation on soil water evaporation, salt movement and soil water and salt distribution in farmland, in an attempt to provide a theoretical basis for amelioration and utilization of the coastal saline soil in Dongying.【Method】The in-lab simulation experiment was designed to have six treatment i.e. T1 (Straw mulching), T2 (Straw incorporation into the 35~40 cm soil layer), T3 (With the ratio of straw in mulching and incorporation set at 1:1), T4 (With the ratio set at 2:1), T5 (With the ratio set at 1:2) and CK (No straw mulching or incorporation). Soil water evaporation and soil salt content was monitored during the experiment.【Result】It was found that: (1) The treatments varied sharply in effect on daily soil water evaporation and exhibited an order of T4 < T5 < T3 < T1 < T2 < CK. Under the same atmospheric condition, either mulching or incorporation or both reduced cumulative soil water evaporation and Treatment T4 was the most obvious in the effect, cutting the cumulative evaporation by 76.13% as compared with CK by retarding the upward movement of soil water from the bottom soil layer, thus greatly reducing soil water loss. The evaporation inhibition rate of Treatment T4 reached 65.89%, being the highest among those of the treatments, so the treatment was the best in the experiment in inhibiting soil water loss through evaporation; (2) During the phase of water leaching and infiltration in the experiment, the treatments also varied significantly in effect on salt leaching. Treatment T3 was the best, with the soil desalination rate in the 0~40 cm soil layer reaching up to 14.83%, while all the other treatments, except Treatment T2, were also found higher than CK in soil desalinization rate. During the phase of of water evaporation, all the treatments were found to have salt accumulated on the surface by a varying degree, and Treatment T4 treatment was the lowest in soil resalinization rate, and much lower than CK; (3) Treatments T3, T4 and T5 were obviously higher than Treatments T1 and T2 in effect of inhibiting soil water evaporation and soil resalinization, with Treatment T4 in particular; and (4) Correlation analysis of cumulative soil water evaporation and cumulative soil salt accumulation shows that the two were positively related, that is, the higher the cumulative soil water evaporation, the higher the soil salt accumulation.【Conclusion】Through the in-lab simulation experiment, it is found that the practice of either mulching or incorporation or both can inhibite soil water evaporation and soil resalinization to a varying extent and the practice of mulching and incorporating straw simultaneously at a ratio of 2:1 in quantity is the best in controlling soil water evaporation and soil resalinization, so it is a good option for amelioration of salt-affected soils.

    • Effects of Intermittent Combined Irrigation on the Characteristics of Soil Water and Salt Movement in Farm Land of Salt-affected Soil

      2017, 54(6):1404-1413. DOI: 10.11766/trxb201705090207

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      Abstract:【Objective】Researchers in the Salt Soil Laboratory of the USA (United States Department of Agriculture,1954) and ASCE (American Society of Civil Engineers,1990) have brought forth a series of advice aiming at ameliorating salt-affected soils. Amelioration of salt-affected soils requires for the first priority removal of excessive soluble salt. However, in actual productive application, the only method available for reducing soluble salt content in the root zone of the crop is to wash the salt off the soil with fresh water. Owing to shortage of fresh water resources, the use of brackish water as replacement has aroused extensive attention. Reasonable exploitation of brackish water can not only improve crop production, but also ameliorate salt-affected soils. To explore characteristics of soil and water movement in the fields under intermittent combined irrigation (ICI), a lab experiment was conducted in an attempt to provide certain theoretical basis and technical support for reasonable use of brackish water in moderately salt-affected soil. 【Method】The experimental system consisted of soil columns and Mariotte bottles. The latter was used to supply water with a constant water head of 1.5~2 cm. The one-dimension vertical water infiltration experiment was designed to have four treatments in terms of interval in intermittent irrigation, i.e. 0 min,30 min,60 min and 120 min and five treatments in terms of combination of the irrigation water, i.e. simple fresh water (F), simple brackish water (B), 2:1 (brackish and fresh water), 1:1 (brackish and fresh water) and 1:2 (brackish and fresh water). During the experiment, wetting front movement and cumulative infiltration was monitored. At the end of the experiment, soil samples were extracted at the soil extraction port as quickly as possible to avoid the effect of water redistribution inside the cylinder, and soil water content was measured with the oven-drying method and electrical conductivity of the soil solution with a conductivity meter. 【Result】Cumulative infiltration was relatively high during the initial stage of infiltration, and dropped drastically with the experiment going on. Measurements done at the same time show that the treatments of ICI were all higher than Treatments F, but differed slightly from Treatment B in cumulative infiltration, and among the treatments of ICI, the same in quantity of water supply, cumulative infiltration increased with the ratio of brackish water. And the infiltration lasted longer when the ratio of fresh water was higher. Cumulative infiltration was in good linear relationship with wetting front movement (R 2>0.99). Determination of soil water content at the same soil depth shows that the treatments of ICI exhibited an order of ICI 2:1 (Brackish water : Fresh water) > ICI 1:1 > ICI 1:2, indicating that soil water content was positively related proportional to ratio of brackish water. Treatments ICI were all higher than Treatment F in irrigation uniformity, which was negatively related to ratio of fresh water. In the 5~45 cm crop root zone, soil desalinization rate was significantly higher in Treatments ICI than in Treatment B, and varied sharply between the treatments. The higher the proportion of fresh water, the higher the soil desalinization rate, the more favorable the salt-water environment for the crop to grow in. Significance tests of the effects of Treatments ICI on soil desalinization rate show that all the treatments reached significant levels, regardless of combination ratio and length of interval, indicating that the parameters of ICI have important on soil salt movement. 【Conclusion】Intermittent combined irrigation is more conducive than other irrigation modes to the formation of a good soil water-salt environment for crops to grow. In actual productive application, a proper combination (fresh water and brackish water ratio and interval) should be designed and used in the light of crop salt tolerance and depth of the main root system active zone, so as to minimize damage of salt stress to crops.

    • The Effect of Gravel on Saturated Hydraulic Conductivity and Water Storage Capacity in Reclaimed Dump Relative to Reclamation Mode

      2017, 54(6):1414-1426. DOI: 10.11766/trxb201705030084

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      Abstract:【Objective】 In open mining, dump is generally a loose rock-earth accumulation body, consisting of coal gangue from mining, topsoil stripped for open mining, rocks and cover soil. The gravels contained in the dump have an important impact on soil hydraulic conductivity and water storage capacity. So far, studies on impact of gravels on soil water have focused mainly on gravels in nature soil, and little has been reported on soil hydrology and erosion of engineering accumulation bodies of mixed rock and soil like dump and dreg dumping site. 【Method】This study was laid out on the Haizhou opencast coal mine. Field investigations were conducted and samples collected for in-lab water infiltration tests and analysis of distribution characteristics of gravels in dumps reclaimed with different vegetation and its impact on saturated hydraulic conductivity and water storage capacity of the soil in an attempt to provide certain theoretical basis for improving utilization efficiency of the water and soil resources. 【Result】 Results show that the total amount of gravels in dump increased with soil depth. The mean content of total gravels in soil profile was the lowest in agricultural land, which may be explained by frequent farming practices. No significant difference was observed in total amount of gravels between different soil layers; In terms of relative mean content of gravels by particle size, the gravels in the dump exhibited an order of (2~10 mm) > (>20 mm) > (10~20 mm), which demonstrates a trend that large-sized gravels are gradually turning into fine ones as affected by a variety of factors. Saturated soil hydraulic conductivity was the highest in shrub land, which was followed by agricultural land and grassland, and it was significantly, positively and linearly related to gravel content. The relationship got closer with increasing particle size of the gravels. Soil water storage capacity was the highest in shrub land and grassland and the lowest in arbor forest land and agricultural land, and it exhibited a significant or extremely significant relationship with content of gravels by particle size; Maximum water-retention capacity was in significant power function relationship with content of gravels by particle size; maximum water-holding capacity was in significant parabolic relationship with the content of gravels 2~10 mm in particle size. For gravels >20 mm in particle size, 14% was the threshold in content affecting soil water storage ability of the soil body. 【Conclusion】The distribution of gravels in dump varies with reclamation mode; Gravel content has a positive effect on saturated hydraulic conductivity of the dump; and gravel content and particle size does too on soil water storage capacity.

    • Effects of Porous Soil Amendments on Soil Properties, Yield and Quality of Flue-cured Tobacco in Bijie

      2017, 54(6):1427-1437. DOI: 10.11766/trxb201705280164

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      Abstract:【Objective】It is obvious that use of soil amendments may improve yield and quality of flue-cured tobacco and hence social, economic and ecological benefits considerably.【Method】In order to explore effects of porous soil amendments on soil properties of tobacco fields and yield and quality of flue-cured tobacco in Bijie, a field experiment was conducted and designed to have four treatments, that is, CK (No amendment), T1 (straw incorporation), T2 (porous soil amendment, T20) and T3 (70% T20 and 30% charcoal).【Result】Compared with CK, application of soil amendments increased soil pH by 0.02~0.23, content of total nitrogen, total phosphorus and total potassium by 1.21%~7.27%, 1.16%~8.14% and 0.83%~4.44%, respectively, and content of alkalyzable nitrogen, available phosphorus and readily available potassium by 3.39%~15.2%, 10.8%~50.9% and 1.78%~37.0%, respectively. In terms of growth of the crop, Treatment T1, T2 and T3 was somewhat higher than CK in plant height, stem diameter, number of effective leaves and leaf area, and in terms of yield and quality of tobacco leaves, they were 3.6%~8.0% higher in yield, 3 030~4 910 yuan hm-2 higher in output value, 3.6%~11.7% higher in proportion of upper grade tobacco leaves, and 1.0~1.8 yuan higher in sales price per kilo. Moreover,flue-cured tobacco leaves from the treatments all had nicotine, total nitrogen, reducing sugar, potassium ion and chloride ion in the suitable range for high quality tobacco, and were higher than those from CK in content of total nitrogen, reducing sugar and potassium ion. Obviously, application of the soil amendments may help regulatechemical composition of flue-cured tobacco leaves, including nitrogen/nicotineratio, sugar/nicotine ratio and sugar/nitrogen ratio,to be reasonable.【Conclusion】Application of suitable soil amendments can effectively improve soil properties and growth and development of the tobacco crop, and yield and quality of flue-cured tobacco in Bijie.

    • Contents and Distribution of Soil Nutrients and Heavy Metal Elements in Farmlands of Xuzhou

      2017, 54(6):1438-1450. DOI: 10.11766/trxb201707280331

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      Abstract:【Objective】Xuzhou is a city with economy based mainly on traditional agriculture and mining. In order to get to know soil fertility and pollution of the farmland soil of the city and provide references for fertilization, pollution control and agricultural layout in the region, a total of 9 232 soil samples were collected from plough layers of the farmlands in Xuzhou for analysis of 17 indices, including total nitrogen (TN), total phosphorus (TP), total potassium (TK), alkalyzable nitrogen (AN), available phosphorus (AP), readily available potassium (AK), B, Mo, Mn and heavy metal elements, such as As, Cd, Cr, Cu, Hg, Ni, Pb and Zn. 【Method】TN was measured with the volumetric method; TP, TK, Mn, Cr, Cu, Ni, Pb and Zn, with the x-ray fluorescent spectroscopy; Mo and Cd, with the inductively coupled plasma mass spectrometry; As and Hg, with the atomic fluorescence spectrometry; B, with the emission spectrometry; AN, with the sodium hydroxide solution diffusion-volumetric method; AK, with the ammonium acetate solution leaching-atomic absorption spectrometry; and AP, with the ammonium bifluoride and hydrochloride leaching- inductively coupled plasma atomic emission spectrometry in acid soils and with the sodium bicarbonate solution leaching-spectrophotometry in alkaline soils. Descriptive statistics was performed with the helo of the IBM Statistics SPSS 20.0 software and Kriging interpolation, spatial analysis and geo-statistics with the aid of the ESRI ArcGIS 9.3. Soil nutrient contents were graded according to DZ/T 0295-2016 and soil heavy metal contents, using the Nemerow index. 【Result】The descriptive statistics showed that the average contents of soil nutrients in Xuzhou were higher than those in Jiangsu and China, while the average contents of heavy metal elements were higher than those in Jiangsu and China, and than the background values of Xuzhou, too. The variation coefficients of AP, AK, Mo and Hg were higher than those of the other elements, which indicated high variability between soil samples. Over 80% of the farmlands were rated as moderate or higher in soil nutrient content, while over 99% of the farmlands were sorted into the category of clean or safe soils. Farmlands lightly polluted by As, Cd, Cu or Ni were very limited in area. The higher soil nutrient contents may be attributed to long-term farming cultivation and application of organic manure, meanwhile, the higher heavy metal contents may come from mining and smelting of coal, iron and copper and relevant industries, as well, like thermal power. All the soil indices exhibited significant characteristics in spatial distribution and their spatial correlations with soil types and farmland types. Spatial distributions of TN, TP, TK, AN, AP and AK contents were apparently quite similar, but those of AN, AP and AK varied sharply, while those of B, Mo and Mn did even more. The distribution of heavy metal elements in farmland soils exhibited a declining trend from north to south. The sharp spatial variation of soils in composition was mainly related to soil type and farmland type. Soils derived from lacustrine sediments were higher than those from hill slope sediments and from river alluvium in nutrient content and heavy metals content, and paddy soils higher than dryland soils and garden soils, too. Besides, landform was also an important influencing factor. 【Conclusion】The average contents of soil nutrients and heavy metal elements in the farmlands of Xuzhou are generally higher than those of Jiangsu and China and than the background values, too. Over 80% of the farmland soils in Xuzhou can be rated moderate or higher in nutrient content level while merely less than 1% is polluted by heavy metal elements. The main factors influencing contents and distribution of soil nutrients and heavy metal elements include soil type, soil parent material, landform tillage, fertilization, as well as mining and industries.

    • Characterization of Mineral-organic Complex in Soil Microaggregates with Synchrotron Radiation Infrared Micro-imaging Method

      2017, 54(6):1451-1458. DOI: 10.11766/trxb201704270011

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      Abstract:【Objective】In this study, the synchrotron radiation infrared micro-imaging method was used to characterize mineral-organic complex in soil microaggregates of the red soils under long-term application of organic manure or chemical fertilizer in the long-term stationary experiment station of the national soil fertility network in Qiyang, Hunan, China. 【Method】Soil samples were collected from the long-term experiment station for fractionation of soil microaggregates using the dry sieving method. The obtained soil microaggregates were spread over on a Whatman GF/A Filter, mounted onto a sieve and fixed to a chimney funnel that transferred warm mist from a humidifier filled with ultrapure water. Excess droplets on the filter were drained. Then the soil microaggregates were frozen at -20 ℃ and directly cut into thin sections (300~600 nm) on an ultramicrotome using a diamond knife. Sections were transferred to infrared-reflecting MirrIR Low-E microscope Slides. 【Result】Results show that clay minerals (3 620 cm-1) and larger molecular organics (i.e., lipids, 2 920 cm-1; proteins, 1 650 cm-1; and polysaccharides, 1 080 cm-1) were distributed in a pattern highly heterogeneous. However, among them clay minerals and polysaccharides were quite similar in distribution pattern, but differed sharply from lipids and proteins. Compared to the soil under long-term chemical fertilization, the soil under long-term application of organic manure had clay minerals and larger molecular organics distributed in soil microaggregates with higher dispersivity. Furthermore, in terms of determination coefficient (R2) with clay minerals, the organic functional groups followed an order of lipid > polysaccharide > protein in both soils, suggesting that affinity of clay minerals with larger molecular organics varied in soil microaggregates, and was not affected by fertilization of either chemical or organic. Meanwhile, the synchrotron radiation microzone infrared spectra further demonstrated that characteristic peaks of both clay minerals and larger molecular organics increased in intensity from the outer to the inner of the soil microaggregates. 【Conclusion】In summary, the synchrotron radiation infrared micro-imaging method provides a novel research means and useful information to the study on characterization of mineral-organic complexes in soil microaggregates.

    • Isolation and Identification of Soil Organic Matter in Inner Mongolia Grassland

      2017, 54(6):1459-1470. DOI: 10.11766/trxb201704190629

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      Abstract:【Objective】Inner Mongolia grassland is not only one of the important meat and milk production areas of China, but also an important ecological barrier in North China. In recent decades, in addition to global climate warming and continuous drought, unreasonable use of the land resources has caused severe degradation of the grassland, and reduction of the soil’s capacity of accommodating rain water. Consequently, the soil is becoming more and more water repellent. In order to find out causes of water repellency and to help to solve the problem, it is necessary to get to know exactly distribution, species and content of the soil organic matter in the grassland, and especially relationship of the organic compounds with soil water repellency, so as to facilitate monitoring and eliminating soil water repellency. The purpose of this paper is to establish a method for separation and purification of soil organic compounds in the grassland, to obtain some certain-structured organic matter, and to lay down some foundations for further studies on relationship of the organic compounds with soil water repellency.【Method】In this paper, soil samples were collected from the surface soil layer (0~5cm) of a tract of forage grassland in the south of Xilinhot city, Inner Mongolia and petroleum ether, chloroform, isopropanol, methanol, isopropanol/acetic acid(7:3), isopropanol/ammonia (7:3), different in polarity were used as extraction agent for ultrasonic extraction of the soil samples. Crude extracts were tentatively identified with UV, IR and GC-MS, and then processed with column chromatography to get different species of organic compounds. 【Result】The following findings were obtained. The crude extract, using isopropanol/ammonia, isopropanol/acetic acid as extraction agents was quite large in quantity, while those using petroleum ether, chloroform, isopropanol and methanol as extraction agents was less. The extracts using different solvents differed in appearance, the crude extracts using petroleum ether, chloroform, and isopropanol appeared to be yellow; while those using isopropanol/acetic acid and isopropanol/ammonia, dark brown. The UV-Vis absorption wavelengths of all the crude extracts were concentrated in the range of 200~480 nm. The crude extracts, though using different extractants, were basically quite similar in infrared spectrum, but their chief absorption peak appeared separately at 2 960 cm−1, 2 920 cm−1, 2 850 cm−1 (C-H stretching vibration), 1 732 cm−1 (C=O) 1 460 cm−1 and 1 375 cm−1 (C-H, C-C bending vibration). Besides a relatively weak absorption peak was observed in the vicinity of 1 667 cm-1, in the IR spectra of the crude extract using methanol and isopropanol/ammonia and isopropanol/acetic acid, reflecting the existence of aromatic skeleton or amide associated with a C=O double bond. Comparison between the GC-MS of the crude extracts and the standard mass spectra reveals that hydrocarbons made up about 95% of the crude extract using petroleum ether, isopropanol or methanol extract, and only about 70% of the total extract using isotropanol/ammonia or isopropanol/acetic acid extracts, and both were dominated with C2323 linear hydrocarbon. Steroid (mainly sitosterol) was only detected in the crude extracts using chloroform, isopropanol/ammonia and isopropanol/acetic acid. The crude extract using isopropanol/ammonia was further separated and purified with column chromatography, and then two portions of substances displaying Rf=0.56 and 0.21(A, B) (petroleum ether: ethyl acetate = 4: 1), respectively, were obtained on the plate. In the GC-MS spectra, the retention time of the compound in Part A varied mainly in the range of 30 ~ 34 min, while that in Part B mainly in the range of 25 ~ 30 min.【Conclusion】The crude extract using petroleum ether, isopropanol or methanol as extractant was composed mainly of linear or cyclic hydrocarbons; and that using chloroform, isopropanol/acetic acid (7:3) or isopropanol/ammonia (7:3) mainly of esters, amides and steroids besides in addition to linear or cyclic hydrocarbons. The crude extract using isopropanol/ammonia (7:3) was separated into Part A and Part B with column chromatography. Part A was identified as steroidal ketones, and Part B as oxygen-free sterenes or sterols with GC-MS and MS library search.

    • Evolution of Soil Phosphorus in Reddish Paddy Soil under Long-term Fertilization Varying in Formulation and Its Response to P Balance

      2017, 54(6):1471-1485. DOI: 10.11766/trxb201703210020

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      Abstract:【Objective】This study aimed to explore characteristics of the evolution of content and availability of soil phosphorus and their responses to phosphorus accumulation or loss (P balance) in reddish paddy soil under long-term fertilization varying in formulation under the double rice cropping system, in an attempt to provide theoretical bases for scientific application of phosphorus fertilizer in the double rice cropping areas of South China. 【Method】Based on a 35 -year long-term fertilization field experiment, researches were carried out on the evolution rules of soil total P, available P and soil P activation coefficient (PAC) in reddish paddy soil as affected by fertilization varying in formulation and history, calculations done of gain or loss of soil P each year and cumulative gain or loss of soil P in the long-term fertilization field experiment varying in formulation, and discussions made of relationships between soil total P, Olsen P, soil PAC and cumulative P balance. 【Result】Results show that soil total phosphorus, soil Olsen phosphorus and soil PAC in CK and Treatment NK (No phosphorus fertilizer applied) remained unchanged or displayed downward trends with the experiment going on. Soil total phosphorus in Treatment NK+PM (N and K fertilizer plus pig manure) exhibited a slow rising trend with the experiment going on, while soil Olsen phosphorus and PAC in the treatment did a downward trend. Soil total phosphorus in treatments NP, NPK, NP+RS and NPK+RS (chemical phosphorus fertilizer or plus rice straw) soared during the first ten years of the experiment, but the trend gradually leveled off during the 25 years that followed. Soil Olsen phosphorus in the above-listed-treatments rose sharply to high value in content during the first one to five years of the experiment, and then the rising trend began to level off with the years passing on. Soil PAC fell drastically in the treatments of no or low phosphorus input, but it ascended in the treatments applied with chemical phosphorus fertilizer or plus organic manure. Compared with the initial background value of the experiment field, soil PAC decreased by 33.2%, 29.7% and 16.6%, respectively in Treatments CK, NK and NK+PM, but increased by 66.2%, 60.6%, 65.6% and 52.9%, respectively in Treatments NP, NPK, NP+RS and NPK+RS. Treatment CK (No fertilization) led to soil phosphorus deficiency, while Treatment PM (applying only pig manure) nearly sustained P balance, and Treatments NP, NPK, NP+RS and NPK+RS resulted in apparent surplus of soil phosphorus. Phosphorus balance was very significantly related to soil total phosphorus, soil Olsen phosphorus and soil PAC. With an average surplus of 100 kg phosphorus per hectare, soil total phosphorus increased by 0.03 g kg-1, and Olsen phosphorus by 1.20 mg kg-1 and PAC by 0.09%. 【Conclusion】 Extraneous phosphorus inputs are the important factors that affect soil phosphorus and soil phosphorus availability. Long-term no phosphorus input and insufficient phosphorus input leads to soil phosphorus deficiency and hence reduction of soil phosphorus content and soil phosphorus availability. Applying chemical phosphorus fertilizer or chemical phosphorus fertilizer plus organic fertilizer promotes soil phosphorus accumulation and improves soil phosphorus fertility.

    • Negative Allelopathic Effects of Root Exudate of Alternanthera Philoxeroides on Growth and Phosphate Dissolution of Inorganic Phosphorus Bacteria

      2017, 54(6):1486-1496. DOI: 10.11766/trxb201705180092

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      Abstract:【Objective】Alternanthera philoxeroides Griseb, a kind of ill weed hard to eliminate in the world, is able to grow in both soils and waters low in available phosphorus (P) and now widely distributed in over twenty provinces (regions or municipalities) in this country, causing enormous hazard to agriculture, forestry, animal husbandry and aquiculture. It is, therefore, essential to get to know how the weed affects microbes transforming inorganic P in soil. Hopefully, the knowledge will help understand its invasive mechanism, and serve as a scientific basis for effective control of the weed.【Method】 Plants of A. philoxeroides were gathered and cultured in deionized water (fresh root weight : deionized water volume = 1 : 1.5) for 48 hours formed of two cycles of day and night, 12 hours each shift, at 25℃2 ℃with light intensity being 15000 Lex in the day shift. Then the plants were removed, leaving the water as root exudate solution of the plant for the follow-on experiment, which was designed to have two types of culture media, liquid and solid, inoculated with three P-dissolving strains of Burkholderia Yabunchi (B05, B07 and B09) and then amended with the root exudate solution atexudates of A. philoxeroides roots(EAR )0.000 (CK), 0.013, 0.025, and 0.050 g ml-1, separately. Bacterial colonies on the solid media were measured for diameters and diameters of their P-dissolving rings and then P-dissolving indexes worked out. And the liquid media were analyzed for proton, organic acids, and dissolved phosphorus with a pH meter, a high performance liquid chromatography (HPLC), and the molybdenum blue colorimetric method, separately.【Result】Bacterial colonies, P-dissolving rings and P-dissolving indexes in the solid culture media decreased with increasing EAR concentration. The effect on was found the highest with Strain B09, which was followed by Strain B05 and B07. In the solid culture media amended with EAR 0.050 g ml-1 of the root exudate, bacterial colonies decreased by 40.32%~50.00% in diameter, by 49.09%~67.98%in diameter of P-dissolving rings, and by 9.86%~27.38% in P-dissolving index. Growth of the PSB in the liquid culture media was also inhibited by EAR in varying degrees, and hence their populations reduced by 48.13%~73.03%. In the liquid culture media amended with EAR 0.050 g ml-1, the amount of P dissolved by phosphate-solubilizing bacteria (PSB) decreased by 47.32% (B05), 11.43% (B07) and 36.00% (B09) as compared with the control. All the three tested strains of bacteria released protons, oxalate and citrate into culture solutions. Besides these, acetate was also found in the culture solution of B05, malate of B09, and acetate and succinate of B07. Oxalate and citrate together accounted for 66.02%~74.72% of total organic acids released from PSB. In addition, the content of inorganic P dissolved by the bacteria was positively related to the efflux of proton (r = 0.836, p< 0.05, n = 12) and total organic acids (r= 0.947, p< 0.05, n = 12). EAR inhibited significantly the release of protons and organic acids from PSB and hence the dissolution of P remarkably.【Conclusion】Obviously EAR has some negative allelopathic effects on PSB, which are reflected in inhibiting reproduction and growth of the bacteria, their release of protons and organic acids, and P-solubilization in varying degrees. In the invasive process of A. philoxeroides, EAR might inhibit PSB solubilizing inorganic P in the soil, thus hindering P mobilization in the soil and reducing P supply to other plants. In contrast, A. philoxeroides is able to absorb P efficiently through its root high in affinity with P to satisfy its own P requirement, which favors multiplication of its own population, competition for P with other plants and formation of pure A. philoxeroides communities.

    • Effect of Long-Term Fertilization and Residual Effect of Liming on Potassium in Rhizosphere of Maize Relative to Growth Stage of the Crop

      2017, 54(6):1497-1507. DOI: 10.11766/trxb201705090045

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      Abstract:【Objective】In attempt to provide a theoretical basis for amelioration of acidified red soil through liming and build-up of potassium (K) pool, efforts have been made to explore residual effect of liming on K in rhizosphere and bulk soil in maize field at different maize growth stages in acidified red soil. 【Method】From a long-term fertilization experiment (Started in 1990), designed to have six treatments, including chemical nitrogen and phosphorus (NP), NP plus lime (NPCa), NPK, NPK plus lime (NPKCa), NPK plus straw (NPKS), and NPKS plus lime (NPKSCa) and conducted on a tract of upland maize field of red soil in Qiyang, Hunan Province, samples of rhizosphere and bulk soils were collected in the maize field at the seedling stage, jointing stage, filling stage and harvesting stage of the crop in 2014 for analysis of contents of different forms of K, pH and contents of exchangeable calcium and magnesium (Ca2 Mg2 ), and exchangeable aluminum (Al3 ).【Result】Results show that 1) compared with Treatment NP, Treatments NPK and NPKS were obviously or 120.4 mg kg-1 and 149.6 mg kg-1, respectively, higher in readily available K (RAK) content in both rhizosphere and bulk soils, however, Treatments NP, NPK and NPKS, all suffered K deficiency in rhizosphere at the jointing and filling stages, with deficit being 18.2%, 34.2% and 26.4%, respectively; 2) comparison of Treatments NPKCa and NPKSCa with Treatments NPK and Treatment NPKS, respectively, shows that liming lowered RAK content, respectively, by 46.0 mg kg-1 and 26.5 mg kg-1 in rhizosphere soil and respectively, by 68.5 mg kg-1 and 56.0 mg kg-1 in bulk soil at the seedling stage, and increased RAK content in rhizosphere by 25.2 mg kg-1 and 33.7mg kg-1, respectively, but reduced the content slightly in bulk soil during the period from jointing to harvesting; comparison of Treatments NPCa, NPKCa and NPKSCa with their corresponding non-liming treatments shows that liming increased soil RAK gain and loss rate in rhizosphere soil by 8.6%, 33.2% and 19.3%, respectively, over the whole growing season; 3) soil RAK content in both rhizosphere and bulk soil was significantly and positively related to the corresponding slowly AK (SAK), potassium saturation (KS), K /(Ca2 Mg2 ) and K /Al3 , and SAK was in ultra-significantly positive relationship and KS in ultra-significantly negative relationship with RAK in relative variation rate. 【Conclusion】Four years after liming in the farmland, under long-term N, P and K fertilization, it is found that liming has increased the contents of RAK and SAK and KS in rhizosphere soil (except at the seedling stage) and the content of (Ca2 Mg2 ) in rhizosphere soil, but not so significantly as in bulk soil, thus eventually alleviating RAK deficiency in rhizosphere soil.

    • Effect of Potassium Carbonate Addition Rate on Surface Characteristics of Corn Stalk Derived Biochar

      2017, 54(6):1508-1517. DOI: 10.11766/trxb201702160054

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      Abstract:【Objective】In recent years, biochar as an environment- friendly material has been arousing more and more attention the world over. The use of biochar as an adsorbent has been proved to be an effective way in managing polluted soil and water. Ordinary biochar is quite low in specific surface area and underdeveloped in internal pore structure, which greatly affects adsorption efficiency of the biochar. Therefore, usually biochar needs activating for higher adsorption capacity. In this study, effect of the amendment of potassium carbonate on surface properties of biochar was studied. 【Method】Activated biochar was prepared under 600℃ from corn stalk amended with potassium carbonate at a varying ratio (stalk/potassium carbonate in mass=1:1, 2:1 and 4:1). Potassium carbonate was prepared into solutions according to the impregnation ratio, 0.60 mol L-1, 1.2 mol L-1 and 2.4 mol L-1 in concentration, separately, and added into corn stalk at a rate of 3 ml per gram of corn stalk in preparation of activated biochar. The biochars prepared in such a way were labeled as KBC-1-600, KBC-2-600 and KBC-4-600 separately;the biochar prepared without the amendment of potassium carbonate was labeled as BC600, non-activated biochar. Basic properties of the biochars, BC (corn stalk biochar) and KBC (potassium carbonate activated biochar) were characterized, with infrared spectrum, surface functional groups, specific surface area, pore size distribution and adsorption kinetics. Naphthalene, as a typical small-sized molecule persistent pollutant (POPs), was selected as adsorbate to evaluate adsorption capacity of KBC and BC. Naphthalene adsorption capacities of KBC and BC and affinities of KBC and BC to naphthalene were analyzed, and prospect of the application of activated carbon was discussed. The pseudo first-order kinetic model, second-order kinetics model and intraparticle diffusion model were used to analyze dynamic process of the adsorption.【Result】With increasing potassium carbonate amendment rate, aromaticity of the biochars increased. When the impregnation ratio was increased from 4:1 to 2:1, hydrophilicity and polarity of the biochars improved, but when the impregnation ratio was further increased from 2:1 to 1:1, hydrophilicity and polarity of the biochars decreased, instead. Potassium carbonate amendment increased specific surface area of the biochards, with KBC-2-600 in particular reaching up to 566 m2 g-1, whereas specific surface area of the ordinary biochar (BC600) was only 86.8 m2 g-1; The KBC600 series of biochars were significantly higher or on average 16 and 4 times higher respectively than BC600 in mesopore volume and micropore volume, and also higher in mesoporosity. The amendment altered the number of functional groups and their saturation on the surface of biochar. KBC was lower than BC in total of functional groups at 1 256 cm-1~3 414 cm-1. With the increasing amendment rate of potassium carbonate, the ester C=O disappeared, reducing hydrogen bond forming capacity, and unsaturated C-O-C increased, enhancing aromaticity and non-polarity. Alteration of the cellulosic cleavage process caused by potassium carbonate is considered to be the main cause triggering changes in functional groups on the surface of the biochar. Kinetic analysis shows that the adsorption of naphthalene onto BC600 and KBC-4-600 could be described by the pseudo-second-order kinetic model. The adsorption process involved simultaneously external surface adsorption and intraparticle diffusion; After activation by potassium carbonate, adsorption capacity of the biochar improved significantly. The fitting of intraparticle diffusion model demonstrates that KBC gets more complicated in internal pore structure.【Conclusion】The amendment of potassium carbonate contributes significantly to improvement of surface active sites and pore complexity of the biochar, thus enhancing its adsorption capacity of nonpolar aromatic pollutants. The potassium carbonate activated biochar has well-developed pore structure, and hence a great potential to be used as highly-efficient adsorbent in remedying polluted soils in future.

    • Effect of Biochar Alleviating Waterlogging Stress of Winter Wheat in Rice-Wheat Rotation Systems

      2017, 54(6):1518-1526. DOI: 10.11766/trxb201705120210

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      Abstract:【Objective】Crop rotation of rice and winter wheat is a common farming practice in areas of the middle and lower reaches of the Yangtze River. However, the paddy soils under such a cropping system are always heavy in texture, and tend to bring about waterlogging stress to the crop of winter wheat during its growing season under monsoon climate of winter wheat, thus inducing severe yield losses or loss of the whole crop. It is, therefore, essential to seek for a low cost and environment friendly method to alleviate yield losses caused by waterlogging stress for the sake of local food security. Biochar is an effective soil amendment and can be used to reduce soil hardening and enhance soil organic carbon sequestration. Nowadays, researches have has been carried out on application of biochar in areas under the crop rotation system in the middle and lower reaches of the Yangtze River. However, little has been reported on quantitative evaluation of the effect of biochar alleviating waterlogging stress of winter wheat in South China. 【Method】Therefore, in the present study, soil column and plot experiments were conducted to investigate effects of application of biochar derived from rice straw in paddy fields under the rotation system on growth of winter wheat at its early stage, in an attempt to obtain a preliminary evaluation of the prospects of biochar application to alleviate waterlogging stress. Effects of biochar application varying in rate on soil bulk density and soil water content at different depths were evaluated through the soil column experiment, and its effects on wheat germination and wheat growth at early stage were through the plot experiment.【Result】Results show that biochar application significantly reduced bulk density of the soil. When biochar was applied at a rate of 10 and 40 t hm-2, soil bulk density was lowered by 7.4% and 11.4%, respectively, compared with CK (the treatment with no biochar applied). Dynamics of the soil in water content varied with soil depth. biochar application facilitated soil water percolation, thus alleviating the risk of waterlogging. Specifically, in the soil applied with biochar, soil water content at 20 cm in depth dropped rapidly after a simulated rainfall event compared with that in CK. The changes in physical properties of the soil applied with biochar indicated that drainage conditions of the soil were improved, favoring growth of winter wheat. In addition, compared with CK, biochar application at a rate of 10 t hm-2 (BC) accelerated seed germination and promoted wheat growth at its early stage. Samples of winter wheat were collected on D90 after sowing for analysis of plant height, taproot length and chlorophyll relative content (SPAD value) of the new fully expanded leaf. It was found that they were all significantly higher in the treatments applied with biochar than in CK (p<0.05). The findings fully demonstrate that biochar application is beneficial to wheat growth at its early stage. However, its effects on dry matter weight of root, stem and leaf were not significant. In terms of characteristics of the root system, the plants in the biochar treatments had longer taproot than those did in CK, but did not differ much in total root length and total root area, which may be explained by the heavy texture of the soil CK. In such soils, the plant can not have its taproot go deep and for compensation have more lateral roots developed for water and nutrient absorption. 【Conclusion】On the whole, biochar application can significantly improve drainage of the soil under crop rotation and benefit growth of the wheat at its early stage. All the findings listed above demonstrate that biochar application has the potential to alleviate waterlogging stress. However, further efforts should be made to study effects of biochar application on physiology and yield of winter wheat subjected to waterlogging so as to validate the hypothesis.

    • Spatial Variability of Ecological Stoichiometry of Soil Nitrogen and Phosphorus in Farmlands of Jiangxi Province and Its Influencing Factors

      2017, 54(6):1527-1539. DOI: 10.11766/trxb201705310212

      Abstract (2508) HTML (0) PDF 7.37 M (5058) Comment (0) Favorites

      Abstract:【Objective】Nitrogen (N) and Phosphorus (P) are two essential mineral nutrients for plant growth, and important parts of organic nutrient and soil fertility. As two restrictive elements in the terrestrial ecosystem, they play important roles in growth and development of plants, community composition of the vegetation and structure and function of the ecosystem as well. As ecosystems vary in soil microbial activity, they do in recycling and transformation of soil N and P and in decomposition and accumulation rate of organic matter, thus leading to significant variation of the ecological stoichiometry of soil N/P. Therefore, the study on spatial variability of the ecological stoichiometry of soil N/P and its influencing factors in the terrestrial ecosystem at a provincial scale is the fundamental basis of the study on changes in trophic structure, population succession and chemical elements recycling in the terrestrial ecosystem.【Method】 Based on the data of the 16 582 soil samples collected in the topsoil layer (0~20 cm) of the farmlands during implementation of the project of soil-test-based formulated fertilization in Jiangxi Province in 2012, values were assigned to the qualitative factors, i.e. parent material, soil type, farmland-use type, straw incorporation pattern and nitrogen fertilization (divided into 4 levels), and one-way variance analysis, ordinary kriging analysis and regression analysis were done of the data to quantify the ability of each factor to explain spatial variability of the ecological stoichiometry of soil N/P ratio independently.【Result】Results show as follows: ① The soil N/P ratio in the topsoil layer ranged from 0.28 to 13.63, with an average of 3.38, which indicates that the soil N/P in the cultivated land ecosystem of Jiangxi Province is at the level of medium on the lower side, and that the biological nitrogen fixation rate in the cultivated land ecosystem is at a quite high level. The coefficient of variation was 45.56%, indicating that soil N/P is moderate in variability. The nuggest/sill ratio was 60.54%, indicating that soil N and P is weak in spatial dependence, varying between structural factor and stochastic factor, and the latter played a more important role in spatial variability of soil N/P ratio. ② Soil N/P ratio was significantly related to elevation (p<0.01, r=-0.038), TN (p<0.01, r=0.681) and TP (p<0.01, r=-0.665), suggesting that elevation is a major factor affecting spatial distribution of soil N/P and that soil N/P depends mainly on TN and TP contents. ③ The spatial distribution of soil N/P ratio appeared to be quite smooth relatively, with high values over in Wuyuan of Shangrao, Jinxian of Nanchang, Xiangdong and Lianhua of Pingxiang, Fenyi of Xinyu, Lichuan of Fuzhou and Dingnan of Ganzhou. ④ The five factors, parent material, soil type, farmland-use type, straw incorporation pattern and nitrogen fertilization rate, all had significant impacts on spatial variability of soil N/P ratio (p<0.01), but varied in degree. Parent material explained 2.4% of the variability; type, sub-type and genus of the soil did 1.8%, 2.2% and 3.0%, respectively; farmland-use type did 2.2%; straw incorporation pattern did 13.0%; and N fertilization rate did 27.2%. 【Conclusion】The factor of N fertilization rate is far more capable of explaining independently spatial variability of the soil N/P ratio than the other factors, indicating that it is the main factor determining soil N/P ratio in the topsoil layer of Jiangxi Province. Therefore, in order to improve the ability of the farmland ecosystem to fix nitrogen biologically and sequestrate nitrogen, here are two suggestions. One is to devote more efforts to improving farmers’ knowledge about the use of chemical fertilizers, especially Nitrogen fertilizer, through propaganda and related technical training, vigorously extrapolating the soil-test-based formulated fertilization technology and stimulating farmers to rationalize fertilizer usage. And the other is to raise subsidies and implement preferential policies for use of organic manure and accelerate development of the green manure industry coupled with the extension of straw incorporation.

    • >Research Notes
    • Spatial Distribution of Soil Inorganic Carbon in Urban Soil and Its Relationship with Urbanization History of the City

      2017, 54(6):1540-1546. DOI: 10.11766/trxb201703300075

      Abstract (2002) HTML (0) PDF 4.56 M (2734) Comment (0) Favorites

      Abstract:Urbanization has a profound impact on soil carbon recycling. Based on spatial specific sampling of the urban soil and inversion of the urbanization history of Nanjing between 1900 and 2010, spatio-temporal relationship between spatial distribution of inorganic carbon in urban soil and urbanization processes was analyzed for assessment of inorganic carbon sequestration potential of urban soil. Results show that inorganic carbon density of the urban soil is closely related to history of the city, and it much higher in historical old regions than in newly urbanized regions, which indicates that the urban soil is highly potential in sequestration of inorganic carbon. The mean inorganic carbon density in the urban soil grows linearly with the development of urbanization. The inorganic carbon pool in the topsoil of the urban area studied reached 2.94 Tg and the area still had a potential of sequestrating1.45 Tg of inorganic carbon in future. All the findings in this study may serve as theoretical basis for elaborating the mechanism of carbon recycling in the urban system and conducting research on inorganic carbon sequestration in urban soil.

    • Effects of Nitrogen Application Rate on Fractionation of Soil Organic Nitrogen Relative to Crop Rotation Mode

      2017, 54(6):1547-1558. DOI: 10.11766/trxb201706230077

      Abstract (2221) HTML (0) PDF 1.54 M (2664) Comment (0) Favorites

      Abstract:A 3 a field experiment, consisting of 6 croppings, was conducted to investigate effects of N fertilization on content and fractionation of soil organic N relative to N application rate and crop rotation mode, paddy/upland (rice/rapeseed, RR) rotation and upland (cotton/rapeseed, CR) rotation. Results show that after the 3 years of crop rotations cultivations, soil total N content in the 0~20 cm soil layer increased remarkably in plots more than 300 kg hm-2 in N input. Compared with CK (No N fertilization, N0-0), soil total N content increased by 13.6%~23.5% and 15.0%~23.0%, respectively, in the treatments 300 kg hm-2 and 375 kg hm-2 in N application rate under either RR or CR rotation. The increase in soil total acidolysable N content accounted for most of the increase in soil total N. Although no significant difference in soil total acidolysable N content was observed between plots under RR and CR rotations, fractionation of the soil acidolysable N varied between plots. The proportion of soil acidolysable ammonium N increased by 33.8% in the plots under RR rotation, much lower than that (53.9%) in the plots under CR rotation, but the increment of unidentified soil acidolysable N in proportion was higher in plots under RR rotation (36.0%) than that (16.6%) in the plots under CR rotation. To sum up, reasonable N fertilization may significantly increase soil organic N content. Fractionation of the soil organic N pool varies sharply between plots under RR and CR rotations. It is, therefore, of important significance to optimize N fertilization for high crop yield and high N utilization efficiency in the light of the characteristics of soil organic N transformation under different rotation systems.

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