• Volume 56,Issue 3,2019 Table of Contents
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    • >Insights and Perspectives
    • Key Role of Matching of Crop-specific N Preference, Soil N Transformation and Climate Conditions in Soil N Nutrient Management

      2019, 56(3):507-515. DOI: 10.11766/trxb201812030523

      Abstract (2729) HTML (1745) PDF 2.03 M (4033) Comment (0) Favorites

      Abstract:Appropriate crop nutrient management synchronizing soil nutrient supply with crop nutrient demand is critical for global food security, soil and agriculture sustainability, and ecological environmental protection. Rational nutrient stewardship should be embodied in application of climate-soil-crop-specific types of fertilizers, at the right rate, right time and right place. However, most of the current N nutrient management practices often fail to take into account the influences of N species preferences of crops, soil N transformation characteristics and climate conditions, thus affecting the effects of the soil N nutrient management practices. Meanwhile, any mismatching of these factors would increase N losses through ammonia volatilization, denitrification, runoff and leaching. Nitrogen transformation is liable to get affected by climatic conditions and responds to plant N uptake characteristics in natural ecosystems. For instance, in subtropical acidic soils, NH4+-N dominated inorganic N pool is mainly a result of low nitrification and relative high nitrate immobilization, which reduces the risk of N loss via leaching or runoff. In contrast, in neutral and alkaline soils in arid and semiarid regions, NO3--N is the dominant inorganic N form, as a result of high nitrification and relative low nitrate immobilization and denitrification, which reduces the risk of N loss via ammonia volatilization under high pH condition. Some crops, such as rice, already adapted to low redox potential and tea, originating from acidic soils, prefer NH4+-N, and most crops growing in dryland, like wheat, tobacco and maize, and a variety of vegetables prefer NO3--N. Therefore, a closed N cycle with minimal N loss in ecosystem might be achieved through rationalizing N nutrient management, exhibiting that the N available in the soil matches the N of the plant’s preference in form. If the applied NH4+-based fertilizers are always maintained in the form of NH4+ in the soil, “preference” for NH4+ of NH4+ preferring crops can often be translated into higher 15N recovery by the crops. In contrast, if the N applied doesn’t match the crop's preference in form, availability of the applied N to the crop depends on ability of the soil to transform the applied N into the preferred N in form. Hence, soil N transformation regulating soil N forms plays an important role in optimizing matching degree N sources with plant’s species-specific N preferences. This paper points out that to satisfy crop N preference, it is essential to have N form in fertilizer, soil N transformation characteristics and climate conditions well coupled and only in this case, can N use efficiency be significantly improved, N application rate lower, and loss of active N via emission into the environment be reduced. Therefore, it could be concluded that (1) NH4+- preferring crops perform best in acidic soils, in low nitrification rate, in humid regions and applied with NH4+-based fertilizers as the sole N source; and (2) NO3--preferring crops perform best in neutral and alkaline soils, in high nitrification rate, in arid and semiarid regions, and applied with NO3--based fertilizer as the main N source. So, these relationships should be taken into account when new N fertilizer management strategies are developed and new species of crops are introduced (e.g. application of nitrification inhibitors to rice paddy fields (prefer NH4+) can increase N uptake and yield). It is expected that this study would provide a scientific basis for development of knowledge-based N fertilizer management practices for a certain crop, soil and climate system. To establish critical values to evaluate coupling degree of the N sources, soil N transformation characteristics, crop N preference and climate conditions, further studies should be conducted.

    • >Reviews and Comments
    • Progresses in Research on Surface Acid-Base Properties of Variable Charge Soils and Their Models

      2019, 56(3):516-527. DOI: 10.11766/trxb201806070303

      Abstract (2125) HTML (1854) PDF 1.50 M (2626) Comment (0) Favorites

      Abstract:Surface acid-base properties of variable charge soils refer to ability of the soil to bind protons, mainly involving density of surface proton reaction active sites (Ds), point of zero charge (pHpzc), , and equilibrium constants of protonation and proton abstraction (pKa). Surface acid-base properties are important indices of great significance to evaluation of acid-base buffering capacity of soils and exposition of mechanisms of soil acidification. Meanwhile, they are also one of the soil properties that are important to exploration of distribution of cations and anions in the soil solid-liquid interface and control of mobility and bioavailability of soil micro-elements. This paper presented a review of approaches to acquisition of the parameters of surface acid-base properties using the surface complexation model (SCM), and the two methods of studying complex soil systems. pHpzc is mainly obtained through macro-titration, but needs to be continuously optimized thorough experiments to reduce the impacts of meaningless factors, while Dsand pKa are usually worked out separately with Gran function and linear extrapolation. At present, extensive researches have been done on surface acid-base properties of soil active component metal oxides, clay minerals and humus with research methods and relevant data approaching perfection. Charge Distribution Multisite Complexation Model (CD-MUSIC) and Non-ideal Competitive Adsorption-Donnan (NICA–Donnan) have been established to describe ion adsorption on minerals and organic matter, separately. With the development of SCM, the research on surface acid-base properties of the complex soil systems or natural soil systems is going on in depth. The component addition (CA) and generalized composite (GC) approaches are recommended for use to simulate the properties of soils. CA is used to predict distribution and morphology of protons in soils and soil solutions by adding up surface properties of various components, and its use has extended from the mineral polymerization model to the mineral-organic polymerization model, because the interaction between the organic and mineral components is very important to the research on natural systems. An LCD model, combining the CD–MUSIC and NICA–Donnan models into a mechanistic framework, is introduced for description of sorption of organic matter to the surface of minerals, and ions binding the two. Furthermore, GC assumes that the surface properties of the soil are uniform and can be obtained by fitting the experimental adsorption data and the surface area. Quality of the fitting depends on how detailed the surface information is, and the GC has developed from 1-site/1- pKa to n-site/n- pKa. Besides, a generalized regression equation is recommended for prediction of acid-base properties merely based on basic chemical properties. Finally, the paper further explores scientific issues that need to be solved for researches related to surface complexation models and future trends of the research on acid-base properties of soils

    • Process of Plant Residue Transforming into Soil Organic Matter and Mechanism of its Stabilization: A Review

      2019, 56(3):528-540. DOI: 10.11766/trxb201811140559

      Abstract (3649) HTML (4372) PDF 4.77 M (5619) Comment (0) Favorites

      Abstract:Organic carbon contained in soil organic matter is the largest terrestrial carbon sink on the globe. Quantity and quality of soil organic matter is a major indicator reflecting soil fertility. Moreover, the processes of formation, transformation and stabilization of soil organic matter are closely related to global climate change. Plant residues are the primary source of soil organic matter, of which the decomposition is subject to the impacts of numerous factors. Soil organic matter and microorganisms vary sharply in spatio-temporal distribution, thus affecting turnover of plant residues. Besides, quantity, quality and input pathway of plant residues per se also governs decomposition of the residues. So, mechanisms of the transformation of plant residues into organic matter and its stabilization remain unclear. In this paper, introduction to and discussion on new findings in relevant studies on transformation of plant residues into soil organic matter in recent years is presented, exploration made of contributions of microbe-derived organic matter and plant-derived organic matter to total soil organic matter, and elaboration done of the mechanism of soil microbe driving formation of soil organic matter formation. Besides, in the study, a review is presented of relevant studies on stability of soil organic matter after input of plant residues. In the end outlooks of the researches in this field are discussed in the paper, in expectation of providing certain reference for future researches on scientifically improving soil carbon sequestration capacity.

    • Research Progress on Soil Organic Carbon Based on Map of Scientific Knowledge

      2019, 56(3):541-552. DOI: 10.11766/trxb201806160270

      Abstract (2319) HTML (839) PDF 20.68 M (2381) Comment (0) Favorites

      Abstract:【Objective】 In order to review progresses of the research on soil organic carbon, 2 258 articles on soil organic carbon published during the period from 1975 to 2018 and pooled into the core set of the ISI Web of Science database were cited for analysis.【Method】 Based on co-citation and pathFinder, CiteSpace was adopted to evaluate the collection of documents in a specific field to explore key paths and knowledge turning points of the evolution of the science field and collate key documents and quantify their corresponding features in the literature, so as to analyze potential dynamic mechanisms of the evolution of the discipline and search for development frontiers of the discipline. CiteSpace is composed mainly of cooperation network analysis (cooperations between authors, countries and institutions) co-occurrence network analysis (characteristic words, keywords, discipline categories) and co-citation analysis (documents, authors, co-cited journals) and some other functional modules. Data were retrieved, processed and introduced into CiteSpace, with time slicing set as 1975—2018 and Year Per Slice as 1 year; Country (Country), Author (Author) and Institution (Institution) selected as node type (Node Type) in turn; annual citation frequency (Top N) being 50 in rank; national, author and institutional maps generated and knowledge patterns, such as basic characteristics, cooperation characteristics, literature co-citation and keyword co-occurrence, analyzed.【Result】 (1) Except for a slight decline in 2006, 2011 and 2015, the annual average number of published articles showed an overall upward trend, indicating that the research on soil organic carbon continued increasing; (2) The study on soil organic carbon has gone through three phases: initiation, development, and stabilization; (3) The study on soil organic carbon is highly interdisciplinary, involving environmental ecology, environmental science, agricultural integration, agronomy, chemistry, agricultural science, ecology, and some other disciplines; (4) The current hot spots of the research are concentrated on soil organic carbon reserves and separation and stabilization of soils; (5) Research tends to deal with management of carbon reserves and cultivated land; and (6) The study on soil organic carbon in China started quite late, but has been developing rapidly, and is now in an important position internationally.【Conclusion】 As an effective tool for analysis of knowledge maps, CiteSpace can be used to clarify the cooperative relationships between countries, authors and institutions in the field. So far, a total of 56 countries have cooperative relations. Although China started late in the research, it has a huge number of researchers, stands on the top in number of published papers and has established close relations with other countries. The study on soil organic carbon involves a wide range of disciplines. Intercross of disciplines can be traced back to the 1990s, and the intercrossing of agriculture, soil, and environment sciences is relatively frequent. The research on soil organic carbon can be divided into 14 topics, with soil organic carbon reserves, mineral fertilization, separation of stable soils, stoichiometric analysis, and residual soil being frontiers of the research.

    • >Soil Engineering
    • New engineering technology of straw enrichment and deep burial(SEDB) in subsoil

      2019, 56(3):553-560. DOI: 10.11766/trxb201806190331

      Abstract (2090) HTML (683) PDF 3.51 M (2480) Comment (0) Favorites

      Abstract:There are three main patterns of straw returning to the field in China: shallow incorporation, surface mulching and, turnover straw with moldboard plow. The shallow incorporation generally causes too much arge pore in the soil while surface mulching will lead to the decrease of ground temperature and the increase of diseases and insect pests in some areas; due to the inability to break the bottom layer of the plough, the effect on lifting the soil organic matter content of the whole soil layer (especially the subsurface layer) is limited. Turnover straw with Moldboard plow consumes more power and charge expenses; in addition to soil layers turnover, the practice induces yield reduction in some areas, and a complexity to manage soil on the following year due to the undercover of undecomposed straw.【Objective】In view of the handicaps caused by long-term shallow tillage, such as the lack of organic matter in the subsurface layer of soil, over-compaction, and the high cost or poor effect of straw return to the field, this paper proposes a simple and effective new pattern of straw returning and the corresponding machine innovation and field engineering technology. The purpose of this engineering technology consist into resolving the bottleneck problem of high cost or poor effect of straw returning to the field, also to provide mechanization means for the straw treatment of upland field and the construction of fertile plough layer.【Method】This technical model is based on the new concept of prioritizing soil subsurface fertilized layer and the enriched straw buried in the soil subsurface layer of the designated belt where strip tillage loosing soil. This new technique is called straw enrichment and deep burial(SEDB).The main engineering technology of this model is the invention of a new straw deep return cylinder plough which can enrich, crush and bury the straw into the soil by means of mechanization. The specific steps include:(1) enrich the corn straw by 4:1~8:1 with the finger-plate rake;(2) the corn straw is buried into the 20~40 cm depth of subsoil in the designated strip with wind-driven injection cylinder plough; (3) the non-buried straw belt is seeded with the no-tillage planter in a normal way to realize the separation of seed planting belt (narrow rows) from straw strip (wide rows) in wide-narrow rows cultivation mode.【Result】This model has the advantages of moldboard plow and mulching of straw. However, it overcomes the disadvantages of both. It is the perfect combination of straw returning to the field and strip minimum tillage. The corn straw, being fully mechnized, can be returned to the field along with each agricultural campaign, without disrupting the sequence of soil layers and affecting the planting in the next year.【Conclusion】The concept of straw enrichment and deep burying is novel and the technology is feasible which has a positive effect on improving soil fertility especially subsoil fertility.

    • Comparative Research on Effects of Ecological Ditches Different in Specification Treating Pollutants in Drainage

      2019, 56(3):561-570. DOI: 10.11766/trxb201806190328

      Abstract (1782) HTML (917) PDF 3.46 M (2671) Comment (0) Favorites

      Abstract:【Objective】With rapid development of the socioeconomy and agriculture of China, the use of chemical fertilizers and pesticides is growing excessive in total amount and rate. As a result, non-point source (NPS) pollution emerges with pollutants flowing into water environments with surface runoff and drainage and via other channels. According to the “Bulletin of the First National Survey of Pollution Sources in China” published by Ministry of Environmental Protection of China in 2010, agricultural NPS pollution contributed up to 57.2 % and 67.4 % to the total discharge of N and P in the country, respectively. Ecological ditches, as a special kind of wetland systems, can be used to manage agricultural NPS pollution with balanced ecological and environmental benefits. In order to understand how ecological ditches, different in depth (E0.80, E1.05 and E1.30), can reduce main NPS pollutants under the same hydraulic surface loading (0.60 m3•m-2•d-1), it is essential to evaluate pollutant removal efficiency and anti-shock loading capacity of the ditches.【Method】For this study, an experiment was conducted at the Zhuanghang Experimental Station (121°23′15″E, 30°53′24″N) of the Shanghai Academy of Agricultural Science, China. The experiment had three eco-ditches, the same in length (90 m) but different in depth (0.80 m, 1.05 m and 1.30 m). Aquatic evergreen species, Vallisneria natans, was grown in all the three eco-ditches, the same in density. Simulated agricultural NPS pollution water was diverted from a river and spiked with a certain amount of urea and KH2PO4 till it was the same in N and P content as that in the effluent of local farmlands. And then it was introduced into the eco-ditch systems dynamically. Before the experiment, the eco-ditch systems were stabilized for a period of time before the experiment began, and the experiment period lasted 20 d. The inflow TN and TP concentrations were 0.86~6.13 mg⸱L-1 and 0.11~0.28 mg⸱L-1, respectively.【Result】Results showed that under the dynamic conditions of the experiment, all the three ecological ditches were all quite high in NPS pollutants removal efficiency, regardless of the difference in depth. The mean ammonia nitrogen (NH4+-N), total nitrogen (TN), total phosphorus (TP) and suspended substance (SS) removal rate of Ditch E0.80was 61.4%, 58.7%, 64.0% and 58.5%, respectively, of Ditch E1.05, 54.7%, 62.5%, 70.2% and 51.1%, respectively, and of Ditch E1.30, 64.8%, 63.1%, 71.8% and 60.8%, respectively, throughout the entire experiment time. Obviously Ditch E1.30 was the highest in pollutant removal efficiency. With the same inflows the same in pollutant concentration, the average TN and TP concentration in the effluent measured at the point of 22.5 m and 45 m down the ditch was the lowest in Ditch E1.30 and the average TN and TP concentration was reduced down to 2 mg⸱L-1 and 0.2 mg⸱L-1 at the point of 27.4 m and 4.9 m, respectively, down the ditch, in Ditch E1.30. The course was much shorter in Ditch E1.30, then in Ditch E0.80. For the latter it was 54.5 m and 9.8 m, respectively. Meanwhile, the concentrations of pollutants in the effluent from Ditch E1.30 were relatively stable, indicating that Ditch E1.30was the highest in anti-shock loading capacity. Conclusion】Compared with Ditch E0.80 and Ditch E1.05, Ditch E1.30 is obviously higher in pollutant removal efficiency and anti-shock loading capacity, when they are used to manage agricultural NPS pollution. So it is recommended that in practice, ditches 1.30 m in depth should be built site-specifically. This research is expected to be of great practical guiding significance to control of agricultural non-point source NPS pollution. However, more researches should be done on further improvement of pollutant handling efficiency of the ecological ditches and on land-saving as well by altering the linear spatial structure, setting up drop dams at intervals, laying down beds of substrates (like zeolite, etc.) at intervals and optimizing plant configuration (keeping plants growing at the bottom and on the walls of the ditches).

    • Short Term Response of Soil Properties and Rice Growth to Land Consolidation in South of Jiangsu Province

      2019, 56(3):571-581. DOI: 10.11766/trxb201806190334

      Abstract (1549) HTML (472) PDF 10.99 M (1935) Comment (0) Favorites

      Abstract:【Objective】As an important means to increase the area of cultivated land, improve farmland infrastructure and raise grain production capacity, land consolidation (merging and leveling) has been widely extrapolalted throughout the country. Land consolidation is often accompanied by landfilling of ponds and pits and field leveling in the Plain of South Jiangsu, which are thought to pose a big risk of disturbing the soil environment. However, so far little attention has been paid to the potential short-term effect of farmland consolidation disturbing soil ecology. The aim of this study is to explore the short-term effect of land leveling relative to area on rice growth and specify soil factors that might affect the growth of rice in a short period of time after land consolidation, in an attempt to provide reference for monitoring soil quality, improving soil fertility and managing the ecology after land consolidation. 【Method】In this study, soil properties and rice NDVI were monitored via remote sensing and field surveys for analysis of short-term effects of land consolidation on soil and rice growth and their relationships, in Gengzhuang Village, Zhixi Town, Jintan District of Changzhou City. With the help of the engineering drawings of the land consolidation projects, remote sensing images, and field surveys, areas of waterbody filling (WF), topsoil cutting (TC), land filling (BT), and undistrubed land (U), were worked out, separately. Field monitoring of soil properties and rice growth in the first growing season in farmlands different in leveling degree. Topsoil samples were collected at 43 sampling sites, including 6 in Waterbody filling area, 15 in topsoil cutting areas, 16 in borrowed topsoil areas, and 6 undisturbed land areas, for analysis of certain basic physical and chemical indices, such as soil texture, pH, organic matter, total N, readily available phosphorus, readily available K, and available Zn and available Si that have important influence on rice growth to determine soil nutrient status of the farmlands. Rice growth was monitored by means of the normalized difference vegetation index (NDVI), which was extracted from the GeoEye remote sensing images of the areas. 【Result】Effects of land consolidation on soil properties and rice growth were monitored via remote sensing and field investigation, Result show:(1) Land leveling seriously affected nutrient status of the topsoil layer, by decreasing the contents of soil organic matter, total nitrogen and available zinc significantly within a short period of time after the leveling, however, it increased the content of available silicon and had little impact on available phosphorus and available potassium. Soil nutrient status varied sharply with type of land consolidation, showing an order of U > BT > FW > TC; (2) NDVI of rice also varied with type of land consolidation, being 0.763 for WF, 0.747 for TC, 0.808 for BT and 0.834 for U and displaying an order of Unworked > BT > FW > TC. (3) NDVI of rice growth was significantly and positively related to contents of soil organic matter, total nitrogen and available zinc,with coefficient of determination being 0.656, 0.617, and 0.625, respectively. 【Conclusion】Spatial variations of the contents of soli organic matter, total nitrogen and available zinc caused by land leveling are the main factors leading to rice NDVI heterogeneity. Land consolidation has serious short-term effects on soil and crop growth. Fertilization to build up the soil and management and protection of the ecology should be adopted to realize the transformation from quantity-and-productivity-based land consolidation to ecology- based one.

    • Impact of Soil Particle Deletion on Erosion Resistance of Purple Soil in Chongqing Based on Strength Index

      2019, 56(3):582-591. DOI: 10.11766/trxb201807060329

      Abstract (1697) HTML (524) PDF 1.68 M (2194) Comment (0) Favorites

      Abstract:【Objective】Under a weather of plentiful rainfall, Chongqing is one of the most seriously eroded areas in China. The aggravating soil erosion causes depletion of soil particles of various sizes from the soil, weakening soil resistance to erosion, thus eventually leading to natural disasters, such as landslide and debris flow. So this paper aims mainly at exploring impacts of depletion of a certain fraction of soil particles on erosion resistance of the purple soil in Chongqing.【Method】 For this study, an indoor experiment was carried out on purple soil of loamy sands. of which soil samples, after being fully dispersed, passed through a standard soil sieve to remove a certain fraction of soil particles and then got blended uniformly again to simulate the soil that had lost a certain fraction of soil particle as a result of soil erosion. In this way, soil samples different in absence of a fraction of soil particles were prepared, and then made the same in water content and density. and reshaped for triaxial consolidation shear tests through controlling suction of the matrix and changing confining pressure. Based on the parameters of cohesion C and internal friction angle φ obtained from the test, analysis of soil erosion mechanism was performed.【Result】Results show: (1) Compared with the sample of original soil, the samples with the fraction (0.25 mm or more) of soil particles removed were higher in surface friction and snap-in force between soil particles, while the samples with the fraction (below 0.25 mm) of soil particles removed were lower; (2) With rising confining pressure, soil erosion resistance of the sample significantly improved. The soil samples with the fraction (0.25 mm or more) of soil particles removed were good in graduation and in compactibility, as well, and hence were enhanced in erosion resistance by a larger margin, while the soil samples with the fraction (less than 0.25 mm) of soil particles removed were poor in graduation and in compactibility and enhanced in erosion resistance by a relatively limited margin; (3) In the consolidation shearing test, soil samples different in graduation formed a suspension-compaction structure, a skeleton-compaction structure, and a skeleton-pore structure, separately, with erosion resistance following an order of skeleton-compaction structure > suspension-compaction structure > skeleton-pore structure. In soil samples with cohesive force being higher than 10 kPa, the main factor affecting soil erosion resistance was internal friction angle of the soil; and (4) Grey correlation analysis shows that soil particles of median size, d30, was quite closely correlated with cohesion c and internal friction angle φ is large, while soil particles of effective size, d10, were not so. Besides, nonuniformity coefficient Cu, curvature coefficient Cc, limited particle size d60, d30, and d10 of a soil sample all had significant impacts on its erosion resistance.【Conclusion】All the findings in the study are expected to be able to serve as experimental data and scientific basis for future studies on mechanisms of shallow landslide and soil erosion in the purple soil area of Chongqing.

    • Shearing Strength of Sandy Clayey Purple Soil Reinforced with Sodium Silicate and Glass Fiber in Combination

      2019, 56(3):592-601. DOI: 10.11766/trxb201807090330

      Abstract (1429) HTML (635) PDF 1.46 M (1918) Comment (0) Favorites

      Abstract:【Objective】Purple soil, a kind of sandy cohesive soil developed from purple sandy mudstone of the Shaximiao Formation of the Jurassic under frequent weathering and erosion, is widely distributed in regions of Chongqing and Sichuan. It is prone to disasters, such as shallow landslides and soil erosion. Purple soil is closely related to engineering construction, but at present there are few researches in the engineering field paying attention to any engineering properties of purple soil. In view of the fact that the soil is prone to geological disasters, it is particularly urgent to study how to reinforce purple soil in construction projects. Though the traditional cement reinforcement is not bad in effect when compared with other reinforcement ways, it will bring about damages to the soil sources. For instance, once reinforced with cement, the soil can never be used again for plant cultivation. In recent years, a novel soil reinforcing technology has emerged and is going to be more and more popular because it is environment-friendly and very good in effect on improving soil strength. Therefore, this study was conducted to explore effect of the use of a mixture of sodium silicate solution, calcium chloride solution and glass fiber on shearing strength of the soil relative to ratio of the three components.【Method】an experiment was conducted in a triaxial chamber that can keep the material therein free from consolidation and drainage, to explore effect of the mixture on soil shearing strength, relative to ratio of the mixture. In the mixture sodium silicate solution and calcium chloride solution, set as 1:1 in ratio, was blended with glass fiber varying in addition rate.【Result】 Results show that sodium silicate solution and calcium chloride solution acted jointly to gradually increased internal friction angle of the soil, but did not affect much its cohesion. When fiber was added in, cohesion significantly increased, and internal friction angle did too, though gradually. When fiber was added alone at a rate of 0.8%, Cohesion of the soil was maximized. When fiber was blended with the soil already treated with the two kinds of solutions at a rate of 20%, deviatoric stress curve of the soil rose gradually with rising glass fiber addition rate, and cohesion of the soil further increased too till fiber addition rate reached 0.8%, however internal friction angle of the soil did not very much.【Conclusion】As cohesion and internal friction angle of a soil are two important indicators of granular structure and erosion resistance of the soil, the research is expected to be able to serve as a scientific basis for control of soil erosion in sand-clayey purple soil areas though modification of the soil.

    • >Research Articles
    • Method for Quantitative Monitoring of Soil Erosion Based on USLE Principle and 3S Technology and Its Application

      2019, 56(3):602-614. DOI: 10.11766/trxb201805310168

      Abstract (1697) HTML (840) PDF 22.94 M (1995) Comment (0) Favorites

      Abstract:[Objective] This study was oriented to develop and establish a method for quantitative monitoring of soil and water loss that is applicable to both the northern and southern parts of the country and to provide a basis for scientific decision-making for regional ecological environment protection in the future. [Method] Based on the principle of the universal soil loss equation (USLE) and the large volumes of measured data of soil erosion and its relevant ecological factors in various soil and water erosion areas in South and North of China, the new method for quantitative monitoring of soil erosion was established using the "3S" (GIS, GPS, RS) technology. This method has been applied to a total area of over 300 000 km2 covering Shandong, Fujian, Jiangsu, Yunnan, Beijing, Hebei and some other regions in China. Its application in Nanjing, Jiangsu Province is the longest in time and the most representative. During 1997-2015, this method was used in a long-term research to quantitatively monitor soil and water loss and soil erosion control in the entire Nanjing area. [Results] Results show that during the 19 years (1997-2015), the annual soil and water loss in Nanjing area reached 276.5×104 t, and the average area light and over in soil erosion level did 863.7 km2, accounting for 13.0 %. of the total area of Nanjing, only a small proportion, which, however, contributed, over 80% to the total loss, so it is still the key front of the battle for management of soil erosion and conservation of regional ecosystem; compared with the results of the monitoring before 2000 year, the area slight and over in soil erosion level were significantly lower in Nanjing area. [Conclusion] This method has its own algorithm and principle of model factors that are more consistent with the reality, so it is higher in accuracy and reliability. The monitoring with this method has validated that the city intensified its efforts in recent years to manage and control soil and water loss control and to supervise and manage the eco-environment in the area with remarkable achievements.

    • Development of Rills on Slopes of Mine-Engineering Dumps and Its Relationship with Water and Sediment in Karst Area

      2019, 56(3):615-626. DOI: 10.11766/trxb201804280005

      Abstract (1366) HTML (913) PDF 1.61 M (2467) Comment (0) Favorites

      Abstract:【Objective】Gravity is an important factor affecting development of runoff sediment and rills on slopes. Large piles of soil, rock and slag generated as waste and formed during the processes of coal mine construction are liable to have inductive geological disasters such as collapse, landslides and debris flow, occur under the action of water and gravity, causing serious impact or even damage to surrounding water resources, land resources, vegetation resources, hydrological cycle and ecological environment quality.【Method】 A few of such piles in a coal mining site of a karst zone were selected as object of the study. Field scouring experiments were conducted on slopes different in condition with varying flow to explore how erosion occurs and proceeds, and how gravity affects development of runoff and sediment and morphology of the rills formed. Field investigations found that the piles in the coal-mining areas of Chongqing varied in slope in the range between 25.5°and 38°. To objectively reflect characteristics of erosions on such piles different in stacking condition, the experiments were carried out on slopes different in gradient, i.e. 25°、30°、 35° and 40°, and had five flow rates, i.e. 10, 15, 20, 25 and 30 L?min-1 designed according to the characteristics of the per-unit width discharge caused by local rainstorms relative to duration and frequency and each round of the scouring experiment lasted 60 min. 【Result】Results show:(1) The erosion on the slopes of the piles could be divided into two phases, sheet erosion (within the initial 3 min after runoff started) and rill erosion which could be further divided into three stages, i.e. rill expansion (3~24 min after runoff started), rill transition (24~30 min after runoff started) and rill stabilization (30 min after runoff started); the time of rill appearance on the slope was negatively related to the discharge flow rate and the slope; rills appeared the fastest in 4s and the slowest in 97 s, and the latter appeared about 24 times later than the former. (2) Gravity was an important factor affecting runoff-sediment yield and its fluctuations on the slopes of the piles. During slope erosion, runoff rate varied in the range between 7.77% and 374.25% in variation coefficient, while sediment yield did in the range of 1.75% ~ 1021%. Gravity could explain more than 17.41% or even up to 99.60% of the total sediment yield during slope erosion. It was tentatively concluded that gravity started to act on development of rills, when runoff and slope reached their respective critical value of 20 L?min-1 and 35°. And (3) Runoff mainly caused rills to develop in depth, while gravity mainly did in width. The two leading functions were quite similar in degree of their effects on development of rills. Gravity turned short, shallow and narrow rills on slopes of loose deposit into long, deep and wide ones, which ranged between 7.89 and 19.73 cm in width between 2.17 and 7.73cm in depth, between 2.12 and 4.36, in width/depth ratio and between 1.35~3.00 m?m-2 in density’ . Mean depth and width of the rills increased with increasing flow rate and with increasing slope gradient, too. Under the same runoff conditions, the sediment yield increased with increasing density of the rills. However, density of the rills first increased and then decreased with increasing flow and slope gradient.【Conclusion】All the findings in this experiment are of important scientific significance to understanding correctly how runoff and sediment occurs and their influencing factors, to establishing models to predict soil erosion on slopes of the mine-engineering waste piles, and to elucidating . scientifically the roles of gravity in inducing collapse and landslide and maintaining slope stability of mine-engineering waste piles.

    • Soil Water Availability and Its Influencing Factors in Soils under Two Types of Shrubberies Typical of the Loess Plateau

      2019, 56(3):627-637. DOI: 10.11766/trxb201807090294

      Abstract (2006) HTML (1288) PDF 1.63 M (2640) Comment (0) Favorites

      Abstract:【Objective】Amygdalus pedunculata Pall and Salix psammophila are shrubs of the Loess Plateau in China, which have widely been used in recent years as pioneer plants in vegetation restoration on the Loess Plateau, thanks to their good ecological adaptability and high economic value. However, how Amygdalus pedunculata Pall and Salix psammophila utilize soil water and its influencing factors are still unclear.This study is oriented to investigate soil water availability in soils under and two types of shrubs (i.e., Amygdalus pedunculata Pall and Salix psammophila seedlings) typical of the Loess Plateau, but different in physiological indices and its influencing factors. 【Method】 A pot experiment, designed to have two species of shrub (Amygdalus pedunculata Pall and Salix psammophila) planted separately in pots containing separately two types of soil (sandy soil and a loamy soil) combined with five levels of water regime (100%, 80%, 60%, 40% and 20% of the soil water holding capacity) and 5 replicates for each treatment, was carried out. Dynamics of physiological indices ( net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO2 concentration (Ci), water use efficiency (WUE), leaf water potential (Ψw), daily transpiration rate (Td), cumulative transpiration rate (Tc)) of the seedlings in each treatment were monitored.【Result】 Results show that all the physiological indices of the Amygdalus pedunculata Pall and Salix psammophila seedlings in the pots regardless of type of the soil they containedremained relatively constant in relative value till the relative water content fell below the soil moisture threshold and then they declined rapidly with soil water depletion going on. The variation curves of the indices could all be fitted with the nonlinear continuous function with R2 ranging between 0.890 5 and 0.986 4. The inflexions on the curves could be deemed as soil moisture threshold (W0), which varied with species of the shrub and index selected, and with type of the soil too. The soil moisture threshold (W0) corresponding to the instantaneous gas indices (Pn and Gs) was higher in the loamy soil than in the sandy soil, whereas a reverse trend was observed with soil moisture threshold (W0) corresponding to the water use efficiency (WUE). The soil moisture threshold (W0) corresponding to the daily transpiration rate (Td) was higher in the sandy soil than in the loamy soil. Water availability was higher in the sandy soil than in the loamy soil when instantaneous gas exchange indices (relative net photosynthetic rate (RPn) and relative stomatal conductance (RGs)) were used as evaluation index, whereas an opposite trend was observed with relative water use efficiency (RWUE) used as evaluation index. The soil moisture thresholds based on instantaneous gas exchange indices (RPn and RGs) at the transient scale were higher than those based on index at the daily scale (relative daily average transpiration rate, RTd). 【Conclusion】 All the findings in this study demonstrate that both soil texture and time scale affect response of the plant in physiological indices to soil water availability. Continuous nonlinear function can be used to well describe dynamics of water availability under Amygdalus pedunculata Pall and Salix psammophila. Net photosynthetic rate (Pn), stomatal conductance (Gs), water use efficiency (WUE) and the transpiration rate (Td) can be used as indices for evaluating soil water availability. It is, therefore, essential to take into account effects of soil texture on water availability to plants in vegetation restoration and ecological construction on the Loess Plateau.

    • Effects of Fertility-Building Practices on Soil Organic Carbon Loss with Sediment in Sloping Cropland of Red Soil

      2019, 56(3):638-649. DOI: 10.11766/trxb201809060451

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      Abstract:【Objective】Soil is the largest carbon pool in the terrestrial ecosystem. Storage and sequestration of soil organic carbon (SOC) is an important factor affecting balance between input of organic carbon with organic matter incorporated into the soil and loss of SOC. Being a major hydraulic erosion stricken area in China, red soil sloping farmlands suffer serious soil erosion, which in turn drives heavy losses of soil organic carbon from the farmlands, posing a problem that should not be ignored. However, so far little is known about status of soil erosion on and SOC loss via soil erosion from red soil sloping farmlands subjected to different fertility-building practices, which seriously affects sustainable development of the local agriculture and eco-environment. Therefore, the objective of this study is to investigate effects of fertility-building practices on surface runoff and soil erosion, and to elucidate dynamics of organic carbon loss with erosion sediment from red soil sloping croplands. 【Method】A field experiment was initiated in 2012 and designed to have 15 erosion plots laid out on a sloping cropland, for five treatments different in fertility building pattern and three replicates for each treatment. The 5 treatments include CK (zero fertilization), NPK (application of chemical NPK fertilizers), NPK+Str (application of NPK fertilizer plus rice straw mulch), NPK+BC (application of NPK fertilizer plus rice straw-derived biochar),and NPK+OM (application of NPK fertilizer plus swine manure). Peanut was planted in all the plots. At the lower end of each plot, a pit was dug for installation of a tipping bucket runoff flow meter connected with an rainfall event counter to keep real-time records of runoff, and entire process of a soil erosion event. A 300 mesh screen was placed under the bucket sm to collect sediment. Runoff, soil erosion sediment and organic carbon concentration in the soil sediment were monitored during the period of 2015—2017.【Result】Results show that in terms of volume of runoff, the five treatments displayed an order of NPK+BC > CK > NPK > NPK+OM > NPK+Str (P< 0.05), and in terms of sediment loss was in the order of CK≈NPK+BC≈NPK > NPK+OM > NPK+Str (P < 0.05). About 69%~83% of the surface runoff and 70%~89% of the soil erosion occurred during the peanut growing season (April - August). Compared with Treatment NPK treatments, Treatment NPK+Str, NOK+BC and NPK+OM significantly increased the concentration of organic carbon in the sediment (P < 0.05). However, Treatment NPK+BC was the highest in total organic carbon loss via soil sediment ( C 52.1 t•km-2•a-1), while Treatments NPK+OM and NPK+Str the lowest. No significant seasonal changes were observed in organic carbon content in sediment. About 78% of the loss of organic carbon with sediment occurred during the peanut growing season (April—August) in each year. 【Conclusion】 All the findings in this study demonstrate that application of NPK Fertilizer plus rice straw mulch and NPK fertilizer plus swine manure (or Treatment NPK+Str and NPK+OM) can reduce soil erosion and organic carbon loss effectively, while application of NPK fertilizer plus rice straw-derived biochar (or Treatment NPK+BC) does not have much effect on soil erosion, and instead it increases the concentration of organic carbon in the sediment, which is attributed to characteristics of the local physical environment and texture of the rice straw-derived biochar, small in particle compositions, and low in density, and making it easy to get lost with surface runoff and erosion sediment and hard to retain in the soil. So it is not recommended to use biochar as supplement in fertility-building for soil erosion control in the red soil regions of China.

    • Effect of Herb Roots Improving Shear Strength of Unconfined Compressed Solum

      2019, 56(3):650-660. DOI: 10.11766/trxb201807030113

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      Abstract:【Objective】The aim of this study was to explore effects and mechanism of herb roots in natural state improving shear strength of unconfined compressed solum, so as to provide a scientific basis for calculating the capacity of herb roots to reinforce slopes and selecting proper species of grasses to grow on slopes.【Method】The experiment was carried out at the experimental farm of the Yunnan Agricultural University, China. In January 2016, a total of 40 PVC tubes, 51cm in length, 110 mm in diameter and 3.2 mm in thickness were all cut in half, and then the halves were bound together by pair with rubber bands. Upland red soil < 5 mm in particle size was packed into in these rubber band fixed tubes with the bottom sealed with plastic film up to 50 cm. The soil in the tubes was 28.31% in moisture content and 0.78 g.cm-1 in dry density. The tubes were divided into four groups, 10 each. Three groups were sown with seeds of Setariaanceps Stapf ex Massey L., Dactylisglomerata L. and Medicago sativa L. 12 seeds each tube, separately, in May, and the other group left unplanted as control for comparison, Besides, the three species of grasses were planted, separately, in the field, 1 m2 each in plot area for determination of tensile strength of the grass roots. In October, out of each group, 7 tubes were picked randomly, placed in water for 24 h until they were fully saturated, and then removed out of water. The tubes were split off and the soil columns inside taken out. Shoots of the plants were cut off. The soil columns were cut into two, 25 cm each, in the middle with a hacksaw. From each half of the soil columns, a section of 20 cm in the middle was taken as test samples and the section was 10.36 cm in diameter. The samples were analyzed for saturation density and saturated water content and tested for unconfined shear strength on a SJ-1A type strain controlling triaxial apparatus (made in Nanjing Soil Instrument Factory, China). The test went on in line with the geotechnical test code (SL237-1999) of China. Before the test the pressure cell and pressure system was removed from the apparatus and then the sample was put on the platform of the triaxial compression system for pressure test with a shearing rate of 4.14 mm?min-1. A dial gauge was used to monitor deformation of the soil column and of the dynamometric ring and record the process of ess-strain until collapse of the sample or the total axial strain reaching 20%. For soil samples that stood the pressure even after the total axial strain reached 20%, their shear strength should be the value that corresponded to the one when the strain reached 15%. After the compression test, the soil columns were separated along the failure surface, and then the roots appearing on the failure surface were counted and measured with an electronic calipers for diameter; Biomass of the roots in the sample was measured after the samples were oven dried. In October, roots of the three species of grasses growing in the field were dug up and measured with an electronic calipers for diameter and with a Shandu SN100 tension tester and a universal testing machine for tensile resistance of each root.【Result】 (1) The root systems of all the species of grasses enhanced the cohesive strength (△C) of the 0~25 cm soil layer by 4.75 kPa for Setariaanceps Stapf ex Massey L., by 4.40 kPa for Dactylisglomerata L. and by 1.39 kPa for Medicago sativa L., and that of the 25~50 cm soil layer by 3.10, 2.32 and 0.71 kPa, respectively; (2) △C (increment in tensile strength) was significantly related to root density (RD) and root area ratio (RAR) of Setariaanceps Stapf ex Massey L. and Dactylisglomerata L. roots in the failure surface and root content (Q) in the soil-root complex. The relationship between Q and △C was the highest. However, △C was not related with mean diameter of the roots (Tr,a). In the case of Medicago sativa L. △C had nothing to do with all the four root parameters.【Conclusion】 Setariaanceps Stapf ex Massey L. is the highest and Medicago sativa L. the lowest in the effect of enhancing shear strength of the soil. △C of Medicago sativa L. varies sharply, being higher in the upper half section than in the lower half section. As Setariaanceps Stapf ex Massey L. and Dactylisglomerata L. are herbs dominated with oblique root, among the three root parameters, RD, RAR and Q, Q is the best index for calculating △C, which makes it feasible to use the probability theory to calcuate stability of the unconfined compression test of samples collected from a number of sampling points on a vegetated slope.

    • Topsoil Magnetic Properties and Its Environmental Significance in West Sichuan

      2019, 56(3):661-671. DOI: 10.11766/trxb201806040188

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      Abstract:[Objective] To clarify the relationship between magnetic susceptibility and climatic factors is the key to applying magnetic susceptibility to inversion of paleoenvironmental evolution. Therefore the study on magnetic properties of the modern topsoil is one of the effective means to establish the relationship between climate and magnetic susceptibility. As far little has been reported in the literature on magnetic properties of surface rock in West Sichuan, and the research in this field will sure help provide a theoretical basis for inversion of paleoclimate and establishment of climate models for the region. [Method] This study was oriented to analyze variation of the topsoil magnetic properties of the region and its influencing factors and mechanism and to explore relationships between the topsoil magnetic properties and environmental factors by taking into account the environmental information, so as to provide scientific data for the study on paleosol and paleoclimate of the West Sichuan leoss region, through analysis of topsoil samples for room temperature magnetism and high temperature magnetism. [Result] The magnetic hysteresis loop shows that the ferrimagnetic mineral low in coercivity was the dominaral magnetic mineral in the soil sample, while M-T curve analysis shows that ferrimagnetic mineral was, in addition to a small amount of magnetite hematite and weakly magnetic hematite, and some lepidocrocite in quite a number of the samples. [Conclusion](1) The fine-grained superparamagnetic (SP) and single domain (SD) ferromagnetic minerals formed during in-situ pedogenic processes in the topsoil of West Sichuan is the dominant factor leading to higher magnetic susceptibility. The mechanism for magnetic enhancement of the topsoil in this area is similar to that in the Loess Plateau. (2) In terms of spatial distribution, the western and southern parts of the West Sichuan Plateau are higher than the eastern and northern parts in magnetic mineral content and in SP and SD particle content, too. Pedogenesis is the strongest in the western part of the Chengdu Plain, where the SP content is higher and the magnetic particles in the topsoil lower in average particle size than those all the other parts of the region. In addition, the topsoil in the area contains relatively more magnetic minerals high in coercivity, which demonstrates that the process of strongly magnetic minerals converting to weakly magnetic minerals did once occur. (3) The influence of climatic factors (especially precipitation) soil magnetic properties is the highest. Through the exploration of topsoil magnetic parameters and climatic factors in West Sichuan, it is found that in the region where the mean annual precipitation (MAP) varies in the range of 600~1000 mm, ?lf andχ fdis positively related with MAP in a whole and so are the magnetic parameters, i.e. χ fd%/HIRM, ARM/HIRM, χARM /SIRM in rainfall interval, but the correlation coefficients of these magnetic parameters with MAP are lower than those in the Loess Plateau, which may be attributed to the complex topography and relatively humid soil forming conditions in the study area.

    • Effect of Ion-strength on the Desorption of Copper Ions Adsorbed by Variable Charge Surface: Variable Charge Soils

      2019, 56(3):672-681. DOI: 10.11766/trxb201803050029

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      Abstract:【Objective】To investigate in depth effects of ionic strength on desorption of Cu(II) pre-adsorbed on surface of variable charges, two variable charge soils, Ali-Haplic Acrisol and Hyper-Rhodic Ferrasol were employed in a successive desorption experiment, in which the soils had been pre-treated with copper ions in de-ionized water or 0.1 mol•L-1 NaNO3 for adsorption and were then treated with a series of NaNO3stripping solutions with concentration ranging from low to high, to desorb the pre-adsorbed Cu(II) from the soils. 【Method】In this study, the two variable charge soils were pretreated with electrodialysis and then subjected to a series of adsorption and desorption tests with varying pH in an attempt to characterize copper ion (Cu(II)) desorption from clay minerals.【Result】Similar to the findings in the studies on kaolinite, Cu(II) adsorption of the soils increased rapidly from 0.05 to nearly 1 in score value within the range of the pH set for this research (pH 3.0~6.3). No matter what concentration of the electrolyte used, all the adsorption score value curves could be fitted with Fischer equation and the degree of fitting reached as high as 0.996 or more. Also it was noteworthy to note that when adsorption occurred in de-ionized water or 0.1 mol•L-1 NaNO3 solution, the same in pH, Cu(II) adsorption was always higher in de-ionized water than in 0.1 mol•L-1 NaNO3 solution in score value, which was attributed to the effect of the high concentration of electrolyte in the solution inhibiting Cu(II) adsorption. The findings of this experiment indicate, 1) that the adsorbed copper ions can be desorbed in de-ionized water and the desorption will decline in score value with desorption going on round after round in the waters the same in pH; 2) that in most cases, pH of the equilibrium liquid remains basically the same, around pH5.0, when the desorption lowers down to almost zero in score value; and 3) that the phenomena of re-adsorption will occur during the first round of desorption in de-ionized water only with pH above a specific pH, when the soils are pre-treated in 0.1 mol•L-1 NaNO3 solution, which means the copper ions will be adsorbed rather than desorbed when the equilibrium liquid is above this specific value in pH. Compared to Ali-Haplic Acrisol, Hyper-Rhodic Ferrasol is much lower in Cu(II) re-adsorption threshold. Similar to what happens in kaolinite, the results of sequential Cu(II) desorptions with NaNO3 solutions varying in concentration from low to high after the soils that had been pre-treated in either de-ionized water or 0.1 mol•L-1 NaNO3 solution, were subjected to three rounds of desorption with de-ionized water demonstrate 1) that Cu(II) that could not apparently be desorbed by de-ionized water, can be desorbed by NaNO3solution, and all the score value curves of pH-desorption follow a trend of rising first and then declining with rising pH regardless of concentration of NaNO3 or rounds of desorption; 2) that the score value of Cu(II) desorption peaks in 0.1 mol•L-1 NaNO3 solution; and 3) regardless of the concentration of NaNO3, there is a relatively gradual rise process before the desorption begins to soar up in score value. In all the case, Ali-Haper Acrisol is higher than Hyper-Rhodic Ferrasol in Cu(II) desorption score value, and in most cases the desorption score value curve has an apparent turning point where the desorption score value abruptly soars up, regardless of concentration of NaNO3 and rounds of desorption. Although the desorption equilibrium suspensions are not consistent in pH at the turning points, however, the pH at the turning points corresponding to the pHch of the desorption equilibrium suspensions are quite consistent, lingering around a special pH, that is, pH3.5, for Cu(II) adsorbed in de-ionized water, and pH3.18 or pH3.39 for CU(II) adsorbed in 0.1 mol•L-1 NaNO3 solution, which means that the copper ions adsorbed near the turning points of the pH-adsorption curves under any adsorption conditions exhibit a similar tendency in the desorption tests, that is climbing gently first and then abruptly soaring up with rising pH of the system. 【Conclusion】All the above-descrobed phenomenon and differences can be attributed to the difference between the two variable charge soils in content of iron oxide and the difference between iron oxide and kaolinite in nature of the surface charge.

    • Morphological Transformation and Migration of Heavy Metals (Pb, Cr and Cu) in Coal Ash Applied to the Soil-Chinese Cabbage System

      2019, 56(3):682-692. DOI: 10.11766/trxb201807250344

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      Abstract:【Objective】So far little has been reported in the literature about morphological transformation of heavy metal elements in coal ash applied as soil amendment and hazards of long-term application of the coal ash to the soil environment and human health, though a quite number of researchers reported that application of coal ash in agriculture is of positive significance. However, statistics of the literatures both at home and abroad indicates that most of their conclusions were based on cultivation of only one crop and analysis of yield and quality of the crop. Therefore, this paper aimed to explore transformation, migration and concentration trend of Pb, Cr and Cu in the soil-Chinese cabbage system under long-term continuous cultivation, in an attempt to provide a certain theoretical basis and support with data for use of coal ash as amendment in agriculture and ecological environment. 【Method】Chinese cabbage was cultivated for four consecutive seasons in pots of brown soil amended with coal ashes different in particle size, i.e. fine coal ash collected with a bag-type dust remover and coarse coal ash collected from a boiler furnace and different in rate, separately. In this project, samples of the soils mixed with coal ash were collected for analyses of chemical fractions of heavy metals (Cr, Cu and Pb) by following the three-step sequential extraction procedure laid down by the EC Reference Bureau (BCR). Contents of heavy metals (Cr, Cu and Pb) in the roots and edible parts of the cabbage were also determined for calculation of enrichment coefficients and transfer coefficients of the heavy metals in the Chinese cabbage and for analysis of migration behavior and bioavailability of the heavy metals in the Chinese cabbage. 【Result】Contents of HOAc(acetic acid) soluble fractions of Pb and Cr in different coal ash treatments were measured, displaying an order of 150 g·kg-1 coarse coal ash > 150 g·kg-1 fine coal ash > 50 g·kg-1 coarse coal ash > 50 g·kg-1 fine coal ash > CK, which indicates that both application rate and particle size of coal ash affected the fraction of HOAc soluble Pb or Cr in content. Analysis of distributions of Pb, Cr and Cu relative to form in the soil exhibits an order of residual fraction > reducible fraction/oxidable fraction > HOAc soluble fraction. All the findings demonstrate that Pb, Cr and Cu remains mainly as residue in the treated soils, and their contents decrease with the cultivation going on season by season. The fraction of extractable Pb and Cr accounted for 150 g·kg-1 or more, and that of HOAc soluble ones increased with the cultivation going on season by season. However, both the fractions of extractable Pb and Cr accounted for 55% or more, and the fraction of HOAc soluble ones decreased with the cultivation going on season by season. Heavy metal enrichment ability of the plant varied in the order of Cu > Cr > Pb, all of which were lower than the threshold value of 1. Therefore, compared with Pb and Cr, Cu was higher in bioavailability. The contents of heavy metals in the root of Chinese cabbage were lower than their respective ones in the edible part, and their transfer coefficients were all > 1. Their transfer capacity was in the order of Cr > Cu > Pb, so the migration ability of Cr in Chinese cabbage was higher than the other two. 【Conclusion】With the plant growing on, contents of the heavy metal residues in the treated soils decrease gradually, while contents of the HOAc soluble fractions increase gradually, indicating that the residues become HOAc soluble. The organic acids secreted from roots of the Chinese cabbage activate the coal ash applied to soil, thus making the heavy metals in the soil gradually transform from residual form into potentially available form and/or HOAc soluble form, thereby enhancing bioavailability of the heavy metals gradually. Although the heavy metal enrichment coefficients of the Chinese cabbage are low, the heavy metal transfer coefficients are high, which will pose a safety hazard with the edible part of the Chinese cabbage.

    • Ammonia Emission Following Fertilization at Booting Stage of Rice Crop in Taihu Lake Region relative to Monitoring Techniques

      2019, 56(3):693-702. DOI: 10.11766/trxb201806280349

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      Abstract:【Objective】 There is a long history, more than 400 years, of fertilization at booting stage of single cropping rice (Oryza sativa L.) in the Taihu Lake region. Historical records show it started in the late Ming Dynasty. Fertilization at the booting stage of rice can effectively improve yield and quality of rice. However, ammonia volatilization is liable to occur when top-dressing fertilizer is broadcasted onto paddy fields. Ammonia emitted from agricultural fields brings about adverse effects on the air and water environment, such as smog and eutrophication. How ammonia emits from paddy ecosystems after fertilization at the booting stage of rice is still not clear. 【Method】Field measurement of ammonia emissions from paddy fields at the booting stage of single cropping rice was conducted in the rice season of 2017 in the Taihu Lake region, using simultaneously three different techniques different in monitoring principle, including micrometeorological mass-balance integrated horizontal flux (IHF), dynamic chamber technique and static chamber technique. For the IHF technique, five layers of passive flux ammonia samplers were placed at a set interval around a mast in the center of circular plots (20-m radius) above the soil-water surface, and this apparatus did not need simultaneous measurement of ammonia concentration and wind speed. For the dynamic technique, air exchange rate of 17 times per minute was adopted, and NH4+-N concentration and pH in the floodwater on the surface of the paddy field was measured after surface application of urea. 【Result】Results show that dynamics of the daily ammonia emissions monitored with the three different techniques were similar in feature. Ammonia emission peaked on the second day after surface application of urea and continued till the 5th day when it stopped. The dynamics of the NH4+-N concentration in the surface floodwater and ammonia emission varied similarly. Monitoring with the IHF technique showed that cumulative ammonia (NH3-N) emission above the rice canopy was 5.45 kg·hm-2, accounting for 6.73% of the applied nitrogen. Monitoring with the dynamic chamber technique showed that ammonia emission from soil-water surface was 17.4 kg·hm-2, accounting for 21.5% of the applied nitrogen, and that ammonia emission from the soil-water surface and ammonia emission flux were linearly related with air temperature. And monitoring with the dynamic chamber technique showed that the optimal timing for air sampling was 8:00~9:00 and 16:00~17:00. What it monitored was ammonia emission potentials from the soil-water surface after surface application of urea, without taking into account the volatilized ammonia captured by the rice canopy. Consequently, the dynamic chamber technique tended to overestimate ammonia emissions from paddy fields at the booting stage of rice after urea application. In using this technique to monitor ammonia emission in different treatments and their replicates, it is essential to have uniform air chamber specifications and air flow rates. Like the dynamic chamber technique, the static chamber technique monitored ammonia emission from the soil-water surface. However, the former was much higher than the latter in air exchange rate in the chamber, because the air exchange was somewhat hindered in the chamber of the latter. So the ammonia flux monitored with the static chamber technique was much lower than that monitored with the dynamic chamber technique. 【Conclusion】The assessment of ammonia emission from paddy fields after fertilization at the booting stage of rice should be based on what is obtained with the micrometeorological IHF method because it monitors ammonia emission above the canopy of the crop. As when topdressing urea is applied to rice at its booting stage, the crop has already formed its canopy, which covers almost the whole soil-water surface of the paddy field and recaptures and absorbs the ammonia emitted from soil-water surface. Hence as a matter of fact, the ammonia emission in the rice ecosystem is not serious. The dynamic chamber technique is only suitable for monitoring ammonia emissions from soil-water surface when the rice plant is still at its growth stages after transplanting.

    • Effects of Reductive Soil Disinfestation on Obstacles and Growth of Replant Seedlings in Sanqi Ginseng Mono-Cropped Soils

      2019, 56(3):703-715. DOI: 10.11766/trxb201806110164

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      Abstract:【Objective】Sanqi ginseng Panax notoginseng [(Burk.) F. H. Chen] is a valuable traditional Chinese medicinal herb grown in Yunnan. It is no good to cultivate the plants continuously in the same field. Reductive soil disinfestation (RSD) is a technique for pre-planting soil treatment that has been proven to be successful in overcoming the obstacles of monocropping of vegetable, flower, etc. However, it is not sure whether RSD can help overcome the obstacles of monocropping of Sanqi ginseng. Therefore, this study was designed to explore effects of RSD on obstacles in monocropping of Sanqi ginseng and growth of seedlings of the crop. 【Method】 A field experiment was carried out, designed to have four treatments, i.e. CK (control without soil treatment); SB [RSD coupled with application of 15 t•hm-2 organic substrate high in C/N ratio, (C/N 94)]; BD [RSD coupled with application of 15 t•hm-2 organic substrate low in C/N ratio (C/N 19)]; and SB+BD [RSD coupled with application of 15 t•hm-2 organic substrate, containing both high and low C/N ones, half by half (m/m=1:1)]. Contents of saponins in the soils were measured with a high performance liquid chromatographer (HPLC), and microbial population and community structure were determined by means of real-time PCR and DGGE. Survival rate and disease incidence of replanted Sanqi ginseng seedlings were also recorded. 【Results】 Results show that RSD significantly helped degrade saponins as compared to CK. The degradation rate of Rb1 and Rh1 in treatments BD and SB+BD reached up to 82.1% and 85.8%~88.1%, respectively. Besides, RSD effectively reduced the population of Fusarium oxysporum (F. oxysporum) and lowered its proportion in the fungi community, with sterilizing rate reaching as high as 99.7%. Furthermore, the number of replanted Sanqi ginseng seedlings survived the transplantation for 5 months was 7.3~8.5 times higher in the RSD treatments than in CK, while disease incidence decreased significantly from 89.0% in CK to 12.9%~16.1% in the RSD treatments. 【Conclusion】Therefore, it is concluded that RSD can remarkably remove the obstacles in mono-cropping of Sanqi ginseng, improve the soil microbial community structure, raise the survival rate, and reduce the disease incidence of replanted Sanqi ginseng seedlings. So it is a promising agricultural practice to overcome the obstacles in monocropping of Sanqi ginseng.

    • Evaluation of Effect of Trichoderma Controlling Fusarium wilt Disease and Its Influencing Factors with Meta-analysis in China

      2019, 56(3):716-727. DOI: 10.11766/trxb201808100354

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      Abstract:【Objective】Currently, numerous researchers and farmers in China are steadily realizing that Trichoderma can not only function to promote plant root growth, but also protect plant roots from infection of soil-borne pathogens. So they focus their researches on using different species of Trichoderma to inhibit fusarium wilt disease in different crops and their approaches. However, it is still not very clear how effective Trichoderma is to control the disease and what are its influencing factors. In this study based on the researches so far done in China, the Meta-analysis method was adopted to evaluate effectiveness of the control and define its influencing factors. 【Method】Based on the papers published in Chinese and in English as well in China addressing the use of Trichoderma to control fusarium wilt disease of different crops, this study used the Meta analysis method to evaluate fusarium wilt disease controlling effect of Trichoderma and to analyze impacts of a variety of factors on effectiveness of the control.【Result】Results show that generally speaking, Trichoderma demonstrates a remarkable fusarium wilt disease controlling effect and its biological control effect reaches more than 60%. Both field experiment and pot experiment were carried out with similar outcomes. Crop family, Trichoderma form, application mode, climate type (field experiment) and usage in combination with other disease control strategies, etc. were factors significantly affecting effectiveness of the control. To be more specific, application of Trichoderma to crops of Solanaceae, Cucurbitaceae and Malvaceae showed the most significant effect; Trichoderma mixed with soil for application, applied in pits and applied in multi-ways simultaneously was higher in effect than that applied in a single way; application of Trichoderma in the form of biomanure or mixture of solid and liquid fungal agents was the first option; and its effect would be more significant when used in areas under the temperate monsoon climate than when used in areas under the subtropical monsoon climate. However, Trichoderma species, experiment type, application rate and application timing was not found to have much impacts on its disease controlling effect in the field and pot experiments. 【Conclusion】 Therefore, in order to more effectively control fusarium wilt disease in the field with Trichoderma, the influencing factors discussed above should be taken into account properly. The findings of this study are also expected to be of some reference value to farmers in practical and efficient application of Trichoderma to control soil-borne fusarium wilt disease in the field.

    • Alleviating Effects of Exogenous Nitric Oxide on Oxidative Damage in Tomato Seedling Leaves under Ca(NO3)2 Stress

      2019, 56(3):728-738. DOI: 10.11766/trxb201806130266

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      Abstract:【Objective】 In relatively enclosed greenhouses, soil salts tend to accumulate gradually in topsoil duo to the special greenhouse environment of no rain water leaching, high temperature and resultant high evaporation, thus leading to serious secondary salinization of the greenhouse soil. According to relevant reports, the high level of Ca(NO3)2 accumulation was one of the main causes of high soil salinity in greenhouses. Nitric oxide (NO) is a kind of micromolecule active material that generally exists inside plants. As a plant hormone and signaling molecule, NO extensively participates in regulating of plants’ responses to various adversity stress. The aim of this paper is to investigate roles of exogenous NO in regulating the antioxidant system of plants under Ca(NO3)2 stress. 【Method】A hydroponic experiment was conducted to investigate effects of foliar spray of sodium nitroprusside (SNP) as exogenous NO donor on growth of tomato (‘Qin Feng Bao Guan’) seedlings, and photosynthetic, reactive oxygen, anti-oxidase activities, and ascorbate-glutathione cycle in their leaves under the stress of 80 mmol·L-1 Ca(NO3)2. 【Result】In the leaves of the tomato seedlings under Ca(NO3)2 stress, foliar spray SNP significantly lowered O2·- production rate, H2O2, malondialdehyde, dehydroascorbic acid and oxidized glutathione in content and electrolyte leakage rate, but heightened or maintained superoxide dismutase, peroxidase, catalase, ascorbate peroxidase, glutathione reductase, dehydroascorbate reductase and monodehydroascorbate reductase in activity; besides, it significantly increased the contents of ascorbic acid and glutathione and their reducing power. As a result, active oxygen damage of the leaves was effectively alleviated, and chlorophyll degradation and photosynthetic rate declining trend were effectively suppressed. 【Conclusion】 Exogenous NO treatment plays an important role in maintaining or improving the activity of antioxidant enzymes and promoting the operation of aseorbate-glutathione (AsA-GSH) cycle in tomato under the stress of Ca(NO3)2, thus relieving the plants of oxidative damage significantly, and improving their leaf membrane system in stability, their photosynthetic function, their tolerance to salt and eventually their growth.

    • Effects of Land Use of Different Patterns on Soil Clay Mineral Compositions in Piedmont Plain of Mountain Tai

      2019, 56(3):739-748. DOI: 10.11766/trxb201806090273

      Abstract (1651) HTML (0) PDF 2.62 M (1903) Comment (0) Favorites

      Abstract:【Objective】It is well known that soil clay minerals play an important role in sustaining soil fertility, and composition of soil clay minerals vary with vegetation and management systems and land use patterns. A field survey of the piedmont plain of Mountain Tai was carried out on variation of clay mineral composition in the aquic brown soil with land use, i.e. wheat-maize rotation, poplar plantation and barren land, its affecting factors and its relationship with soil fertility indices.【Method】Based on the field survey, soil samples were collected from the fields different in land use for extraction of < 2 μm soil clay particle with pipette method and analysis of composition of the extracted clay and relevant indices with the X-ray diffraction (XRD) method. XRD was applied to the clay samples for XRD patterns after the samples were treated separately with (a) the magnesium saturation and air-drying method, (b) magnesium saturation followed glycerol salvation, or (c) potassium saturation and heating at 300oC or 500oC method.【Result】Qualitative analysis of the experimental XRD patterns reveals that the soils, regardless of land use patterns, had illite as dominant clay mineral, which consisted of well crystallized illite (WCI) and poorly crystallized illite (PCI), vermiculite and kaolinite in the next, and mixed-layer minerals the least. Quantitative information of clay mineral fraction derived from the fitting procedure for the different sub-fractions allowed for determination of complex mineralogy of the < 2 μm clay fraction in the soil samples. Results show that the soil samples varied in percentage of clay mineral fractions with land use. The barren land was the highest in illite in the topsoil, reaching 75.8% and being, 26.4%, 23.6% than higher the agricultural soil and plantation respectively. The content of illite was significantly lower in the subsoil than the topsoil, especially for barren land. PCI varied similarly to illite in content. WCI content reflected weathering degree of the soil, hence it increased successively barren land to, plantation and agricultural soil. Vermiculite content in the topsoil was not significantly different between the three different land. However, it varied more remarkably in the subsoil than in the topsoil and in order of as barren land > agricultural soil > plantation. Kaolinite content was similar to vermiculite content in variation in the soils. Barren land soil was lower than the other two in soil organic carbon content and content of inorganic-organic complexes, too.【Conclusion】The content of illite in the soil negatively related to the content of vermiculite, but positively related to soil available potassium, which is attributed to the transformation between illite and vermiculite. The content of soil organic carbon and the formation of inorganic-organic complexes with sodium dispersion grows in agricultural soil as affected by tillage, fertilization, and so on, which inhabit movement of the clay minerals in the soil layer, enhance weathering of the soil minerals, and increase availability of the potassium embedded in illite. Nowadays more and more barren land is reclaimed into plantation and meadowland, thus increasing vegetation coverage and hence soil organic carbon content, and controlling erosion of the land.

    • Soil Conservation Effect of Haloxylon Ammodendron Bushes in Hexi Oasis-Desert Ecotone

      2019, 56(3):749-762. DOI: 10.11766/trxb201806260176

      Abstract (1484) HTML (0) PDF 2.84 M (1824) Comment (0) Favorites

      Abstract:【Objective】In fragile ecosystems of the arid regions, soil revegetation effect is closely related to soil conservation effect. Haloxylon Ammodendron forest play a quite important role in soil quality evolution in oasis-desert ecozones by protecting and ameliorating the soil. Especially its wind-breaking and sand-fixing effects and its generation of litter, which decomposes and transforms into organic matter and soil nutrients, are the most direct external environmental factors that affect soil quality evolution the most significantly. To explore soil conserving and restoring effects ofHaloxylon Ammodendronforests, affecting factors of the effects and relationships between the factors, and internal mechanism of the effects, stands of Haloxylon Ammodendronforest different in age were selected for the study in an attempt to provide a theoretical basis for management of soil quality in the Hexi Oasis-desert Ecotone.【Methods】The paper adopted the concept of space as a substitute for time in typical sampling in the ecozone. Three stands of Haloxylon Ammodendron forest different in age (20a, 30a and 40a)’ and a tract of bare land were set for long-term monitoring and soil sampling for analysis of soil mechanical composition, chemical properties, microbial population and enzyme activity, and multiple comparisons, variance analysis and correlation analysis were used to analyze variation rules of and relationships between the factors.【Results】Results show that soil protecting effects of the forest varied with growth and age of the forest. Wind decreased gradually in speed when approaching the forest. The effect was more obvious at the lee side than at the windward side. At the height of 20 cm, 50 cm, 100 cm and 200 cm above the ground in the forest wind speed decreased by 13.75%, 14.55%, 15.0% and 7.34% or more, respectively. Obviously the wind reducing effect is higher in the middle and lower part of the forests than in the upper part, and about 1.05~2.04 times of that at the top of the plants. With the forest growing in age, the magnitude of wind reduction increased from 12.66% to 20.41%. In terms of wind reduction magnitude at the height of 20cm, 50cm and 100cm above the ground, the three stands displayed an order of stand 30 years old > stand 40 years old > stand 20 years old, but in terms of at the height of 200 cm, they exhibited a different order, i.e. stand 40 years old > stand 30 years old > stand 20 years old. In the stands of Haloxylon Ammodendron forest, regardless of age, the proportions of silt and clay were much lower that those of coarse sand and fine sand in the surface layer, and with the increase in soil depth, the contents of silt and clay decreased slightly, but were still significantly higher than that in the bare land. With the forest growing in age, the content of silt and clay increased and the content of coarse sand decreased, and both leveled off at the age of 30. The stands all peaked in nutrient content, microorganism population and enzyme activity at the age of 30, exhibiting an order of stand 30 years old > stand 40 years old > stand 20 years old, and were all over 1.02 times higher than those in the bare land. The content of soil nutrients decreased with soil depth,. The populations of soil actinomycetes and fungi and the activity of invertase was the highest in the surface soil, then in the subsoil layer and the lowest in the bottom layer. The activity of catalase and alkaline phosphatase was just in a reverse order. No obvious regularity was observed for soil bacteria in population, but good relationships were observed of the factors of the soil conservation effect of Haloxylon Ammodendronforest with soil mechanical composition, soil nutrient status, and microorganism population and enzyme activity. Wind breaking effect of the forest was significantly related to soil mechanical composition (r>0.87).【Conclusions】Considering the soil protecting and ameliorating effects of Haloxylon Ammodendronforest, the forest 30 years in stand age is the most suitable for the local habitat conditions and the highest in soil conserving effect. So in management of Haloxylon Ammodendron forests over 30 years in stand age, it is recommended to cut down trees selectively for thinning, and adopt water conserving and nutrient supplementing measures and some others so as to ensure healthy growth of the forests and enable them to keep on playing their ecological role in wind breaking and sand fixing in the ecozone.

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