• Volume 55,Issue 4,2018 Table of Contents
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    • >Reviews and Comments
    • Effects of Storage on Soil Biochemical Properties and Application of Stored Soil

      2018, 55(4):783-796. DOI: 10.11766/trxb201711270354

      Abstract (2075) HTML (6450) PDF 1.07 M (4216) Comment (0) Favorites

      Abstract:Biochemical properties of a soil sample may reflect the ecology and environment of the sampling area at the time when it was collected. So soil samples are of ultra-important scientific research value. For various research purposes, soil samples, before use, need certain pretreatment and storage for a certain period of time, which may last for several days or even over a hundred years. Quite a number of large-scale soil sample banks have been established the world over, storing various types of soil samples, which are of significant application value. It is essential for usage of the long-stored soil samples to ensure whether their biochemical properties change during their storage process. In this research, changes in soil biochemical properties relative to storage conditions were summarized, including soil elements, soil nutrients, soil metabolic activities, pH, soil microbes, soil enzymes and soil pollutants. The research found that the contents of soil carbon, nitrogen, phosphorus and metal elements remained almost unchanged in the soil samples during their storage; that information about soil microbial community structure and DNA/RNA sequences could still be extracted from the soil samples; that persistent organic pollutants, hardly degraded, could exist in the samples for long; and that although soil enzyme activities decreased with the storage going on, the differences between the enzymes in activity were preserved. Therefore, long-stored soil samples are still valid for analysis of element contents, microbial communities, DNA/RNA sequence, soil organic pollutants and soil enzyme activities for comparison study. However, contents of readily available nutrients and soil metabolism-related indices varied irregularly during the storage, which indicates that only fresh soil samples can be used for analysis of these indices like nitrate nitrogen, ammonium nitrogen, exchangeable cation and soil respiration rate. Soil samples for long-term storage should be air-dried and then kept in sealed glass bottles at room temperature. There are several issues that matter in the use of long-stored soil samples: 1) Avoiding environmental contamination when soil samples are collected and analyzed; 2) Adopting suitable biochemical analysis methods to guarantee stability and reliability of the measurements; and 3) Considering the differences existing in effect of storage on soil samples relative to soil type. With analytical technology developing on and on, more and more historical environmental information will be excavated from the long-stored soil samples, which will yield higher scientific values.

    • >Healthy Soil for Sustainable Development
    • Effects of Oxygenated Irrigation on Nutritional Characteristics of Cotton and Soil Fertility

      2018, 55(4):797-803. DOI: 10.11766/trxb201712290372

      Abstract (1711) HTML (967) PDF 1.16 M (2321) Comment (0) Favorites

      Abstract:【Objective】In this study a simulation experiment and a field experiment was carried out, using the cotton variety of Xinluzao 41 to explore effect of oxygenation of irrigation water on content of dissolved oxygen in the irrigation water and effect of oxygenated irrigation on soil nutrient, soil microbes, and nutrient uptake and yield of cotton, the yield of cotton、soil Nutrients and soil microbial quantity in cotton field was studied. 【Method】In the simulation experiment, irrigation water was oxygenated with the aid of a micro bubble generator to four different levels of dissolved oxygen in concentration, that is, CK without oxygenation, O2 21%, O2 30%, and O2 50%. Concentration of dissolved oxygen in the irrigation water was continuously monitored in the main pipe and drip-irrigation pipes. In the field experiment, irrigation water was oxygenated by physical means (PO), by chemical means (CO) and by no means (CK). 【Result】Results show that in oxygenated irrigation, oxygen concentration in the irrigation water increased significantly with oxygenation, but decreased with length of the pipe, and decay intensified with increasing dissolved oxygen concentration, so 12~14 mg L-1 was; The optimal concentration of dissolved oxygen for oxygenation of irrigation water oxygenated irrigation significantly increased yield of the cotton, which was 11.39% and 11.42% higher in Treatment PO and CO than CK; oxygenated irrigation enhanced nutrient uptake of the cotton, thus lowering the nutrient contents (NPK) and organic manure content as well in the soil; Treatment CO was significantly or 27.23% and 9.61% lower than CK in soil ready available N and soil organic manure content, and Treatment PO was significantly or 5.78% lower than CK in soil readily available K; Oxygenated irrigation also promoted growth of bacteria, fungi amd microorganisms in the cotton field. Treatment PO and CO was 28.38% and 21.05%, respectively, higher in soil bacterial population and 27.86% and 20.63%, respectively, higher in soil total microbial biomass than CK. The difference between treatments was significant. Correlation analysis of soil nutrient and soil microbial population shows that the population of actinomyces is significantly and positively relatd to the contents of available N and organic matter; the population of soil bacteria is to the total amount of microorganism; and the content of available N is to the content of organic matter. 【Conclusion】All the findings in this study demonstrate that cotton roots are very sensitive to oxygen and that oxygenated irrigation can further exploit the yield potential of cotton, and no matter how much the irrigation water is oxygenated, promote to a varying extent growth and nutrient uptake of cotton.

    • Coupling Effect of Water and Fertilizer on Grape under Drip Irrigation in Extremely Arid Regions

      2018, 55(4):804-814. DOI: 10.11766/trxb201710090366

      Abstract (1694) HTML (712) PDF 1.42 M (2734) Comment (0) Favorites

      Abstract:【Objective】 Grape plantation is a special pillar industry of the Turpan-Hami region of Xinjiang. As the region is extremely arid, short of rain, and very high in evapotranspiration rate, the grape plantations in that region are often perplexed by problems in water and nutrient management, such as over-dozed irrigation, high cost with low efficiency, etc.. To solve these problems, a field experiment on drip fertigation was conducted to explore coupling effect of water and fertilizer on grape yield, and further on coordinating and complementary effects of the two, in an attempt to work out a quota for drip irrigation and a rate for fertilization suitable to the grape plantations in the region. 【Method】 The experiment used a technique integrating drip irrigation with fertilization and was designed to have three levels of irrigation quota, i.e. W1, high volume ( 10 950 m3 hm-2); W2, moderate volume (5 500 m3 hm-2) and W3, low volume (5 500 m3 hm-2), three levels of fertilization rate, i.e. F1, high rate (750 kg hm-2); F2, moderate rate (450 kg hm-2) and F2, low rate (300 kg hm-2), and a control, CK (conventional furrow irrigation at 12 750 m3 hm-2 and no sidedressing). Fertilizer was applied in the sprouting period (the first ten-day period of May), the fruit bearing period (the first ten-day period of June), and early fruit maturing period (the first ten-day period of July), once each time, making up a total of 3 times a year. So, the fertilizer applied to the fertilization treatment were divided into three portions in line with the ratio of 1:2:2, and applied sequentially, that is. 60 kg hm-2, 120 kg hm-2 and 120 kg hm-2 for Treatment F3, 90 kg hm-2, 180 kg hm-2 and 180 kg hm-2 for Treatment F2, and 150 kg hm-2, 300 kg hm-2 and 300 kg hm-2 for Treatment F1. 【Result】 Results show that water consumptions at all the growth stages exhibited a trend of rising first and then falling in all the treatments, and the total water consumption was not only related to the quota of water irrigated, but also to water consuming capability of the grape vine per se during its growth period and length of its growing season. The plants in the fruit bulging and maturing periods were highest in water consumption and then in the blooming period and the branch and tendril mature period, and the lowest in the sprouting and new shoot growing periods. The grape yield in Treatment W1F1, W1F2, W1F3, W2F1, W2F2, W2F3, W3F1, W3F2, W3F3 and CK was 38 221 kg hm-2, 31 844 kg hm-2, 33 213 kg hm-2, 38 179 kg hm-2, 37 393 kg hm-2, 32 273 kg hm-2, 32 230 kg hm-2, 28 743 kg hm-2, 29 157 kg hm-2 and 29 276 kg hm-2 respectively. The relations of grape yield (Y) with water consumption (W), and nitrogen rate (F) could well be described with a binary quadratic polynomial, expressed as: Y=-9 197+10.04W-7.713F-0.000 6W2+0.010 4F2+0.000 9WF, from which extremes were worked out, indicating that the optimal irrigation quota and nitrogen application rate is 8 736 kg hm-2 and 390 kg hm-2, respectively, that may bring the yield up to as high as 34 393 kg hm-2. 【Conclusion】 With the same irrigation dosage, the treatments, the highest in fertilization rate were the highest in yield, averaged to be 36 210 kg hm-2, and the lowest in fertilization rate, the lowest in yield, averaged to be 31 548 kg hm-2. With the same fertilization rate, the treatments, the highest in irrigation dosage, were the highest in yield, which meant that water and fertilizer has great positive effects on grape yield. The yield could be increased by increasing irrigation dosage within a reasonable range, and the yield would decrease once irrigation was done beyond the range. However, optimum grape yield could still be obtained with the irrigation dosage cut off by no more than 56%, and fertilization rate by around 25%. Comparison of the predicted yield using the mathematical model with the measured yield shows that grape yield in this region could be maintained at a relatively high level with the irrigation quota set to be 8 250~9 000 m3 hm-2 and fertilization rate to be 300~450 kg hm-2.

    • Effect of Straw Biochar on Utilization of Soil Phosphorus and Growth of Bok Choi in Greenhouse in Dianchi Lake Basin

      2018, 55(4):815-824. DOI: 10.11766/trxb201709210394

      Abstract (2041) HTML (883) PDF 1.47 M (2327) Comment (0) Favorites

      Abstract:【Objective】Lake Dianchi is a lake the most serious in eutrophication in China. Most of the phosphorus applied in farmlands in the Dianchi Lake watershed is finally imported into the Lake, which is an important reason for eutrophication of the Lake. Biochar as a soil amendment can be used to improve soil physical and chemical properties, adsorb soil phosphate, and hence reduce phosphorus loss from the soil. In order to improve bio-availability of soil phosphorus, increase yield of crops, reduce phosphorus pollution of the soil and the environment, and provide a theoretical basis for management and application of biochar in the soil environment, this study was carried out. 【Method】In this study, an indoor simulation and greenhouse pot experiments were conducted to explore effects of biochar on loss and utilization of phosphorus in the production of bok choi and yield of the crop. The experiment was designed to have a gradient of five levels of biochar application rate, and four levels of phosphate application rate, thus making up 20 treatments and three replicates for each. Bok choi was planted in single-compartment planting boxes in a greenhouse. Each box contained 5 kg of soil and had 8 bok choi plants. After the application of biochar, the soils in the boxes were analyzed for total phosphorus and available phosphorus, separately and ratio of the two calculated. After the plants were harvested, the soils in the boxes were analyzed again for fertilizer utilization efficiency and phosphorus loss and effects of the biochar. On D3 (Three days after sowing), germination rate and cotyledon flattening rate of the plants were measured. On D10, D20, D30 and D40, plant height and plant weight was checked of the plants harvested, and effects of the biochar on growth of bok choi were analyzed. After harvesting of the crop, effect of the biochar on yield of bok choi analyzed, calculated and converted into yield per hectare. 【Result】Application of biochar may improve P utilization efficiency of bok choi in greenhouse. In the treatment, 8% in biochar application rate and 33 kg hm-2,(1/2 of the conventional rate) in P2O5 application rate, P fertilizer utilization efficiency increased from 14.77% up to 31.21% or by 111.3%, thus reducing P loss by 43.83%, and germination rate of the crop increased by 7%~ 9%, cotyledons flattening rate by 10%~ 12%, plant height by 69.51%, plant weight by 71.75% and yield by 31.87%. The effect of biochar on plant height appeared the most significantly during the period of D20 ~ D40 and that on plant weight did during the period of D30 ~ D40. 【Conclusion】The application of 8% corn stalk-derived biochar can increase the content of soil available phosphorus in greenhouse, reduce the loss of phosphorus, improve the growth of bok chai Therefore, it can be used as a good soil amendment in greenhouse.

    • Effects of Organic Manure on Soil Nutrients and Aggregate Composition in Soil under Mono-Cropping of Soybean

      2018, 55(4):825-834. DOI: 10.11766/trxb201711100361

      Abstract (1736) HTML (540) PDF 1.79 M (2456) Comment (0) Favorites

      Abstract:【Objective】Effects of organic manure on soil nutrients, crop yield, and composition and stability of soil aggregates in the soil under mono-cropping soybean were explored through a seven-year field experiment, designed to have three treatments, in respect to type of organic manure, i.e. JF (Composted chicken droppings), JG (corn stalk) and JZ (Fungi residues).【Method】 In this study, soil samples were collected and analyzed regularly for variations of nutrient contents, composition and stability of soil aggregates, and mean weight diameter of water stable soil aggregates. 【Result】 Results show that application of organic manure improved soil nutrient contents in the soil under mono-cropping of soybean, and altered composition of soil aggregates significantly by increasing the fraction (0.25~2 mm) of aggregates obviously. All the treatments were higher than CK in content of alkaliyzable N, readily available P, readily available potassium, organic matter, microbial biomass C, microbial biomass N and microbial biomass P. Treatment JF was the most obvious in such effect on content of alkalyzable nitrogen, or 13.85% higher than CK; Treatment JG was the most on content of readily available phosphorus or 4.13% higher than CK; Treatment JF was the most on content of readily available potassium or 8.97% higher than CK; Treatment JG was the most on content of organic matter or 7.28% higher than CK. Treatment JZ, though not so good as the other two, was still significantly higher than CK in nutrient content. Application of the organic manures improved yield of soybean, and Treatment JF was the most remarkable in this effect. The application also effectively raised the content of soil microbial biomass carbon in the soil and Treatment JZ was the most in this effect. Treatment JF and JG did have some effect, too,, but not so significant. All the three treatments increased significantly the content of nitrogen in the soil, and Treatment JF was more obvious than Treatment JG and JZ in this effect, which indicates that organic manures can significantly increase the content of soil microbial biomass nitrogen. Treatment JG was the most effective in improving the content of soil microbial biomass phosphorus in the soil and Treatments JF and JZ were, too, though not so significantly. Treatments JG and JZ significantly improved the metabolic entropy of soil microorganisms, but Treatment JF was lower than CK in metabolic entropy. Mean weight diameter of the soil aggregate in the three treatments increased, exhibiting an order of JF > JG > JZ. The three treatments increased the fraction (> 1 mm) of soil aggregates more than the others In Treatment JF, JG and JZ the fraction (> 1mm) of aggregates accounted for 29.52%, 38.97% and 29.07%, respectively, of the soil aggregate stability index, and the fraction (> 0.25 mm) of aggregates was significantly higher than that in CK in stability index, which suggests that the organic manures applied into the soil can effectively improve stability of the soil aggregates, and the proportion of water-stable soil aggregates. It can be seen that application of the organic manures is very effective in increasing mean weight diameter and water stability of the soil aggregates in soybean fields. The three types of organic manure all can effectively improve soil aggregate stability, and Treatment JG is the most effective, increasing by 89.79% or being 4.293 In terms of soil aggregate stability index, the treatments exhibite an order of JG (4.293) > JZ (3.788) > JF (3.720) > CK (2.262). Application of the organic manures significantly improve soil aggregation, increasing the fraction (> 0.25 mm) of water stable aggregates and its mean weight diameter, preservation probability and stability index.【Conclusion】The organic manures can significantly improve soil fertility, and composition and water stability of the soil aggregates in the soybean fields. This study is expected to be able to provide certain reference for improving soil fertility and increasing soybean yield, which is of great significance to overcoming the obstacle of mono-cropping of soybean.

    • Effects of Straw Return on Soil Physico-chemical Properties of Chernozem in Northeast China and Maize Yield Therein

      2018, 55(4):835-846. DOI: 10.11766/trxb201709260363

      Abstract (2123) HTML (1247) PDF 1.85 M (2689) Comment (0) Favorites

      Abstract:【Objective】With developing agriculture, the amount of crop residues increases, too, posing a serious environmental concern of how to rationally utilize the by-product. Incorporation of crop residue into the field is one of the optimal ways to recycle crop residue. In Northeast China, straw is returned into the field normally in two ways. One is to plow the returned straw into soil, and the other leave the straw over on the surface of the field as mulch. However, the traditional ways do have some shortcomings, for instance, the returned straw is hard to decompose in the soil; it affects seedling emergence; it makes tillage difficult, and so on. Consequently a now straw returning method is, hereby, invented, that is, even incorporation of straw (EIS), which is implemented in two steps, 1) straw is crashed into pieces, 1~2 cm in length and spread over the field by the combine harvesting the crop; and 2) the straw is plowed evenly into the 0~70 cm soil layer, using the crashing-ridging technology. When the new method is applied, the soil pan is tilled loose, thus reducing the soil bulk density, and improving the soil structure. However, so far little has been done on effects of this new straw incorporation method on soil physico-chemical properties and maize yields. Therefore, in this study, a field experiment was carried out to evaluate effects of EIS on soil physico-chemical properties and maize yields by comparing EIS with other straw returning modes or methods.【Method】The field experiment, laid out in a mono-cropping maize field of chernozem soil in the Zhengbang Farm of Nong'an County, Jilin Province, was designed to have four treatments, i.e. Treatment CK (no straw returned), Treatment SM (straw returned as mulch), Treatment EIS (straw incorporated evenly into the soil using the crashing-ridging technique) and Treatment SP (straw plowed into the soil). Soil bulk density was determined plot by plot using the cutting ring method, and soil compactness, too, with a soil compactness meter; soil aggregates composition analyzed with the dry-sieving and wet-sieving methods; and fulvic acid (FA) and humic acid (HA) extracted with the modified humus component extraction method for analysis of structure with the Fourier transform infrared spectroscopy. Besides, maize yields of the treatments were calculated.【Result】Compared with CK, Treatment EIS and Treatment SP significantly reduced soil bulk density by 33.11% and 28.38%, respectively, and Treatment SM did only by 12.16%, and similar trends were found in terms of effects on soil compactness. As for content of >0.25 mm water-stable soil aggregates, Treatment EIS was 16.71%, 13.18% and 24.29% higher than Treatment CK, SP and SM, respectively. However, all the straw returning treatments increased mean weight diameter (MWD) and water stability coefficient (K), as compared with CK. Treatment EIS, SP and SM was 80.28%, 61.69% and 47.04% higher than Treatment CK in MWD, and 33.69%, 23.71% and 11.40% higher in K. Moreover, Treatment EIS, SP and SM increased soil organic carbon content in the surface soil layer by 27.8%, 15.9% and 7.5%, respectively. Meanwhile, Treatment EIS significantly increased the content of soil humus substances (HEC), soil humic acid carbon (HAC) and fulvic acid (FAC) by 47.6%, 63.3% and 33.8%, respectively, as compared with CK. Among all the straw returning treatments, Treatment EIS was the most significant in effect of increasing the content of HEC, HAC and FAC, being, 28.2%, 26.3% and 30.4%, respectively, higher than Treatment SP and 8.2%, 12.1% and 4.3%, respectively, higher than Treatment SM. Treatments EIS and SP increased soil HAC/FAC, too, being 25% and 21.6% than CK. Moreover, Treatment EIS altered the composition of humus more significantly than all the other treatments, by increasing the proportion of alkyl C and the ratio of aliphatic C/aromatic C, but Treatment SP was relatively higher than Treatment EIS in effect of raising the content of aromatic C.【Conclusion】All the findings in this experiment demonstrate that straw returning decreased soil bulk density and soil compactness, accelerated the accumulation of soil organic C and various components of humus, significantly changed the content of >0.25 mm soil water-stable aggregates and the values of mean weight diameter (MWD) and K, improved the structure of soil HA and increased maize yield, with the practice of EIS (even incorporation of straw) in particular, which suggests that the practice of EIS might be an ideal straw returning method to improve physico-chemical properties of the soil and maize yield.

    • Effect of Pretreatment of Chicken Manure with SPORL Method on Organic Matter Content Therein and Screening of Optimal Conditions

      2018, 55(4):847-856. DOI: 10.11766/trxb201709250365

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      Abstract:【Objective】Thanks to its peculiar shape, fresh chicken droppings or manure, after solid-liquid separation, can be processed easily to remove sands and other inorganic substances therein. The solid part of the manure contains a large volume of lignocellulose. After being air-dried naturally, the solid part was treated with the SPORL(Sulfite pretreatment to overcome recalcitrance of lignocelluloses) method to explore feasibility of recycling the part as fertilizer. 【Method】Ammonium sulfite was used as catalyst, of which single factor tests were carried out to assess effects of four main influencing factors, namely, dosage of ammonium sulfite, temperature, temperature holding time and liquid/solid ratio. The tests show that the solid part, 5:1~15:1 in solid/liquid ratio, pretreated with 10%~20% of ammonium sulfite (relative to dry weight of the solid, w/w) at 120~140℃ for 30~60 min was high in organic matter content. Based on results of the single factor tests, conditions for the pretreatment were redesigned and optimized with the response surface methodology and content of organic matter in the solid as response indicators. The Design-Expert software was used to analyze variance of the multiple regression equation.【Result】The following findings were obtained. 1) When the ammonium sulfite dosage varied between 0% and 15%, the content of organic matter increased with rising ammonium sulfite dosage, but when it above 15%, the content decreased significantly. 2) When pretreated at 130℃, the solid part was the highest in organic matter content, reaching up to 319.4 g kg-1, but the content turned downward gradually when the temperature continued to rise. 3) With the temperature holding time and the liquid-solid ratio increasing, the content of organic matter in the solid part decreased gradually. To sum up the content of organic matter was high in the solid part, 5:1~15:1 in solid/liquid ratio, pretreated with ammonium sulfite 10%~20% in dosage at 130~150℃ for 30~60 min. And it is predicted that the content may reach as high as 359.1 g kg-1 in the solid part of chicken manure, 5:1 in solid/liquid ratio, pretreated with ammonium sulfite 13.4% in dosage at 127℃, for 30 min. In validation tests the content was 365.8 g kg-1 on average, 6.7 g kg-1 less than the predicted, which indicates that the regression equation is reliable and accurate for use to analyze and predict organic matter contents in the solid part of chicken manure.【Conclusion】In a word, in chicken manure treated with ammonium sulfite as catalyst in a reactor under high temperature and high pressure, lignosulfonates is formed and then turned into humic acid which contains mixture of lignohumic acids, fulvic acids, and a smaller proportion of low-molecular organic compounds. This method can be used to improve chicken droppings into organic manure with high organic matter content, and increase the value of value-added utilization of waste. So this method may have a good prospect of application to the industry of turning chicken droppings into organic manure.

    • >Research Articles
    • Spatial Distribution and Dynamics of Soil Organic Carbon and Total Nitrogen in Apple Orchards in Coastal Regions

      2018, 55(4):857-867. DOI: 10.11766/trxb201711190549

      Abstract (1916) HTML (803) PDF 2.08 M (2571) Comment (0) Favorites

      Abstract:【Objective】 Soil organic carbon (SOC) and soil total nitrogen (STN) are two key indicators of soil fertility and quality, and closely related to soil productivities of farmlands and orchards. As the largest apple producer in the world, China has orchards distributed in all the corners of the country across different climate zones, in a huge variety of soils and under different management practices. Therefore, the orchards vary sharply in spatio-temporal distribution of soil C and N between different regions. However, as for spatial distribution and dynamics of SOC and STN in the apple orchards of the coastal regions, little system study has been made and little is known about differences and commons between the orchards in inland and coastal regions. In order to optimize management of the orchards, spatial distribution and dynamics of contents and densities of SOC and STN in large-scale apple orchards typical of the coastal region were studied.【Method】A total of 488 soil samples were collected from the surface soil layers of apple orchards different in age in Jiaodong, Shandong Province, East China for analysis of SOC, STN, SOCD (soil organic carbon density), STND (soil total N density), spatial distribution of C/N ratios, and their dynamics and affecting factors. 【Result】 Results show that the average SOC and STN content in the orchards of that region was 10.80 and 1.42 g kg-1, respectively, the average SOCD and STND was 2.81 and 0.37 kg m-2, respectively, and the average soil C/N ratio was 7.70. Compared with the inland apple orchards located in West Liaoning, suburbs of Beijing, Weibei of Shaanxi and Ili of Xinjiang, the apple orchards in Jiaodong were generally higher in SOC and STN, but lower in C/N ratio. The apple orchards in Jiaodong are often located in temperate humid hilly areas, quite loose in soil texture, and enjoy rich hydrothermal resources, endowed by the maritime climate of the Yellow Sea. All the natural conditions, generally speaking, are favorable to accumulation of soil carbon and nitrogen. The Nugget/Sill ratio of SOC, STN, SOCD, STND and C/N was 0.432, 0.340, 0.420, 0.387 and 0.301, respectively, indicating that the spatial heterogeneity is moderate in level, as affected jointly by structural and stochastic factors in the area. The conclusion is quite consistent with that of the researches on SOC and STN in inland orchards. With the orchards established, SOC and STN appeared to be on a rising trend, but after 30 years of cultivation, SOC began to decline, while STN kept on rising, though at a slower pace. SOC and STN did not synchronize in accumulation, with C/N ratio declining first, then rising and declining again. SOC and STN in the apple orchards of Jiaodong were also affected by soil type, which is determined by its parent material and inherits certain properties of its parent materials. Moreover, the distribution of soils has its zonality, which also makes the orchards in Jiaodong different from the inland ones in SOC and STN. Terrain is only a minor factor affecting SOC and STN in the orchards of Jiaodong, which is mainly because the orchards there sit mainly on low hills and mounds, low in undulation and soil water loss. But the strong soil acidification in the orchards of Jiaodong may affect the activity of soil microbes, and in turn, the cycling of soil C and N. However, in inland orchards the soils are mostly alkaline ones, which have strong acid buffering capacity, so the impact of soil acidification is insignificant therein. 【Conclusion】The apple orchards in Jiaodong are generally high in carbon and nitrogen content and hence soil fertility and they have their own especific characteristics of spatio-temporal variation, and much higher soil C and N turnover rates and more dramatic dynamic variation, compared with inland orchards.

    • Structure Characteristics of Camponotus Japonicus Nests in Northern Part of Loess Plateau and Influencing Factors

      2018, 55(4):868-878. DOI: 10.11766/trxb201711270565

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      Abstract:【Objective】Large-scaled restoration of vegetation in the northern part of the Loess Plateau has promoted development of land-dwelling animals or soil animals in that region by providing abundant food and suitable habitats. Nesting activities of soil animals markedly increase the amount of soil macropores, which in turn significantly affect the transformation, storage and utilization of precipitation. The pores formed by soil animals and plant roots are often tubular and have smooth inner walls good in water stability, and hence significantly contribute to the migration of soil moisture. In recent years, quite a number of studies have been reported investigating macropores formed in the soil by plant roots in the Loess Plateau, but little has dealing with macropores formed by soil animals in the region. Therefore, this study aimed to investigate characteristics of ant nests (Camponotus japonicus) and identify factors controlling their nest structure in the Liudaogou Catchment. 【Method】In this paper, Camponotus japonicus in the Liudaogou Catchment, north of the Loess Plateau was selected as the research object. Subterranean nests of the ants and the native Messor aciculatus were filled with thin mush of orthodontic plaster in the field to produce 3D images of the ant nests for comparison to check their similarities and differences. Besides, a total of 21 iron buckets (20 cm in diameter x 20 cm in height) packed with loam were used to raise worker ants in so as to explore relationship between volume of the nest and number of the worker ants. Moreover, worker ants were introduced into plastic buckets (30 cm diameter x 40 cm height) packed with sand to assess effects of soil moisture content and soil bulk density on structure of the Camponotus japonicus nests. 【Result】The Camponotus japonicus nests in the field stretched out vertically as tunnels and horizontally as a series of planular chambers linked with the tunnels. The nest tunnels ranged from 4.1 to 6.6 mm in diameter and went as deep as 63 cm down into the soil. The cross-sectional area of the planular chambers ranged from 606 to 2 117 mm2. The nests had 1 to 3 entrances each. The ant nests in the lab did not vary much in diameter of the tunnel, cross-sectional area of the chamber, and number of the entrances from those in the field. Limited by the volume of the PVC cylinder, the nests went only 30 cm deep, with the channels winding downward without lateral branches developed. Significant differences were observed between the nests of Camponotus japonicus and Messor aciculatus in diameter of the channel, shape and cross-sectional area of the chamber, and depth of the nest. As the ants increased in colony size, the nests gradually increased in size. The Camponotus japonicus community can survive in the soil with moisture content ranging from 60 to 200 g kg-1. In a proper range of soil moisture, soil texture did not affect much structure of the Camponotus japonicus nests. However, in the sand soils low in moisture content, ant nests were rarely found. Soil bulk density also greatly affected structure of the ant nests, reducing length of the nest, number of the branches, number of the node and total volume of the ant nest when it got heavier. However, tunnel of the nest did not vary much in diameter with soil moisture contents or soil textures. Diameter of the tunnels mainly depends on body size of the ants. 【Conclusion】The research elucidated on a small scale the characteristics of the soil-dwelling ants (Camponotus japonicus) and their affecting factors. All the findings may broaden the scope of the study on soil macropores in the northern part of the Loess Plateau. Such knowledge could in turn be used to develop strategies for enhancing the soil water storage capacity and restoration of sustainable vegetation in the arid region of the Loess Plateau.

    • Characteristics and Simulation of Transport of Sulfadiazine in Undisturbed Soil Columns

      2018, 55(4):879-888. DOI: 10.11766/trxb201711300213

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      Abstract:【Objective】Veterinary antibiotics are extensively used in livestock rearing industries all over the world for preventive and therapeutic treatments and growth promotion of poultry and/or animals. Antibiotics of the sulfonamide serial are commonly used in China, but once used, they are not so readily to be absorbed by the animals and are hence excreted along with feces and urine, which are often used as manure to build up soil fertility. After repeated application of the manure, sulfonamides therein tend to remain and accumulate in the soil and migrate from the soil into groundwater in certain environment. Long-term exposure to low concentrations of these antibiotics could be detrimental to non-target terrestrial and aquatic organisms. Therefore, investigation of the leaching behavior of these antibiotics in natural soils is the first logical step to assess their ecological risks and then develop corresponding pollution control strategies. 【Method】In this research, focus was laid on one of the widely used sulfonamides: sulfadiazine (SDZ), which is a compound slightly hydrophilic and low in adsorptivity in soils. Solute displacement experiments were performed to study migration processes of SDZ in undisturbed soil columns (Column I: 0~15 cm, and column II: 15~30 cm). Breakthrough curves (BTCs) of SDZ and tracer bromide were measured and modeled using numerical models that took into account reversible and irreversible kinetic sorption sites, as well as dynamic and stagnant area with the aid of the Hydrus-1D software. After calibration the numerical model was then used to predict and simulate residing and migrating behaviors of the substance in 200 cm soil columns relative to leaching velocity. 【Result】Results show that the BTCs in Soil Column Ⅱ were shifted to the left as compared with ColumnⅠ, which implied that, migration of SDZ was faster in the deeper soil layers. This is mainly due to changes in physical and chemical properties of the soil, such as humic acid content, cation exchange capacity and pH, with soil depth. The tested models all fitted the BTCs of SDZ and tracer bromide reasonably well. However, the TRM model which took into account dynamic and stagnant areas provided a better description of BTCs of SDZ than all the others did with R2> 0.91, RMSE < 0.061, f< 0.154, which indicates that the stagnant area is an important contributor to soil adsorption of SDZ. The predicted results show that when leaching velocities were the same, peak concentration of SDZ decreased and outflow lasted longer with soil depth. Measurements at the same depth show that with leaching velocity increasing from 0.017 cm min-1 to 0.030 cm min-1 and then to 0.100 cm min-1, SDZ migration was accelerated, and SDZ concentration in the effluent increased too. When the leaching velocity was 0.100 cm min-1, SDZ could quickly penetrate the soil profile and move into groundwater, and its breakthrough curve was no longer symmetrical, incurring a phenomenon of trailing. 【Conclusion】All the findings in this study may not only help improve knowledge of the mechanisms of retention and transport of the antibiotics in undisturbed water-saturated porous media, but also further demonstrate that the traditional solute transport model based on convection-dispersion-equation can accurately describe and predict the fate and transport of the antibiotics in soils.

    • Further Study on Spatial Distribution and Background Value of Chromium in Soil in Xijiang River Basin, Guangxi, China

      2018, 55(4):889-899. DOI: 10.11766/trxb201710300414

      Abstract (1908) HTML (756) PDF 2.44 M (2252) Comment (0) Favorites

      Abstract:【Objective】To comprehensively explore content of Chromium and its distribution in the soil of the Xijiang River Basin in Guangxi Province, and background value of Chromium in the soil, field investigations were carried out in the basin. 【Method】A total of 2 022 samples of upland soil, paddy soil, mining soil, sediment and natural soil were collected for analysis of Chromium content and further spatial distribution with the aid of ArcGIS. Chromium background values were recalculated using the mathematical statistics method. Cr pollution of the agricultural soils was evaluated using the single factor pollution index method. 【Result】Results show: (1). In terms of geometric mean of Cr-contents in the soils, the four types of soils followed an order of mining soil (104.2mg kg-1) > paddy soil (91.06 mg kg-1) > natural soil (82.66 mg kg-1) > upland soil (74.52 mg kg-1). (2). Comparative analysis shows that as against the Cr content in the samples of natural soil as background value of Cr in the Xijiang River Basin, about 4.05%、4.98% and 28.75% of the upland, paddy and mining soil samples were overstandard; (3) Interpretation of the Cr content spatial distribution map of the basin reveals that lands high in Cr content were distributed mainly in Nandan County, Jinchengjian, Du’an Yao Autonomous County. Dahua Yao Autonomous County, Heshan City, Huanjiang Maonan Autonomous County, Luocheng Mulao Autonomous County, Liucheng County, Xincheng County, Jinxiu Yao Autonomous County, Pingnan County, Tengxian County and Changwu County, indicating they were areas under intensive impacts of natural and anthropogenic activities. (4). This study found that the soil Cr background value of the basin was 82.66 mg kg-1, which was 1.6 times as high as that of the province (56.5 mg kg-1) and 2% lower than the criterion (90 mg kg-1) for soil Cr specified in the " Standard for Soil Environmental Quality " (GB15618-1995).【Conclusion】 The comprehensive analysis of the heavy metal Cr contents in the soils of the Xijiang River Basin, the mining soil was the highest in Cr pollution and followed by the paddy soil and upland soil. If the baseline value, 233.0 mg kg-1 is set as the unified standard, about 4.05%, 4.98% and 28.75%, respectively, of the dryland soil, paddy soil and mining soil exceeded the criterion. All the findings in this study may provides a reference for formulation of a more scientific and reasonable standard. Though the agricultural soil in the basin, as a whole, is still quite clean, it is essential to avoid agricultural activities around the mining areas.

    • Evaluation of Function of Soil as Archive of Cultural History— A case study of the Yangshao Village Cultural Relic Site, Henan Province

      2018, 55(4):900-910. DOI: 10.11766/trxb201705120366

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      Abstract:【Objective】At present, the issue of how to evaluate of function of the soil as archive of cultural history remains to be at the stage of theory and concept. Most indices and standards of the evaluation are rather qualitative than quantitative. As a special kind of soil formed under the impacts of fossil human activities, only when its recognition and identification is performed in combination with quantitative analysis, will it be feasible to define accurately the function of the soil as archive of cultural history, which will then provide scientific basis for protection of the soils that possess such functions.【Method】In this paper, qualitative methods were used in combination with quantitative methods to evaluate the function of the soil. An evaluation index system and a set of evaluation standards were established. The evaluation index system consisted of two categories, remains/relics and diagnostic indices. The former included ash pit, ash layer, cultural layer, pottery shards, stoneware and human remains, among which ash pit, ash layer and cultural layer were sorted into indices of remains, and the rest into indices of relics, while the latter did chroma, magnetic susceptibility, particle size, free iron, total mineral, clay mineral, micromorphology, organic carbon isotope, bulk density, spore pollen, charcoal shavings and phytolith. The remains/relics indices are much more important and valuable than diagnostic indices to scientific research, while relics are more valuable than remains to soil research, so the indices of relics are more important than those of remains. Once the indices of relics are detected, it can be concluded immediately that the soil is cultural soil formed under the impact of fossil human activities, whereas if no index of relics is found, it has to be ruled out in diagnosis whether the soil has been affected by fossil human activities. On such a basis, the function of soil as archive of cultural history could be divided into six grades. Grade I indicates that the function is complete with all remain/relic indices detected, and found in large quantity. Grade II indicates that the function is apparent, with numerous relic indices, and only some remain indices detected. Grade III indicates that only part of the function is apparent with large volumes of remains indices and some relic indices found. Grade IV indicates that the function is not apparent, with none of the remains/relic indices found, and all the diagnostic indices up to the standard. Grade V indicates that the sampling profiles have only a few of the diagnostic indices up to the standard. Grade VI indicates that none of the remains/relic indices are found and that all the sampled profiles have none of the diagnostic indices up to the standard.【Result】 Based on the method of evaluation, two soil profiles in the Yangshao Village cultural relic site of Henan Province, one containing obvious evidence of ancient human activities (cultural profile in short) and the other doing none (natural profile in short), were chosen to build evaluation system. In the area of the grade I, all relic and remain indices are found, precious pottery is found, and different areas of ancient human activities are found like making pottery, grave, living and eating, and different eras of cultural layers are also found. They are abundant and value in research which need protection. In this area, there are many scientific issues like how did ash layer form under what ancient human purpose of using fire? Framing or sacrificing or eating? This area was a perfect place for the corporation of archaeologists and pedologists. In the area of the grade II, relic indices are abundant while remains indices are rare, the value of cultural protection and scientific research is high. Lots of cultural profiles are hard to explain, which need the corporation of archaeologists and pedologists. In the area of the grade III, remains indices are abundant while relic indices are rare, the value of cultural protection and scientific research is a bit high. In the area of the grade IV, apparent relic and remains indices are not found, but diagnostic indices of sampling profiles are up to the standard, the value of cultural protection and scientific research is general. In the area of the grade V, only party of diagnostic indices of sampling profiles are up to the standard, the value of cultural protection and scientific research is little. In the area of the grade VI, none of relic and remain exist, and all diagnostic indices are below to the standard, the value of cultural protection and scientific research is none, but it is necessary to pay attention to ecological protection, so as not to affect the ecological environment of the core protection area. 【Conclusion】The evaluation helps us define the need for protective input and research value of soils relative to function grade. The merit of the evaluation method is the realization of semi quantitative evaluation of the function. Based on its own soil characteristics, each relic site can be evaluated using indices and data selected for their sharp contrast in the index system. Therefore, this method is of certain extendability.

    • Spatial Variability of Soil Moisture, Organic Matter Content and Soil Texture in Coal Mining Subsidence Area as Affected by Land Use

      2018, 55(4):911-922. DOI: 10.11766/trxb201711090497

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      Abstract:【Objective】In the primary energy structure of China, coal will remain to be the main component for a long time. The aim of this study was to explore mechanisms for soil moisture, nutrients and particles migrating and transforming in the micro topography of a slope in the coal mining subsidence area, and to provide an important basis of theoretical and practical values for scientific decision-making for comprehensive management of eco-environment in mining areas. 【Method】Cultivated land and forest land in a plain coal mining subsidence, typical of the JIULISHAN mining in Jiaozuo City, Henan Province, China, were selected as object of the study. Soil samples were collected from various layers (0~10 cm, 10~20 cm, 20~30 cm, 30~40 cm and 40~50 cm) of the soil profiles various in position (center, bottom, middle, top and control) along a subsidence slope of cultivated land and forest land for analysis of moisture content, organic matter content and texture. And then a comparative analysis was done of the acquired data for determination of spatial variability of the indices. 【Result】It was found that the cultivated land was significantly lower (p<0.05) in soil moisture content and clay content (<0.002 mm) but significantly higher (p<0.01) in sand content (2~0.02 mm) than the forest land. Along the slope the soils in the middle or bottom were the lowest in soil moisture content, organic matter content and silt content (0.02~0.002 mm) but the highest in sand content and clay content, while along the soil profiles, significant accumulation of soil moisture, organic matter and sand were observed in the surface layer, but that of soil clay was in the bottom layer. Along the slope of the subsidence area, soil properties of the forest land varied largely with slope gradient, and infiltration flow of soil percolating water intensified horizontal variability of soil organic matter, sand and clay content, forming obvious clay deep soil layers (> 30 cm) and carbon “pools” at the bottom of the slope of forest land. However, in the cultivated land, soil properties were mainly affected by cracks, and priority flow of soil percolating water dulled vertical variability of the soil texture, meanwhile affected by slope gradient, horizontal surface flow appeared, forming obvious sandy surface soil layers (0~20 cm) and carbon “source” in the middle and bottom of the slope of cultivated land.【Conclusion】It is, therefore, suggested that the land in such plain subsidence in coal mining areas should be reclaimed mainly into cultivated land and then into forest land as complement. After the subsidence was temporarily stabilized, as the first phase of land reclamation, the lands in the center of the subsidence and on the upper-slope should be reclaimed into farmland to avoid further loss of clay and soil degradation, while lands at the mid- and down slopes, be turned into contour forest and shrub belts, about 40~60 m wide and corresponding to the underground coal mining roadway boundary. Both of the stops may play a key role in controlling soil water and nutrient losses and improving eco-environment of the area.

    • Unconfined Compressive Strength of Jute-Fiber-Fortified Collapsing Hill Soil

      2018, 55(4):923-932. DOI: 10.11766/trxb201710160189

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      Abstract:【Objective】Collapsing hill is a phenomenon of slope erosion of soil or weathered rocks, collapsing and accumulating at the foot of the hill under hydraulic and gravity actions. Its harm is great in degree and hard to control. Fiber reinforcement is a new type of soil improvement technology to improve mechanical properties of the soil by amending a certain amount of fiber or fiber mesh into the soil evenly. It has, in recent years, been attracting much interest of scholars in conducting researches and experiments. But so far little has been reported on unconfined compressive strength of jute-fiber-fortified collapsing hill soil. Therefore, in this study experiments were carried out to explore mechanism of amending jute fiber into collapsing hill soil enhancing compressive strength and stability of the soil composite. 【Method】 In this study, the experiment was laid out in two-factor randomized block design and carried out to characterize stress-strain and unconfined compressive strength of the jute fiber- fortified collapsing hill soil composite. In the experiment, unconfined compressive strength of the composite was investigated relative to quanty and distribution of the jute fiber amended in four layers of the soil composite, i.e.. Eluvial layer A, Argic layer Bt, Deposition layer B and Parent material layer C. 【Result】 It was found that optimal reinforcement conditions (quanty and distribution) varied with the soil layer. For Eluvial layer A, jute fiber should be applied at 1 and distributed vertically; for Argic layer Bt, applied at 3 and blended evently; for Deposition layer B, applied at 1 and distributed horizontally; and for Parent material layer C, applied at 5 and distributed is horizontally, thus improving the unconfined compressive strength of the four layers by 7.97%, 19.24%, 15.35% and 42.88%, respectively, as compared with the unfortified soil. When starch was amended to jute fiber in the experiment, it took some time to cure the composite. And it was found that unconfined compressive strength of the four-layers was significantly related to the curing time. The strength was maximized after 7 days, 7 days, 5 days and 3 days of curing, increasing by 14.45% 15.07%, 8.90% and 8.07%, respectively.【Conclusion】Based on the experimental study, effect of the reinforcement is evaluated quantitatively, which demonstrates that a new technology of layered fortification for preventing and managing slope disintegration. All the findings in this study may serve as important scientific basis for prevention and control of collapsing slope erosion.

    • Effects of Biochar Addition on Thermal Properties of Loamy Soil

      2018, 55(4):933-944. DOI: 10.11766/trxb201710300388

      Abstract (2026) HTML (1102) PDF 2.91 M (2824) Comment (0) Favorites

      Abstract:【Objective】Soil thermal properties, including soil thermal capacity, conductivity, and diffusivity, play crucial roles in partitioning of surface-energy and heat transmission across the soil profile and consequently affect spatiotemporal dynamics of soil temperature that determines soil micrometeorology. As a soil amendment being able to improve a series of soil physiochemical properties, Biochar has gained wide attention. However, little information is available in the literature on integrated effects of biochar application on soil thermal properties. 【Method】A two-year field experiment using wheat straw derived biochar was conducted in a field of loamy soil in East China. The experiment was designed to have three treatments different in biochar application rate: 0 t hm-2 (BC0), 25 t hm-2 (BC25) and 50 t hm-2 (BC50) and three replicates for each. A total of 9 plots were arranged in a random complete block design. Tomato was grown under drip irrigation for two seasons. Soil thermal properties, i.e. thermal capacity, conductivity and diffusivity, were measured using the heat-pluse method in two ways: (1) lab-analysis of undisturbed soil cores collected from the plots with set soil water content; and (2) in-situ measurement under natural conditions. Besides, soil bulk densities, soil water retention curves, soil pore size distributions and soil water contents of the plots were also measured. 【Result】 In soils with controlled soil water content, soil thermal capacity increased with soil water content in the range from 1.13 J cm-3 K-1 to 2.80 J -3 K-1, from 1.16 J cm-3 K-1 to 2.75 J cm-3 K-1and from 1.07 J cm-3 K-1 to 2.74 J cm-3 K-1 in Treatmenta BC0, BC25 and BC50, respectively. Soil thermal capacity was significantly decreased by biochar application in the treatments moderate in soil water content (20%~30%), whereas the effects was insignificant in the treatments low (0~15%) or high (> 35%) in soil water content. Similarly, soil thermal conductivity increased with soil water content, in the range from 0.24 W m-1 K-1 to 1.16 W m-1 K-1, from 0.19 W m-1 K-1 to 1.09 W m-1 K-1 and from 0.18 W m-1 K-1 to 1.03 W m-1 K-1 in Treatment BC0, BC25 and BC50, respectively, and was significantly higher in the treatments amended with biochar, regardless of soil water content. Soil thermal diffusivity varied in the range from 0.23 m2 s-1 to 0.45 m2 s-1, from 0.16 m2 s-1 to 0.42 m2 s-1, and from 0.17 m2 s-1 to 0.41 m2 s-1 in Treatment BC0, BC25 and BC50, respectively. Soil thermal diffusivity was significantly lower in the treatments amended with biochar either low (0~15%) or high (>35%) in soil water content, while insignificant difference was detected in thermal diffusivity between treatments moderate in soil water content (20%~30%), but different in biochar application rate. Under field conditions, soil thermal capacity was significantly higher in Treatment BC50 than in Treatment BC0, but significantly lower in Treatment BC25 than in Treatment BC0. Biochar application had significant effects on soil thermal conductivity and diffusivity under field conditions. Treatments BC25 and BC50 were significantly lower in thermal conductivity and diffusivity than Treatment BC0 and lower in soil bulk density, too. However, soil total porosity was significantly increased by biochar application, which was mainly attributed to the increase in macropores (> 0.03 mm). Besides, biochar application also affected soil water retention curves in shape and soil water content was significantly higher in the treatments applied with biochar than Control during the growing seasons.【Conclusion】 Biochar application can significantly affect soil thermal properties through the two main mechanisms as follows: (1) biochar application promotes soil aggregation, thus forming large volumes of air filled pores; and (2) biochar application alters soil hydrological properties, thus increasing soil water content and hence soil thermal capacity and conductivity. In field conditions, the negative effects biochar application brings about on soil structure are much stranger than the positive ones it has on soil water content.

    • Physicochemical and Mineralogical Properties of Bentonites in South Jiangsu, China

      2018, 55(4):945-954. DOI: 10.11766/trxb201711240517

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      Abstract:【Objective】 Bentonite, as is widely used in industry and agriculture, has become an research hotspot in material science agricultural science and environmental science. Montmorillonite is the main mineral component of bentonite, and its content and unique mineralogical properties determine the economic and application values of bentonite. Bentonite ore is found widely distributed in Jiangsu Province. From the perspective of the current development and utilization of bentonite in China, the mineral is mined at a local small-scale to make low-level processing products. It is necessary to study how to further exploit the mineral resource. In this paper, based on the researches reported, the bentonites in South Jiangsu were chosen for analysis of their mineralogical properties, in an attempt to provide certain scientific basis for further development and reasonable utilization of the mineral. 【Method】To comprehensively explore mineralogical properties of the mineral, bentonite samples were collected from eight major bentonite mines in South Jiangsu and analyzed for pH, mineral composition, chemical composition, particle size distribution, cation exchange capacity and cation composition. 【Result】Results show that the natural bentonites in South Jiangsu tend to be high in pH, with an average being about 8.83 and are mainly composed of montmorillonite and a certain amount of associated minerals, which vary in type and content with origin of the samples. X-ray deflection analysis shows that the 8 samples are all calcium-based bentonites. Their chemical composition and cation composition varies somewhat in line with their metallogenic environments. Generally their CECs tend to be low. In the samples, CEC is found to be closely and positively related to the content of montmorillonite. All the findings in this study on physicochemical and mineralogical properties of the bentonite in South Jiangsu demonstrate that it has a good prospect in exploiting the resource.【Conclusion】The natural bentonites in South Jiangsu are all of the calcium-based type, and composed mainly of montmorillonite and certain associated minerals, which vary slightly with the origin of the samples. The samples also vary slightly in chemical composition due to their difference in metallogenic environment. The samples are generally basic in pH, which is mainly attributed to derivation of the mineral from its parent rock under an alkaline environment. The natural bentonite in South Jiangsu is generally low in cation exchange capacity, which is related to the content of montmorillonite in bentonite. The relationship is positive and significant. The content of montmorillonite decreases with increasing particle size, and montmorillonite exists mainly in particles <50 μm in size.

    • Effects of Various Influencing Factors of Soil Soluble Organic Nitrogen Components under Different Long-term Fertilization Treatments in Paddy Soil

      2018, 55(4):955-966. DOI: 10.11766/trxb201712180415

      Abstract (1922) HTML (1094) PDF 3.16 M (2798) Comment (0) Favorites

      Abstract:【Objective】 This paper was oriented to study changes in content and composition of soil soluble organic nitrogen (SON) and their influencing factors in paddy field under long-term fertilization varying in scheme, in an attempt to provide certain scientific bases for revealing chemical essence and ecological functions of SON in paddy soil and rationalizing fertilization schemes. 【Method】A 33-year long-term fertilization experiment, designed to have four treatments: CK (no fertilizer), NPK (chemical fertilizer), NPKM (chemical fertilizer + cattle manure) and NPKS (chemical fertilizer + straw) was selected as object of the study. With the aid of automatic amino acid analysis and Fourier infrared spectrum analyzer coupled with redundancy analysis (RDA) method, effects of the long-term fertilization treatments on content and composition of SON and main influencing factors in the paddy soil were explored. Soil SON was extracted with hot water. Portions of soil samples from the treatments, 5.0 g each, were put into flasks with stopper, separately, with 25 ml of deionized water each, incubated at 70 ℃ for 18 h, shaken for 5 min on a shaker, and filtered through a 0.45 um filter membrane. The extracts were analyzed for total soluble N (TSN) with the high-temperature catalytic oxidation method and a TOC analyzer (Shimadzu, Japan) and for concentrations of soil inorganic nitrogen (SIN) (NH4+–N, NO3-–N and NO2-–N) with a continuous-flow analyzer (Systea, Italy). The concentration of SON was calculated as the difference between TSN and the sum of SIN in the extracts. 【Result】Long-term fertilization significantly affected content and composition of the SON in the paddy soil relative to treatment. SON in the treatments accounted for 46.16%~62.45% of the TSN in the paddy soil under the long-term fertilization , making up an important component of the soil soluble nitrogen storage in the paddy field. The content of soil SON in Treatment NPK, NPKM and NPKS was 23.49%, 58.70% and 106.30% respectively higher than that in CK, which indicates that Treatment NPKS, long-term application of chemical fertilizer plus straw is more conducive to accumulation of SON in the paddy soil under the premise that the same amount of NPK is applied. The content of free amino acid nitrogen in Treatment NPK, NPKM and NPKS was 32.27%, 84.42% and 95.21% respectively higher than that in CK, accounting for 31.94%~39.23% of that of the total SON, separately. The free amino acids in the treatment exhibited a decreasing order of neutral amino acids > acidic amino acids > basic amino acids in content, and were dominantly composed of threonine, serine, sarcosine, glycine, alanine and isoleucine. The contents of acidic and basic free amino acid nitrogen were significantly increased in Treatments NPKM and NPKS. The content of soluble protein nitrogen in Treatment NPK, NPKM and NPKS was 20.83%, 70.00% and 95.83% respectively higher than that in CK, accounting for 4.72%~5.32% of that of the total SON, separately, which indicates that application of chemical fertilizer in combination with organic manure or straw, especially Treatment NPKS, can significantly increase the content of soil soluble protein nitrogen. Functional groups of the soil soluble nitrogen in Treatments NPKM and NPKS, especially in the latter, are reflected as amide compound featured infrared absorption peak at 3 400, 1 630~1 650, 1 400~1 460 and 1 310 cm-1 along the spectrum. RDA results show that SON varied significantly with treatment in content and composition. SON in Treatments CK and NPK was mainly affected by soil bulk density, while that in Treatments NPKM and NPKS was by organic matter, total nitrogen, microbial biomass nitrogen, protease and glutaminase.【Conclusion】 SON is closely related to fertilization treatment in content and composition, and addition of organic manure can significantly increase the contents of soil SON, acid and alkaline free amino acids and soluble protein nitrogen. The increased SON in Treatments NPKM and NPKS is mainly small molecule easily mineralized nitrogen and large molecule nitrogen of unknown forms. Free amino acids, amides and soluble proteins are the main components of SON in paddy soil. Bulk density, organic matter, total nitrogen, microbial biomass nitrogen, protease and glutaminase are the main factors affecting content and composition of SON in paddy field, but vary in degree with treatment.

    • Fingerprints of Carbon Metabolisms of Gourd as Rootstock and Watermelon as Scion in Rhizosphere of Different Types of Soils — Characteristics and Differences

      2018, 55(4):967-976. DOI: 10.11766/trxb201711250562

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      Abstract:【Objective】 Grafting, as an ancient horticulture technology, can prevent soil borne diseases effectively during watermelon planting. Studies in the past demonstrated close relationships between soil-borne diseases and microbiota, but it is still unknown how rhizospheric microbial activity is affected by rootstock-scion interaction. The objective of the present study is to elucidate effects of rootstock-scion interaction on microbial activity in the rhizosphere of watermelon grafted on gourd in a variety of soils. 【Method】 Four types of soils were collected including black soil (from Jilin), red soil (from Hainan), yellow-brown soil (from Jiangsu) and desert grey soil (from Xinjiang) and four types of seedlings (bottle gourd, watermelon, watermelon grafted on bottle gourd rootstock and bottle gourd grafted on watermelon rootstock) were planted in the four types of soils, separately. Rhizosphere soils were collected after 45 days. The BIOLOG method was used to explore differences between the treatments of the experiment in soil microbial activity. 【Result】Two-way PERMANOVA (Permutational multivariate analysis of variance) showed that soil microbial activity varied remarkably with soil type (R2= 0.534, p<0.001), and significant differences were observed in utilization of microbial carbon sources between grafted plants, i.e. grafted watermelon and grafted gourd (R2= 0.075, p<0.001). The treatment of watermelon was the highest in comprehensive utilization level of carbon source by rhizospheric microbiota, and followed by the treatment of grafted bottle gourd, the treatment of grafted watermelon, and the treatment of bottle gourd in the end. Principal component analysis (PCA) also showed that rootstock-scion interaction had an influence on microbial carbon sources utilization in different soil types. Heatmap analysis further demonstrated that grafting varied the microbial utilization of 31 sole carbon sources. For instance, the microorganisms in own-root bottle gourd rhizosphere utilized less carbohydrates, amino acids, polymers, phenols and amines compared to own-root watermelon and grafted plants, whereas they utilized more carboxylic acids such as γ-hydroxybutyric acid and α-keto butyric acid. On the contrary, the microbiome in own-root watermelon rhizosphere preferred to metabolize more carbohydrates, amino acids, polymers, phenols and amines, but less carboxylic acids. Compared with own-root watermelon treatment, grafted watermelon showed a lower absorbance level of various carbon sources such as carbohydrates, amino acids, which suggested that rootstock-scion interaction changed microbial metabolic pattern in rhizosphere. Aggregated boosted tree analysis (ABT) proved that soil available nutrients (such as readily available potassium and readily available phosphorus) were main influencing factors of carbon utilization by microbiota. 【Conclusion】 Both soil types and plant types can affect microbial activity in rhizosphere. Rootstock-scion interaction varied microbial metabolic pattern significantly. This study evaluated responses of microbial activity in rhizosphere to rootstock scion interaction in different types of soils, with results which may serve as theoretical basis for control of soil-borne diseases.

    • Negative Allelopathic Effects of Extract of Coptis chinensis Hair Root on Inorganic Phosphorus-Dissolving Bacteria

      2018, 55(4):977-986. DOI: 10.11766/trxb201712250571

      Abstract (1524) HTML (893) PDF 2.94 M (2358) Comment (0) Favorites

      Abstract:【Objective】Coptis chinensis is a medicinal herb traditionally cultivated and used for many centuries in China. As it is now cultivated extensively in large areas and often continuously for years in a row, sustainable development of the industry has come across serious obstacles caused by mono-cropping. it is, therefore, essential to explore allelopathic effects of this medicinal plant on soil microorganisms, in order to understand mechanisms of the occurrence of obstacles in the mono-cropping and provide certain scientific basis for lifting the obstacles. Method】To that end, an indoor experiment was carried out culturing three strains of inorganic phosphorus dissolving bacteria, B05, B07 and B09 of Burkholderia Yabunchi bacteria, using the solid and liquid culturing techniqu, During the experiment, extract of fibrous roots of C. chinensis (ERC) was spiked to explore allelopathic effects of the extract on growth, reproduction, and tricalcium phosphate dissolving capacity of the three strains. Fresh C. chinensis roots were soaked in deionized water at 251 C for 24 h to extract active components, and then the solution was filtrated through a 50 mol L-1 filter, and diluted to ERC 0.1 g L-1. For spiking of the extract, the experiment was designed to have four treatments, i.e. 0 (CK), 500 (low concentration), 1 000 (middle concentration), and 2 000 mg L-1 (high concentration). 【Result】Results show that the higher the concentration of the ERC, the smaller the size of bacterial colonies, the diameter of P-dissolving halos and the lower the P-dissolving index on the solid culture medium. ERC also inhibited the growth and reproduction of iPDB in variable degrees, reducing the population of iPDB by 35.98%~52.98% in the liquid culture medium as compared with the blank control (without ERC). All the three strains of bacteria tested in the liquid culture released protons, oxalate, and citrate into the solution. Besides, acetate was found in the culture solution with B05, malate with B09, and acetate and succinate with B07. In addition, iPDB varied greatly in tricalcium phosphate dissolving capacity in the culture solution. The mean amount of P dissolved was 228.31 mg L-1 for B05, 311.64 mg L-1 for B07, and 174.89 mg L-1 for B09. Inorganic P dissolution by these bacteria was positively related to efflux of proton (r= 0.877, p 0.05, n= 12) and organic acids (r= 0.604, p 0.05, n= 12). When ERC inhibited efflux of protons and organic acids in culture solutions, it reduced P dissolution by 21.68%~60.55%. 【Conclusion】 During the growing period, C. chinensis roots released allelopathic chemicals, which affected adversely community structure and physiological and ecological functions of the iPDB, thus reducing bio-availability of inorganic P in the soil, which could be one of the possible reasons why obstacles occur in mono-cropping of C. chinensis.

    • Effects of anaerobic soil disinfestation (ASD) on tomato bacterial wilt and soil bacterial community

      2018, 55(4):987-998. DOI: 10.11766/trxb201712240611

      Abstract (2123) HTML (1597) PDF 3.55 M (2511) Comment (0) Favorites

      Abstract:【Objective】Anaerobic soil disinfestation (ASD) has been proven to be a promising non-chemical environment-friendly method to control soil-borne diseases, plant parasitic nematodes and weeds, especially in horticulture. However, it is still not so clear about mechanisms of the effects. In this paper, both pot and field experiments were conducted to study the effects of ASD on tomato bacterial wilt (a kind of soil-borne disease), structure and diversity of soil microbial community, soil properties and crop growth, in an attempt to elucidate mechanisms of ASD controlling soil-borne diseases and improving soil health.【Method】The pot experiment was designed to have five treatments anaerobically disinfected, i.e. Treatment DRB (addition of rice bran), Treatment DWB (addition of wheat bran), Treatment DTB (addition of tea seed bran), Treatment DRS (addition of straw) and Treatment D (addition of none), and one control (CK); and the field experiment had only four treatments, i.e., DRB, DWB, DTB and CK. Effects of the treatments on incidence of wilt, amount of the pathogen, crop growth, soil physiochemical properties (soil pH, Eh, temperature, conductivity) were analyzed. Furthermore, 16S rDNA gene (V3+V4 region) sequencing was done to analyze the composition of soil bacterial community relative to treatment.【Result】Results show that compared with CK, ASD inhibited bacterial wilt by 100% in all the four treatments added with organic material, and by 83.3% in Treatment D. All the treatments, except for Treatment DRB, significantly promoted tomato growth. ASD significantly increased soil temperature, soil pH and conductivity, but reduced soil Eh and decreased the population of Ralstonia solanacearum in the soil by 97.3% ~ 99.1%. Compared with CK, ASD reduced incidence of the disease by 29.4 ~ 42.7% and increased yield of the crop by 2.5~4.7 times. Sequencing of 16s rDNA gene shows that CK and Treatments D and DRB were higher than Treatments DWB, DTB and DRS in bacterial diversity (Shannon index, Simpson index, ACE and Chao 1 index). Principal component analysis and cluster analysis show that the treatments varied sharply in species, abundance and diversity of soil bacteria community. Treatments DWB, DTB and DRS were lower in relative abundance of Crenarchaeota, Acidobacteria, Actinobacteria, Chloroflexi, Gemmatimonadetes and Proteobacteria in treatments were reduced compared with CK and Treatments D and DRB, but significantly higher in Firmicutes (mostly anaerobic bacteria), which became the dominant species in the soil bacterial community in Treatments DRB, DWB, DTB and DRS. Besides, ASD significantly decreased the relative abundance of Burkholderiaceae and Ralstonia.【Conclusion】 ASD is an effective approach to control soil-borne bacterial wilt, and improve soil quality and crop productivity. ASD coupled with addition of organic materials significantly changed the soil bacterial community in structure, composition and diversity, and significantly increased the abundance of anaerobic and anaerobically tolerant bacteria, which may be one of the mechanisms of ASD preventing and controlling bacterial wilt.

    • >Research Notes
    • Prediction of Soil Heavy Metals Content Based on Sequential Gaussian Simulation and Evaluation of Its Uncertainties:A Case Study of Soil Hg Content in Yixing

      2018, 55(4):999-1006. DOI: 10.11766/trxb201801100322

      Abstract (1656) HTML (1102) PDF 2.81 M (2632) Comment (0) Favorites

      Abstract:Quantitative prediction of soil heavy metal content and evaluation of its uncertainties is of great practical significance to ecological risk assessment. In this study, a total of 1 155 soil samples for Hg content analysis were sorted into two disjoint datasets, a simulation dataset of 309 samples and a validation dataset of 846 samples. In order to validate accuracy and reliability of the results of the usage of the Sequential Gaussian Conditional Simulation (SGCS) method, comparison was performed of this method with the Simple Kriging Interpolation method based on the same Semi-variance model parameters. Furthermore, Sequential Gaussian Indicator Simulation (SGIS) was used to delineate areas with soil Hg content beyond the threshold value, and to explore for uncertainties with single points and multi-point combination. Results show that the E-type of 100 rounds of SGCS and the SK prediction are quite similar, the difference between the two is small in Average Prediction Error and Root Mean Square Error. This paper sampled the 1 st, 25 th, 50th, 75th, and 100th round of single implementation of the SGCS method for comparison with the 846 points in the verification dataset in simulated value and interpolated value. The Mean Prediction Error and the Mean Square Prediction Error of the five rounds of single implementation are coincidentally and relatively higher, (within the range of 0~ 0.01). When threshold was set to be 0.15 mg kg-1, the single-point critical probability is relatively higher. However, its confidence level is by a certain degree not enough to delineate polluted areas. Multi-point joint probability should be used to evaluate the reliability of the contaminated area.

    • Research on Spatial Distribution of Soil Organic Matter in Hainan Island Based on Three Spatial Prediction Models

      2018, 55(4):1007-1017. DOI: 10.11766/trxb201710240410

      Abstract (1826) HTML (1410) PDF 3.52 M (2769) Comment (0) Favorites

      Abstract:The knowledge about spatial distribution characteristics of soil organic matter (SOM) contents is of important significance to development of the agriculture. Models different in simulation mechanism are used to predict distribution of SOM contents, because different regions have soils of different soil properties and different environmental factors affecting soil properties. It is, therefore, essential to choose an optimal suitable model site-specifically for the prediction, this paper is oriented to explore for a model that is capable of predicting spatial distribution of SOM contents in a tropical region complicated in relief, like Hainan Island. Ordinary kriging (OK), regression-kriging (RK) and random forest (RF) were the three models used to predict spatial distribution of SOM contents in the Hainan Island based on the training set of 128 samples, combined with topographic factors, normalized vegetation index, soil types and landuse types, and then the predictions were validated with a validating set of 32 validation points in the study area for comparison of prediction accuracy. Results show: (1) The optimal fitting model for prediction of distribution of organic matter contents in the 0 ~ 5,0 ~ 20, 20 ~ 40 and 40 ~ 60 cm soil layer is RF, RF,RF and OK, respectively. RK and RF can better describe local variation of SOM contents; (2) The mean value of SOM contents in the four soil layers was 19.67, 15.89, 10.30 and 8.07 g kg-1, respectively, showing a spatial distribution trend that SOM contents are higher in the southwest and northeast parts and lower in the west and southeast parts of the island.

    • Effects of Reclamation on Distribution of Soil Carbon and Nitrogen in Saline Soil of the Yellow River Delta

      2018, 55(4):1018-1027. DOI: 10.11766/trxb201712250421

      Abstract (1624) HTML (718) PDF 3.32 M (1945) Comment (0) Favorites

      Abstract:Comparison was made of a tract of virgin saline-alkali soil land (CK) with farmlands different in cultivation history, that is, < 5, 10 ~ 15, 20 ~ 25, 30 ~ 35 and 50 ~ 60 years of wheat or corn mono-cropping, using the space- substituting-time method to explore effects of land cultivation on horizontal and vertical distributions of soil carbon and nitrogen content in the 0 ~ 100 cm topsoil layer of the saline-alkali land in the Yellow River Delta. Results show that land cultivation significantly increased the contents of soil organic carbon, inorganic carbon, total carbon, total nitrogen, and available nitrogen, especially in the topsoil layer, and the effects became more significant with the cultivation going on, but leveled off after 30 years of cultivation. Groundwater table is a factor affecting nutrient accumulation in deep soil layers, to a certain extent. Organic carbon was significantly and positively related to total N, but in farmlands, C/N exhibited a declining trend, which leveled off after 30 years of cultivation. However, the C/N in the farmlands of the region is lower than the average of the country, which indicates that in long-cultivated farmlands, it is still essential to further increase the level of soil organic carbon.

    • Dynamic change and Comprehensive Evaluation of Soil Environment of Rhizosphere of Pseudostellaria Heterophylla Relative to Fertility

      2018, 55(4):1028-1039. DOI: 10.11766/trxb201712180451

      Abstract (1761) HTML (1180) PDF 4.00 M (2409) Comment (0) Favorites

      Abstract:This study aims to explorate temporal variation of the soil environment in the rhizosphere of Pseudostellaria heterophylla as related to soil nutrient condition, in an attempt to find out a comprehensive method for evaluation of the soil environment in the rhizosphere of P. heterophylla, and to provide a theoretical basis for guiding efficient cultivation of P. heterophylla. In this study, P. heterophylla was planted in three plots different in soil nutrient condition, changes in soil chemical properties, soil enzyme activity and microbial population structure were monitored regularly, and multiple-factor comparisons done. Then principal component analysis of the data was performed for comprehensive evaluation. The results of the study show that during the whole growth period, total phosphorus, slowly available potassium, readily available phosphorus and readily available potassium varied the most significantly in content and S-AI (Soil acid invertase) and S-CAT (Soil catalase) did in activity in the rhizosphere soil of P. heterophylla in all the plots. However, organic matter, total nitrogen and alkalytic nitrogen did not vary much in content and S-ACP (Soil acid phosphatase), S-UE (Soil urease) and S-PPO (Soil polyphenol oxidase) did neither in activity in the growing period as a whole. After the plant matured soil bacteria and actinomycetes increased significantly and fungus decreased significantly in population. Among the 16 soil environmental indices, significant correlations were found between some of them. In principal component analysis, five components were extracted with basic eigenvalue being higher than 1. Then comprehensive scoring was performed based on the function expressions of five components. The results show that the higher each soil nutrient in content, the higher the comprehensive score, the better the soil environment. During the growth period of P. heterophylla, soil phosphorus and soil potassium vary sharply, making it essential to supplement P and K fertilizers timely, which may be one of the effective measures to improve soil environment in the rhizosphere of P. heterophylla. It is, therefore, advisable to conduct comprehensive scoring based on principle component analysis to objectively and efficiently evaluate the soil environment in the rhizosphere of P. heterophylla.

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