Abstract:To analysis ancient soil properties is an important means to obtain paleoenvironmental information. To restore ancient environment and ancient human activities by interpreting the ancient soil information has become a hotspot for research both at home and abroad. This paper summarized the progress of domestic and overseas researches on particle size of soil grain, soil micromorphology, soil element, soil magnetic susceptibility, PAHs and remains of biology of paleosol in recent years. According to these researches, particle size of soil grain can reflect the cause of soil deposit, hydrodynamic condition, climatic and agricultural production conditions in cultural site. Pedogenic environment, land use conditions, farming pattern and human disturbance can be speculated by soil micromorphology. Different soil elements reflect different palaeoenvironment, Ca, P, Mg are indications of ancient human living area and household refuse, Fe, Ca, Sr, Zn are indications of cookhouse, Hg, Cu, Pb and Br are indications of manufacturing area. All of these are closely linked with ancient human activities, besides, Ca, Mg, Sr are in closely contact with farming area. Soil magnetic susceptibility reflects stratigraphic age, the ancient climate conditions and ancient human activity. The age of vegetations, major crops, natural environment, climate variation and the changes of ancient human environment can be inferred by remains of plants include macroremains, pollen and spores and phytolith. PHAs reflect the flame cultivation. Animal remains such as teeth and bones of animals, they infer the animal species, animal producing area, natural environment and profession model. All these researches have made extraordinary outstanding contributions on restoring palaeoenvironment and ancient human activities, however, a lack of combination of different subjects and exploration of new methods still hinders the way of further study. Therefore, what needs to be done in the future are to enhance the combination of soil science and archaeology, to improve the theories of studying paleosol in ancient culturerelices. An integrated diagnosis index for paleosol in ancient culture relices needs to be established, methods on analyzing process-response relationship between soil process and resultant soil property need to be improved, and also, studies on Soil cultural heritage function need to be enriched. At last, for going a step further, to set up a new branch of soil science called archaeological soil science step by step.

Abstract:Soil is probably the most challenging of all natural environments for microbiologists, and the hotspot for discovering of novel biomolecules and genetic resources. Cultivation of environmental microorganisms was ignored and marginalized in the tremendous progress of “meta-omics” technologies. Nevertheless, by cultivation-based approaches, researchers can acquire novel microorganisms that are undetected by molecular methods, be allowed for the verification and testing of hypotheses of metabolic potential and function of novel genes determined by the meta-omic data and also do the microbial foundational research or industrial production. In the era of meta-omics, cultivation method is still useful in understanding the detailed metabolism and functions of those environmental organisms, and this makes the genetic manipulation, confirming certain functions, and the research of environmental function of microorganisms possible. The challenge is to bring these recalcitrant microorganisms into the laboratory for future exploration. This review summarizes the reasons why microbes are not growing in the lab such as. Then we focus on the advanced cultivation techniques. The methods of modifications to growth media include using low substrate concentrations, adding growth-limiting factors into media and changing gelling reagents. Modifications to growth conditions include extending incubation time, incubating in a optimum oxygen level, and using low-temperature strategies. The strategies of cultures in situ or cultures in simulated natural conditions include “growth chamber” and “trap for in situ cultivation”. The methods of community culture and co-culture also elevated the possibility of novel bacteria from environmental samples. Cultivation of soil microorganisms by assistance of culture-independent methods such as metagenomics and metaproteomics have been developed to improve the cultivating process. Finally, we propose the directions of isolation of soil microbes in the future.

Abstract:A field experiment was carried out in the oasis at the edge of the mid-reaches of the Heihe River to determine effects of water-saving irrigation on cotton yield and irrigation water productivity (IWP) in different soil conditions. The objective of the work is to provide some scientific basis for rationalizing the utilization of agricultural soil and formulating soil-specific irrigation strategies in the region. The experiment was designed to have five different types of soils, (sand soils, S1 and S2, loamy sand soil, S3, and sandy loam soil, S4 and S5) forming gradients in soil fertility and mechanical composition and three irrigation levels (conventional full irrigation (I1), 10.5% and 21.0% less water-saving irrigations (I2, I3)). The results of the experiment show that compared with Treatment I1, Treatments I2 and I3 were a bit lower in biomass of shoots and leaf area of a single plant at any growth stages and in biomass of stem at the harvesting stage, but 11.6% and 11.2% higher in yield of seed cotton, respectively. The average cotton IWP was 0.51 kg m^-3 and 0.57 kg m^-3 in Treatments I2 and I3, respectively, and increased by 24.4% and 39.0% relative to the IWP（0.41 kg m^-3）in Treatment I1. Besides, treatments different in soil texture varied sharply in shoot biomass, leaf area, yield of seed cotton and yield components, as well as cotton IWP. With increasing soil organic matter (SOM) content and clay+silt content, yield of seed cotton and IWP increased, but decreased in Treatment S5 which was the highest in organic matter and silt caly contents, displaying a polynomial relationship. Significant interactions between soil texture and irrigation rate were observed in their effects on pre-frost lint yield, biomass and seed cotton yield. In Treatment S5, Treatment I1 brought about over-flourishing vegetative growth of the crop and delayed the boll-opening stage, thus leading to reduction of the pre-frost flower ratio, seed cotton yield and IWP, while Treatments I1 and I2. significantly increased crop IWP. In oases at the edge of deserts deficient in water resources, cultivation of cotton with low water requirement in newly reclaimed land of sandy soil and adoption of water-saving irrigation management should be an optimal option to realize regional water conservation and reasonable land use.

Abstract:A three-year field experiment was carried out to explore effects of timing of plastic film mulching and freezing saline water irrigation (FSWI) on salt and water dynamics in coastal saline soil and cotton growth. The experiment was designed to have five treatments, that is, mulching after ice melt percolation (MI), mulching after sowing with FSWI (SI), no mulching with FSWI (NI), mulching in autumn without FSWI (AN) and no mulching without FSWI (CK). Results show that in the plot with FSWI, ice melt decreased salt content and soil adsorption ratio (SAR) in the surface frozen soil layer gradually from 12.15 g L^-1 and 18.7 to 0.03 g L^-1 and 1.07, respectively. During the three years of FSWI, the soil salt content in the surface soil layer decreased year by year according to the measurement at the same time period. In 2006, 2007 and 2008, the soil salt content in the top soil (0～20 cm) before FSWI was 19.8, 15.4 and 12.4 g kg^-1, respectively. In the plots after freezing saline water irrigation, all the water and salt from irrigation and large number of water and salt from soil was leached to the soil layer below 1m. Soil salts came back quickly after the melt percolated down the profile. So mulching 9 days after melt percolation would obtained a better effect of preserving soil water and inhibiting return of soil salt. The effect of Treatment MI was the best, and so was its effect on seed germination rate and seed cotton yield, which was 63.78% and 3 200 kg hm^-2, respectively. The treatment was followed by Treatments AN, SI, NI and CK, in effect. After the three years of FSWI, Treatment AN also obtained a high germination rate of 59.63% and a high yield of 2 600 kg hm^-2 in the fourth year though when there was no freezing saline water irrigation. While in the plots of no mulching or later mulching, no ideal yield was obtained even though they received FSWI in all the three consecutive years.

Abstract:The south coastal area of the Laizhou Bay is seriously subjected to soil salinization as a result of seawater intrusion. Soil salinization has become a major factor that hinders the regional agricultural production and development. In order to explore rules of the spatial distribution of salt ions and dominant salt ions in soil profiles in the research area, 14 sampling sections were arranged at 6km intervals in this study, containing 76 soil profiles. Soil samples were collected from the 0~30cm, 30~60cm and 60~90cm soil layers, separately, of each profile. A portion (about 1/3) of each sample was taken out from the same soil profile and blended into a mix for analysis. Classical statistical and geo-statistical methods were used in combination to analyze statistical characteristics and spatial distribution of salt ions in the soil profiles in the area. Cluster analyses of the soil ions were also done. Results show that within the 0~1m soil layer, soil salts displayed an obvious trend of accumulating in the bottom; The dominant soil salt ions in the research area were Na⁺、SO4^2- and Cl^-, existing in the form of NaCl and Na₂SO₄. These findings may serve as reference for the future researches on monitoring and assessment of soil salinization in this area. The analyses of the three ions in the soil has fully explained the problem of soil salinization in the south coastal area of the Laizhou Bay. Partial correlation analysis of the salt ions in the soil shows that the ions varied sharply . Cluster analysis indicates that the salt ions in the soil consisted mainly of three categories of salt ions: Category I: K , Mg² , Ca² and SO₄^2-; Category II: Na , and Category III: Cl^-. The total salt content displayed a moderate spatial autocorrelation in the 30~60cm soil layer, and strong ones in the other two layers, which suggests that the spatial variation of the soil salt properties was mainly affected by natural factors. Spatial distribution of the salt ions in the soil appeared in pattern of strips and patches. Ca² concentration was relatively high in the middle, and slightly lower in the northern and southern parts of the region; Mg² was relatively high in the southern and western parts and relatively low in the northern part; K was relatively high in the northern part and low in the central part; while Na 、SO₄^2-and Cl^- was quite similar in spatial distribution, appearing to be high in the central part, relatively low in the northern part and lower in the southern part. SAR was quite similar to Na in spatial distribution pattern. The soil salinization in this region was mainly of the types of sulfate, chloride-sulfate and sulfate-chloride, and was quite low in degree in most parts of the region and moderate in some parts, leaving some small areas of severely salt-affected soil, saline soil and non-salt-affected. The research findings may have guiding significance for agricultural production in the region, as well as for scientific amelioration and comprehensive utilization of salt-affected soils in the study area.

Abstract:Particle size distribution and material composition was measured of sediments of erosion from slopes of red soils (five different types of red soils derived from three different kinds of parent materials, i.e, Shale, Quaternary red clay and Granite) as affected by rainfall kinetic energy of artificial rainfall. Rainfall kinetic energy was controlled by either leaving the slopes bare or covering them with mesh. Results show that particle size distribution of the sediments of erosion was influenced significantly by parent material and rainfall erosive force. That is to say, soils derived from the same parent material would generate erosion sediments similar in particle composition and mesh coverage increased the content of fine fractions (non-dispersed) in sediments which was due mainly to the interaction between stability of aggregates and erosive force of rainfall on the slope. The sediments from red soils derived from Shale (HS) and Granite (soil TG1 and TG2) were enriched with silt and clay (dispersed) (1.15 to 3.14 in enrichment rate) while those from soil HQ1 and HQ2 derived from Quaternary red clay enriched with sands with the highest enrichment rate reaching 3.84. In sediments from soil HS, TG1 and TG2, organic matter (OM), free iron oxide (Fed) and aluminum oxide (Ald) were mostly distributed in fine particles smaller than 0.05 mm (non-dispersed) in size; however, in sediments from HQ1 and HQ2, they were concentrated in two particle size fractions, i.e. >0.25 mm and <0.05 mm. Among them, OM was the most obvious with enrichment rate varying from 1.05 to 9.88. In the sediments OM, Fed and Ald were extremely significantly related to each other (r≥0.82). So were they with cation exchange capacity, Fed, Ald, amorphous silica and clay in the original soils, indicating that these substances in the sediments influence each other and depend largely on their content in the original soils.

Abstract:Rill erosion is a serious environmental problem threatening the agricultural production safety and sustainable societal development in the Loess Plateau, China. It is, therefore, very important and urgent to quantify dynamic process of the rill erosion. To that end, an indoor simulation experiment was carried out the scouring and backfilling method. Erosion process was analyzed through observing variation of the shape of rills and measuring volume of erosion along the rill segment by segment. Cumulative amount of erosion along the rills was worked out by refilling the separated rill segments with water to their original elevation. The sediment concentration was calculated by dividing the cumulative amount of erosion at each segment by the total volume of the water flow during the erosion period. A typical silty-loam soil was sampled from the Loess Plateau of China (109° 19′ 23″ E, 36° 51′ 30″ N) and used as experimental soil in this study. The soil contains 16.31% clay (<0.005 mm), 61.35% silt (0.005 to 0.05 mm), and 22.34% sand (>0.05 mm). The soil was air-dried and then passed through an 8 mm sieve. In order to a complete continuous erosion process, an experimental trough, 3.0 wide and 12.0 m long, filled with loess, was used. In the trough six experimental rills, 0.1 m wide and 12 m long, were built to simulate well-develped rills. The trough was put at horizontal position for soil packing. At the bottom, the trough was densely packed with a 5cm thick layer of local clay soil, made compact with a hammer to simulate the plow pan layer, 15 g cm^-3 in bulk density. The upper 20 cm of the trough was packed with loess in layers, about 5 cm each, to make the soil even in bulk density, ranging approximately between 1 150 to 1 200 kg m^-3. The soil surface was raked to make it as rough as natural condition. Cumulative volume of erosion of a rill was the sum of erosion volumes of the eleven rill segments (0～0.5 m, 0.5～1 m, 1～2 m, 2～3 m, 3～4 m, 4～5 m, 5～6 m, 6～7 m, 7～8 m, 8～10 m, 10～12 m) of a rill. Total amount of erosion sediment was measured volumetrically by a collecting vat at the outlet of each rill during the experiment. The experiment was designed to have five slope gradients, i.e. 5˚, 10˚, 15˚, 20˚ and 25˚ for the trough, three flow rates, i.e. 2, 4 and 8 L min^-1 and three replicates. Results show that the process of rill erosion was not constant along a rill, with cumulative rill erosion and sediment concentration increasing exponentially and margin of the increase declining with rill length till the extreme in the end, which means that cumulative amount of erosion and sediment concentration increases rapidly at the initial segments of the rills, and the increase rate (the slope of the curve) attenuates gradually to approach zero along the rill. Flow rate and slope gradient were the two major factors affecting rill erosion, but the former seemed to have more influence than the latter. The comparison of the cumulative amount of erosion measured with the volumetric method with the result of direct measuring at the rill outlet validated the accuracy of the former, and the comparison of the sediment concentration measured with the water backfilling method with the result of direct measuring demonstrated that the former was quite accurate in and applicable to investigating distribution of erosion sediment along a rill. The findings of this study may serve as certain basis for consummating the research on soil rill erosion process, assessing sediment concentration from rill erosion and establishing a prediction model for farmland rill erosion.

Abstract:The traditional chemical methods, though still commonly used at present, for monitoring heavy metal pollution of soils are both time- and fund-consuming, while magnetic method is simple and inexpensive, and can be used to detect heavy metal pollution of soils nondestructively, with a soil-magnetic-susceptibility based soil heavy metal pollution grading system available. For use of that technology, a total of 99 topsoil (0～15 cm) samples were collected with the grid method in Kaifeng City (China) for analysis of Cr, Cu, Ni and Zn with atomic absorption spectrometry (F-AAS), Cd and Pb with inductively coupled plasma/mass spectrometry (ICP-MS), As with atomic fluorescence spectrophotometer (AFS), and χLF and χHF (low and high frequency magnetic susceptibility) with a MS2 magnetic susceptibility meter made by Bartington Ltd., Britain. The ordinary Kriging interpolation method was used to work out spatial distribution of soil magnetic susceptibility（χLF）in the city. Soil heavy metals pollution was assessed by pollution load index (PLI). Based on analysis of relationship between PLI and χLF, a soil heavy metal pollution grading system was established. Results show that the concentrations of As, Cd, Cr, Cu, Ni, Pb and Zn in the topsoil of Kaifeng are 6.31, 1.05, 53.11, 36.40, 23.87, 36.71 and 164.03 mg kg ^-1, respectively, and in line with their contamination factor values (CF), the heavy metals follow an order of Cd (10.48) ＞ Zn (2.28) ＞ Pb (1.68) ＞ Cu (1.51) ＞ Ni (0.81) ＞ Cr (0.80) ＞ As (0.65). The average PLI of the 7 heavy metals in the samples is 2.53, indicating that as a whole, the soil is moderately polluted with heavy metals, of which cadmium is the major pollutant. Soil χLF in Kaifeng varies in the range from 39.97×10^-8m³ kg^-1to 1123×10^-8m³ kg^-1with an average of 125.7×10^-8, while χFD does in the range from 0.61% to 5.94% with an average of 2.82%. The spatial distribution of soil χLF in Kaifeng City has three major characteristics, i.e. 1) Soil χLF displays a declining gradient from southeast to northwest; 2), A fairly large tract of the northern part of the old city district (within the ancient city walls); and 3) A few fairly high peaks of soil χLF appear alongside the Longhai Railway and are mainly distributed in the vicinity of the railway station and the east and west freight stations. Moreover, the contents of As, Cd, Cr, Cu, Ni, Pb and Zn in the soils and PLI are significantly and positively correlated with soil χLF, and the heavy metals display an order of Zn > Cu > Cd > Pb > As > Cr > Ni in terms of degree of the correlation, but contents of the heavy metals are negatively or poorly related with χFD, suggesting that the pollutants in the soils of Kaifeng City are closely related to all sorts of human activities. Dust from industrial production processes, exhaust from running vehicles, abrasion of aged pavement and stacks of solid waste, all are sources of large volumes of magnetic particular pollutants, which ultimately settle down into the soil with atmospheric precipitation or surface runoff, thus not only causing rise of heavy metals contents in the soil, but also enhancing magnetism of the soil. A significant positive relationship (R² = 0.814, p＜0.01) is observed between PLI and χLF, which suggests that soil χLF can be used to grade or evaluation soil heavy metal pollution in the city, and a regression equation, PLI = 0.011χLF + 0.320 (r = 0.663), is developed between the two parameters. When soil χLF is ≤62×10^-8m³ kg^-1, it means that the soil is not polluted; when soil χLF is 62×10^-8＜χLF≤153×10^-8m³ kg^-1, it means the soil is slightly polluted; and when soil χLF is 153×10^-8＜χLF≤244×10^-8m³ kg^-1, it means the soil is moderately polluted; and when soil χLF is＞244×10^-8m³ kg^-1, it means the soil is highly polluted. It should be noted that the grading is tentative and further studies should be done on its universality.

Abstract:A vegetable production base, typical of the area along the Yangtze River in Nanjing, was selected as a case for study. Concentrations of heavy metals in topsoil, soil profiles, fertilizers and atmospheric deposition were measured for analysis of spatial variation of soil heavy metal anomaly and sources of the heavy metals in the soils. Results show that (1) the average content of cadmium (Cd), arsenic (As), mercury (Hg), lead (Pb), copper (Cu), zinc (Zn) and chromium (Cr) in topsoil was 0.33, 11.2, 0.09, 36.2, 45.4, 120 and 98.7 mg kg^-1, respectively, all higher than their respective soil background value in Nanjing; Concentrations of Cd in 49% of the soil samples were found to be above the criteria of GradeⅡof the Standard for Soil Environmental Quality of China, implying higher Cd accumulations in the soils. (2) The concentrations of heavy metals in the topsoils were closely related to soil pH, soil organic matter and soil textures of the area; Spatial distribution of the heavy metals in topsoil, except Cr, was characterized by a trend of tending to be higher in the southeast and lower in the northwest, which was consistent with the spatial distribution of soil organic matter and opposite to the spatial distribution of soil pH; Concentrations of the heavy metals were higher in silty clay soils than in silty clay loam and silty loam soils. (3) Accumulation and distribution of the heavy metals in the soils was also related to the terrain, the layout of agriculture and industry, and the perennial dominant wind direction in the study area. The maximum values of Cd, Cu and Zn contents were found in the southeast of the study area and the maximum values of As in the centre. Concentrations of Hg tended to be high in areas with intensive agriculture and peaked in the northeast of the study area, while the highest concentration of Pb was found in the northwest and southeast of the study area. (4) In addition to the natural geological background, agricultural fertilization and atmospheric deposition were also important contributors to heavy metals accumulation in the soils of the area. In terms of concentrations of Cd in fertilizers, a decreasing order was found of commodity chemical fertilizer > organic fertilizer > manure > rapeseed cake. Contents of Cd, As and Hg were higher in chemical fertilizer, while contents of Pb and Cr higher in organic fertilizer. The contents of Cu and Zn in organic fertilizer were much higher than those in the other fertilizers, which were mainly related to the higher concentrations of Cu and Zn in the feed of livestock. As heavy metals in the soil has the feature of long-term accumulation, long-term intensive application of fertilizers high in heavy metals would lead to heavy metal accumulation in the soil, with a risk of gradually exceeding the standard for soil environmental quality or environmental capacity. The content of Cr in the atmospheric deposition was approximate to the background value of the soil in Nanjing. Compared with other researches on atmospheric deposition in Nanjing, this study found higher contents of Cu and Zn, which is probably because some of the sampling sites were quite close to industry parks in the vicinity and hence affected by chemical activities of the plants. Atmospheric deposition flux varied sharply from month to month, and contents of heavy metals increased obviously in winter, especially in the northwest industrial area. Contents of Pb and Cu in the atmospheric deposition varied in a similar way. Thus, it could be inferred that they have similar sources in the study area.

Abstract:Fast qualification of soil organic matter (SOM) is important to crop production and evaluation of soil quality. Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) makes it feasible to quantify soil organic matter content in a rapid way. In this study, FTIR-PAS was applied to measure SOM in the soils collected from paddy fields in Lishui District of Jiangsu Province. Support vector machine (SVM) was utilized to build calibration models. Principal component analysis (PCA), partial least squares (PLS) and independent component analysis (ICA) were performed separately to extract principal components (PCs), latent variables of PLS (LVPLS) and independent components (ICs) from the soil spectra as input of support vector machine (SVM). Hence, three SVM calibration models were built up. Meanwhile, PLS was also used to form a calibration model as control. Results show that the ICs-based SVM model performed best in prediction of SOM, with correlation coefficient (R2), root-mean-square error (RMSEP) and ratio of performance to standard deviation (RPD) being 0.808, 0.575 and 2.28 respectively. Furthermore, F-test demonstrates that this model was significantly superior over the PCs-based SVM model, but was quite similar to the LVPLS-based SVM model and the classic PLS-based SVM model. Besides, no significant difference was observed between the predictions using the calibration models and the determination using the chemical method, as was demonstrated by t-test. It can, therefore, be concluded that the technology of infrared photoacoustic spectroscopy can be used as a new means for rapid determination of soil organic matter content.

Abstract:As a core index of soil fertility, soil organic matter has played an important role in global carbon recycling and agricultural production. Field sampling, laboratory analysis and spatial interpolation are used as chief means of assessing content of soil organic matter in farmlands. Due to differences in soil forming factors and human activity, spatial distribution of soil organic matter contents and its driving force may vary from region to region under study, which in turn causes variation of applicable interpolations with the region. Fujian is a province very complicated in landform, as affected by the jointly actions of tectonic movement and long-term exogenic agencies, so the farmlands there are very high in land-use intensity and in spatial variability as well. Therefore, efficient site-specific point-plane expanding models will help expose laws of the spatial distribution of soil organic matter in farmlands of the province and realize precision agricultural nutrient management. In this study, nine counties, namely Minhou, Jian’ou, Yongding, Datian, Hanjiang, Fuding, Nan’an, Tong’an and Zhangpu, representative of 9 different types of landforms in Fujian Province, China, were selected for case study. Based on the data collected from the 29 320 sampling sites, scattered in these nine counties, of the soil testing-based fertilizer recommendation project sponsored by the Ministry of Agriculture of China, statistical characteristics for soil organic matter contents in farmlands were analyzed using the statistical software SPSS and GS+ and a semi-variance model established. In line with the principle of “for mean errors (ME), the closer to zero, the better and for root mean square errors (RSME), the smaller the better, and RSME should be given the first priority” impacts of different interpolation methods on accuracy of the reckoning of soil organic matter contents were evaluated and eventually a point-plane expanding model with the higher accuracy in predicting soil organic matter contents in the farmlands of Fujian Province was defined. Results show that the mean soil organic matter content of farmlands in Fujian Province was 27.83 g kg^-1, and its coefficient of variation was 37.87%, displaying a strong spatial autocorrelation and for semi-variance function the exponential model fitted the best. For prediction of organic matter contents in farmlands of Minhou County, Jian’ou City, Yongding County, Hanjiang District and Fuding City, the optimal geo-statistical interpolation method was the pan-kriging method, while the optimal deterministic interpolation method was the inverse distance weighting method, however, the former was higher than the latter in prediction precision. For Datian County, the optimal geo-statistical interpolation method was the simple kriging method, while the optimal deterministic interpolation method was the inverse high-order surface function method, however, the former was still higher than the latter. For Nan’an City, Tong’an District and Zhangpu County, the optimal geo-statistical interpolation method was the ordinary kriging method, while the optimal deterministic interpolation method was the tension spline function method, nevertheless, the former was higher, too, except for Zhangpu County. On the whole, in regions, like Minhou, Jian’ou, Yongding, Hanjiang and Fuding, that have similar distribution areas of plain or basin, hills and mountains, the use of the pan–kriging method in spatial interpolation of soil organic matter contents is relatively high in prediction precision, while in regions, like Datian, that are dominated with mountains the use of the simple kriging method is more advisable and in regions, like Nan’an, Tong’an and Zhangpu, that are dominated with plains or table lands, the use of the ordinary kriging method or the tension spline function method is.

Abstract:To understand how soil water evaporates from soil columns different in layered structure and soil columns homogeneous in soil texture, five soil columns were prepared by filling soil into Plexiglas cylinders, 90 cm in height, 23.5 cm in inner diameter and 0.9 cm in thickness of the wall. Three of them were packed with sandy soil and sandy loess, layer by layer alternatively but different in thickness of the layers (11.25, 22.5 and 45 cm) and two with sandy soil and sandy loess separately and homogeneously. The soil columns were irrigated till they were saturated and then let drain with a 2 cm water layer at their bottoms for 30 days and then they were ready for the evaporation experiment. The columns were sealed at the bottom to ensure zero flux from the lower end. During the experiment, cumulative evaporation, relative evaporation rate and profile water content were monitored and AE/PE ratios (actual evaporation rate / potential evaporation rate) were calculated and meanwhile, evaporation processes from the five soil columns were simulated and analyzed using the HYDRUS-1D model and optimized soil hydraulic parameters based the drainage processes of the two homogeneous soil columns. The soil hydraulic parameters were obtained through optimization of the calculation of profile water contents during the drainage processes in the two homogeneous soil columns. Then the optimized hydraulic parameters were used to simulate drainage processes in the three layered soil columns with much better effect that lowered the relative error by 1% to 9%. Besides, the optimized hydraulic parameters based on variation of profile water content in the two homogeneous soil columns during the drainage processes were used to simulate evaporation processes of the soil columns. Actual evaporation from the columns was determined by weighing the columns on D 0, 2, 4, 9, 14, 22, 30, 34, 40, 45, 49, 53 and 56. Moreover, 12 cm long TDR probes were placed in the columns, one every 10 cm to measure profile water content on D 0, 8, 14, 22, 30, 40 and 56. Analysis of the measurements and simulations show that in the homogeneous column of sandy loess the first phase of evaporation lasted 34 days, and as a result, its cumulative evaporation was the highest, reaching 110.8 mm, while in the homogeneous column of sandy soil and the other three layered columns, the first phase evaporation lasted only one day, so their cumulative evaporation was as low as around 6 mm. The layered soil column with sand on the surface was relatively stable in profile water content, indicating that sand mulch could dramatically reduce soil evaporation. In addition, the three layered soil columns did not differ much in soil evaporation, demonstrating that an 11.25 cm-thick overlay of sandy soil is enough to reduce soil evaporation significantly. Although the simulations agreed well with the observations, the simulation of soil evaporation could be further improved in precision by using drainage-process-based optimized hydraulic parameters and the HYDRUS-ID model. Improving the accuracy of the simulation of soil water characteristic curve and soil hydraulic conductivity and taking into account the coupling effect of water, vapor and heat in soil columns is the major approach to reducing simulation deviation. The findings in the experiment may have some important significances in guiding soil water management in arid and semiarid regions.

Abstract:To investigate effects of change in ion-strength and depletion of organic matter on desorption of copper ions, a test was conducted on using electrolyte solutions, including de-ionized water, varied in NaNO₃ concentration from low to high, to desorb successively copper ions adsorbed by Hyper-Rhodic Ferralsol, which is a typical variable charge soil collected from Kunming, China. Results show that de-ionized water and NaNO₃ electrolyte solutions (0.01 mol L^-1 NaNO₃, 0.1 mol L^-1 NaNO₃ and 1 mol L^-1 NaNO₃) differed in effect on Cu(II) desorption with pH of the solutions. In de-ionized water, the pH-dependent Cu(II) desorption rate displayed a linear declining curve, and almost down to zero around pH5.3, on which frequency of the desorption did not have any effect. In NaNO₃ solutions, except for the solution 1 mol L^-1 in concentration, Cu(II) desorption rate peaked when pH lingered in the range of 4.4~4.6. Compared with Cu(II) desorption in OM depleted Hyper-Rhodic Ferralsol, that in the original Hyper-Rhodic Ferralsol was much higher in rate during its first time desorption test, and pH-Cu(II) desorption changed in shape of its rate curve and the desorption peak appeared at a lower pH. However, the pH-desorption rate curve as a whole was not much affected in tendency. The effects of overlapping of the electronic double layers and the relationship between ion strength and surface potential on repulsive potential of the surface sorption layer to copper ions could be used to explain how de-ionized water desorbed copper ions from the soil. According to the relationship between the surface potential and ion-strength, the decrease in ion-strength always means increase in absolute value of surface potential of the sorption layer, that is to say, when the surface potential of the soil is positive, the repulsive potential will increase with increasing surface charge and on the same time, the decreasing ion-strength will also lead to expansion of the diffusion layer, which will eventually result in neutralization of more charges through overlapping of electronic double layers. The two above-mentioned causes would both trigger desorption of adsorbed copper ions in de-ionized water. The appearance of peaks of Cu(II) desorption rate could also be explained as effect of hydrolysis. As the ratio of hydroxide copper ions increases with increasing pH and hydroxide copper ion is lower than Cu²⁺ in valence its electrostatic attraction to the surface of the adsorption layer is weaker than that of Cu² , which makes it easier for adsorbed hydroxide copper ions to be replaced by Na , so the increasing ratio of hydroxide copper ions along with pH increases the desorption rate of copper ions. On the other hand, the density and amount of negative charges on soil surface increase with increasing pH. Such a change favors adsorption of Cu² , rather than desorption of the ions. When pH of the system reaches a certain threshold value and the positive effect of hydrolysis on desorption is offset by the negative effect of increased amount and density of negative charges, the apparent Cu(II) desorption rate will be at its maximum, and begin to decline. Base on the above-mentioned observation, it is held that there is ample reason to believe that the induced hydrolysis of copper ions on soil surface is also effective on exchangeable copper ions, in other words, the copper ions that are adsorbed in the diffusion layer are also very likely to be hydrolyzed. Besides, this paper also has some lines devoted to the discussion of the relationship between pH0 of kaolinite and the threshold pH value, at which the rising slope of the adsorption rate curve with rising pH undergoes a sudden change.

Abstract:In China, as a result of excessive application of fertilizers, farmland soil acidification has been accelerated in the recent decades, especially in facilitated cultivation systems, and in places where leaching is weak, secondary soil salinization could be observed. The presence of soluble inorganic salts in the soil has some significant effects on determination of soil pH(H₂O) (pH in soil-water suspension). Since pH is one of the most important parameters in evaluating soil acidification, it is necessary to study in depth to explore effects of several common soluble salts on determination of farmland soil pH (H₂O). To accurately evaluate soil acidification of cultivated lands under secondary salinization, effects of six kinds of soluble salts (Ca(NO₃) ₂, KNO₃, MgSO₄, K₂SO₄, CaCl₂ and KCl) in farmland soils (fluvo-aquic soil, cinnamon soil, paddy soil and red soil), especially in greenhouse soils, on determination of soil pH(H₂O) were explored in this study. Besides, comparison was done between four methods in effect of eliminating the effect of soluble salts, with potassium nitrate being the object of the study. The four methods were 1) replacing pH(H₂O) with lime potential, 2) using 0.01 mol L^-1 CaCl₂ instead of de-ionized water in extracting soil, 3) figuring out the effect of the soluble salt on determination of soil pH with a model first and deducting what was figured out from the value of pH(H₂O) determined, and 4) leaching out soluble salts from the soil with distilled water or 50℃ 50% ethyl alcohol solution first and then air-drying the soils for determination of soil pH(H₂O). Results show that the presence of 10 g soluble salt per kilogram soil may bring down soil pH by 0.09~0.87, and both soil electric conductivity and concentration of soluble salts are significantly related to pH and △pH (extent of the drop in pH) in a natural logarithm manner. The six kinds of soluble salts in the same soil differ quite much in effect on determination of soil pH and the sequence of the salts in terms of intensity of the effect varies with soil type and combination of salt ions in the soil. On the whole, the effects of nitrate and chloride are greater than that of sulfate, and the effect of calcium chloride higher than those of calcium nitrate, magnesium sulfate and three potassium salts. However, there is no significant difference between the three potassium salts. The effect of a kind of salts varies with soil type, and the four types of soils display a descending order of cinnamon soil > paddy soil > fluvo-aquic soil > red soil. All the four methods can be used to reduce or eliminate the effect of KNO3 on determination of soil pH. The presence of 6.9 g of potassium nitrate per kilogram soil lowers soil pH(H2O) by 0.24~0.71, or by -0.38~0.19 when the effect of the soluble salt is taken into account or eliminated. In terms of simplicity and effectiveness of the four methods, they follow an order of Method 1) > Method 2) > Method 3) > Method 4). Apparently, elimination of the effects of soluble salts on determination of soil pH can help improve accuracy of the evaluation and risk assessment of soil acidification in farmlands under secondary salinization, and contribute to formulation of reasonable effective risk controlling measures.

Abstract:Pollution of groundwater and soil by heavy metals and organic substances is getting increasingly serious. In the polluted soil or water, the pollutants often exist simultaneously, to remedy the soil or water, the method of fixation through adsorption is one of the most effective ways. Organically-modified soils can effectively adsorb organic compounds. Amphoteric surfactant modified soils can adsorb organic substances and heavy metals at the same time, but their organic pollutants adsorption capacity is not so high as cationic modified soils. In order to enhance their capacity, they are further modified with another type of surfactant modifier. For that end, bentonite was modified with dodecyl dimethyl betaine (BS-12) + Tween20 complex varying in ratio by wet chemical method and effects of the modified bentonites adsorbing Cd² relative to ratio of the modifier (in terms of total carbon ratio of Tween20/BS-12, set at 0.25, 0.5, 1 and 1.5), temperature (20，30 and 40℃), pH (3, 5 and 7), ionic strength (0.05，0.10 and 0.50 mol L^-1) were explored using the batch experiments and control variate method, and mechanism of the adsorption was studied from the aspects of adsorption isotherms (Model fitting, using the CurveExpert 1.4 nonlinear fitting software and the stepwise approximation method for nonlinear fitting), temperature effects and thermodynamics. Results show that the equilibrium Cd² adsorption capacity of Tween20 complex modified bentonite varied with modification ratio, displaying an order of BS 0.25T > BS 0.5T > BS > BS 1 T > BS 1.5 T > CK, which means that when the ratio ranged between 0 and 0.5, the capacity rose with the ratio, but when the ratio exceeded 0.5, the capacity decreased with the rising ratio, which demonstrates that the Tween20 modification ratio, less than 0.5, is in favor of Cd² adsorption on modified bentonite. The adsorption isotherms of Cd² on modified bentonite can be described with the Langmuir model. Within the experimental range that ensured Cd² soluble, the rise of pH under the acid condition increased Cd² adsorption, somewhat, as a result of strong competition between H and heavy metal ions for adsorption sites. Ionic strength has some strong impacts on Cd² adsorption capacity of the modified bentonite, mainly in three ways: (1) Forming ion pairs or affecting pH of the solution, thus altering the activity of free metal ions; (2) Triggering competition between K and Cd² for adsorption in the supportive electrolyte; (3) Causing the supportive electrolyte to compress its double electrical layer, i.e. diffusion layer, thus altering the adsorptive surface of the soil sample, As a result, the soil sample weakened its Cd² adsorption under increasing ionic strength. With rising temperature, the modified soil increased its Cd² adsorption, showing a positive relationship. Thermodynamic parameters show that Cd² adsorption on modified bentonite is a entropy controlled spontaneous process. Cd² adsorptions on all the soil samples are endothermic processes. It can, therefore, be concluded that modification of amphoteric bentonites with Tween20 to a certain ratio can increases the soil Cd² adsorption capacity; amphoteric modifier BS-12 and nonionic modifier Tween20 are used jointly to modify bentonite, altering its electrical attraction and hydrophobic bonds, thus increasing negative charge of the surface layer and thickness of the hydrophobic layer of the bentonite. When Tween20 modification ratio is low, the interlayer spacing expands in bentonite, thus leading to increase in Cd² adsorption, while higher modification ratio brings about a thick layer thickening, blocking negative charge sites on the surface of the modified soil, thus lowering the soil’s Cd² adsorption capacity.

Abstract:Nitrification plays an important role in global nitrogen recycling and exists ubiquitously on earth. Nitrification activity determines nitrogen transformation process and is solely catalyzed by ammonia oxidizers and nitrite oxidizers. Nitrification has been intensively investigated, generally, on a field scale in a single location but little has been done on a large scale. On a global scale, soil varies and distributes in the epigeosphere regularly according to certain laws as affected by different hydrothermal conditions. Meanwhile, soil microbial communities exhibit distinct biogeographic patterns and their distribution is mainly influenced by contemporary environmental factors and historical evolutionary factors. However, almost little is known about spatial patterns of functionally important biogeochemical processes that are mainly driven by microbial communities. In this study, here we report the construction of a soil nitrification database, meta-analysis of nitrification activity in ecosystems typical of China and main driving forces of nitrification rate on a national scale. From the 2 900 papers published both abroad and at home during the period of 1959-2013 on soil nitrification and found available in the literature database of soil science, 111 papers were collected according to the same data mining standards. A total of 288 sets of data were obtained on soil nitrification activity in the soils in 26 provinces of China. Based on the data extracted from the papers and acquired from the online database, a Soil Nitrification Information System (SNIS), was constructed. The system covers data, like sample locations, soil properties (including pH, total nitrogen, nitrate nitrogen, organic carbon, available phosphorous, clay content, etc.) and nitrification activity. Nitrification activity was assessed by three parameters including net nitrification rate, potential nitrification rate and gross nitrification rate using the conventional analytical methods. One-way analysis of variance (ANOVA) and the least significant difference test (LSD) were employed to explore difference in nitrification activity between different ecosystems, that is, farmland, grassland, forest land, desert and wetland. Pearson correlation analysis was employed to reveal relationships between soil properties and nitrification activity. Single factor models were used to estimate correlation coefficients between nitrification activity and soil properties. Net nitrification rate varied with the ecosystem, displaying a decreasing order of from farmland (NO₃⁻-N 1.39±0.27 mg kg^-1 d^-1) > grassland (0.74±0.17) > forest (0.66±0.16) > desert (0.17±0.08) > wetland (0.06±0.04). The net nitrification rate of the farmland ecosystem is significantly higher than those of the others. In terms of potential nitrification rate, grassland (7.41±3.73) ranks first among the five ecosystem and was followed by farmland (4.97±0.43), forest (1.06±0.24) and the other two, showing differences significant on a 0.05 level, while in terms of gross nitrification rate, forest land (7.76±0.43) did first and was followed by farmland (5.72±0.86), grassland (5.25±1.76) and the others. Pearson correlation analysis shows that in the farmland ecosystem, net nitrification rate was closely related to soil nitrate nitrogen and available phosphorous, and potential nitrification rate to soil pH, nitrate nitrogen, organic carbon and available phosphorous, while in the forest ecosystem, net nitrification rate was to soil available nitrogen and carbon-nitrogen ratio. Statistic analysis demonstrates that on the national scale, nitrification activity varied significantly between the ecosystems and nitrification rate was significantly lower in natural ecosystems than in anthropogenic ecosystems, and soil pH and nitrate nitrogen concentration appeared to be good indicators of soil nitrification activity in these ecosystems.

Abstract:Production of exopolysaccharide (EPS) using wastewater is an optimal approach to treating wastewater by turning it into resource and hence a hot pot in the study of EPS. To screen out a high-EPS-producing strain of Purple Phototrophic Bacteria (PPB), an in-lab experiment was carried out cultivating 11 strains of PPB in a kind of chemically composed medium and media of organic wasterwater composed of wastewaters from soybean-prosessing and corn starch production at different ratios, separately. In the end of the experiment, the media were analyzed for extraction of EPS and for comparison. Results show that the strains of PPB varied in EPS producing capacity and that organic wastewater was more conducive to EPS production than the chemical medium. After two cycles of comparison, Strain J4 was screened out to be the highest- EPS-producing strain. In the wastewater from soybean processing, Strain J4 produced as high as 140 mg g^-1 cell dry weight of EPS and as a result, it reduced wastewater COD by over 90%. The analysis with Sephadex G-50 chromatography shows that the EPS produced by J4 is high in molecular weight and has a certain research value. To sum up, through the cultivation experiment, a strain of high-EPS-producing PPB, J4 was obtained, and was proved to be able to produce large volumes of EPS by organic wastewater, which could be used as a basis for finding and producing cheap polysaccharide materials.

Abstract:Polycyclic aromatic hydrocarbons (PAHs), being nowadays the major environmental pollutants, can bring about adverse effects on soil microbial community. Classical biological indicators, such as dehydrogenase activity, substrate induced respiration rate and community level physiological profiles, are widely used to evaluate toxicity of PAHs to soil ecosystems. However, it is not feasible to use them to monitor soil pollution in a real-time continuous way. Microbial fuel cells (MFCs) are a kind of devices that convert chemical energy of organic substrates into electrical power through the catalysis of electrogenic bacteria. As the current which is closely related to metabolic activity of the electrogenic bacteria can be recorded immediately and continuously, MFCs have already been used as a biosensor to monitor wastewater treatment. Electrogenic bacteria are known to be widely distributed in soil. They generate electricity while decomposing soil organic matter and are extremely sensitive to environmental change. Pollutants creating stress on soil microbes may also inhibit the activity of electrogenic bacteria. Thus electrical signals generated by soil micro-organisms could be used as an indicator to detect soil pollution. The objectives of the study are to determine feasibility of the use of the electrical signals to evaluate pyrene toxicity in soil, and understand how soil electrogenic bacteria respond to pyrene pollution. Synthetic PAHs contaminated soils were prepared, different in amount of pyrene spiked, i.e. 0 (as control), 60, 120, 180 and 240 mg kg-1 pyrene and then packed into MFCs anode chambers, separately. To accelerate the electricity generation, 4% (w/w) glucose was thoroughly mixed into the soil before packing. Voltage of MFCs was real time monitored every 10 min for 110 h. To examine reliability of the use of electrical signals in toxicity detection, dehydrogenase activity in the pyrene contaminated soil was also measured simultaneously. After the MFCs operated for 110 h, electrochemical activity of the soil microbes was determined using cyclic voltammetry. Bacterial community diversity on the MFCs anode biofilm was determined through phylogenetic analysis of 16S rRNA genes with the PCR-DGGE and sequencing methods. All the DGGE band sequences were submitted to the GenBank and assigned with accession number, KJ128061 - KJ128073. Results show that the cells started to generate electricity after 6 h of operation. Peak voltages from MFCs of pyrene-contaminated soils were monitored varying between 240 ~ 270 mV, while that from control reached 305 mV. The coulomb production of the MFCs within the 110 h decreased significantly with the rate of pyrene added, and significantly (p < 0.01) correlated with soil dehydrogenase activity. Cyclic voltammogram shows that the soil of control treatment had higher redox peaks than the soil spiked with 240 mg kg-1 pyrene with ranging at potentials around -100 mV and 100 mV while no peaks were observed in the fumigated and sterilized soil, illustrating that pyrene addition weakened electrochemical activity of the soil micro-organisms. DGGE patterns show that after 110 h of operation, the bacterial community on the MFCs anode biofilm differed significantly from that in the soil in structure. Sequencing and phylogenetic analysis of the DGGE bands reveal that the bacteria on the anode biofilm was highly similar to the known electrogenic bacteria, including Sporolactobacillus, Clostridium, Enterobacter, Bacillus and Ethanoligenens. Pyrene addition decreased the abundance of Bacillus. This study demonstrates that the electrical signals generated by soil micro-organisms could satisfactorily be used to evaluate pyrene toxicity in the soil. The mechanisms of pyrene reducing electricity generation include inhibition of electrical activity of soil micro-organisms and alteration of the structure of the electrogenic bacterial community on the anode. In future the study in this field should be oriented toward monitoring of more pollutants varying in a wider range of concentrations, and optimization of the configuration and operation of MFCs to shorten their startup time and to improve their sensitivity of electrical signals.

Abstract:Multi-scale autocorrelation is an important basis of the study on spatial heterogeneity and spatial co-occurrence patterns of soil animals. A sampling field, 50 m × 50 m, was set up in farmland of the Sanjiang Plain Marsh and Wetland Ecological Experiment Station. The farmland had a history of more than 30 years of cultivation. The sampling field was divided into 100 subsamples and intensive samplings were done at the nodes of a 10 × 10 regular grid with 5 m inter-sample distances. Overall Moran’s I and Local Moran’s I were used to determine multi-scale spatial autocorrelations for mean density of the aboveground, belowground and above-belowground mite communities. Results show that the number of species and mean density of mite communities varied sharply between aboveground and belowground ones. Overall spatial autocorrelation analysis revealed that the mean density of the belowground mite communities showed significantly spatial autocorrelations was 35~40 m in August and 5~30 m in October, and of the above-belowground mite communities was 5~10 m, 35~45 m and 5~35 m, respectively, showing obvious multi-scale spatial autocorrelations between them and obvious multi-scale spatial autocorrelations also existed between dominant mite groups that were often large in number and commonly observed miter groups in the soil mite communities. Local spatial autocorrelation analysis indicates that significant local autocorrelations existed between the whole soil mite community and mite communities above the ground, under the ground and above-belowground in mean density, thus forming a horizontal distribution pattern with coexisting “patches” and “gaps”. All the above listed findings demonstrate that multi-scale spatial autocorrelation is an important feature of the belowground and above-belowground mite communities in farmland of the Sanjiang Plain, with mean densities of the mide communities and species forming a horizontal pattern with coexisting “patches” and “gaps”.

Abstract:Soil organic carbon and its labile components are sensitive indicators of changes in soil carbon pool. Therefore, the study on soil organic carbon and its labile components is of great significance to the research of global climate change. A field survey was carried out of tidal flats and natural wetlands in Hangzhou Bay with samples of soils at 0~10 cm, 10~20 cm, 20~30 cm in depth collected for analysis of changes in soil organic carbon (SOC), soil dissolved organic carbon (DOC), soil readily oxidizable carbon (ROC) and light fraction organic matter (LFOM) in bare mudflat and mudflats under Phragmites australis, Spartina alterniflora and Scirpus mariqueter, and relationships between various fractions of organic carbon and soil physico-chemical properties. Results indicate that (1) the mean SOC content in soils of the three soil layers was 3.87~5.08 g kg^-1, 6.46~6.78 g kg^-1, 4.33~4.48 g kg^-1 and 4.99~5.25 g kg^-1 in mudflat under Phragmites australis, Spartina alterniflora, and Scirpus mariqueter, and bare mudflat; the mudflat under Spartina alterniflora was the highest and followed by bare mudflat in mean SOC content; soil TN and SOC varied in a similar trend, regardless of vegetation; (2) The mudflat under Spartina alterniflora was the highest in mean DOC and LFOM content, being 90.69~98.90 mg kg^-1 and 2.35~2.95 g kg^-1 respectively, while the bare mudflat the lowest, however, the bare mudflat was the highest in mean ROC content, being 2.06~2.22 g kg^-1; (3) No significant difference was observed between the mudflats under Phragmites australis, Spartina alterniflora, andScirpus mariqueter in DOC/SOC ratio, but in ROC/SOC ratio, a decreasing order was found of bare mudflat > mudflat under Scirpus mariqueter > mudflat under Phragmites australis > mudflat under Spartina alterniflora; (4) SOC was significantly and positively related to DOC, ROC and LFOM; Besides, SOC was also significantly and positively related to TN and soil moisture content; but all the SOC fractions were negatively related to soil pH (p<0.01). All the findings indicate that the invasion of Spartina alterniflora is not so bad because the plants help enhance wetlands’ carbon sequestration capacity, and the labile fractions of organic carbon are good indicators of changes in soil organic carbon pool in wetlands.

Abstract:Applying biochar to soils may cause a win–win situation resulting in C sequestration and improvement of soil fertility and soil physical quality, depending on soil moisture condition, soil temperature and soil C/N ratio. An in-lab incubation experiment, laid out in quadratic general spinning design, was conducted to investigate effects of application of maize stalk and biochar made from maize stalk on N transformation in and N₂O emission from Loessal soil. Results show that in the soil applied with maize stalk, net nitrogen mineralization was influenced mainly by content of organic carbon, and then by contents of water and nitrogen, but in the soil applied with biochar, it was mainly by content of nitrogen and then by contents of water and organic carbon. The difference between the two carbon sources in effect on net N mineralization was extremely significant (p<0.01). Compared with maize stalk, biochar increased soil NO₃⁻-N and NH₄⁺-N concentrations, and significantly decreased N₂O emission. In the soil applied with biochar, the concentration of inorganic nitrogen changed slowly during the entire incubation period, while in the soil applied with maize stalk, it did drastically in the first two weeks of the incubation. Hence, it is obvious that application of biochar is conducive to reduction of emission of the greenhouse gas, N₂O.

Abstract:A field experiment was carried out using a cultivar of cabbage that suits the area of Chongqing for cultivation, to study effects of SOP and MOP on yield, quality and nutrients of cabbage, so as to provide a scientific basis for designing a reasonable K fertilizer application technique for production of hazard free cabbage. Results show that application of K fertilizer increased the yield, either biomass or commodity, of cabbage significantly by 4.32%~14.6%. The effects were the most significant in treatments moderate (K2) in K application rate, regardless of forms of potash, and the effects did not differ much between treatments the same in application rate, but different in potash form. But in terms of cost, potassium chloride was superior. K application increased the content of amino acids in cabbage in all the treatments, especially in Treatment K1(S), by 56.9%;decreased VC content in cabbage in all the treatments except for Treatment K2(Cl), which increased the content by 6.8%; reduced nitrate content in cabbage in all the treatments, particularly in Treatment K3(S), by as much as 12.3%; increased reduced sugar content in cabbage in all the treatments with Treatment K1(Cl) in particular; and mineral nutrients, except for Zn, in cabbage to a certain extent in all the treatments. The nutrients in the cabbage were mostly dominated with non-protein forms. Protein-N was significantly and negatively related with amino acid in content in cabbage in all the K treatments, while protein-P was reversely with amino acid, and non-protein-P was significantly and positively related with VC content. Compared with N and P, K, regardless of its form, was more closely related to the quality of cabbage. Total-K and protein-K was in a significantly positive relationship with VC content, but in a negative one with nitrate in the cabbage. To sum up, potassium chloride is a kind of K fertilizer more suitable for cabbage cultivation, preferably at 225 kg hm^-2.

Abstract:Experiments were carried out using extractants prepared out of deionized water with tea polyphenols (TPs, including tea extracts, catechin and epigallocatechin gallate) and low-molecular-weight organic acids (LMWOAs, including oxalic acid, citrate acid and malic acid) 5 mmol L^-1 each in concentration, separately, to extract 3 types of acid soil (Albic Fe-accumuli-Stagnic Anthrosols, Typic Haplic-Perudic Argosols and Dystric Purpli-Udic Cambosols) for comparison between the two groups of extractants in effect of mobilizing soil mineral elements in the soils. Results show that the effects of TPs mobilizing soil Si, Al and Fe were higher in Dystric Purpli-Udic Cambosols than in Albic Fe-accumuli-Stagnic Anthrosols and Typic Haplic-Perudic Argosols, the three organic LMWOAs differed in the effect, displaying an order of oxalic acid > citric acid > malic acid, and their effects were more significant than TPs’ in the Albic Fe-accumuli-Stagnic Anthrosols and in the Typic Haplic-Perudic Argosols, but not in the Dystric Purpli-Udic Cambosols, where TPs were higher than malic acid in the effect (especially in effect of mobilizing Si, TPs were even higher than all the LMWOAs), which demonstrates that TPs really play an important role in desilicating primitive soil through complexing action and proton effect, and hence predicts that tea cultivation may be conducive to the evolution of the soils into zonal soils; The effects of TPs and LMWOAs were more significant on Al than on that Si and Fe in all the three soils, and moreover, mobilization of Si, Al and Fe occurred simultaneously, which indicates that TPs and LMWOAs may get complexed more efficiently with Al, thus lowering its toxicity, but on the other hand, increasing its mobility and facilitating its entrance into water body and the environment. In terms of effect mobilizing soil base ions, in case of Ca, malic acid was higher than TPs; in the case of Mg and K, LMWOAs were higher than TPs; and in the case of Na, tea extracts ranked first, and were followed by citric acid and then malic acid, and in Albic Fe-accumuli-Stagnic Anthrosols, TPs were higher than LMWOAs. The effects of LMWOAs and TPs mobilizing soil base cations, especially Ca, K and Na, were the highest in Albic Fe-accumuli-Stagnic Anthrosols, and the three base cations though followed an order of Ca > Mg > K in amount mobilized, they were being mobilized simultaneously. So the use of Albic Fe-accumuli-Stagnic Anthrosols for tea cultivation would promote mobilization and migration of Ca, K and Na, which would improve bioavailability of these base cations on the one hand and accelerate soil acidification on the other. It is, therefore, essential to further intensify systematic study of the effects of TPs on mobilization and migration Si, Al and Fe in primitive soils and the effects of conversion of Albic Fe-accumuli-Stagnic Anthrosols into tea gardens on mobilization and migration of base cations in the soil.

Abstract:A comparative analysis was done of the SWI (Soil Water Index) acquired by the ERS (European Remote Sensing Satellites) using scatterometers in 1992-2000 vs the data of farmland soil moisture in the Loess Plateau obtained through field investigations and in addition, effects of rainfall, vegetation, land use and irrigation on inversion of the data were analyzed. Results show that inversion of the remote sensed SWI reflects quite well the spatio-temporal variation of soil water in the Loess Plateau, displaying a general trend similar to that of soil moisture in actual distribution in the region, that is, spatially it is relatively high in the south and the east and low in the north and the west, and temporally high in summer and fall and low in spring. Besides, W_swi, soil volumetric water content converted from SWI, are found to be in an extremely significant positive relationship with the measured soil moisture contents in the 0~10 cm soil layer of farmland, which implies that the soil moisture data acquired through inversion of ERS data are very approximate to the actual conditions of near surface soil moisture, and hence the technique can be used to estimate surface soil moisture in the study area. Moreover, high correlation coefficients are found between W_swi and with measured values of soil moisture in the surface soil layer in intensive agricultural plain areas, whereas they are not so high in areas interlaced with farming, forestry and animal husbandry. It is also found in the study that the measured values of soil moisture tend to be higher than those from inversion of the ERS data in relatively dry seasons, mainly due to irrigation that increases soil moisture content in the field. This finding indicates that when using ERS data for estimation of soil moisture contents, it is also essential to take into account the factor of human activities in addition to natural environmental factors, such as landform, soil, vegetation, climate, etc.