Abstract:The geochemistry of major and trace elements of soils derived from the Lower-Cambrian black shales (the black-shale soils) were studied by samples of typical soils and corresponding parent rocks from Dongping, Yanxi, Taojiang and Ningxiang in central Hunan province (China), using ICP-MS and XRF techniques. Results show that the black-shale soils were strongly weathered, with chemical weathering index (CIA) values of higher than 73. Due to the higher intensity of chemical weathering, the chemical compositions of the soils are characterized by distinct depletion of CaO and Na₂O, and by significant enrichment of Al₂O₃and Fe₂O₃. The soils were also enriched with heavy metals including Mo, Cd, Sn, Sb, U, V, Cr, Co, Ni, Cu, Zn, Tl, Pb and Th, when compared to the China average soils, and the complex enrichment indexes (EI) are higher than 3 in average with the highest up to 17.0. This heavy metal enrichment of the soils probably reflected the chemical components of the parent rocks. Assessment using the geoaccumulation index ( I_geo) shows that the soils are contaminated by heavy metals Mo, Cd, Sb, Sn, U, V, Cu, Tl and Ba, for which the contamination of metals Mo, Cd and Sb is the most heavy, reaching moderate to extreme pollution degrees. Significant correlations of heavy metals to major elements indicate that heavy metals in the soils are hosted mostly in clay minerals and Fe-oxides (goethite), among which metals Ba, Sn, Th and Sc are hosted in clay minerals, metals Zn, Ni, Mn, Co, Cd, Tl and Pb in Fe-oxides, and metals Cr, V, Mo, Sb and U neither in clay minerals nor in Fe-oxides (goethite). Elemental ratios of Zr/Hf, Ta/Nb and Nd/Sm of the soils are similar to each other with values of 36.20, 0.085 and 5.30, respectively, and these ratios are also consistent to those of their corresponding parent rocks. In addition, the REE distribution patterns of the soils from different area are similar, and similar to that of their corresponding parent rocks. The rare earth elements were not differentiated during pedogenesis. Therefore, it is suggested that the heavy metal contamination of the soils was caused originally by metals from the parent rocks (black shales) in the area, which is a natural source of soil heavy-metal contamination.

Abstract:Predictive soil mapping is applied to a survey area, 1 km₂ in acreage, based on fuzzy c-means algorithm (FCM) and spatial interpolation. First of all, a group of characteristic soil horizons were established out of 123 soil profiles and auger sampling sites through analyzing their morphological quantitative attributes. A multi-attribute data set of n soil individuals p attributes was submitted to FCM. The best partition was obtained with four classes, which were consistent with the main soil-forming processes of the area in terms of variations of landscapes, parent materials and land-use types. Then, the spatial variability of fuzzy memberships was investigated and distribution pattern of the fuzzy membership classes were mapped by kriging interpolation using ArcGIS geostatistical package after the modified symmetry Log-ratio transform of original compositional data. Finally, the interpolated partial memberships were post-processed to produce compositional maps of maximum soil memberships, which had a common reference basis with the well-known choropleth map produced by conventional soil survey.

Abstract:Comprehensive analysis of the Miocene palaeosol in Qin’an area, Tianshui, Gansu, covering micromorphology, particle size, of CaCO₃ content, Rb/Sr, CIW, magnetic susceptibility and chroma, revealed the palaeosol was more developed than the modern soil in the region, and of the soils, however, the palaeosol in the middle and late period of the early Miocene epoch was relatively lower in development degree. The soil is Cinnamon soil-Carbonating Cinnamon soil formed in humid/semi-humid forest/forest-steppe environment, suggesting that monsoon already appeared in Asia as early as that period, with intensity, though quite weak, still quite stronger than the modern one. The palaeosol of the middle Miocene was stronger in development degree, and is Cinnamon soil to brown soil formed in warm and humid climate, suggesting that the monsoon prevailed in Asia in that period and was much stronger than the modern ones.

Abstract:Nitrogen (N) recycling in agricultural soils plays a key role in the terrestrial N cycle. A thorough understanding of N storage and its spatial distribution in Chinese paddy soils would be helpful to research on N cycle. Total soil N density and total soil N storage of paddy soils in China was evaluated based on the data of 1 490 paddy soil profiles and the 1∶1 000 000 soil database of China. Results showed that the mean nitrogen density of paddy soils at a depth of 0~100 cm was 12.4 Mg hm^-2, and the N storage was 569 Tg. Nitrogen density varied substantially with the soil subgroups and regions. Submergenic paddy soils were the highest in mean N density (19.7 Mg hm^-2) among all paddy soil subgroups, whereas Bleached paddy soils the lowest (8.71 Mg hm^-2), and Southwest China was the highest (17.4 Mg hm^-2), while South China had the lowest (11.5 Mg hm^-2). The variation of N density in both paddy soil subgroups and soil regions are quite significant, but it was higher between soils subgroups than between regions. This indicates that spatial variation of soil N in paddy soils was sensitive to surface water regime rather than climate.

Abstract:The impact of rapid economic development on soil pH is obvious in peri-urban areas. A case study of a peri-urban area of Wuxi was conducted to study spatio-temporal variation of soil pH in the area and explore its relationship with soil chemical properties and its affecting factors. Results indicate that soil pH varies significantly (3.74～8.50). When the field changed from paddy field into vegetable garden, its soil became acidic with mean pH value decreasing from 6.43 to 5.40. Soil pH also decreased significantly in soils around industrial enterprises, while it increased in soils around towns and alongside highways. Soil acidity is determined jointly by exchangeable H⁺and Al³⁺. Their appearance in vegetable plots led to reduced total exchangeable base and base saturation degree, and hence lower pH in the soil. Comprehensive analysis shows that agricultural activities, including change of land use, continuous intensive utilization and heavy application of inorganic fertilizers, were major factors affecting soil pH, while construction of highways and towns bringing in alkaline substances to the soil followed in contribution. Therefore, higher organic manure application rate and paddyupland rotation is suggested for the study area.

Abstract:An experiment was carried out using the principle of iodinestarch staining tracing heterogeneous flow in soil to depict movement of heterogeneous water flow and transport of solute. In two experimental plots, 1.0 m×1.0 m each, 60 mm of iodide solution was applied. A profile was dug layer by layer till 70 cm in depth. Then starch solution was sprayed over the profile, making the area the iodide solution passed through stained. Image analysis and calibration experiments were conducted to characterize soil color and iodine concentration. Annular histogram method was introduced to represent heterogeneous flow features with taking concentration spatial distribution and heterogeneity information into consideration. The iodine-starch staining tracing method was proved to be a better one to display the pattern of heterogeneous flow, and the annular histogram analysis demonstrated that the discrete degree of iodide concentration distribution increased with the decrease in concentration. To describe heterogeneity of the flow, it is necessary to take into account the heterogeneous features of the flow going in vertical and horizontal directions. Similarity of heterogeneous flows declined with the increase in distance the flows covered.

Abstract:Soil surface charge was measured with the potentiometric back-titration technique, and its characteristics evaluated with the Multi-Langmuir model. Results show that the variable surface charge of yellow soil and yellow brown soil varied in the range of 0~45 cmol kg^-1, of red soils in the range of 0~22 cmol kg^-1 and of latosolic red soil and latosol in the range of 0~14 cmol kg^-1, depending on pH of their respective soil suspension. The multi-Langmuir model was used to simulate surface charge, assuming that the three-site model might be adopted to describe the relationship of variable charge with pH. Of yellow soil, yellow brown soil, Hunan red soil, Jiangxi red soil, latosolic red soil and latosol, pK¹ was 4.45, 4.46, 4.76, 4.62, 4.66 and 4.74, respectively; and Q^v1 was 11.65, 9.64, 9.31, 7.14, 4.86 and 5.95 cmol kg^-1 respectively. Yellow soil and yellow brown soil was about 0.3 lower than red soil, latosolic red soil and latosol in pK¹. An extremely significant linear correlation of pK¹ with ZPC was observed and so was an extremely significant positive correlation of Q^v(i) with organic matters.

Abstract:Adsorption-desorption of bensulfuron methyl, a kind of herbicide, in two types of soils treated with charcoal different in particle size, separately, was studied, using the batch equilibration technique, with focus on effect of charcoal amendment on adsorption-desorption of bensulfuron methyl in soils. Results show that the adsorption-desorption isotherms of bensulfuron methyl in charcoal and soils fitted the Freundlich equation (r>0.90). Charcoal showed a great adsorption capacity for bensulfuron methyl, and the smaller the particle size of charcoal, the higher the adsorption of bensulfuron methyl. The amendment of charcoal improved adsorption of bensulfuron methyl in the soils. The adsorption of bensulfuron methyl in the soils increased with the rate of charcoal amended. Desorption of bensulfuron methyl from charcoals and the soils displayed significant hysteresis, which was shown by the higher adsorption slope (1/n^ads) compared to the desorption slope (1/n^des). The hysteresis was closely related with the initial concentration of bensulfuron methyl and the content of charcoal in the soils, and the hysteresis index (H) increased with the rate of charcoal amended. This research suggests that charcoal can be used as artificially added adsorbent to efficiently control the pesticide in the soil from leaching.

Abstract:Revegetation is one of the most effective means to prevent and control soil desertification. To investigate effects of revegetation on soil respiration in the Tengger Desert, the technique of Li-6400-09 soil respiration chamber was adopted in measuring soil respiration rates of an area revegetated in 1989 and a shifting sand area, and the root-partitioning techniques in separating rhizospheric respiration from soil basal respiration. Results show that soil CO₂ efflux was significantly affected by the vegetation restoration. The total soil respiration rate was found be significantly increased from 0.107±0.008 μmol m^-2 s^-1 to 0.483 ± 0.033 μmol m^-2 s^-1 and obvious seasonal fluctuation of the rate was observed. The revegetation not only greatly enhanced rhizospheric respiration rate, but also dramatically increased basal respiration rate through improving soil surface environment, capturing dust, and developing cryptogamic crusts. Furthermore, the patchy distribution of shrubs and spatial heterogeneity of soil nutrients in the revegetated area led to spatial heterogeneity of the soil respiration therein .

Abstract:A hydroponic experiment was carried out to study effects of higher ammonium rate on yield and quality of pakchoi growing under low light intensity. Results show 1) compared with natural light intensity, low light intensity, decreased significantly yield of pakchoi, but contents of nitrate and chlorophyll in the leaves of pakchoi cultured in sole nitrate solution increased by 106% and 23.3%, respectively, while content of soluble sugar and protein decreased by 7.0% and 34%; and 2), under low light intensity, compared with the treatment of sole nitrate nutrition, the treatment of nutrient solution with 15% ammonium had fresh weight and soluble protein content increased by 56.6% and 24%, and nitrate content decreased by 29%. which indicated that properly enhanced ammonium nutrition could improve yield and quality of pakchoi growing under low light intensity.

Abstract:Effect of long-term fertilization on potassium (K) supplying capacity of paddy and purple soils of China was investigated by employing the quantity/intensity (Q/I) approach. Results show that after long-term fertilization, the treatments of the experiment were found to be in the order of NPKM > NPK > CK > N and NP for both paddy soil and purple soil, in terms of K⁺ equilibrium activity ratio (AR₀^K, in the same order for paddy soil and in the order of NPKM>NPK and CK>N and NP for purple soil in terms of soil labile K (K_L), non-specific K (-ΔK₀) and specific K (K_X). They followed the sequence of NP>N>CK>NPKM and NPK, for purple soil in terms of potential buffering capacity (PBC^K), while PBC^K in paddy soil remained nearly unchanged after 15 years fertilization. The paddy soil was greater in AR₀^K, K_L and-ΔK₀, but lower in PBC^K (21.7 to 29.1) and exchange free energies (-ΔG) (11.4 to 13.9 kJ mol^-1) than the purple soil (PBC^K values of 48.2 to 125.8 and-ΔG values of 14.9 to 19.9 kJ mol^-1). In Treatments N and NP, AR₀^K, K_L,-ΔK₀ and K_X decreased and PBC^K and-ΔG increased, and as a result, soil K depletion was intensified especially in purple soil. The trend of soil K depletion was retarded in Treatments NPK and NPKM. In the experiment, soil K depletion was greater in the purple soil than in the paddy soil, maybe because the K or organic manure application rate was not adequate in the purple soil.

Abstract:An experiment was carried by soil culture and sand culture on variation of cation exchange capacity(CEC) of roots, readily available K and slowly available K in rhizospheric and non-rhizospheric soils of flue-cured tobaccos (Nicotiana tabacum L.) different in genotype (i.e. Nongda 202, K326 and NC89), and activating effects of root exudates, and population of rhizospheric microbes on soil K. Results showed that in terms of soil readily available K in both rhizospheric and non-rhizospheric soils, the three treatments followed the order was Nongda202＞K326 ＞NC89. Root exudates from tobaccos, regardless of genotype, activated potassium in the soils. However, among the three Nongda 202 showed the strongest effect, and the differences between Nongda 202, K326 and NC89 were extremely significant. The number of fungi in the rhizospheric soils of the three genotypes of flue-cured tobacco increased over those in the non-rhizospheric soils, especially in the rhizospheric soil of Nongda 202, much higher than of K326 and NC89. However, the difference between the latter two was not significant. The differences among the three genotypes of tobacco in population of rhizospheric bacteria were extremely significant, but not in number of actinomycete. Nongda 202 was the higher than NC89 and K326 in CEC of the root exudates, but the latter two were not so different. So it is important to pay attention to physiological properties of the roots in selecting K-enriching tobacco varieties.

Abstract:A four-year stationary fertilizer experiment under a rotation system of winter wheat- summer maize and cabbage-capsicum was carried out in couple with systematic analysis of soil nutrients to study soil N, P, K, S, Zn and B supply capacities, balance of N, P, K, gaining or waning of nutrients, and hence rational application rates of N, P, K in croplands and vegetable fields of Hebei. Results show that under the rotation system of wheat-maize, the yield of winter wheat was 7 278～7 475 kg hm^-2in Treatment NPKZnS (CK), and only 50％~52%, 84％~87%, 91％~95%, and 92％~93% of the former in Treatment PKZnS, NKZnS, NPZnS, NPKS and NPKZn, respectively; while the yield of summer maize was 8 396～9 041 kg hm^-2 in CK and only 55％~59%, 83％~86%, 79％~91%, and 89％~94% of the former in Treatment PKZnS, NKZnS, NPZnS and NPKS, respectively. The differences between the treatments were significant. The nutrients as crop yield limiting factors, followed a decreasing order: N > P > K > Zn > S. Apparent N, P and K balance in the soil was maintained by applying 1/2N, 1/2P, and 1/2K For the wheatmaize rotation, 450～500 kg hm^-2 N, 135～150 kg hm^-2P₂O₅, and 90～135 kg hm^-2K₂O was recommended, with P and S applied in wheat season and K and Zn in maize season. In the rotation of Chinese cabbage and capsicum, the yield of Chinese cabbage was 113.9 t hm^-2 in Treatment NPKZnB (CK), and only 57%, 64%, and 87% of the former in Treatment PKZnB, NKZnB and NPZnB, respectively, while the yield of capsicum was 23.7 t hm^-2 in CK, and only 46%, 46%, 68%, 88%, 85% of the former in Treatment PKZnB, NKZnB, NPZnB, NPKB and NPKZn, respectively. Significant differences were observed between the treatments. The nutrients, as crop yield limiting factors, were found to be in the order of N > P > K >Zn> B. For cabbage, the application rate of 200 kg hm^-2 N, 90 kg hm^-2P₂O₅, and 150 kg hm^-2K₂O was, recommended, while for capsicum 300 kg hm^-2 N, 170～180 kg hm^-2P₂O₅, and 400 kg hm^-2K₂O was done. The yield response of capsicum to boron and zinc was also significant.

Abstract:The Tianmu Mountain National Nature Reserve is a wellrecognized Gene Pool rich in biodiversity. However, the richness of its botanical diversity is declining as a result of invasion of Phyllostachy pubescens into natural broadleaf forests in some district. To investigate variation of soil bacteria community in response to the change in the aboveground vegetation, soil samples were collected at three sites, i.e. bamboo groves, mixture of bamboo and broadleaf tree and broadleaf forest. To explore variation of the soil bacterial structure, 16S-rDNA-V3-fragment base-DGGE (denaturing gradient gel electrophoresis) and clone sequence BLAST technologies were applied. Results show a total of over 30 16S rDNA V3 fragments were obtained from the soil samples, and DGGE analysis of the 16S rDNA V3 fragments revealed little variation in fingerprint, but it was found that each had its own characteristic strip. The bacterial structures in the soils of the bamboo groves and the broadleaf forest were more similar to each other than to that of the mixed forest. The clone sequence BLAST of the DGGE bands demonstrated that the soil bacteria in the studied zone could mainly be classified as Proteobacterium, Firmicutes, Acidobacteria,Actinobacterium and some unnamed strains, and most of them were found unculturable. Based on the findings of the study, it can be concluded that the soil bacteria in the Tianmu Mountain National Nature Reserve are rich in diversity, that the bacterial communities in the soils under different forest stands have their unique species, though not dominant, and that the invasion of bamboo has not caused any significant changes in structure and diversity of the soil bacterial community.

Abstract:Aiming at improving phytoremediation of Cd-, Pb- and Zn-contaminated soil, a pot experiment was carried out using Brassica juncea as a hyperaccumulator to explore effects of Bacillusme gaterium and Bacillus mucilaginosus compound (Treatment A) and Aspergillus niger ferment (Treatment B) on phytoremediation of Cd-, Pb- and Zn-contaminated soil. Results show that Treatment A not only promoted growth of the hyperaccumulator by 24.73%, but also helped improve availability of Cd, Pb and Zn in the soil by 15.02%, 7.65% and 2.23%, respectively, thus increasing Cd, Pb and Zn uptake by 52%, 121% and 23%, respectively, and eventually improving significantly the effect of phytoremediation. In light of their effects on physiological and bio-chemical indexes (SOD, POD and CAT), Treatment A was less harmful than Treatment B to the hyperaccumulator. So the microbial compound in Treatment A is an effective one that has a high value in use in the field of phytoremediation of contaminated soils. However, Aspergillus niger ferment is not suitable for the phytoremediation of contaminated soils.

Abstract:Methane production and oxidation in paddy fields not only affects methane emission from the fields, but also influences isotopic carbon composition of the methane emitted into the atmosphere; but in turn, by determining isotopic carbon composition of emitted methane, quantitative study of the processes of methane production and oxidation is made feasible. Since the 1980s, the stable carbon isotope technique has been widely applied in the research on methane in paddy abroad. By introducing the fundamental principles of the stable carbon isotope technique and their application in the research on methane production and oxidation in paddy fields, and discussing some uncertain factors of its application in the study, the paper provides the study of methane emission from paddy fields in China with a new strong means.

Abstract:Analysis was conducted of quantitative characteristics and budget of N in soil under the winter-wheat/summer-maize rotation system in the North China Plain, and optimal N potential evaluated. Results show that the N input was mainly through chemical fertilizer, organic manure, rainfall, irrigation, biological fixation and seeds in the system, contributing 545 kg hm^-2 yr^-1, 68 kg hm^-2 yr^-1, 21 kg hm^-2 yr^-1, 15 kg hm^-2 yr^-1, and 5 kg hm^-2 yr^-1, respectively, totaling N input was 669 kg hm^-2 yr^-1, while the N output with harvested crops was only 311 kg hm^-2 yr^-1. In addition, the N losses through ammonium volatilization, denitrification and leaching was 120, 16 and 136 kg hm^-2 yr^-1, respectively, making the total N output up to 583 kg hm^-2 yr^-1with a surplus of 86 kg hm^-2 yr^-1 N. Intensifying N management to improve its use efficiency in combination with intensifying application of organic manure is the long-term task in N management in the North China Plain.

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