Abstract:The quantitative evaluation on effect of spatial scale on soil and water loss is the key issue of“scale, pattern and process”of soil and water loss because soil and water loss is the representative process with variability in multi-scale. The sediment of Wu-qiao-he watershed was estimated in three spatial scales based on high resolution digital elevation model and GEOWEPP in this paper. Results showed that there were obvious discrepancy on the characteristics of watershed soil and water loss in different spatial scales. The total sediment per year decreased from 3.79 10⁵ t to 1.25 10⁵ t and 0.84×10⁵ t the sediment of unit area per year decreased from 33.09 t hm^-2 to 10.94 t hm^-2 and 7.29 t hm^-2 and the ratio of carrying sediment decreased from 1.000 to 0.331 and 0.220 when the spatial scales varied from slope to sub-watershed and watershed. The sediment of watershed outlet could be known and at the same time, the intensity and spatial distributing of soil erosion could be described based on GIS and GEOWEPP and the measures of soil and water conservation could be rather disposed.

Abstract:Based on the data of daily rainfall collected by the Dongcun Hydrological Station in Lianshui Basin, Jiangxi Province from 1967 to 2005, Values of rainfall erosiveness were calculated respectively using Zhou Fujian et al. (Model A), Zhang Wenbo, et al. (Model B),Wu Suye (Model C), Shi Zhihua, et al. (Model D), WISCHMEIER, et al (Model E), and CREAMS (Model F). Results of the calculations were analyzed, using effective coefficient and relative deviation, demonstrating that Model C is relatively quite ideal, for its effective coefficient is higher, reaching 0.97 and its relative deviation lower, being 0.073. The monthly rainfall models (A, C, E), in comparison with the daily rainfall models (B, D, F), are higher in effective coefficient and lower in relative deviation, which prove that the former are superior to the latter. However, both groups are positive in trend coefficient, being 0.058 and 0.196, respectively, indicating an increasing trend in rainfall erosiveness in the Lianshui River Valley during the 39 years. The latter one is higher than the former, which explains that the use of the daily rainfall models would get higher R values than the use of the monthly rainfall models.

Abstract:P. Barr� et al. put forth a hypotheses in 2007 that in soils of the temperate zone plant’s uplift of potassium and silicon from lower soil horizons buffers K and Si depletion from illite-like minerals (illite and illite/smectite) in the upper soil horizon, thus leading to the long existence of high amount of illite-like minerals. To verify whether the hypothesis exists in soils of the tropical region, chronosequence soil samples were selected from 6 profiles (1×10⁴ a, (9.0±2.0)×10⁴ a,(14.6±0.9)×10⁴a, 64×10⁴ a, (133±18)×10⁴ a, （181±8）×10⁴ a) derived from Quaternary basalts formed after volcano eruptions in different time periods in Hainan Island, southern tropical China, for analysis of the variation of clay minerals in these soils, using the classical X-ray diffraction technique. Soil potassium, silicon, and active silicon of the samples were also determined. Results show that illite-like minerals existed only in the soils older than (133±18)×10⁴ a, where the contents of potassium and silicon were found to be higher in the upper soil horizons than in the lower soil horizons, while a contrary tendency was detected with the content of gibbsite, and the content of active silicon generally decreased with the soil age. Consequently, it is held that during the forming process of the soils of the tropical regions, P. Barr� hypotheses might exist in the initial period of soil development, and in the presence of biological complex potassium and complex silicon as well, but it would disappear finally due to the intensive K and Si depletion of the soils in the tropical regions.

Abstract:The double-ring infiltrometer is widely used to measure soil saturated hydraulic conductivity. To investigate effects of ratio of the outer to the inner rings, i.e. the buffer index of double-ring infiltrometer, on measurement of saturated hydraulic conductivity, 16 sets of field experiments were laid out and conducted using 16 double-ring infiltrometers with 4 inner-ring diameters (20 cm, 40 cm, 80 cm, and 120 cm) and 4 buffer indices (0.2, 0.33, 0.5 and 0.71). Results show that uncertainty of the measured saturated hydraulic conductivity decreased with increasing diameter of the inner-rings. Saturated hydraulic conductivities in the infiltrometers with an inner-ring diameter of 20cm varied in a broad range, while those in the infiltrometers with inner-ring diameters of 120cm and 80cm were always close to each other and less in variation. However, no rising or falling tendency was observed for the increasing buffer indices. It is concluded that the inner-ring diameter is a more important factor to be considered than the buffer index in practice, and a larger inner-ring diameter, such as 80cm, is proposed as a lower limit of the inner-ring size to obtain reliable in-situ measurement of hydraulic conductivity.

Abstract:Spatial variation and influencing factors of CEC of the soil in the Dagu River Basin were studied with geostatistical and multiple regression analysis methods. Results show that CEC of the soil in the upper and under layers displayed significant positive correlations with organic matter, clay and silt, and significant negative correlation with sand. The correlation coefficient was the biggest between CEC and clay, and the smallest between CEC and silt. In terms of contribution of the factors to CEC, they were in the order of clay > organic matter > sand, and the mean contribution of clay was 1.5~2.5 times as much as that of organic matter. The cokriging method, which used clay as instrumental variable, produced more accurate results than the ordinary kriging method, and reduced RMSE of the soils in the upper and under layers by 18.94% and 41.05%, respectively. Furthermore, the relationship between the secondary and the primary variables governed accuracy of the estimation. Soil CECs were higher in the middle east, northwest and middle southwest of the Dagu River Basin, but much lower in the north and southwest tip. Hence the two regions are critical ones for soil amelioration. The soil fertility therein can be improved by increasing application of organic manure and adopting other soil building practices.

Abstract:Field water retention capacities (θ_{-30 kPa}) and wilting coefficients (θ_{-1 500 kPa}) of ninety soil samples in the Dagu River Basin were predicted separately with four PTF_S, i.e. point regression method, linear regression method, nonlinear regression method and artificial neural network method, and their spatial variabilities were analyzed with the aid of traditional statistic and geostatistic methods. The traditional statistics revealed that the nonlinear regression method was the best with the variation coefficients of θ_{-30 kPa} of all the soil samples, being always less than θ_{-1 500 kPa}, however, no matter measured or predicted values, both belonged to the category of moderate in spatial variability. The geostatistics also showed that both measured and predicted θ_{-30 kPa} and θ_{-1 500 kPa} demonstrated varied nugget effects, moreover, θ_{-30 kPa} always had stronger spatial dependence than θ_{-1 500 kPa} did. Analysis of the parameters of semivariance model for θ_{-30 kPa} and θ_{-1 500 kPa} ultimately revealed that the artificial neural network model could most truthfully characterize spatial variability of the soil water retention capability in the experimental zone.

Abstract:A spatial interpolation method based on GARBF neural network was used to study available zinc in soil. Comparison between GARBF neural network, RBF neural network and Ordinary Kriging interpolation method in fitting capacity and spatial interpolation capacity, with determination coefficient between measured values and predicted values of the training sample set, approximate error and interpolation error of test samples cited as criteria for evaluation. Results show that in terms of the fitting capacity, the three methods applied to the same area under two different sampling schemes (a & b) followed the sequence of GARBF > RBF > Ordinary Kriging. When average absolute error and root mean square error were chosen to judge precision of the interpolation methods, comparison between GARBF and RBF showed that the approximate errors of the training samples were reduced by 0.22 ~ 0.25 in Scheme a and by 0.10 ~ 0.11 in Scheme b, and the interpolation errors of the test samples by 0.13 ~ 0.11 in Scheme a and by 0.02 ~ 0.13 in Scheme b. Comparison between GARBF and Ordinary Kriging showed that the approximation errors of the training samples were reduced by 1.12 ~ 1.40 in Scheme a and by 1.45 ~ 1.88 in Scheme b and the interpolation errors of the test samples by 0.20 ~ 0.24 in Scheme a and by 0.14 ~ 0.32 in Scheme b. So it is obvious that the GARBF neural network is the least in error and the highest in interpolation precision. The GARBF interpolation map reveals that the application of genetic algorithm overcomes the tendency of neural networks to land in local optima and expands the scope of search of spatial information pertaining to soil, thus to a certain extent avoiding a similar problem of “smooth effect” like Ordinary Kriging. The findings of this study could provide a practical analysis tool and decision-making basis for precision fertilization and prevention of soil pollution.

Abstract:Novel 16S-rRNA targeted oligonucleotide probes (FW_iso_62 and FW_iso_761) were designed to detect Bordetella sp. by fluorescence in situ hybridization (FISH). Strong fluorescence signals with the probes were observed in 20% ~ 60% formamide concentrations. Quantification of Bordetella sp. in soil was developed with the selected probe of FW_iso_62 and its competitor combined with Nycodenz and DAPI technique. The advantages of the established DAPI_FISH: eliminate autofluorescence of soil particles masking the bacterial signals; ensure a large amount of bacteria in one picture for reliable statistical analysis; and keep efficiently in situ information of the bacteria 1,2,4-trichlorobenzene degrading. Bordetella bacteria were investigated in soils with the established method. The Bordetella bacterium was not detected in the agricultural soil, which was not exposed to chlorobenzenes. On the contrary, a lot of Bordetella bacteria (3.78×10⁶ cell g^-1) were determined in the soil contaminated with chlorobenzenes. When the 1,2,4-TCB-degrading Bordetella strain and its community in the contaminated soil were re-inoculated into the agricultural soil, the Bordetella numbers increased and accounted for 1.7％ and 3.8％ of the DAPI counts after incubation for 1 month, respectively. The probes developed in this study are useful for detecting Bordetella bacteria in complicated environmental samples.

Abstract:Under the same field conditions, attenuation of organophosphorous pesticides (OPs) in the soil is directly associated with the structural characters of the pesticide per se. Relationships of half-life of OPs in flooded soil and dry soil with theoretical linear solvation energy, topological parameters, physic-chemical properties, quantum chemical descriptors and the Dragon descriptors were studied with the best subset regression analysis method. A series of QSAR models were thus developed. Results show that the models developed from Dragon descriptors were the best at explaining the mechanism of attenuation of OPs in the soils. The model analysis indicated that steric topological orientation plays a key role in attenuating process of OPs, no matter whether the soil is submerged or dry.

Abstract:Cr(Ⅲ) adsorption, desorption and oxidation by birnessite was studied in this paper. Results show that amount of total Cr(Ⅲ) increased with the amount of Cr(Ⅲ) added, and the adsorption process could be well described with the Langmuir equation. The concentration of Cr(Ⅵ) resulting from oxidation of Cr(Ⅲ) showed an extremely significant positive linear relationship with the initial concentration of Cr(Ⅲ) added, while the oxidation rate did a reverse one. Moreover, effects of pH, temperature on the adsorption and oxidation processes were also examined. The adsorption at 308.2 K was remarkably lower than at 298.2 K, while the oxidation and oxidation rate at 308.2 K were obviously higher than at 298.2 K, which suggest that high temperature favored oxidation, but disfavored adsorption. This finding could also be proved by thermodynamic parameters (ΔG^o and ΔH^o) of the adsorptive process. Adsorption decreased with increasing pH of the adsorption solution, while the oxidation and oxidation rate increased. The results indicated that high pH favored oxidation, but disfavored adsorption.

Abstract:From the aspect of process, formation and transformation of humus are essentially microbebased biochemical processes, while from that of difference in energy level between the initial and final stages, these processes could also be considered as an issue of the thermodynamic stability. In the soil there are quite a number of factors affecting these processes, such as type and content of clays, vegetation, microorganisms, soil moisture, temperature, air composition, chemical composition and concentration of soil solution, acidity, status of redox, etc. But from the angle of thermodynamics, in order to calculate reaction equilibrium constant (logK_R) and Gibbs energies (ΔG_f^θ) at a given temperature of 25℃, those soil conditions could be simplified into 3 parameters: water activity (H₂O), oxygen partial pressure (P_O2) and carbon dioxide partial pressure (P_CO2), since all organic substances are composed of these three elements and would eventually be decomposed into H₂O and CO₂that contain these three elements. According to this new idea and principle mentioned above, this paper cited black soil as an example to explore approaches to the study on factors driving formation and transformation and thermodynamic stability of HA and FA, and to the calculation ofΔG_f^θ, logK_R and range of thermodynamic stability of HA and FA with “the elemental compositionsoil condition parameter method”. Meanwhile, a simulated incubation in the lab of soil with organic matter was conducted to study effect of mono-environmental factors like O₂ and CO₂ on accumulation of HA and FA. Results show that the molecular formula of HA and FA is nC₂₁H₂₁O₉N and nC₂₄H₃₃O₁₇N, respectively. In soils low in O₂, high in moisture and high in CO₂ concentration, FA was relatively stable whereas HA was on the contrary. In the incubation experiment, high CO₂ concentration and low O₂concentration would result in higher FA/HA ratio. This method and the findings in this study could help explain and speculate the rule of spatial variability of the composition of soil humus, and provide guidance to regulation of soil fertility and soil carbon sequestration.

Abstract:pH of leachate plays an important role in translocation of matters in the soil and form of substances in soil solution in subtropical acid soils. To study relation between H⁺ released in nitrification and pH of soil leachate in the soils, an indoor simulated leaching experiment was carried out for 112 days using soil samples different in nitrification intensity amended with 0, 150, and 300 mg kg^-1 (NH₄HCO₃)-N, separately and leached 17 times, once a week Results show that the leachates from the acid soils were not necessarily acid, and their pH values depended on combined effect of H⁺ release rate from nitrification and acid buffering capacity of the soils. When nitrification brought the concentration of NO₃^- in the leachate up to a certain level, pH value of the leachate dropped abruptly. The critical point NO₃^-concentration showed a linear positive relationship (p<0.05) with the soil base saturation and the application rate of (NH₄HCO₃)-N. Therefore, leachates from the upland soil highest in nitrification intensity with base saturation 81% remained neutral, while leachates from the soil under shrubbery, moderate in nitrification intensity and 21% in base saturation dropped below 4.0 in pH value.

Abstract:A field experiment was conducted in 2006 to monitor CH₄ and N₂O emissions from rice fields as affected by strip mulching of wheat straws. The experiment was designed to have three treatments, i.e. (i) no wheat straw applied (Treatment CK); (ii) incorporating wheat straws evenly into the topsoil (Treatment WI); and (iii) strip mulching of wheat straws over the field (Treatment WM). Results show that compared with Treatment CK, Treatment WM significantly increased CH₄ mission by 2.7-fold. No significant difference in N₂O emission was observed between Treatments CK and WM. Compare with Treatment WI, Treatment WM decreased CH₄ emission significantly by 32%, while enhancing N₂O emission by 5.1-folds. The GWP of CH₄ and N₂O emitted from rice field was greatest in Treatment WI, which was followed by Treatments WM and CK, and the differences between them reached significant level. Compared with Treatments CK and WI, Treatment WM increased rice grain yield by 27% and 17%, respectively. Based on these results, the best management of wheat straw prior to rice cultivation is mulching of strips of wheat straws over the field.

Abstract:In a microplot ¹⁵N-labelled fertilizer N experiment, where measures were taken to inhibit bio-immobilization of nitrogen, application of ¹⁵N-labelled KNO₃ to wheat prior to its shooting stage，and the microplot experiment being carried out in Treatment CK (a treatment of another field experiment that has never been fertilized) successfully exposed another process that affected uptake of soil N by crops, i.e. dilution of soil N pool or substitution of N in the pool by fertilizer N. The crops applied with N fertilizer absorbed less soil N than those applied with nothing, showing negative ANI. Biological N immobilization and dilution of (fertilizer N on) soil N pool are two opposite and intermingled actions. Counteraction and balance of the two actions might lead to positive ANI or negative ANI depending on which one is stronger. As is affected by the abovediscussed process, it is almost impossible to assess N fertilizer recovery rate with reliable result by means of field experiment using either ¹⁵N-labelling method or traditional difference method. As an alternative, the proportion method could help skid over the obstacle and has been verified in this experiment with better results.

Abstract:Field experiments were carried out to study effect of chemical fertilizer (CF) and different composts on yield of rapeseeds, nitrogen use efficiency and soil nitrogen supply and soil microbial diversity. Pig manure compost (PMC)，Chinese medicinal herb residue compost (MRC) and chicken manure compost (CMC) were mixed separately with chemical fertilizers (nitrogen, phosphorus and potassium). All the treatments, except the CK, received the same rate of nitrogen, phosphorus and potassium. Results show that all the fertilization treatments were higher in yield than CK. Compared with Treatment CF, the treatments of organic-inorganic compound increased the yield by 12.7%～33.2%, promoted nitrogen uptake and increased dry matter accumulation, thus increasing nitrogen use efficiency. Besides, they also improved soil nitrogen supply compared with Treatment CF and CK. Eighbor Joining analysis indicated that, in terms of bacteria in the soils, the five treatments could be classified into three clusters. The soil bacterial communities in Treatment CF and CK belonged to the same cluster, while Treatment MRC to the second cluster, and Treatments PMC and CMC to the third cluster. Application of organic fertilizers altered soil bacterial communities, while application of CF had little effect.

Abstract:A field experiment, designed to have 5 N levels, i.e. 0, 100, 150, 200 and 250 kg hm^-2, was conducted in 2005 to study effects of N application rate on uptake, accumulation, and translocation of N by rice germ plasm 4007 high in nitrogen use efficiency (NUE), and yield of the crop, with a native rice cultivar (Wuyunjing15, WJ15) as CK. Results show that increasing N application significantly stimulated N accumulation in rice plants at all growth stages. The highest was found during the stages between mid-tillering and jointing, being 32.7%～41.6% of the total of the whole growth period. When N application rate increased from 0 up to 250 kg hm^-2, N translocation was also enhanced, rising from N 72.0 kg hm^-2 to 104 kg hm^-2 for 4007, and N 57.0 kg hm^-2 to 96.5 kg hm^-2 for WJ15, but their nitrogen translocation rate declined from 66.2% to 51.3% and from 57.1% to 46.8% for 4007 and WJ15, respectively. Of the N in grains, 65.3%～87.6% came from vegetative organs of the plant, and only 12.4%～34.7% was absorbed from soil at the reproductive stage. Thanks to the higher harvest index (HI) and nitrogen harvest index (NHI), 4007 showed higher mean nitrogen apparent recovery efficiency (RE_N) and nitrogen agronomic efficiency (AE_N), about 24.5% and 95.6% higher than WJ15 did, respectively. The experiment suggests that the optimal N application rate is 150 kg hm^-2 and 200 kg hm^-2, respectively, for 4007 and WJ15 to maintain a better grain yield and a better nitrogen use efficiency.

Abstract:The long-term fertilization experiments located at the south edges of the Loess Plateau were used to study effects of different fertilizer treatments, i.e., no fertilizer(CK), fallow (FA), NPK fertilizer (NPK), NPK +organic manure(MNPK), and NPK +straw(SNPK), on content, structural characteristics and biodegradation of dissolved organic carbon(DOC) in the soil. The contents of DOC in the surface layers (0~20cm in depth) of soils different in fertilization treatment ranged from 4.65 to 8.94 mg kg^-1, and averaged 6.42 mg kg^-1. The fertilization treatments followed the order of MNPK > SNPK > NPK > FA > CK. The special absorption value at 280 nm (UV280) and the humification index (HIXem) of DOC solution indicated that significant differences existed between soils different in treatment in structural characteristics of DOC, and in terms of proportion of complex aromatic compounds in the soil, the five treatments followed the order of SNPK > MNPK > FA > NPK > CK. After 7 days of biodegradation incubation, the biodegradation rates in the treatments ranged from 19.32% to 48.49%, and averaged 28.58%, and the treatments followed the order of CK > FA > NPK > SNPK > MNPK. The UV280 and HIXem of DOC solution before and after biodegradation indicated that the proportion of dissolved organic matter more complex in structure increased with the duration of incubation.

Abstract:Based on a long-term field experiment initiated in 1989 and conducted in the National Agro-Ecological Experiment Station located in Fengqiu County, Henan Province, China, dynamic changes of microbial biomass C and N, and microbial activity during the growth period of summer maize as related to different continuous fertilization management were investigated in 2007.At the same time, effect of long-term fertilization on microbial biomass and activity and their relationship with soil organic carbon content was also discussed. The experiment was designed to have 7 treatments, i.e. organic manure (OM), half organic manure plus half fertilizer N (1/2OM+1/2NPK), fertilizer NPK (NPK), fertilizer NP (NP), fertilizer NK (NK), fertilizer PK (PK) and control (CK).Results show that temporal variation of soil microbial biomass C and N, and microbial activity was significant during the growth period of summer maize. The dynamics of microbial biomass C and microbial activity were consistent, and their extremely positive correlation suggests that microbial biomass C can be used as an indicator of microbial activity.Fertilization significantly affected soil microbial biomass and microbial activity.The 7 treatments generally showed a decreasing order of OM > 1/2OM+1/2NPK > NPK > NP > PK > NK > CK indicating that organic matter was beneficial to soil biochemical environment and soil microbial activity.Compared with Treatment OM, the other chemical treatments revealed a trend of decreasing soil microbial biomass and weakening microbial activity.It was particularly significant in treatments unbalanced in nutrient, with Treatment NK showing the worst effect, probably because element P is an important element for making up cell wall and membrane for most bacteria.Positive relationship of microbial biomass and enzyme activity with soil organic C was also observed.

Abstract:Effects of repeated application of fungicide carbendazim at a rate of 0.94, 1.88, 4.70 kg hm^-2 calculated by active ingredient (a.i.) on diversity of soil microbial communities were studied using BIOLOG and its degradation dynamics in soil was investigated under field conditions. The degradation rate of carbendazim after the first application in the soil was 0.11, 0.25 and 0.74 mg kg^-1d^-1, in treatments of 0.94, 1.88 and 4.70 kg hm^-2 calculated by a.i., respectively, and rose to 0.8, 0.39 and 1.00 mg kg^-1d^-1, respectively after the fourth application, showing a significant trend of the degradation rate rising with the application frequency. A significant inhibitory effect of carbendazim on average well color development (AWCD) was observed after the first application. The AWCD values then increased slightly with the application frequency Shannon, Simpson and Shannon indexes of the soil microbial communities in the soil were also inhibited by the first application, which suggested that the richness, evenness and dominant character of soil communities in the treated soils were altered by the repeated application of carbendazim. However, after the second application, soil microorganisms gradually adapted to carbendazim and recovered to the level in the control without carbendazim treatment.

Abstract:A study was carried out to investigate effects of cadmium stress on growth of rice seedlings, mitosis and chromosomal aberration of root tip cells. Results show that root elongation and the mitotic index of the root tip cells were significantly decreased with the increasing Cd concentration and treatment duration. Cd increased the proportion of metaphase cells, while decreasing those of prophase, anaphase and telaphase cells. Cd induced chromosomal aberrations of different types of root tip cells at their metaphase and anaphase, with frequency rising with Cd concentration and treatment duration. C-mitosis and chromosomal bridge were the main types of chromosomal aberration in root tip cells exposed to 1~10 μmol L^-1 Cd for 24 h, accounting for 32.64%～78.29%, while the percentage of chromosomal adhesion, chromosomal breakage and micronuclei for 76.44%～93.96% in root tip cells exposed to 25~200 μmol L^-1 Cd for 24~72 h. All these results suggest that Cd obviously retards mitosis and induces chromosomal aberration in root tip cells of rice seedlings.

Abstract:Hydroponic experiments were conducted to investigate dynamics of Na uptake and salt tolerance of 4 varieties of winter wheat different in genotype, i.e. Xiaoyan-6, NR-9405, Shaan-229 and RB-6. Results indicate that the sodium absorption dynamics of winter wheat could be divided into two phases.When salt concentration was low (-1), the parameters of Na uptake dynamics, V_max was 0.50, 0.30, 0.58 and 0.55 ⁺，mg g^-1h^-1, and K_m 18.50, 3.89, 70.90 and 30.68 mmol L^-1 of Xiaoyan-6, NR-9405, Shaan-229 and RB-6, respectively; But when salt concentration was high（> NaCl 80 mmol L^-1）, V_max was Na⁺1.81, 1.56, 2.11 and 2.11 mg g^-1h^-1 and K_m 107.20, 70.29, 121.06 and 102.67 mmol L^-1, respectively. In the low salt condition, the sodium exclusion rate was almost 90%, while in the high salt condition it was only 50%～60%. Sodium exclusion rate varied slightly with the genotypes of winter wheat, and it was 50% higher of Xiaoyan-6 and NR-9405 than of Shaan-229 and RB-6 in the low salt condition. On the contrary, the sodium absorption rate of Shaan-229 and RB-6 was 15% higher than that of Xiaoyan-6 and NR-9405, while the sodium exclusion rate was 10% lower in the high salt condition, The higher sodium absorption rate and the lower sodium exclusion rate in the high salt condition may be responsible for the salt sensitivity of Shaan-229 and RB-6.

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