Spatial Variability of Soil Cation Exchange Capacity in Hilly Tea Plantation Soils Under Different Sampling Scales

Studies on the spatial variability of the soil cation exchange capacity （CEC） were made to provide a theoretical basis for an ecological tea plantation and management of soil fertilizer in the tea plantation. Geostatistics were used to analyze the spatial variability of soil CEC in the tea plantation site on Mengding Mountain in Sichuan Province of China on two sampling scales. It was found that, （1） on the small scale, the soil CEC was intensively spatially correlative, the rate of nugget to sill was 18.84% and the spatially dependent range was 1 818 m, and structural factors were the main factors that affected the spatial variability of the soil CEC; （2） on the microscale, the soil CEC was also consumingly spatially dependent, and the rate of nugget to sill was 16.52%, the spatially dependent range was 311 m, and the main factors affecting the spatial variability were just the same as mentioned earlier. On the small scale, soil CEC had a stronger anisotropic structure on the slope aspect, and a weaker one on the lateral side. According to the ordinary Kriging method, the equivalence of soil CEC distributed along the lateral aspect of the slope from northeast to southwest, and the soil CEC reduced as the elevation went down. On the microscale, the anisotropic structure was different from that measured on the small scale. It had a stronger anisotropic structure on the aspect that was near the aspect of the slope, and a weaker one near the lateral aspect of the slope. The soil CEC distributed along the lateral aspect of the slope and some distributed in the form of plots. From the top to the bottom of the slope, the soil CEC increased initially, and then reduced, and finally increased.

Cokriging of Soil Cation Exchange Capacity Using the First Principal Component Derived from Soil Physico-Chemical Properties

As soil cation exchange capacity （CEC） is a vital indicator of soil quality and pollutant sequestration capacity,a study was conducted to evaluate cokriging of CEC with the principal components derived from soil physico-chemical properties.In Qingdao,China,107 soil samples were collected.Soil CEC was estimated by using 86 soil samples for prediction and 21 soil samples for test.The first two principal components （PC1 and PC2） together explained 60.2% of the total variance of soil physico-chemical properties.The PC1 was highly correlated with CEC （r=0.76,P0.01）,whereas there was no significant correlation between CEC and PC2 （r=0.03）.The PC1 was then used as an auxiliary variable for the prediction of soil CEC.Mean error （ME） and root mean square error （RMSE） of kriging for the test dataset were-1.76 and 3.67 cmolc kg-1,and ME and RMSE of cokriging for the test dataset were-1.47 and 2.95 cmolc kg-1,respectively.The cross-validation R2 for the prediction dataset was 0.24 for kriging and 0.39 for cokriging.The results show that cokriging with PC1 is more reliable than kriging for spatial interpolation.In addition,principal components have the highest potential for cokriging predictions when the principal components have good correlations with the primary variables.

A statistical reappraisal of the relationship between liquid limit and specific surface area, cation exchange capacity and activity of clays

More than 500 datasets from the literature have been used to evaluate the relationships of specific surface area (SSA),cation exchange capacity (CEC) and activity versus the liquid limit (LL).The correlations gave R^2 values ranging between 0.71 and 0.92.Independent data were also used to validate the correlations.Estimated SSA values slightly overestimate the measured SSA up to 100 m^2/g.Regarding the estimated CEC values,they overestimated the measured CEC values up to 20 meq/(100 g).A probabilistic approach was performed for the correlations of SSA,CEC and activity versus LL.The analysis shows that the relations of SSA,CEC and activity with LL are robust.Using the LL values,it is possible to assess other basic engineering properties of clays.

The Cation Exchange Capacity of Fibrous Feedstuff and Its Nutritive Characteristics

Current researches on the nutritive characteristics of fibrous feedstuff through determining the feedstuff cation exchange capacity (CEC) to evaluate its nutritive value at home and abroad were comprehensively discribed. and the methods of determining CEC value and the correlation between CEC value and chemical compositions, pH value, and the effect of CEC value on the digestion kinetics in ruminants were also emphatically introduced. The results of research showed that the CEC values of different feedstuff are different, closely correlated with nitrogen and acid detergent fibre (ADF) and lignin (LIG) content of the feedstuff. At the same time, there are markedly effect of CEC value in diet on the nutrients flow of digesta in the digestive tract of ruminants, the degradation rate and digestibility of nutrients in the rumen.

Soil exchangeable base cations along a chronosequence of Caragana microphylla plantation in a semi-arid sandy land,China

As a pioneer leguminous shrub species for vegetation re-establishment, Caragana microphylla is widely distributed in the semi-fixed and fixed sandy lands of the Horqin region, North China. C. microphylla planta- tions modify organic carbon （SOC）, nitrogen （N） and phosphorus dynamics, bulk density and water-holding capacity and biological activities in soils, but little is known with regard to soil exchange properties. Variation in soil ex- changeable base cations was examined under C. microphylla plantations with an age sequence of 0, 5, 10, and 22 years in the Horqin Sandy Land, and at the depth of 0-10, 10-20, and 20-30 cm, respectively. C. microphylla has been planted on the non-vegetated sand dunes with similar physical-chemical soil properties. The results showed that exchangeable calcium （Ca）, magnesium （Mg）, and potassium （K）, and cation exchange capacity （CEC） were significantly increased, and Ca saturation tended to decrease, while Mg and K saturations were increased with the plantation years. No difference was observed for exchangeable sodium （Na） neither with plantation years nor at soil depths. Of all the base cations and soil layers, exchangeable K at the depth of 0-10 cm accumulated most quickly, and it increased by 1.76, 3.16, and 4.25 times, respectively after C. microphylla was planted for 5, 10, and 22 years. Exchangeable Ca, Mg, and K, and CEC were significantly （P〈0.001） and positively correlated with SOC, total N, pH and electrical conductivity （EC）. Soil pH and SOC are regarded as the main factors influencing the variation in ex- changeable cations, and the preferential absorption of cations by plants and different leaching rates of base cations that modify cation saturations under C. microphylla plantation. It is concluded that as a nitrogen-fixation species, C. microphylla plantation is beneficial to increasing exchangeable base cations and CEC in soils, and therefore can improve soil fertility and create favorable microenvironments for plants and creatures in the semi-arid sandy land ecosystems.

Geotechnical Characterization of Termite Mound Soils of Congo

This study is to determine the activities and correlations in the fundamental properties of the termite mounds soils Cubitermes spp and Macrotermes sp. The Intrinsic properties depend on the mineralogy, organic composition and texture of soil. Grain size, Atterberg limits and soil blue values are geotechnical properties that were used to characterize the two soils. On the basis of the geotechnical properties, specific surface area, cation exchange capacity, relative activity, surface activity and soil activity were determined. The correlations obtained in the intrinsic soil properties are linear and polynomial fits. Indeed, the relationship between the plasticity index and the blue value of a soil on the one hand and between the specific surface area and the cation exchange capacity on the other hand, is a linear fit for all soils in general. The relationship between plasticity index and specific surface area is a linear fit for the soils (C, M). Correlations in intrinsic soil properties that have a coefficient of determination close to 1 can be used in geotechnical engineering to predict one of the two desired parameters.

Levels of Selected Essential and Non-Essential Metals in the Soil and Ginger (<i>Zingiber officinale</i>) Cultivated in Wolaita Zone, Ethiopia

Ginger (Zingiber officinale) is an important spice and medicinal plant used in different parts of the world. The objective of current study was to determine the level of essential and non-essential metals in ginger and its correlation with concentration of metals in the supporting soil. The level of K, Na, Ca, Mg, Mn, Fe, Zn, Cu, Co, Cd and Pb in soil and ginger cultivated in the selected districts of Wolaita zone, Southern Ethiopia were determined using flame atomic absorption spectrometry. A 0.5 g ginger sample was digested using a mixture of 4 ml HNO3 and 1.5 ml HClO4 at 210°C for 150 minutes, and a 0.5 g soil sample was digested employing a mixture of 6 ml aqua-regia and 1 ml H2O2 at 280°C for 150 minutes. The metal concentrations range in dry weight basis for ginger samples is decreasing in the order: K (1691 - 3487 mg/kg) > Mg (701 - 1583 mg/kg) > Ca (862 - 1476 mg/kg) > Na (398 - 776 mg/kg) > Mn (325 - 672 mg/kg) > Fe (6.14 - 11.92 mg/kg) > Zn (5.30 - 10.09 mg/kg) > (0.12 - 0.23 mg/kg) for Pb. The concentration of Cd, Cu and Co in ginger samples were below the limit of detection. The results revealed that ginger has the ability to accumulate relatively higher amounts of K and Mg among the determined essential metals. The soil samples have been found to be acidic pH, sandy clay loam in texture, a very low electrical conductivity and moderate level of (CEC, organic carbon, available phosphorus and total nitrogen). Although, a positive correlation between the levels of K, Mg, Zn, Mn in ginger and soil samples were observed. All the non-essential metals analyzed in this study were below the permissible ranges set by FAO/WHO.

Characterization of the Activity, Mineralogy and Correlations between the Properties of Clayey Soils

The activity is related to the mineralogy and geological history of clays. Soils with the same value of the liquidity limit or plasticity index can have very different characteristics depending on the amount and type of clay minerals. The methylene blue value characterizes the activity of the clays and reflects the surface activity. Ten inactive soils contain minerals (kaolinite, illite), these soils absorb little water. Two swelling soils have normal activity and are composed of minerals (kaolinite, illite, Montmorillonite). The relationships between clayey soils properties, their activities and between the activity and the liquidity limit are defined. The correlations obtained are linear fit and exponential and sigmoidal fits. The correlations obtained with a coefficient of determination of R2 (0.859 - 0.999) can be used to characterize and predict certain parameters of fine-grained soils as a function of clay content.

Enhancing soil water holding capacity and provision of a potassium source via optimization of the pyrolysis of bamboo biochar

Rapid expansion of cultivated bamboo negatively impacts on biodiversity and soil microbial community.As such,it is important to properly manage and use bamboo to prevent and control such issues.This study focuses on optimizing pyrolysis conditions to produce bamboo biochar for agricultural soil amendment,particularly soil potassium(K)and water holding capacity.Bamboo chips were pyrolyzed under nitrogen gas at 400,600,and 800℃ for 1 and 2 h of retention.A total of six biochar products were created:400-1(i.e.,400℃ in 1 h),400-2,600-1,600-2,800-1,and 800-2.The 600℃ bamboo biochar products were observed to have the greatest potential in increasing soil K and water holding capacity.The 600-1 product had the highest potassium content(4.87%),with a water holding capacity of 3.73 g g^(−1),while the 600-2 product had the second-highest potassium content(4.13%)and the highest water holding capacity(4.21 g g^(−1))and cation exchange capacity.The K release in 600℃ products was larger and slower than that of the 400℃ and 800℃ products,respectively.The results also indicated that the physicochemical characteristics of bamboo biochar,such as yield,pH,surface area,water holding capacity,and K content,were significantly impacted by temperature,retention time,or a combination of these parameters.The outcomes from this study are a valuable reference for bamboo biochar production targeting agricultural soil amendment,particularly when it is directed at increasing soil K and water holding capacity.

Properties of Phosphoric Acid Doped Poly(benzimidazole/sulfone/siloxane/amide)/Sulfonated Polystyrene/Silica Nanoparticle-based Proton Exchange Membranes for Fuel Cells

New siloxane and sulfone containing poly（benzimidazole/sulfone/siloxane/amide） （PBSSA） has been prepared for the formation of hybrid membranes （PBSSA/PS-S/SiNPs） with sulfonated polystyrene （PS-S） and 0.1 wt%-2 wt% silica nanoparticles （SiNPs）. Field emission scanning electron micrographs showed good dispersion of filler, formation of dense nanoporous honeycomb like structure and uniform ionic pathway in these hybrids. The porous membrane structure was responsible for the fine water retention capability and higher proton conductivity of the new hybrids. Increasing the amount of nanoparticles from 0.1 wt% to 2 wt% increased the tensile stress of acid doped PBSSA/PS-S/SiNPs nanocomposites from 65.7 MPa to 68.5 MPa. A relationship between nanofiller loading and thermal stability of the membranes was also experientially studied, as the glass transition temperature of phosphoric acid doped PBSSAJPS-S/SiNPs nanocomposites increased from 207℃ to 215 ℃. The membranes also had higher ion exchange capacity （IEC） around 2.01 mmol/g to 3.01 mmol/g. The novel membranes with high IEC value achieved high proton conductivity of 1.10-2.34 S/cm in a wide range of humidity values at 80 ~C which was higher than that of perfluorinated Nafion 117 membrane （1.1 × 10^-1 S/cm） at 80 ~C （94% RH）. A H2/O2 fuel cell using the PBSSA/PS-S/SiNP 2 （IEC 3.01 retool/g） showed better performance than that of Nation 117 at 40 ℃ and 30% RH.

A nanoscale observation to explain the discrepancy of electron exchange capacities between biochar containing comparable surface redox-active moieties

Biochar,possessing electron exchange capacities(EEC),is generally involved in environmental redox reactions due to the presence of redox-active moieties(RAMs).The phenomenon that chars containing comparable RAMs possess differential EEC revealed that the accessibility of RAMs is important to the redox properties.However,many studies have focused on the type of RAMs,whereas the distribution has been insufficiently investigated.Herein,we achieved nanoscale observation of electroactive moieties on the surface of six chars using a conductive atomic force microscope.For the two specific kinds of chars with submicron particles and opposite current distributions,the submicron particles took up only 1-4‰wt of biochar accounting for approximately 30-50%of electron-donating capacity(EDC),and electron-accepting capacity(EAC)became 87%and 1.40 times as before after removing submicron particles,respectively.Meanwhile,the combined impact of RAMs and surface topography(that uneven distribution of RAMs resulted in outstanding EEC by enhancing accessibility)was clarified.Furthermore,direct evidence of the link between char structure and EEC(that condensed aromatic structures were indispensable to EAC while both heteroatoms and amorphous aromatics contributed to EDC)was established.These findings can aid in understanding the functions of biochar in biotic and abiotic redox processes.

Mutual influence of copper and paraquat on their adsorption in soil

Paraquat and copper (Cu) are commonly used and detected in soil.Therefore,it is important to understand their mobility in the environment.In this study,the competitive effects of paraquat and Cu on their adsorption in five representative Chinese soils were investigated using batch adsorption equilibrium experiments and spectroscopic analysis.The results showed that the adsorption of paraquat in soil varied with soil type and was positively correlated with both soil cation exchange capacity and organic matter content.Paraquat exerted a more remarkable suppression effect on the adsorption of Cu than Cu on the adsorption of paraquat.In the presence of 0.12 and 0.19 mmol L-1paraquat,Cu adsorption decreased by 16%and 22%in Heilongjiang soil and by 24%and37%in Jiangxi soil,respectively.In the presence of 0.1 and 0.2 mmol L-1Cu,paraquat adsorption decreased by 4%and 8%in Heilongjiang soil and by15%and 19%in Jiangxi soil,respectively.Exchange selectivity involving symmetric cation (paraquat2+and Cu2+) exchange is the probable basis for the suppression effect.The ultraviolet-visible absorption experiments suggested that the formation of Cu-paraquat complexes was unlikely to happen in a solution or at the soil surface.Copper K-edge X-ray absorption spectroscopy indicated that Cu in soil may have some water as hydration layers as the nearest neighbors,and each Cu atom was coordinated with five oxygen atoms.These findings greatly improve our knowledge of the molecular-scale adsorption mechanisms of paraquat and Cu in soil and can be used to predict the behavior,transport,and fate of paraquat and Cu in agricultural soils.

Investigating the spectral characteristic and humification degree of dissolved organic matter in saline-alkali soil using spectroscopic techniques

Soil samples were collected from the areas surrounding Wuliangsuhai Lake in China. Dissolved organic matter （DOM） was extracted from the samples and characterized by fluorescence and UV-Vis spectra. Spectral properties and humification degree of DOM were studied. The results indicated that both humic- and protein- like fluorophores were present in the DOM spectra, and the former was the dominant component. The analysis of humification （HIX） and r （A, C） indices revealed that the maximum humification degree in three agricultural soils （AAF, ASC, and ASW） was presented in the second soil layer （20-40 cm）. However, the humification degree of the two Halophytes soils （SSE and GKF） decreased with increasing depth. One index, I344/270, showed that humification degree increased gradually with an increasing proportion of humic-like acid. There was a significant positive correlation between humification degree （HIX） and aromaticity （SUVA254）, indicating that a higher aromaticity corresponded to a higher humification degree. Land use was an important factor responsible for the major difference of cation exchange capacity （CEC） in different soils, which led to a higher CEC value in the second soil layer for the three agricultural soils. CEC values and humification degree had the same trend for all five soils. The correlation analysis showed that there was a significant positive correlation between HIX and CEC,and a negative correlation between the r （A, C） index and CEC, indicating that humification degree increases gradually with increasing CEC values.

Nitrogen fertilization and potassium requirement for cereal crops under a continuous no-till system

Nitrogen(N)and potassium(K)are the most required nutrients for corn and wheat production.Increasing the N application rate usually boosts crop yields.However,many uncertainties remain for K management.Potassium deficiency results in yield losses,but K application rate based on the percentage of K+in the cation exchange capacity(CEC)is doubtful,especially in soil with high CEC.A field trial was conducted to examine the effects of KCl application before sowing corn and wheat,by raising the percentage of K+in CEC at pH 7.0(CECpH7.0)to approximately 2.5%,3.5%,and 4.5%,and adding N as a topdressing(75,150,and 225 kg ha-1 to corn and 40,80,and 120 kg ha-1 to wheat)on the nutrition and yield of corn and wheat under a continuous no-till system(30 years).Exchangeable K+content increased in the topsoil(0–20 cm depth)up to 7.2 mmolc dm-3 after K application at the highest rate,which,however,did not result in significant increases in nutrient uptake and yields for both corn and wheat.The N application rate positively affected the uptake and removal of all macronutrients by corn and wheat.Applying N as a topdressing increased yields of corn and wheat by up to 83%and 22%,respectively.Our results suggest that in the soil with a high CECpH7.0(162.1 mmolc dm-3),the recommendation for K application made by considering the percentage of K+in the CECpH7.0 may result in excessive application of K fertilizer to crops with high K-recycling potential grown under a continuous no-till system.