Coral sandy soils widely exist in coral island reefs and seashores in tropical and subtropical regions.Due to the unique marine depositional environment of coral sandy soils,the engineering characteristics and respons...Coral sandy soils widely exist in coral island reefs and seashores in tropical and subtropical regions.Due to the unique marine depositional environment of coral sandy soils,the engineering characteristics and responses of these soils subjected to monotonic and cyclic loadings have been a subject of intense interest among the geotechnical and earthquake engineering communities.This paper critically reviews the progress of experimental investigations on the undrained behavior of coral sandy soils under monotonic and cyclic loadings over the last three decades.The focus of coverage includes the contractive-dilative behavior,the pattern of excess pore-water pressure(EPWP)generation and the liquefaction mechanism and liquefaction resistance,the small-strain shear modulus and strain-dependent shear modulus and damping,the cyclic softening feature,and the anisotropic characteristics of undrained responses of saturated coral sandy soils.In particular,the advances made in the past decades are reviewed from the following aspects:(1)the characterization of factors that impact the mechanism and patterns of EPWP build-up;(2)the identification of liquefaction triggering in terms of the apparent viscosity and the average flow coefficient;(3)the establishment of the invariable form of strain-based,stress-based,or energy-based EPWP ratio formulas and the unique relationship between the new proxy of liquefaction resistance and the number of cycles required to reach liquefaction;(4)the establishment of the invariable form of the predictive formulas of small strain modulus and strain-dependent shear modulus;and(5)the investigation on the effects of stress-induced anisotropy on liquefaction susceptibility and dynamic deformation characteristics.Insights gained through the critical review of these advances in the past decades offer a perspective for future research to further resolve the fundamental issues concerning the liquefaction mechanism and responses of coral sandy sites subjected to cyclic loadings associated with seismic events in marine environments.展开更多
This paper presents the development of a new remediation technology for contaminated sandy soil using humic acid (HA). Distribution of amount of Cr (VI) in the aqueous or solid system containing humic acid and sandy s...This paper presents the development of a new remediation technology for contaminated sandy soil using humic acid (HA). Distribution of amount of Cr (VI) in the aqueous or solid system containing humic acid and sandy soil, was studied using batch experiments, es-pecially for effects of reaction time, pH, concentrations, temperature and irradiation on the reduction of Cr (VI), and the optimum reaction conditions. The results indicated a significant increase of the adsorption of Cr (VI) because of the complexion reaction between HA and Cr (VI) that occurred under acidic condition. The reaction mechanisms of HA with chromium on sand surfaces were certified. Thus it came to a conclusion that HA could be used effectively on remediation of Cr (VI)–contaminated soil and groundwater in a wide range of pH, with or without sunlight. These results suggest that the organic-inorganic complex—such as sandy soils coated with humic substances—is important as a metal reservoir in the environment.展开更多
Soil moisture is a critical state affecting a variety of land surface and subsurface processes. We report investigation results of the factors controlling vertical variation of soil moisture and sand transport rate of...Soil moisture is a critical state affecting a variety of land surface and subsurface processes. We report investigation results of the factors controlling vertical variation of soil moisture and sand transport rate of three types of dunes on the south- eastern margin of the Mu Us Sandy Land. Samples were taken from holes drilled to a depth of 4 m at different topographic sites on the dunes, and were analyzed for soil moisture, grain-size distribution and surface sediment discharge. The results show that: (1) The average soil moisture varies in different types of dunes, with the following sequences ordered from highest to lowest: in the shrubs-covered dunes and the trees-covered dunes the sequence is from inter-dunes lowland to windward slope to leeward slope. The average moisture in the bare-migratory sand dunes is sequenced from inter-dunes lowland to leeward slope to windward slope. (2) Vegetation form and surface coverage affect the range of soil moisture of different types of dunes in the same topographic position. The coefficient of variation of soil moisture for shrubs-covered dunes is higher than that of other types of dune. (3) The effect of shrubs on dune soil moisture is explained in terms of the greater ability of shrubs to trap fine-grained atmospheric dust and hold moisture. (4) The estimated sand transport rates over sand dunes with sparse shrubs are less than those over bare-migratory dunes or sand dunes with sparse trees, indicating that shrubs are more effective in inhibiting wind erosion in the sandy land area.展开更多
To assess the effects of savanna afforestation on soil phosphorus (P) transformations in eastern Horqin Sandy Land, China, P fractions and phosphomonoesterase activities were examined in two soil horizons (0-5 cm a...To assess the effects of savanna afforestation on soil phosphorus (P) transformations in eastern Horqin Sandy Land, China, P fractions and phosphomonoesterase activities were examined in two soil horizons (0-5 cm and 5-20 cm) under a savanna and an adjacent 30-year-old Mongolian pine (Pinus sylvestris L. vat. mongolica Litv.) plantation on a P-deficient semi arid sandy soil. The results showed that all soil P fractions and phosphomonoestcrase activities decreased with soil depth at both sites except that labile organic P under the plantation was constant with soil depth, In contrast to savanna, soils trader Mongolian pine plantation had lower phosphomonoesterase activities and concentrations of all P fractions (with an exception of Al-P), lower proportions of organic P and Ca-P in total P, and higher proportions of labile P, Al-P and Fe-P in total P. These results suggested that P transformations mainly occurred in surface soils, and P recycled through litterfall was the most important source of plant available P. Mongolian pine afforestation enhanced the bioavailability of both organic P and Ca-P. simultaneously reduced soil P pools. indicating that protection of forest floor and P fertilization are necessary to maintain the sustainable functioning of Mongolian pine plantations.展开更多
A bentonite-humic acid(B-HA) mixture added to degraded soils may improve soil physical and hydraulic properties, due to effects such as improved soil structure and increased water and nutrient retention, but its effec...A bentonite-humic acid(B-HA) mixture added to degraded soils may improve soil physical and hydraulic properties, due to effects such as improved soil structure and increased water and nutrient retention, but its effect on soil physicochemical and biological properties, and grain quality is largely unknown. The effect of B-HA, added at 30 Mg ha^(-1), was studied at 1,3, 5 and 7 years after its addition to a degraded sandy soil in a semi-arid region of China. The addition of B-HA significantly increased water-filled pore space and soil organic carbon, especially at 3 to 5 years after its soil addition to the soil. Amending the sandy soil with B-HA also increased the content of microbial biomass(MB)-carbon,-nitrogen and-phosphorus, and the activities of urease, invertase, catalase and alkaline phosphatase. The significant effect of maize(Zea mays L.) growth stage on soil MB and enzyme activities accounted for 58 and 84% of their total variation, respectively. In comparison, B-HA accounted for 8% of the total variability for each of the same two variables. B-HA significantly enhanced soil properties and the uptake of N and P by maize in semi-arid areas. The use of B-HA product would be an effective management strategy to reclaim degraded sandy soils and foster sustainable agriculture production in northeast China and regions of the world with similar soils and climate.展开更多
This paper describes a quasi-static test program featuring lateral cyclic loading on single piles in sandy soil. The tests were conducted on 18 aluminum model piles with different cross sections and lateral load eccen...This paper describes a quasi-static test program featuring lateral cyclic loading on single piles in sandy soil. The tests were conducted on 18 aluminum model piles with different cross sections and lateral load eccentricity ratios, e/d, (e is the lateral load eccentricity and d is the diameter of pile) of 0, 4 and 8, embedded in sand with a relative density of 30% and 70%. The experimental results include lateral load-displacement hysteresis loops, skeleton curves and energy dissipation curves. Lateral capacity, ductility and energy dissipation capacity of single piles under seismic load were evaluated in detail. The lateral capacities and the energy dissipation capacity of piles in dense sand were much higher than in loose sand. When embedded in loose sand, the maximum lateral load and the maximum lateral displacement of piles increased as e/d increased. On the contrary, when embedded in dense sand, the maximum lateral load of piles decreased as e/d increased. Piles with a higher load eccentricity ratio experienced higher energy dissipation capacity than piles with e/d of 0 in both dense and loose sand. At a given level of displacement, piles with circular cross sections provided the best energy dissipation capacity in both loose and dense sand.展开更多
We analyzed the heat conductivity and volumetric heat capacity of sandy soil contaminated in two scenarios of oil pollution, and also determined the temperature dependencies of these changed thermophysical properties....We analyzed the heat conductivity and volumetric heat capacity of sandy soil contaminated in two scenarios of oil pollution, and also determined the temperature dependencies of these changed thermophysical properties. In the first pollution scenario, the oil product was introduced into wet river sand, and in the second case, dry sand was contaminated by the oil product and was then moistened with water. By considering these two scenarios as multicomponent dispersion systems with varying degrees of contamination and humidity, and by using a polystructural granular model with pore spaces and closed inclusions, we calculated that the heat conductivity of the sandy soil increased under the first pollution scenario and decreased under the second, but the change in the volumetric heat capacity of the sandy soil was proportional only to the amount of oil pollution, not the manner in which it was introduced. We also determined the temperature dependencies of these two thermophysical properties of sandy soil when polluted by oil, of which information will be useful for future containment and remediation of oil-contaminated soil.展开更多
The concentrations and chemical forms of copper(Cu) and zinc(Zn) in surface soils directly influence the movement of Cu and Zn. In this study, thirteen sandy soil samples with a wide range of total Cu and Zn concentra...The concentrations and chemical forms of copper(Cu) and zinc(Zn) in surface soils directly influence the movement of Cu and Zn. In this study, thirteen sandy soil samples with a wide range of total Cu and Zn concentrations were collected for evaluating the relationships between Cu and Zn release and extraction time, ratio of soil to water, pH and electrolyte types. The results indicated that Cu released in batch extraction that represents long-term leaching was mainly from exchangeable, and carbonate bound Cu fractions, and Zn released in the batch extraction was mainly from its carbonate bound fraction. However, the Cu and Zn leached from the soils using the column leaching that represents short-term leaching were mainly from their exchangeable fractions. Soil column leaching at different pH values indicated that the amounts of leached Zn and Cu were greatly affected by pH. The Cu and Zn release experiments with varying extraction times and ratio of soil to water suggest that long-term water-logging in the soils after rain may increase contact time of the soils with water and the release of Cu and Zn to water from the soils, and total amounts of Cu or Zn released from the soils increase, but the Cu or Zn concentration in the surface runoff decrease with increasing rainfall intensity. The increased Ca concentration in soil solution increased stability of organic matter-mineral complexes and might decrease the dissolution of organic matter, and thus decreased the release of Cu-binding component of organic matter. However, high concentration of Na in the soil solution increased the dispersion of the organic matter-mineral complexes and increased dissolution of organic matter and the release of Cu from the soils.展开更多
The property of hydrophilic polymers capable absorbing huge volumes of water led to many practical applications of these new materials in arid regions for improving the water retention in sandy soils. Effects of four ...The property of hydrophilic polymers capable absorbing huge volumes of water led to many practical applications of these new materials in arid regions for improving the water retention in sandy soils. Effects of four carboxymethylcelluloses (CMC) mixed at various rates with the sandy soil, on the water-holding capacity and hydraulic conductivity (Ks) when leached with distilled water (simulating rain), tap water, and saline water were evaluated. The maximum water absorption of CMCs ranged between 80 and 100 kg. kg^-1 of polymer; however, the absorbent swelling capacity decreased significantly with increasing the salt concentration in the solution. The water absorption capacity of CMCs decreased significantly when incorporated in the sandy soil compared to that of the absorbent alone. Application of CMC increased significantly the available water content up to 3 ± 0.5 times. All soils treated with CMCs showed a significant lower in Ks compared to the control soil. Meanwhile, Ks was found increased with increasing the salt concentration in the leaching solution. This understanding of characteristics of the absorbents and the interactions among absorbents, soil, and irrigation water quality would be of help in water management of sandy soil展开更多
[ Objective] The study aims at discussing the feasibility of urban sewage sludge applied to desertification forestland. [ Method] Through the simulated leaching test, the effects of sewage sludge application on the co...[ Objective] The study aims at discussing the feasibility of urban sewage sludge applied to desertification forestland. [ Method] Through the simulated leaching test, the effects of sewage sludge application on the content of nutrients and heavy metals in aeolian sandy soil were ana- lyzed. [ Result] After the simulated leaching with sewage sludge, the contents of total nitrogen (TN), total phosphorus (TP), available nitrogen (AN) and available phosphorus (AP) in each layer of aeolian sandy soil increased significantly, and the increase in 0 -20 cm soil was more signifi- cant than that in 20 -40 and 40 -60 cm soil. Meanwhile, the content of each heavy metal in 0 -20 cm soil rose significantly, while the increase was small in 40 -60 cm soil. In addition, after the application of sewage sludge, the Nemrew Index of aeolian sandy soil was 0.67, lower than the na- tional soil quality standard of forestland (0.70), and the short-time application of sewage sludge to sandy soil did not cause serious pollution. How- ever, if sewage sludge has been applied to aeolian sandy soil for a long term, the potential hazard of heavy metals (especially Cd) caused by loneterm accumulation should be paid more attention to.展开更多
Soil microorganisms play a key role in the function of soil ecosystem,yet our knowledge about how microbial communities respond to the typically sandy soil environmental properties along the soil profile is still insu...Soil microorganisms play a key role in the function of soil ecosystem,yet our knowledge about how microbial communities respond to the typically sandy soil environmental properties along the soil profile is still insufficient.We investigated the soil microbial community patterns from top(0–20 cm)to clay-layer(>80 cm)of the typical sandy soils in three regions in China with different levels of precipitation,including Lishu County in Jilin Province(LS),Langfang City in Hebei Province(LF)and Zhengzhou City in Henan Province(ZZ).Our findings showed that small-size aggregates(<0.5 mm)rather than large ones(³0.5 mm)dominated the soil profile.The relative abundances of Actinobacteria,Crenarchaeota and Firmicutes were highly related to aggregate proportions of the deep clay-layer soil.The network analysis revealed the distinct community patterns among modules,evidencing niche differentiation along the soil profile.The keystone species OTU_11292 was observed having migrated clearly into the other module of the clay-layer soil.Different roles of the OTU_30(belonging to Gemmatimonadetes)in soil processes might partly explain the different microbial distribution between top-and clay-layer soils.These findings provided new insights into the candidate mechanisms of microbial diversity maintenance and community patterning of sandy soils,which were necessary for better understanding of ecological rules guiding long-term agricultural practice.展开更多
Alfalfa is a perennial herbaceous forage legume that is remarkably and negatively affected by monocropping.However,the contribution of the changes in bacterial communities to soil sickness in alfalfa have not been elu...Alfalfa is a perennial herbaceous forage legume that is remarkably and negatively affected by monocropping.However,the contribution of the changes in bacterial communities to soil sickness in alfalfa have not been elucidated.Therefore,we investigated bacterial community structures in response to monocropped alfalfa along the chronosequence.Continuous cropping remarkably reduced bacterial alpha diversity and altered community structures,and soil pH,total P and available P were strongly associated with the changes of bacterial diversity and community structures.Intriguingly,10 years of monocropped alfalfa might be a demarcation point separating soil bacterial community structures into two obvious groups that containing soil samples collected in less and more than 10 years.The relative abundances of copiotrophic bacteria of Actinobacteria and Gammaproteobacteria significantly increased with the extension of continuous cropping years,while the oligotrophic bacteria of Armatimonadetes,Chloroflexi,Firmicutes and Gemmatimonadetes showed the opposite changing patterns.Among those altered phyla,Actinobacteria,Chloroflexi,Alphaproteobacteria and Acidobacteria were the most important bacteria which contributed 50.86%of the community variations. Additionally, the relative abundances of nitrogen fixation bacteria ofBradyrhizobium and Mesorhizobium obviously increased with continuous cropping years, while theabundances of Arthrobacter, Bacillus, Burkholderiaceae and Microbacterium with potential functionsof solubilizing phosphorus and potassium remarkably decreased after long-term continuouscropping. Furthermore, bacterial cooccurrence patterns were significantly influenced by continuouscropping years, with long-term monocropped alfalfa simplifying the complexity of the cooccurrencenetworks. These findings enhanced our understandings and provided references for forecasting howsoil bacterial communities responds to monocropped alfalfa.展开更多
Background:The uptake of arsenic by vegetables from soil irrigated with arsenic enriched groundwater poses a major health hazard.The edible portion of these vegetables transfer arsenic to the human beings.The uptake o...Background:The uptake of arsenic by vegetables from soil irrigated with arsenic enriched groundwater poses a major health hazard.The edible portion of these vegetables transfer arsenic to the human beings.The uptake of arsenic was studied in bean(Phaseolus vulgaris L.)and lettuce(Lactuca sativa L.)in a controlled greenhouse pot culture with calcareous sandy soil as substrate.The plants were irrigated with water containing sodium arsenate at concentrations 0.1,0.25 and 0.5 mg L^(-1).The total arsenic concentration of the different plants parts was determined by ICP-MS,following microwave-assisted acid digestion.The change in plant biomass production and essential macroelements(Mg,P,K)and microelements concentration(Fe,Mn,Cu,Zn)was also studied.Results:The As concentration in the bean was in the order:root>stem>leaf>bean fruit and in lettuce:root>leaves.At the highest dose(0.5 mg L^(-1))the As concentration in the bean fruit and lettuce leaves was 22.1μg kg^(-1)and 1207.5μg kg^(-1)DW,respectively.Increasing As concentration in the irrigation water resulted in decreased edible biomass production in bean,while in lettuce the edible biomass production increased.Neither plant exhibited any visible toxicity symptoms.No significant change was observed in the macro and microelements concentration.The total and the water-soluble arsenic in soil amounted to 3.5 mg kg^(−1)and 0.023 mg kg^(−1),respectively.The transfer factor was found to increase with increase in the As treatment applied.The transfer factor range for bean from root to fruit was 0.003–0.005,and for lettuce from root to leaves was 0.14–0.24.Conclusion:Considering the FAO-WHO recommended maximum tolerable daily intake(MTDI)limit of 2.1μg kg^(-1)body weight,and the biomass production,both plants should not be cultivated at As treatment level higher than 0.1 mg L^(-1).展开更多
The eutrophication problem has drawn attention to nutrient leaching from agricultural soils, and an understanding of spatial and temporal variability is needed to develop decision-making tools. Thus, eleven sites were...The eutrophication problem has drawn attention to nutrient leaching from agricultural soils, and an understanding of spatial and temporal variability is needed to develop decision-making tools. Thus, eleven sites were selected to monitor, over a two-year period, spatial and temporal variation of runoff discharge and various forms of N in surface runoff in sandy agricultural soils. Factors influencing the variation of runoff discharge and various forms of N in surface runoff were analyzed. Variation of annual rainfall was small among 11 sites, especially between 2001 and 2002. However, variation of annual discharge was significant among the sites. The results suggest that rainfall patterns and land use had significant effect on discharge. The concentrations of total N, total kjeldahl N (TKN), organic matter-associated N (OM-N), NO3- -N, and NHn+-N in the runoff ranged widely from 0.25 to 54.1, 0.15 to 20.3, 0.00 to 14.6, 0.00 to 45.3, and 0.00 to 19.7 mg/L, respectively. Spatial and temporal variations in the N concentration and runoff discharge were noted among the different sites. Annual loads of N in the runoff varied widely among monitoring sites and depend mainly on runoff discharge. High loads of total N, OM-N, NO3--N, and NHn+-N in the runoff either in citrus groves or on vegetable farms occurred from June to October for each year, which coincided with the rainy season in the region. This study found that N in surface runoff was related to rainfall intensity, soil N level, and fertilizer use.展开更多
Biochar amendment improves the physical,chemical and biological characteristics of different soil types under different climatic and environmental conditions.In this study,effects of biochar or live pasture plants exi...Biochar amendment improves the physical,chemical and biological characteristics of different soil types under different climatic and environmental conditions.In this study,effects of biochar or live pasture plants existing alone or co-existing on selected soil properties of sandy loam soil under humid lowland tropical climatic conditions were investigated.The changes measured in the amended soil,with or without plants,were compared to the unamended and unplanted soils.Biochar amendment with or without pasture improved moisture retention,lowered bulk density,increased pH and kept the electrical conductivity within ranges conducive for pasture growth.Generally,contents of all the nutrients increased following biochar amendment,however pasture establishment without amendment resulted in depletion of available potassium and magnesium.Under all treatment conditions,soil organic carbon and soil organic matter were significantly depleted.Cogon grass is invasive under all land use systems and contributes to greenhouse gas emissions through slash-and-burn.Using biomass from the grass instead of burning would mitigate CO2 emissions from the tropics.展开更多
Cellulose decomposing fungi play an important role in litter decomposition and are decisive in nutrient cycling in sandy land ecosystems. Thirty-one strains were isolated to select efficient cellulose decomposers, and...Cellulose decomposing fungi play an important role in litter decomposition and are decisive in nutrient cycling in sandy land ecosystems. Thirty-one strains were isolated to select efficient cellulose decomposers, and four efficient cellulose decomposing fungi (NM3-1, NM3-2, NM3-3, and NM3-4) were screened using a CMC (carboxymethyl cellulose) carbon source in dune soil of Horqin Sandy Land. They were identified as Asperigillus calidoustus, Fusarium oxysporum, Fusarium solani, and Hypocrea lixii by rDNA-ITS molecular biological methods. Cloth decomposition rates were 15.71%, 15.89%, 17.29%, and 17.89% by the four efficient decomposers incubated for 30 days, respectively. Screening of efficient cellulose decomposers can not only increase the dune soil functional microbe bank, but can also accelerate litter decom- position and available nutrient input in the Horqin Sandy Land.展开更多
Soil water deficit is increasingly threatening the sustainable vegetation restoration and ecological construction on the Loess Plateau of China due to the climate warming and human activities.To determine the response...Soil water deficit is increasingly threatening the sustainable vegetation restoration and ecological construction on the Loess Plateau of China due to the climate warming and human activities.To determine the response thresholds of Amygdalus pedunculata(AP)and Salix psammophila(SP)to soil water availability under different textural soils,we measured the changes in net photosynthetic rate(Pn),stomatal conductance(Gs),intercellular CO2 concentration(Ci),leaf water potential(ψw),water use efficiency(WUE)and daily transpiration rate(Td)of the two plant species during soil water content(SWC)decreased from 100%field capacity(FC)to 20%FC in the sandy and loamy soils on the Loess Plateau in the growing season from June to August in 2018.Results showed that Pn,Gs,WUE and Td of AP and SP remained relatively constant at the beginning of soil water deficit but decreased rapidly as plant available soil water content(PASWC)fell below the threshold values in both the sandy and loamy soils.The PASWC thresholds corresponding to Pn,Gs and Ci of AP in the loamy soil(0.61,0.62 and 0.70,respectively)were lower than those in the sandy soil(0.70,0.63 and 0.75,respectively),whereas the PASWC thresholds corresponding to Pn,Gs and Ci of SP in the loamy soil(0.63,0.68 and 0.78,respectively)were higher than those in the sandy soil(0.58,0.62 and 0.66,respectively).In addition,the PASWC thresholds in relation to Td and WUE of AP(0.60 and 0.58,respectively)and SP(0.62 and 0.60,respectively)in the loamy soil were higher than the corresponding PASWC thresholds of AP(0.58 and 0.52,respectively)and SP(0.55 and 0.56,respectively)in the sandy soil.Furthermore,the PASWC thresholds for the instantaneous gas exchange parameters(e.g.,Pn and Gs)at the transient scale were higher than the thresholds for the parameters(e.g.,Td)at the daily scale.Our study demonstrates that different plant species and/or different physiological parameters exhibit different thresholds of PASWC and that the thresholds are affected by soil texture.The result can provide guidance for the rational allocation and sustainable management of reforestation species under different soil conditions in the loess regions.展开更多
The paper reports the study on validity, absorbing and using in potassium of wine-grapes grown on aeolian sandy soil in Ningxia. The result shows that the content of slow release potassium and available potassium is l...The paper reports the study on validity, absorbing and using in potassium of wine-grapes grown on aeolian sandy soil in Ningxia. The result shows that the content of slow release potassium and available potassium is low. The amount of available potassium and fixed potassium increases with raising amount of applied potash. Slow release potassium can be quickly replenished when available potassium is depleted, but slow release potassium is exhausted too, and the buffering capacity of supplying potassium is low. The content of potassium in grains and plants increases with the increasing amount of applied K in different treatments. The sequence of potassium recovery rate in different soil is as follows: sand-loam>fine-sand>coarse-sand. The capacity of supplying potassium in high-fertility soil is better than that in low-fertility soil, and rate of potassium recovery is high. Potassium nutrient affects growth and quality of wine-grapes.展开更多
In this study, soil column was used to study the new nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on nitrate (NO3^-- N) and potassium (K) leaching in the sandy loam soil and clay loam soil. The ...In this study, soil column was used to study the new nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on nitrate (NO3^-- N) and potassium (K) leaching in the sandy loam soil and clay loam soil. The results showed that DMPP with ammonium sulphate nitrate (ASN) ((NH4)2SO4 and NHaNO3) or urea could reduce NO3^--N leaching significantly, whereas ammonium (NH4^+-N) leaching increased slightly. In case of total N (NO3^--N+NH4^+-N), losses by leaching during the experimental period (40 d) were 37.93 mg (urea), 31.61 mg (urea+DMPP), 108.10 mg (ASN), 60.70 mg (ASN+DMPP) in the sandy loam soil, and 30.54 mg (urea), 21.05 mg (urea+DMPP), 37.86 mg (ASN), 31.09 mg (ASN+DMPP) in the clay loam soil, respectively. DMPP-amended soil led to the maintenance of relatively high levels of NH4^+ -N and low levels of NO3^--N in soil, and nitrification was slower. DMPP supplementation also resulted in less potassium leached, but the difference was not significant except the treatment of ASN and ASN+DMPP in the sandy loam soil. Above results indicate that DMPP is a good nitrification inhibitor, the efficiency of DMPP seems better in the sandy loam soil than in the clay loam soil and lasts longer.展开更多
Increased food demand from the rapidly growing human population has caused intensive land transition from desert to farmland in arid regions of northwest China. In this developing ecosystem, the optimized fertilizatio...Increased food demand from the rapidly growing human population has caused intensive land transition from desert to farmland in arid regions of northwest China. In this developing ecosystem, the optimized fertilization strategies are becoming an urgent need for sustainable crop productivity, efficient resources use, together with the delivery of ecosystems services including soil carbon(C) and nitrogen(N) accumulation. Through a 7-year field experiment with 9 fertilization treatments in a newly cultivated farmland, we tested whether different fertilizations had significant influences on soil C and N accumulation in this developing ecosystem, and also investigated possible mechanisms for this influence. The results showed that applying organic manure in cultivated farmland significantly increased the soil C and N accumulation rates; this influence was greater when it was combined with chemical fertilizer, accumulating 2.01 t C and 0.11 t N ha^(–1) yr^(–1) in the most successful fertilization treatment. These high rates of C and N accumulation were found associated with increased input of C and N, although the relationship between the N accumulation rate and N input was not significant. The improved soil physical properties was observed under only organic manure and integrated fertilization treatments, and the significant relationship between soil C or N and soil physical properties were also found in this study. The results suggest that in newly cultivated farmland, long term organic manure and integrated fertilization can yield significant benefits for soil C and N accumulation, and deliver additional influence on physical properties.展开更多
基金National Natural Science Foundation of China under Grant No.52278503。
文摘Coral sandy soils widely exist in coral island reefs and seashores in tropical and subtropical regions.Due to the unique marine depositional environment of coral sandy soils,the engineering characteristics and responses of these soils subjected to monotonic and cyclic loadings have been a subject of intense interest among the geotechnical and earthquake engineering communities.This paper critically reviews the progress of experimental investigations on the undrained behavior of coral sandy soils under monotonic and cyclic loadings over the last three decades.The focus of coverage includes the contractive-dilative behavior,the pattern of excess pore-water pressure(EPWP)generation and the liquefaction mechanism and liquefaction resistance,the small-strain shear modulus and strain-dependent shear modulus and damping,the cyclic softening feature,and the anisotropic characteristics of undrained responses of saturated coral sandy soils.In particular,the advances made in the past decades are reviewed from the following aspects:(1)the characterization of factors that impact the mechanism and patterns of EPWP build-up;(2)the identification of liquefaction triggering in terms of the apparent viscosity and the average flow coefficient;(3)the establishment of the invariable form of strain-based,stress-based,or energy-based EPWP ratio formulas and the unique relationship between the new proxy of liquefaction resistance and the number of cycles required to reach liquefaction;(4)the establishment of the invariable form of the predictive formulas of small strain modulus and strain-dependent shear modulus;and(5)the investigation on the effects of stress-induced anisotropy on liquefaction susceptibility and dynamic deformation characteristics.Insights gained through the critical review of these advances in the past decades offer a perspective for future research to further resolve the fundamental issues concerning the liquefaction mechanism and responses of coral sandy sites subjected to cyclic loadings associated with seismic events in marine environments.
基金supported by the National Key Technologies R&D Program in the 11th Five-year Plan (2004BA901A15)the Key Program of National Natural Science Foundation of China (Grant No. 90702001)
文摘This paper presents the development of a new remediation technology for contaminated sandy soil using humic acid (HA). Distribution of amount of Cr (VI) in the aqueous or solid system containing humic acid and sandy soil, was studied using batch experiments, es-pecially for effects of reaction time, pH, concentrations, temperature and irradiation on the reduction of Cr (VI), and the optimum reaction conditions. The results indicated a significant increase of the adsorption of Cr (VI) because of the complexion reaction between HA and Cr (VI) that occurred under acidic condition. The reaction mechanisms of HA with chromium on sand surfaces were certified. Thus it came to a conclusion that HA could be used effectively on remediation of Cr (VI)–contaminated soil and groundwater in a wide range of pH, with or without sunlight. These results suggest that the organic-inorganic complex—such as sandy soils coated with humic substances—is important as a metal reservoir in the environment.
基金funded by the National Natural Science Foundation of China (41140028, 41340043)the Central University Research Foundation, Chang'an University (310827152014)the State Key Laboratory of Loess and Quaternary Geology (SKLLQG)
文摘Soil moisture is a critical state affecting a variety of land surface and subsurface processes. We report investigation results of the factors controlling vertical variation of soil moisture and sand transport rate of three types of dunes on the south- eastern margin of the Mu Us Sandy Land. Samples were taken from holes drilled to a depth of 4 m at different topographic sites on the dunes, and were analyzed for soil moisture, grain-size distribution and surface sediment discharge. The results show that: (1) The average soil moisture varies in different types of dunes, with the following sequences ordered from highest to lowest: in the shrubs-covered dunes and the trees-covered dunes the sequence is from inter-dunes lowland to windward slope to leeward slope. The average moisture in the bare-migratory sand dunes is sequenced from inter-dunes lowland to leeward slope to windward slope. (2) Vegetation form and surface coverage affect the range of soil moisture of different types of dunes in the same topographic position. The coefficient of variation of soil moisture for shrubs-covered dunes is higher than that of other types of dune. (3) The effect of shrubs on dune soil moisture is explained in terms of the greater ability of shrubs to trap fine-grained atmospheric dust and hold moisture. (4) The estimated sand transport rates over sand dunes with sparse shrubs are less than those over bare-migratory dunes or sand dunes with sparse trees, indicating that shrubs are more effective in inhibiting wind erosion in the sandy land area.
基金This work was supported by Innovation Research Project of Chinese Academy of Sciences (KZCX3-SW-418), National Natural Science Foundation of China (30471377) and sustentation project of the Institute of Applied Ecology of Chinese Academy of Sciences (SLYQY0409).
文摘To assess the effects of savanna afforestation on soil phosphorus (P) transformations in eastern Horqin Sandy Land, China, P fractions and phosphomonoesterase activities were examined in two soil horizons (0-5 cm and 5-20 cm) under a savanna and an adjacent 30-year-old Mongolian pine (Pinus sylvestris L. vat. mongolica Litv.) plantation on a P-deficient semi arid sandy soil. The results showed that all soil P fractions and phosphomonoestcrase activities decreased with soil depth at both sites except that labile organic P under the plantation was constant with soil depth, In contrast to savanna, soils trader Mongolian pine plantation had lower phosphomonoesterase activities and concentrations of all P fractions (with an exception of Al-P), lower proportions of organic P and Ca-P in total P, and higher proportions of labile P, Al-P and Fe-P in total P. These results suggested that P transformations mainly occurred in surface soils, and P recycled through litterfall was the most important source of plant available P. Mongolian pine afforestation enhanced the bioavailability of both organic P and Ca-P. simultaneously reduced soil P pools. indicating that protection of forest floor and P fertilization are necessary to maintain the sustainable functioning of Mongolian pine plantations.
基金financial support provided by the National Special Fund for Agro-scientific Research in the Public Interest of China(201303126)Agricultural Science and Technology Achievements Transformation Demonstration of Production and Application Technology and Popularization of Sandy Soil Amendment,Inner Mongolia,China(sq2012eca400008)。
文摘A bentonite-humic acid(B-HA) mixture added to degraded soils may improve soil physical and hydraulic properties, due to effects such as improved soil structure and increased water and nutrient retention, but its effect on soil physicochemical and biological properties, and grain quality is largely unknown. The effect of B-HA, added at 30 Mg ha^(-1), was studied at 1,3, 5 and 7 years after its addition to a degraded sandy soil in a semi-arid region of China. The addition of B-HA significantly increased water-filled pore space and soil organic carbon, especially at 3 to 5 years after its soil addition to the soil. Amending the sandy soil with B-HA also increased the content of microbial biomass(MB)-carbon,-nitrogen and-phosphorus, and the activities of urease, invertase, catalase and alkaline phosphatase. The significant effect of maize(Zea mays L.) growth stage on soil MB and enzyme activities accounted for 58 and 84% of their total variation, respectively. In comparison, B-HA accounted for 8% of the total variability for each of the same two variables. B-HA significantly enhanced soil properties and the uptake of N and P by maize in semi-arid areas. The use of B-HA product would be an effective management strategy to reclaim degraded sandy soils and foster sustainable agriculture production in northeast China and regions of the world with similar soils and climate.
基金Thailand Research Fund and Commission on Higher Education,Ministry of Education,Thailand Under Grant No.MRG5180268
文摘This paper describes a quasi-static test program featuring lateral cyclic loading on single piles in sandy soil. The tests were conducted on 18 aluminum model piles with different cross sections and lateral load eccentricity ratios, e/d, (e is the lateral load eccentricity and d is the diameter of pile) of 0, 4 and 8, embedded in sand with a relative density of 30% and 70%. The experimental results include lateral load-displacement hysteresis loops, skeleton curves and energy dissipation curves. Lateral capacity, ductility and energy dissipation capacity of single piles under seismic load were evaluated in detail. The lateral capacities and the energy dissipation capacity of piles in dense sand were much higher than in loose sand. When embedded in loose sand, the maximum lateral load and the maximum lateral displacement of piles increased as e/d increased. On the contrary, when embedded in dense sand, the maximum lateral load of piles decreased as e/d increased. Piles with a higher load eccentricity ratio experienced higher energy dissipation capacity than piles with e/d of 0 in both dense and loose sand. At a given level of displacement, piles with circular cross sections provided the best energy dissipation capacity in both loose and dense sand.
文摘We analyzed the heat conductivity and volumetric heat capacity of sandy soil contaminated in two scenarios of oil pollution, and also determined the temperature dependencies of these changed thermophysical properties. In the first pollution scenario, the oil product was introduced into wet river sand, and in the second case, dry sand was contaminated by the oil product and was then moistened with water. By considering these two scenarios as multicomponent dispersion systems with varying degrees of contamination and humidity, and by using a polystructural granular model with pore spaces and closed inclusions, we calculated that the heat conductivity of the sandy soil increased under the first pollution scenario and decreased under the second, but the change in the volumetric heat capacity of the sandy soil was proportional only to the amount of oil pollution, not the manner in which it was introduced. We also determined the temperature dependencies of these two thermophysical properties of sandy soil when polluted by oil, of which information will be useful for future containment and remediation of oil-contaminated soil.
文摘The concentrations and chemical forms of copper(Cu) and zinc(Zn) in surface soils directly influence the movement of Cu and Zn. In this study, thirteen sandy soil samples with a wide range of total Cu and Zn concentrations were collected for evaluating the relationships between Cu and Zn release and extraction time, ratio of soil to water, pH and electrolyte types. The results indicated that Cu released in batch extraction that represents long-term leaching was mainly from exchangeable, and carbonate bound Cu fractions, and Zn released in the batch extraction was mainly from its carbonate bound fraction. However, the Cu and Zn leached from the soils using the column leaching that represents short-term leaching were mainly from their exchangeable fractions. Soil column leaching at different pH values indicated that the amounts of leached Zn and Cu were greatly affected by pH. The Cu and Zn release experiments with varying extraction times and ratio of soil to water suggest that long-term water-logging in the soils after rain may increase contact time of the soils with water and the release of Cu and Zn to water from the soils, and total amounts of Cu or Zn released from the soils increase, but the Cu or Zn concentration in the surface runoff decrease with increasing rainfall intensity. The increased Ca concentration in soil solution increased stability of organic matter-mineral complexes and might decrease the dissolution of organic matter, and thus decreased the release of Cu-binding component of organic matter. However, high concentration of Na in the soil solution increased the dispersion of the organic matter-mineral complexes and increased dissolution of organic matter and the release of Cu from the soils.
文摘The property of hydrophilic polymers capable absorbing huge volumes of water led to many practical applications of these new materials in arid regions for improving the water retention in sandy soils. Effects of four carboxymethylcelluloses (CMC) mixed at various rates with the sandy soil, on the water-holding capacity and hydraulic conductivity (Ks) when leached with distilled water (simulating rain), tap water, and saline water were evaluated. The maximum water absorption of CMCs ranged between 80 and 100 kg. kg^-1 of polymer; however, the absorbent swelling capacity decreased significantly with increasing the salt concentration in the solution. The water absorption capacity of CMCs decreased significantly when incorporated in the sandy soil compared to that of the absorbent alone. Application of CMC increased significantly the available water content up to 3 ± 0.5 times. All soils treated with CMCs showed a significant lower in Ks compared to the control soil. Meanwhile, Ks was found increased with increasing the salt concentration in the leaching solution. This understanding of characteristics of the absorbents and the interactions among absorbents, soil, and irrigation water quality would be of help in water management of sandy soil
文摘[ Objective] The study aims at discussing the feasibility of urban sewage sludge applied to desertification forestland. [ Method] Through the simulated leaching test, the effects of sewage sludge application on the content of nutrients and heavy metals in aeolian sandy soil were ana- lyzed. [ Result] After the simulated leaching with sewage sludge, the contents of total nitrogen (TN), total phosphorus (TP), available nitrogen (AN) and available phosphorus (AP) in each layer of aeolian sandy soil increased significantly, and the increase in 0 -20 cm soil was more signifi- cant than that in 20 -40 and 40 -60 cm soil. Meanwhile, the content of each heavy metal in 0 -20 cm soil rose significantly, while the increase was small in 40 -60 cm soil. In addition, after the application of sewage sludge, the Nemrew Index of aeolian sandy soil was 0.67, lower than the na- tional soil quality standard of forestland (0.70), and the short-time application of sewage sludge to sandy soil did not cause serious pollution. How- ever, if sewage sludge has been applied to aeolian sandy soil for a long term, the potential hazard of heavy metals (especially Cd) caused by loneterm accumulation should be paid more attention to.
基金the financial supports of the National Basic Research Program of China(Grant no.2016YFD0200306)the National Natural Science Foundation of China(Grant no.41877412)the Scholarship of the‘National 1000(Young)Talents Program’of China.
文摘Soil microorganisms play a key role in the function of soil ecosystem,yet our knowledge about how microbial communities respond to the typically sandy soil environmental properties along the soil profile is still insufficient.We investigated the soil microbial community patterns from top(0–20 cm)to clay-layer(>80 cm)of the typical sandy soils in three regions in China with different levels of precipitation,including Lishu County in Jilin Province(LS),Langfang City in Hebei Province(LF)and Zhengzhou City in Henan Province(ZZ).Our findings showed that small-size aggregates(<0.5 mm)rather than large ones(³0.5 mm)dominated the soil profile.The relative abundances of Actinobacteria,Crenarchaeota and Firmicutes were highly related to aggregate proportions of the deep clay-layer soil.The network analysis revealed the distinct community patterns among modules,evidencing niche differentiation along the soil profile.The keystone species OTU_11292 was observed having migrated clearly into the other module of the clay-layer soil.Different roles of the OTU_30(belonging to Gemmatimonadetes)in soil processes might partly explain the different microbial distribution between top-and clay-layer soils.These findings provided new insights into the candidate mechanisms of microbial diversity maintenance and community patterning of sandy soils,which were necessary for better understanding of ecological rules guiding long-term agricultural practice.
基金This work was supported by grants from National Key Research and Development Program of China(2017YFD0200604)Key Research Program of Frontier Sciences,CAS(ZDBS-LYDQC017)+5 种基金the National Natural Science Foundation of China(41671251)Earmarked Fund for China Agriculture Research System(CR34)Heilongjiang Provincial Natural Science Foundation of China(D2018009)the Grass-field Rotation Scientist Studio of Heilongjiang Province(202004)Outstanding Youth Fund of Heilongjiang Academy of Agricultural Sciences(2020JCQN003)Youth Innovation Promotion Association,CAS(2017276).
文摘Alfalfa is a perennial herbaceous forage legume that is remarkably and negatively affected by monocropping.However,the contribution of the changes in bacterial communities to soil sickness in alfalfa have not been elucidated.Therefore,we investigated bacterial community structures in response to monocropped alfalfa along the chronosequence.Continuous cropping remarkably reduced bacterial alpha diversity and altered community structures,and soil pH,total P and available P were strongly associated with the changes of bacterial diversity and community structures.Intriguingly,10 years of monocropped alfalfa might be a demarcation point separating soil bacterial community structures into two obvious groups that containing soil samples collected in less and more than 10 years.The relative abundances of copiotrophic bacteria of Actinobacteria and Gammaproteobacteria significantly increased with the extension of continuous cropping years,while the oligotrophic bacteria of Armatimonadetes,Chloroflexi,Firmicutes and Gemmatimonadetes showed the opposite changing patterns.Among those altered phyla,Actinobacteria,Chloroflexi,Alphaproteobacteria and Acidobacteria were the most important bacteria which contributed 50.86%of the community variations. Additionally, the relative abundances of nitrogen fixation bacteria ofBradyrhizobium and Mesorhizobium obviously increased with continuous cropping years, while theabundances of Arthrobacter, Bacillus, Burkholderiaceae and Microbacterium with potential functionsof solubilizing phosphorus and potassium remarkably decreased after long-term continuouscropping. Furthermore, bacterial cooccurrence patterns were significantly influenced by continuouscropping years, with long-term monocropped alfalfa simplifying the complexity of the cooccurrencenetworks. These findings enhanced our understandings and provided references for forecasting howsoil bacterial communities responds to monocropped alfalfa.
基金supported by the Hungarian Scientific Research Foundation grant,NVKP_16-1-2016-0044.
文摘Background:The uptake of arsenic by vegetables from soil irrigated with arsenic enriched groundwater poses a major health hazard.The edible portion of these vegetables transfer arsenic to the human beings.The uptake of arsenic was studied in bean(Phaseolus vulgaris L.)and lettuce(Lactuca sativa L.)in a controlled greenhouse pot culture with calcareous sandy soil as substrate.The plants were irrigated with water containing sodium arsenate at concentrations 0.1,0.25 and 0.5 mg L^(-1).The total arsenic concentration of the different plants parts was determined by ICP-MS,following microwave-assisted acid digestion.The change in plant biomass production and essential macroelements(Mg,P,K)and microelements concentration(Fe,Mn,Cu,Zn)was also studied.Results:The As concentration in the bean was in the order:root>stem>leaf>bean fruit and in lettuce:root>leaves.At the highest dose(0.5 mg L^(-1))the As concentration in the bean fruit and lettuce leaves was 22.1μg kg^(-1)and 1207.5μg kg^(-1)DW,respectively.Increasing As concentration in the irrigation water resulted in decreased edible biomass production in bean,while in lettuce the edible biomass production increased.Neither plant exhibited any visible toxicity symptoms.No significant change was observed in the macro and microelements concentration.The total and the water-soluble arsenic in soil amounted to 3.5 mg kg^(−1)and 0.023 mg kg^(−1),respectively.The transfer factor was found to increase with increase in the As treatment applied.The transfer factor range for bean from root to fruit was 0.003–0.005,and for lettuce from root to leaves was 0.14–0.24.Conclusion:Considering the FAO-WHO recommended maximum tolerable daily intake(MTDI)limit of 2.1μg kg^(-1)body weight,and the biomass production,both plants should not be cultivated at As treatment level higher than 0.1 mg L^(-1).
文摘The eutrophication problem has drawn attention to nutrient leaching from agricultural soils, and an understanding of spatial and temporal variability is needed to develop decision-making tools. Thus, eleven sites were selected to monitor, over a two-year period, spatial and temporal variation of runoff discharge and various forms of N in surface runoff in sandy agricultural soils. Factors influencing the variation of runoff discharge and various forms of N in surface runoff were analyzed. Variation of annual rainfall was small among 11 sites, especially between 2001 and 2002. However, variation of annual discharge was significant among the sites. The results suggest that rainfall patterns and land use had significant effect on discharge. The concentrations of total N, total kjeldahl N (TKN), organic matter-associated N (OM-N), NO3- -N, and NHn+-N in the runoff ranged widely from 0.25 to 54.1, 0.15 to 20.3, 0.00 to 14.6, 0.00 to 45.3, and 0.00 to 19.7 mg/L, respectively. Spatial and temporal variations in the N concentration and runoff discharge were noted among the different sites. Annual loads of N in the runoff varied widely among monitoring sites and depend mainly on runoff discharge. High loads of total N, OM-N, NO3--N, and NHn+-N in the runoff either in citrus groves or on vegetable farms occurred from June to October for each year, which coincided with the rainy season in the region. This study found that N in surface runoff was related to rainfall intensity, soil N level, and fertilizer use.
基金The study was supported by Final Year Project Funds from the PNG University of Technology to the Department of Agriculture.
文摘Biochar amendment improves the physical,chemical and biological characteristics of different soil types under different climatic and environmental conditions.In this study,effects of biochar or live pasture plants existing alone or co-existing on selected soil properties of sandy loam soil under humid lowland tropical climatic conditions were investigated.The changes measured in the amended soil,with or without plants,were compared to the unamended and unplanted soils.Biochar amendment with or without pasture improved moisture retention,lowered bulk density,increased pH and kept the electrical conductivity within ranges conducive for pasture growth.Generally,contents of all the nutrients increased following biochar amendment,however pasture establishment without amendment resulted in depletion of available potassium and magnesium.Under all treatment conditions,soil organic carbon and soil organic matter were significantly depleted.Cogon grass is invasive under all land use systems and contributes to greenhouse gas emissions through slash-and-burn.Using biomass from the grass instead of burning would mitigate CO2 emissions from the tropics.
基金financially supported by the National Science and Technology Support Program (2011BAC07B02)National Natural Science Foundation of China (41401620 and 41171414)the Key Laboratory of Desert and Desertification Foundation (KLDD-2014-010) from Cold and Arid Regions Environmental and Engineering Research Institute,CAS
文摘Cellulose decomposing fungi play an important role in litter decomposition and are decisive in nutrient cycling in sandy land ecosystems. Thirty-one strains were isolated to select efficient cellulose decomposers, and four efficient cellulose decomposing fungi (NM3-1, NM3-2, NM3-3, and NM3-4) were screened using a CMC (carboxymethyl cellulose) carbon source in dune soil of Horqin Sandy Land. They were identified as Asperigillus calidoustus, Fusarium oxysporum, Fusarium solani, and Hypocrea lixii by rDNA-ITS molecular biological methods. Cloth decomposition rates were 15.71%, 15.89%, 17.29%, and 17.89% by the four efficient decomposers incubated for 30 days, respectively. Screening of efficient cellulose decomposers can not only increase the dune soil functional microbe bank, but can also accelerate litter decom- position and available nutrient input in the Horqin Sandy Land.
基金This study was financially supported by the National Natural Science Foundation of China(41601221)the Ministry of Science and Technology of China(2016YFC0501605)+2 种基金the Youth Innovation Promotion Association of Chinese Academy of Sciences(2019052)the Bingwei Outstanding Young Talent Project from the Institute of Geographical Sciences and Natural Resources Research,Chinese Academy of Sciences(2017RC203)the Scientific Research Program from the State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau,Institute of Soil and Water Conservation,Chinese Academy of Sciences and Ministry of Water Resources(A314021402-2010)。
文摘Soil water deficit is increasingly threatening the sustainable vegetation restoration and ecological construction on the Loess Plateau of China due to the climate warming and human activities.To determine the response thresholds of Amygdalus pedunculata(AP)and Salix psammophila(SP)to soil water availability under different textural soils,we measured the changes in net photosynthetic rate(Pn),stomatal conductance(Gs),intercellular CO2 concentration(Ci),leaf water potential(ψw),water use efficiency(WUE)and daily transpiration rate(Td)of the two plant species during soil water content(SWC)decreased from 100%field capacity(FC)to 20%FC in the sandy and loamy soils on the Loess Plateau in the growing season from June to August in 2018.Results showed that Pn,Gs,WUE and Td of AP and SP remained relatively constant at the beginning of soil water deficit but decreased rapidly as plant available soil water content(PASWC)fell below the threshold values in both the sandy and loamy soils.The PASWC thresholds corresponding to Pn,Gs and Ci of AP in the loamy soil(0.61,0.62 and 0.70,respectively)were lower than those in the sandy soil(0.70,0.63 and 0.75,respectively),whereas the PASWC thresholds corresponding to Pn,Gs and Ci of SP in the loamy soil(0.63,0.68 and 0.78,respectively)were higher than those in the sandy soil(0.58,0.62 and 0.66,respectively).In addition,the PASWC thresholds in relation to Td and WUE of AP(0.60 and 0.58,respectively)and SP(0.62 and 0.60,respectively)in the loamy soil were higher than the corresponding PASWC thresholds of AP(0.58 and 0.52,respectively)and SP(0.55 and 0.56,respectively)in the sandy soil.Furthermore,the PASWC thresholds for the instantaneous gas exchange parameters(e.g.,Pn and Gs)at the transient scale were higher than the thresholds for the parameters(e.g.,Td)at the daily scale.Our study demonstrates that different plant species and/or different physiological parameters exhibit different thresholds of PASWC and that the thresholds are affected by soil texture.The result can provide guidance for the rational allocation and sustainable management of reforestation species under different soil conditions in the loess regions.
文摘The paper reports the study on validity, absorbing and using in potassium of wine-grapes grown on aeolian sandy soil in Ningxia. The result shows that the content of slow release potassium and available potassium is low. The amount of available potassium and fixed potassium increases with raising amount of applied potash. Slow release potassium can be quickly replenished when available potassium is depleted, but slow release potassium is exhausted too, and the buffering capacity of supplying potassium is low. The content of potassium in grains and plants increases with the increasing amount of applied K in different treatments. The sequence of potassium recovery rate in different soil is as follows: sand-loam>fine-sand>coarse-sand. The capacity of supplying potassium in high-fertility soil is better than that in low-fertility soil, and rate of potassium recovery is high. Potassium nutrient affects growth and quality of wine-grapes.
基金Project supported by the National Natural Science Foundation of China(No. 30571082)the Science and Technology Committee of ZhejiangProvince (No. 021102084)the Agriculture Department of ZhejiangProvince (No. SN 200404) and BASF Company of Germany.
文摘In this study, soil column was used to study the new nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on nitrate (NO3^-- N) and potassium (K) leaching in the sandy loam soil and clay loam soil. The results showed that DMPP with ammonium sulphate nitrate (ASN) ((NH4)2SO4 and NHaNO3) or urea could reduce NO3^--N leaching significantly, whereas ammonium (NH4^+-N) leaching increased slightly. In case of total N (NO3^--N+NH4^+-N), losses by leaching during the experimental period (40 d) were 37.93 mg (urea), 31.61 mg (urea+DMPP), 108.10 mg (ASN), 60.70 mg (ASN+DMPP) in the sandy loam soil, and 30.54 mg (urea), 21.05 mg (urea+DMPP), 37.86 mg (ASN), 31.09 mg (ASN+DMPP) in the clay loam soil, respectively. DMPP-amended soil led to the maintenance of relatively high levels of NH4^+ -N and low levels of NO3^--N in soil, and nitrification was slower. DMPP supplementation also resulted in less potassium leached, but the difference was not significant except the treatment of ASN and ASN+DMPP in the sandy loam soil. Above results indicate that DMPP is a good nitrification inhibitor, the efficiency of DMPP seems better in the sandy loam soil than in the clay loam soil and lasts longer.
基金funded by the National Natural Science Foundation of China (41201284, 41401337)the China Postdoctoral Science Foundation (2013M542406)
文摘Increased food demand from the rapidly growing human population has caused intensive land transition from desert to farmland in arid regions of northwest China. In this developing ecosystem, the optimized fertilization strategies are becoming an urgent need for sustainable crop productivity, efficient resources use, together with the delivery of ecosystems services including soil carbon(C) and nitrogen(N) accumulation. Through a 7-year field experiment with 9 fertilization treatments in a newly cultivated farmland, we tested whether different fertilizations had significant influences on soil C and N accumulation in this developing ecosystem, and also investigated possible mechanisms for this influence. The results showed that applying organic manure in cultivated farmland significantly increased the soil C and N accumulation rates; this influence was greater when it was combined with chemical fertilizer, accumulating 2.01 t C and 0.11 t N ha^(–1) yr^(–1) in the most successful fertilization treatment. These high rates of C and N accumulation were found associated with increased input of C and N, although the relationship between the N accumulation rate and N input was not significant. The improved soil physical properties was observed under only organic manure and integrated fertilization treatments, and the significant relationship between soil C or N and soil physical properties were also found in this study. The results suggest that in newly cultivated farmland, long term organic manure and integrated fertilization can yield significant benefits for soil C and N accumulation, and deliver additional influence on physical properties.