Mapping the spatial distribution of soil nitrate-nitrogen (NO3-N) is important to guide nitrogen application as well as to assess environmental risk of NO3-N leaching into the groundwater. We employed univariate and h...Mapping the spatial distribution of soil nitrate-nitrogen (NO3-N) is important to guide nitrogen application as well as to assess environmental risk of NO3-N leaching into the groundwater. We employed univariate and hybrid geostatistical methods to map the spatial distribution of soil NO3-N across a landscape in northeast Florida. Soil samples were collected from four depth increments (0-30, 30-60, 60-120 and 120-180 cm) from 147 sampling locations identified using a stratified random and nested sampling design based on soil, land use and elevation strata. Soil NO3-N distributions in the top two layers were spatially autocorrelated and mapped using lognormal kriging. Environmental correlation models for NO3-N prediction were derived using linear and non-linear regression methods, and employed to develop NO3-N trend maps. Land use and its related variables derived from satellite imagery were identified as important variables to predict NO3-N using environmental correlation models. While lognormal kriging produced smoothly varying maps, trend maps derived from environmental correlation models generated spatially heterogeneous maps. Trend maps were combined with ordinary kriging predictions of trend model residuals to develop regression kriging prediction maps, which gave the best NO3-N predictions. As land use and remotely sensed data are readily available and have much finer spatial resolution compared to field sampled soils, our findings suggested the e?cacy of environmental correlation models based on land use and remotely sensed data for landscape scale mapping of soil NO3-N. The methodologies implemented are transferable for mapping of soil NO3-N in other landscapes.展开更多
Under the indoor simulant conditions, toxic effects of crude-oil-contaminated soil which was put into aquatic environment on the young fishes Carassius auratus and their hepatic antioxidant system after a 20-d exposur...Under the indoor simulant conditions, toxic effects of crude-oil-contaminated soil which was put into aquatic environment on the young fishes Carassius auratus and their hepatic antioxidant system after a 20-d exposure were investigated. Results showed that the relationship between the mortality of C. auratus and the exposed doses could be divided into 3 phases: fishes exposed to the low dose groups (0.5-5.0 g/L) were dead due to the ingestion of crude-oil-contaminated soils in aquatic environment; at the medium dose groups (5.0-25.0 g/L) fishes were dead due to the penetration of toxic substances; at the high dose groups (25.0-50.0 g/L) fishes were dead due to environmental stress. The highest mortality and death speed were found in the 1.0 g/L dose group, and the death speed was sharply increased in the 50.0 g/L dose group in the late phase of exposure. The activities of superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST) and the content of malaondialdehyde (MDA) in the hepatic tissues of C. auratus were induced significantly. The activity of SOD was increased and then decreased. It was significantly inhibited in the 50.0 g/L dose group. The activity of CAT was highly induced, and restored to a level which is little more than the control when the exposed doses exceeded 10.0 g/L. The activity of GST was the most sensitive, it was significantly induced in all dose groups, and the highest elevation was up to 6 times in the 0.5 g/L dose group comparing with the control. The MDA content was significantly elevated in the 50.0 g/L dose group, and the changes of the MDA content were opposite with the changes of GST activity.展开更多
Dajingshan,Fenghuangshan and Meixi reservoirs are located in Zhuhai,a coastal city in southern China,and they function to supply drinking water to Zhuhai and Macao.For eff ectively supplying waster,they are hydrologic...Dajingshan,Fenghuangshan and Meixi reservoirs are located in Zhuhai,a coastal city in southern China,and they function to supply drinking water to Zhuhai and Macao.For eff ectively supplying waster,they are hydrologically connected and Dajingshan Reservoir first receives the water pumped from the river at Guangchang Pumping Station,and then feeds Fenghuangshan Reservoir,and the two well-connected reservoirs are mesotrophic.Meixi Reservoir is a small and oligotrophic water body and feeds Dajingshan Reservoir only in wet seasons when overfl ow occurs.Particulate organic matter(POM)was collected from three hydrologically connected water supply reservoirs,and seasonal variations of POM were ascertained from stable carbon and nitrogen isotopes in wet and dry seasons,and the ef fects of pumping water and reservoir connectivity on POM variations and composition were demonstrated by the relationships of the stable isotope ratios of POM.Seasonality and similarity of stable carbon and nitrogen isotopes of POM varied with hydrodynamics,connectivity and trophic states of the four studied water bodies.The two wellconnected reservoirs displayed more similar seasonality for δ^(13)C_(POM) than those between the river station and the two reservoirs.However,the opposite seasonality appeared for δ^(15)N_(POM) between the above waters and indicates dif ferent processes aff ecting the stable carbon and nitrogen isotopes of POM.δ^(13)C_(POM) and δ^(15)N_(POM) changed little between wet and dry seasons in Meixi Reservoir-a low productive and rain-driven system,suggesting little POM response to environmental changes in that water system.As expected,connectivity enhanced the similarity of the stable isotope ratios of POM between the water bodies.展开更多
Twenty-six soil samples were collected from five soil profiles at different climatological and ecological regions in central Sudan. Soil profile was dug in each studied area and morphological profile description was c...Twenty-six soil samples were collected from five soil profiles at different climatological and ecological regions in central Sudan. Soil profile was dug in each studied area and morphological profile description was carried out for different horizons. All samples were analyzed using two different methods to determine Cation Exchange Capacity (CEC) and exchangeable sodium percentage (ESP). Statistical analysis (T-test) was used in order to investigate the differences between soil samples for the studied locations. Significant differences appeared when compared the two methods for CEC determination at Gedaref area, Wad Medani and Nile flood plain and that appeared in evaluation of ESP at Nile flood plain and Shambat area. The results also revealed that, the developed method used in this study was more practical, simple and reliable for determination of CEC and ESP as the currently used in most soil laboratories. In addition, it will be safer than the other methods in some problematic soils. The adoption of this developed method is advisable because it is less time consuming as it omits the washing step. In contrast, the old method cannot be a good substitute in laboratories which have no possibility to determine sodium by using flame photometer. We conclude that when the developed method is used to determine CEC and ESP time will be saved, that fewer amounts of chemicals will be used and that accurate results will be achieved.展开更多
Despite the CaCO<sub>3</sub> estimation using titration method was not reliable, but up to the present time, some soil laboratories in Sudan still used this method. The objective of this study was to compa...Despite the CaCO<sub>3</sub> estimation using titration method was not reliable, but up to the present time, some soil laboratories in Sudan still used this method. The objective of this study was to compare and assess the results of calcimetric and titrimetric methods of quantitative estimation for soil calcium carbonate of different soils in Sudan. 26 soil samples from five soil profiles were collected from different climatological and ecological regions in central Sudan. CaCO<sub>3</sub> equivalent was estimated using calcimeter and titration methods in order to find accurate, rapid and suitable method for soils of Sudan. The results revealed that there are no significant differences between calcimeter and titration methods for calcium carbonate estimation in all studied samples except in samples from Gedaref area. We concluded that when the Calcimeter method used for CaCO<sub>3</sub> estimation, the differences between one person and another in detecting titration end point would be avoided, rapid and accurate results would be obtained compared to titration method. Additionally, time would be saved;fewer amounts of chemicals would be used. From this study, we highly recommend using calcimeter method for CaCO<sub>3</sub> estimation for soils of Sudan.展开更多
Biochar is a carbon-rich(】60%)organic material derived from incomplete combustion of fossil fuels and biomass.It consists of a continuum ranging from slightly charred material through char and charcoal to soot,and is...Biochar is a carbon-rich(】60%)organic material derived from incomplete combustion of fossil fuels and biomass.It consists of a continuum ranging from slightly charred material through char and charcoal to soot,and is ubiquitous in the atmosphere,marine sediment,soil and water.Moreover,】80%of biochar produced ends up in soils,where it resides for hundreds to thousands of years.Because of its resistance to biological and chemical breakdown, biochar can serve as a pool of C with long residence time in the soil.As a result,there has been increasing attention given to the potential of biochar to sequestrate carbon and counteract展开更多
<p align="justify"> <span style="font-family:Verdana;">Soil salinity is one of the major yield-limiting factors for crop production in many agricultural regions all over the world. Besi...<p align="justify"> <span style="font-family:Verdana;">Soil salinity is one of the major yield-limiting factors for crop production in many agricultural regions all over the world. Besides following efficient management practices at the field scale to reduce accumulation of salts in the effective root-zone, the effective use of treatments to alleviate the effects of salinity stress and improve crop salt tolerance is a promising solution to ensure crop production in such adverse conditions. A field experiment was carried out to investigate the effect of foliar spray with plant-based biostimulant (<i>i.e.</i> with and/or without 3% yeast extract), three levels of proline (0, 25, and 50 mM), and combined with potassium fertilizers, as potassium sulfate, 48% K<sub>2</sub>O (0, 50, and 100 kg/fed.) on growth promotion, chemical composition of garlic leaves, bulb quality parameters as well as yield and its components of garlic plant grown under moderate saline soil. Results revealed that the interaction between foliar spray with yeast extract at 3% and proline at 50 mM combined with proper K level at 100 kg/fed., was the best interaction treatment for increasing vegetative growth parameters, <i>i.e.</i> plant height, number of leaves per plant, and mineral contents (N, P, K, S, Ca and Mg in leaves), and proline content of garlic leaves after 135 days from planting time, total yield/fed., and garlic yield quality parameters at harvesting time. In conclusion, the detrimental effects of salinity stress can be alleviated by stress tolerance-inducing compounds, such as yeast extract and proline with proper application rate of K fertilization during the growing season of garlic crop.</span> </p>展开更多
Iron (Fe) is a vital element for the survival and proliferation of all plants;therefore, Fe-biofortification by the application of chemical and organic fertilizers is being as an effective approach to fight hidden hun...Iron (Fe) is a vital element for the survival and proliferation of all plants;therefore, Fe-biofortification by the application of chemical and organic fertilizers is being as an effective approach to fight hidden hunger retards the growth and development of crop plants. Two experiments were carried out to investigate the effect of potassium and exogenous organic acids on iron uptake by two different plants<span>:</span><span> one is monocotyledon</span><span>,</span><span><span> maize (<i></i></span><i><i><span>Zea mays</span></i><span></span></i> L.) and the second is dicotolydon pea (<i></i></span><i><i><span>Pisum sativum</span></i></i><span> L.) grown under controlled conditions. The seedlings were grown in sand culture in a greenhouse experiment and irrigated with one-tenth strength modified nutrient solution of Hoagland and Arnon as a base solution (pH 7.5), containing different iron treatments (0, 1, and 5 ppm as FeSO</span><sub>4</sub>·<span>7H</span><sub><span>2</span></sub><span>O) combined with potassium nutrition (0, 5, 10, and 50 ppm as K</span><sub><span>2</span></sub><span>SO</span><sub><span>4</span></sub><span>). After 30 days, the best interaction treatment was selected for further experiment including 5.0 ppm Fe as FeSO</span><sub>4</sub><sup>.</sup><span>7H</span><sub><span>2</span></sub><span>O and 50 ppm K as K</span><sub><span>2</span></sub><span>SO</span><sub><span>4</span></sub><span> in combination with 1</span><span> </span><span>×</span><span> </span><span><span>10<sup>-</sup></span><sup><span>5</span></sup><span> mole/liter of one </span></span><span>of </span><span>the following organic acids: Citric acid, Oxalic acid, Formic acid, Acetic acid, Propionic acid, Tartaric acid, Succinic acid, Fumaric acid, Malic acid, Glutamic acid, besides the free organic acid nutrient solution as a control. Results revealed that the interaction between 5.0 ppm Fe and 50 ppm K was the best interaction treatment for increasing biomass production and iron uptake of maize and pea seedlings under applied condition. Furthermore, exogenous application of organic acids improves uptake and translocation of nutrient such as iron, potassium and phosphorus by the maize and pea plants. In conclusion, potassium nutrition and exogenous organic acids have the potential to stimulate Fe-uptake of monocot and dicot plants and mediate iron-biofortified crops.</span>展开更多
The Soil and Water Assessment Tool(SWAT) has been widely used throughout the world to model crop growth and nutrient uptake in various types of soils.A greenhouse experiment was performed to validate the process equat...The Soil and Water Assessment Tool(SWAT) has been widely used throughout the world to model crop growth and nutrient uptake in various types of soils.A greenhouse experiment was performed to validate the process equations embedded in SWAT for describing the growth and nutrient uptake of tomatoes in south Florida.The scaled growth curve of greenhouse-grown tomatoes was in close agreement with the theoretical model for field conditions,with the scaling factors being the maximum canopy height and the potential heat units.Similarly,the scaled leaf area index(LAI) growth curve and the scaled root depth curve for greenhousegrown tomatoes agreed with the SWAT functions,with the scaling factors being the maximum LAI and maximum root depth.The greenhouse experiment confirmed that the growth of biomass is a linear function of the intercepted photosynthetically active radiation.The fractions of nutrients in the plant biomass under greenhouse conditions were found to be on the order of 60% of those fractions observed in the field.Values of the initial P distribution(0.2 mg kg -1),initial ratio of mineral stable P to mineral active P(50:1),and initial ratio of humic N to humic P(2.4:1) were determined from soil measurements and can be used for field simulations.The conventional saturation-excess model for soil-water percolation was used to predict the movement of water in the top 10 cm of the greenhouse containers and the results agreed well with measurements.展开更多
Background:Florida’s Everglades is a vast freshwater peatland that has been impacted by the alterations of hydrological pattern and water quality which led to changes in plant species composition and biodiversity.In ...Background:Florida’s Everglades is a vast freshwater peatland that has been impacted by the alterations of hydrological pattern and water quality which led to changes in plant species composition and biodiversity.In this study,carbon and nitrogen stable isotopes(δ13C andδ15N)in cattail(Typha domingensis)are evaluated as indicators of environmental changes in the Everglades wetlands along nutrient and hydrological gradients represented by reference sites with total phosphorus(TP)<10μg L−1,transition sites with TP≥10μg L−1<20μg L−1 and impacted sites with TP≥20μg L−1 which differed in hydrology or habitats(marsh and canal).Results:Cattailδ13C values decreased significantly from reference(–24.1‰),transition(–26.8‰)to the impacted sites(–28.2‰).In contrast,δ15N values increased significantly from reference(–5.2‰),transition(2.4‰)to the impacted site(5.9‰).In response to a poor hydrological condition,cattail in marsh area displayed 13C enrichment(–26.0‰)and 15N depletion(0.2‰).By contrast,cattail grown in the canal sites with favorable hydropattern displayed 13C depletion(–27.6‰)and 15N enrichment(5.9‰)from the canal sites with more favorable hydrological condition.Conclusions:The different patterns for the changes inδ13C andδ15N in cattail suggested that increased nutrients led to increased stomatal conductance and 13C fractionation during carbon uptake and decreased 15N fractionation with increasing nitrogen demand while poor hydrological condition coupled with low nutrients led to reduced plant growth indicated by higherδ13C and lowerδ15N values.Findings from this study suggested thatδ13C in emerged macrophytes such as cattail can be used as an indicator for environmental stress whileδ15N is a robust indicator for wetland eutrophication.展开更多
Essential plant nutrients contained in residues and wastes generated during biofuel processing can be recovered for further production of bioenergy biomass. The objective of this study was to determine the relative ag...Essential plant nutrients contained in residues and wastes generated during biofuel processing can be recovered for further production of bioenergy biomass. The objective of this study was to determine the relative agronomic efficiency of “processed” biofuel residual (PBR). Liquid biofuel residual was “processed” by precipitating phosphate and ammonium in the residual with magnesium into a struvite-like material. Then, in a series of greenhouse experiments, we evaluated the fertility potential of PBR, using sweet sorghum (Sorghum bicolor (L.) Moench), as a test bioenergy crop. We compared the agronomic effectiveness of PBR to inorganic commercial fertilizers, biosolids, and poultry manure as nutrient sources. The sources were either applied alone or in combination with supplemental essential plant nutrients (S, K, Mg, and micronutrients). In each of the greenhouse experiments, the crop was grown for 12 wk on soil of minimal native fertility. After each harvest, sufficient water was applied to the soil in each pot over a 6-wk period to yield ~2 L (~one pore volume) of leachate to assess potential total N and soluble reactive phosphorus (SRP) losses. Dry matter yields from the PBR treatment applied alone were significantly greater than yields from inorganic fertilizers, biosolids, and poultry manure treatments applied alone, and similar to yields obtained when the supplemental essential plant nutrients were added to the inorganic fertilizer, biosolids, and manure treatments. Leachate N and SRP concentrations from the PBR treatment were significantly lower than in the treatments with inorganic fertilizers, poultry manure, and biosolids. We conclude that PBR can substitute for inorganic fertilizers and other organic sources of plant nutrients to produce bioenergy biomass cheaply, without causing offsite N and P losses in vulnerable soils.展开更多
Overabundance of phosphorus (P) in soils and water is of great concern and has received much attention in Florida, USA. Therefore, it is essential to analyze and predict the distribution of P in soils across large are...Overabundance of phosphorus (P) in soils and water is of great concern and has received much attention in Florida, USA. Therefore, it is essential to analyze and predict the distribution of P in soils across large areas. This study was undertaken to model the variation of soil total phosphorus (TP) in Florida. A total of 448 soil samples were collected from different soil types. Soil samples were analyzed by chemical reference method and scanned in the visible/near-infrared (VNIR) region of 350-2 500 nm. Partial least squares regression (PLSR) calibration model was developed between chemical reference values and VNIR values. The coefficient of determination (R2) and the root mean squares error (RMSE) of calibration and validation sets, and the residual prediction deviation (RPD) were used to evaluate the models. The R2in calibration and validation for log-transformed TP (log TP) were 0.69 and 0.65, respectively, indicating that VNIR calibration obtained in this study accounted for at least 65% of the variance in log TP using only VNIR spectra, and the high RPD of 2.82 obtained suggested that the spectral model derived in this study was suitable and robust to predict TP in a wide range of soil types, being representative of Florida soil conditions.展开更多
Dear Editor,The increased demand for economic and environmental benefits with the application of controlled release fertilizers(CRFs)has prompted the need for simple and viable prediction of controlled nitrogen releas...Dear Editor,The increased demand for economic and environmental benefits with the application of controlled release fertilizers(CRFs)has prompted the need for simple and viable prediction of controlled nitrogen release(CNR).Sigmoid pattern CRFs(SCRFs)has different release mechanisms and coating processes from parabolic pattern CRFs(PCRFs).The CNR rate of an SCRF can be very slow at low temperatures;much more time is needed to release the same quantity of nutrients as conventional fertilizers.However,the opposite is展开更多
Background:Evaluation of carbon(C),nitrogen(N),and phosphorus(P)ratios in aquatic and terrestrial ecosystems can advance our understanding of biological processes,nutrient cycling,and the fate of organic matter(OM)in ...Background:Evaluation of carbon(C),nitrogen(N),and phosphorus(P)ratios in aquatic and terrestrial ecosystems can advance our understanding of biological processes,nutrient cycling,and the fate of organic matter(OM)in these ecosystems.Eutrophication of aquatic ecosystems can change the accumulation and decomposition of OM which can alter biogeochemical cycling and alter the base of the aquatic food web.This study investigated nutrient stoichiometry within and among wetland ecosystem compartments(i.e.,water column,flocculent,soil,and aboveground vegetation biomass)of two subtropical treatment wetlands with distinct vegetation communities.Two flow-ways(FWs)within the network of Everglades Stormwater Treatment Areas in south Florida(USA)were selected for this study.We evaluated nutrient stoichiometry of these to understand biogeochemical cycling and controls of nutrient removal in a treatment wetland within an ecological stoichiometry context.Results:This study demonstrates that C,N,and P stoichiometry can be highly variable among ecosystem compartments and between FWs.Power law slopes of C,N,and P within surface water floc,soil,and vegetation were significantly different between and along FWs.Conclusions:Assessment of wetland nutrient stoichiometry between and within ecosystem compartments suggests unconstrained stoichiometry related to P that conforms with the notion of P limitation in the ecosystem.Differences in N:P ratios between floc and soil suggest different pathways of organic nutrient accumulation and retention between FWs.Surface nutrient stoichiometry was highly variable and decoupled(or close to decoupled as indicated by<25%explained variation between parameters),in particular with respect to P.We hypothesize that decoupling may be the imprint of variability in inflow nutrient stoichiometry.However,despite active biogeochemical cycles that could act to restore nutrient stoichiometry along the FW,there was little evidence that such balancing occurred,as the degree of stochiometric decoupling in the water column did change with distance downstream.This information is only the beginning of a larger journey to understand stoichiometric processes within wetland ecosystems and how they relate to ecosystem function.展开更多
基金Project supported by the United States Department of Agriculture through the "Nutrient Science for Improved Watershed Management" program (No.2002-00501)
文摘Mapping the spatial distribution of soil nitrate-nitrogen (NO3-N) is important to guide nitrogen application as well as to assess environmental risk of NO3-N leaching into the groundwater. We employed univariate and hybrid geostatistical methods to map the spatial distribution of soil NO3-N across a landscape in northeast Florida. Soil samples were collected from four depth increments (0-30, 30-60, 60-120 and 120-180 cm) from 147 sampling locations identified using a stratified random and nested sampling design based on soil, land use and elevation strata. Soil NO3-N distributions in the top two layers were spatially autocorrelated and mapped using lognormal kriging. Environmental correlation models for NO3-N prediction were derived using linear and non-linear regression methods, and employed to develop NO3-N trend maps. Land use and its related variables derived from satellite imagery were identified as important variables to predict NO3-N using environmental correlation models. While lognormal kriging produced smoothly varying maps, trend maps derived from environmental correlation models generated spatially heterogeneous maps. Trend maps were combined with ordinary kriging predictions of trend model residuals to develop regression kriging prediction maps, which gave the best NO3-N predictions. As land use and remotely sensed data are readily available and have much finer spatial resolution compared to field sampled soils, our findings suggested the e?cacy of environmental correlation models based on land use and remotely sensed data for landscape scale mapping of soil NO3-N. The methodologies implemented are transferable for mapping of soil NO3-N in other landscapes.
基金supported by the National Natural Science Foundation of China (No. 20777040)the Hi-TechResearch and Development Program (863) of China (No.2007AA061201).
文摘Under the indoor simulant conditions, toxic effects of crude-oil-contaminated soil which was put into aquatic environment on the young fishes Carassius auratus and their hepatic antioxidant system after a 20-d exposure were investigated. Results showed that the relationship between the mortality of C. auratus and the exposed doses could be divided into 3 phases: fishes exposed to the low dose groups (0.5-5.0 g/L) were dead due to the ingestion of crude-oil-contaminated soils in aquatic environment; at the medium dose groups (5.0-25.0 g/L) fishes were dead due to the penetration of toxic substances; at the high dose groups (25.0-50.0 g/L) fishes were dead due to environmental stress. The highest mortality and death speed were found in the 1.0 g/L dose group, and the death speed was sharply increased in the 50.0 g/L dose group in the late phase of exposure. The activities of superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST) and the content of malaondialdehyde (MDA) in the hepatic tissues of C. auratus were induced significantly. The activity of SOD was increased and then decreased. It was significantly inhibited in the 50.0 g/L dose group. The activity of CAT was highly induced, and restored to a level which is little more than the control when the exposed doses exceeded 10.0 g/L. The activity of GST was the most sensitive, it was significantly induced in all dose groups, and the highest elevation was up to 6 times in the 0.5 g/L dose group comparing with the control. The MDA content was significantly elevated in the 50.0 g/L dose group, and the changes of the MDA content were opposite with the changes of GST activity.
基金Supported by the National Natural Science Foundation of China(No.31170436)the Science and Technology Project of Guangdong Province(No.2013B080500022)
文摘Dajingshan,Fenghuangshan and Meixi reservoirs are located in Zhuhai,a coastal city in southern China,and they function to supply drinking water to Zhuhai and Macao.For eff ectively supplying waster,they are hydrologically connected and Dajingshan Reservoir first receives the water pumped from the river at Guangchang Pumping Station,and then feeds Fenghuangshan Reservoir,and the two well-connected reservoirs are mesotrophic.Meixi Reservoir is a small and oligotrophic water body and feeds Dajingshan Reservoir only in wet seasons when overfl ow occurs.Particulate organic matter(POM)was collected from three hydrologically connected water supply reservoirs,and seasonal variations of POM were ascertained from stable carbon and nitrogen isotopes in wet and dry seasons,and the ef fects of pumping water and reservoir connectivity on POM variations and composition were demonstrated by the relationships of the stable isotope ratios of POM.Seasonality and similarity of stable carbon and nitrogen isotopes of POM varied with hydrodynamics,connectivity and trophic states of the four studied water bodies.The two wellconnected reservoirs displayed more similar seasonality for δ^(13)C_(POM) than those between the river station and the two reservoirs.However,the opposite seasonality appeared for δ^(15)N_(POM) between the above waters and indicates dif ferent processes aff ecting the stable carbon and nitrogen isotopes of POM.δ^(13)C_(POM) and δ^(15)N_(POM) changed little between wet and dry seasons in Meixi Reservoir-a low productive and rain-driven system,suggesting little POM response to environmental changes in that water system.As expected,connectivity enhanced the similarity of the stable isotope ratios of POM between the water bodies.
文摘Twenty-six soil samples were collected from five soil profiles at different climatological and ecological regions in central Sudan. Soil profile was dug in each studied area and morphological profile description was carried out for different horizons. All samples were analyzed using two different methods to determine Cation Exchange Capacity (CEC) and exchangeable sodium percentage (ESP). Statistical analysis (T-test) was used in order to investigate the differences between soil samples for the studied locations. Significant differences appeared when compared the two methods for CEC determination at Gedaref area, Wad Medani and Nile flood plain and that appeared in evaluation of ESP at Nile flood plain and Shambat area. The results also revealed that, the developed method used in this study was more practical, simple and reliable for determination of CEC and ESP as the currently used in most soil laboratories. In addition, it will be safer than the other methods in some problematic soils. The adoption of this developed method is advisable because it is less time consuming as it omits the washing step. In contrast, the old method cannot be a good substitute in laboratories which have no possibility to determine sodium by using flame photometer. We conclude that when the developed method is used to determine CEC and ESP time will be saved, that fewer amounts of chemicals will be used and that accurate results will be achieved.
文摘Despite the CaCO<sub>3</sub> estimation using titration method was not reliable, but up to the present time, some soil laboratories in Sudan still used this method. The objective of this study was to compare and assess the results of calcimetric and titrimetric methods of quantitative estimation for soil calcium carbonate of different soils in Sudan. 26 soil samples from five soil profiles were collected from different climatological and ecological regions in central Sudan. CaCO<sub>3</sub> equivalent was estimated using calcimeter and titration methods in order to find accurate, rapid and suitable method for soils of Sudan. The results revealed that there are no significant differences between calcimeter and titration methods for calcium carbonate estimation in all studied samples except in samples from Gedaref area. We concluded that when the Calcimeter method used for CaCO<sub>3</sub> estimation, the differences between one person and another in detecting titration end point would be avoided, rapid and accurate results would be obtained compared to titration method. Additionally, time would be saved;fewer amounts of chemicals would be used. From this study, we highly recommend using calcimeter method for CaCO<sub>3</sub> estimation for soils of Sudan.
文摘Biochar is a carbon-rich(】60%)organic material derived from incomplete combustion of fossil fuels and biomass.It consists of a continuum ranging from slightly charred material through char and charcoal to soot,and is ubiquitous in the atmosphere,marine sediment,soil and water.Moreover,】80%of biochar produced ends up in soils,where it resides for hundreds to thousands of years.Because of its resistance to biological and chemical breakdown, biochar can serve as a pool of C with long residence time in the soil.As a result,there has been increasing attention given to the potential of biochar to sequestrate carbon and counteract
文摘<p align="justify"> <span style="font-family:Verdana;">Soil salinity is one of the major yield-limiting factors for crop production in many agricultural regions all over the world. Besides following efficient management practices at the field scale to reduce accumulation of salts in the effective root-zone, the effective use of treatments to alleviate the effects of salinity stress and improve crop salt tolerance is a promising solution to ensure crop production in such adverse conditions. A field experiment was carried out to investigate the effect of foliar spray with plant-based biostimulant (<i>i.e.</i> with and/or without 3% yeast extract), three levels of proline (0, 25, and 50 mM), and combined with potassium fertilizers, as potassium sulfate, 48% K<sub>2</sub>O (0, 50, and 100 kg/fed.) on growth promotion, chemical composition of garlic leaves, bulb quality parameters as well as yield and its components of garlic plant grown under moderate saline soil. Results revealed that the interaction between foliar spray with yeast extract at 3% and proline at 50 mM combined with proper K level at 100 kg/fed., was the best interaction treatment for increasing vegetative growth parameters, <i>i.e.</i> plant height, number of leaves per plant, and mineral contents (N, P, K, S, Ca and Mg in leaves), and proline content of garlic leaves after 135 days from planting time, total yield/fed., and garlic yield quality parameters at harvesting time. In conclusion, the detrimental effects of salinity stress can be alleviated by stress tolerance-inducing compounds, such as yeast extract and proline with proper application rate of K fertilization during the growing season of garlic crop.</span> </p>
文摘Iron (Fe) is a vital element for the survival and proliferation of all plants;therefore, Fe-biofortification by the application of chemical and organic fertilizers is being as an effective approach to fight hidden hunger retards the growth and development of crop plants. Two experiments were carried out to investigate the effect of potassium and exogenous organic acids on iron uptake by two different plants<span>:</span><span> one is monocotyledon</span><span>,</span><span><span> maize (<i></i></span><i><i><span>Zea mays</span></i><span></span></i> L.) and the second is dicotolydon pea (<i></i></span><i><i><span>Pisum sativum</span></i></i><span> L.) grown under controlled conditions. The seedlings were grown in sand culture in a greenhouse experiment and irrigated with one-tenth strength modified nutrient solution of Hoagland and Arnon as a base solution (pH 7.5), containing different iron treatments (0, 1, and 5 ppm as FeSO</span><sub>4</sub>·<span>7H</span><sub><span>2</span></sub><span>O) combined with potassium nutrition (0, 5, 10, and 50 ppm as K</span><sub><span>2</span></sub><span>SO</span><sub><span>4</span></sub><span>). After 30 days, the best interaction treatment was selected for further experiment including 5.0 ppm Fe as FeSO</span><sub>4</sub><sup>.</sup><span>7H</span><sub><span>2</span></sub><span>O and 50 ppm K as K</span><sub><span>2</span></sub><span>SO</span><sub><span>4</span></sub><span> in combination with 1</span><span> </span><span>×</span><span> </span><span><span>10<sup>-</sup></span><sup><span>5</span></sup><span> mole/liter of one </span></span><span>of </span><span>the following organic acids: Citric acid, Oxalic acid, Formic acid, Acetic acid, Propionic acid, Tartaric acid, Succinic acid, Fumaric acid, Malic acid, Glutamic acid, besides the free organic acid nutrient solution as a control. Results revealed that the interaction between 5.0 ppm Fe and 50 ppm K was the best interaction treatment for increasing biomass production and iron uptake of maize and pea seedlings under applied condition. Furthermore, exogenous application of organic acids improves uptake and translocation of nutrient such as iron, potassium and phosphorus by the maize and pea plants. In conclusion, potassium nutrition and exogenous organic acids have the potential to stimulate Fe-uptake of monocot and dicot plants and mediate iron-biofortified crops.</span>
文摘The Soil and Water Assessment Tool(SWAT) has been widely used throughout the world to model crop growth and nutrient uptake in various types of soils.A greenhouse experiment was performed to validate the process equations embedded in SWAT for describing the growth and nutrient uptake of tomatoes in south Florida.The scaled growth curve of greenhouse-grown tomatoes was in close agreement with the theoretical model for field conditions,with the scaling factors being the maximum canopy height and the potential heat units.Similarly,the scaled leaf area index(LAI) growth curve and the scaled root depth curve for greenhousegrown tomatoes agreed with the SWAT functions,with the scaling factors being the maximum LAI and maximum root depth.The greenhouse experiment confirmed that the growth of biomass is a linear function of the intercepted photosynthetically active radiation.The fractions of nutrients in the plant biomass under greenhouse conditions were found to be on the order of 60% of those fractions observed in the field.Values of the initial P distribution(0.2 mg kg -1),initial ratio of mineral stable P to mineral active P(50:1),and initial ratio of humic N to humic P(2.4:1) were determined from soil measurements and can be used for field simulations.The conventional saturation-excess model for soil-water percolation was used to predict the movement of water in the top 10 cm of the greenhouse containers and the results agreed well with measurements.
基金from an Overseas Research collaboration grant(2018AHB020)funded by Hubei Province,China.
文摘Background:Florida’s Everglades is a vast freshwater peatland that has been impacted by the alterations of hydrological pattern and water quality which led to changes in plant species composition and biodiversity.In this study,carbon and nitrogen stable isotopes(δ13C andδ15N)in cattail(Typha domingensis)are evaluated as indicators of environmental changes in the Everglades wetlands along nutrient and hydrological gradients represented by reference sites with total phosphorus(TP)<10μg L−1,transition sites with TP≥10μg L−1<20μg L−1 and impacted sites with TP≥20μg L−1 which differed in hydrology or habitats(marsh and canal).Results:Cattailδ13C values decreased significantly from reference(–24.1‰),transition(–26.8‰)to the impacted sites(–28.2‰).In contrast,δ15N values increased significantly from reference(–5.2‰),transition(2.4‰)to the impacted site(5.9‰).In response to a poor hydrological condition,cattail in marsh area displayed 13C enrichment(–26.0‰)and 15N depletion(0.2‰).By contrast,cattail grown in the canal sites with favorable hydropattern displayed 13C depletion(–27.6‰)and 15N enrichment(5.9‰)from the canal sites with more favorable hydrological condition.Conclusions:The different patterns for the changes inδ13C andδ15N in cattail suggested that increased nutrients led to increased stomatal conductance and 13C fractionation during carbon uptake and decreased 15N fractionation with increasing nitrogen demand while poor hydrological condition coupled with low nutrients led to reduced plant growth indicated by higherδ13C and lowerδ15N values.Findings from this study suggested thatδ13C in emerged macrophytes such as cattail can be used as an indicator for environmental stress whileδ15N is a robust indicator for wetland eutrophication.
文摘Essential plant nutrients contained in residues and wastes generated during biofuel processing can be recovered for further production of bioenergy biomass. The objective of this study was to determine the relative agronomic efficiency of “processed” biofuel residual (PBR). Liquid biofuel residual was “processed” by precipitating phosphate and ammonium in the residual with magnesium into a struvite-like material. Then, in a series of greenhouse experiments, we evaluated the fertility potential of PBR, using sweet sorghum (Sorghum bicolor (L.) Moench), as a test bioenergy crop. We compared the agronomic effectiveness of PBR to inorganic commercial fertilizers, biosolids, and poultry manure as nutrient sources. The sources were either applied alone or in combination with supplemental essential plant nutrients (S, K, Mg, and micronutrients). In each of the greenhouse experiments, the crop was grown for 12 wk on soil of minimal native fertility. After each harvest, sufficient water was applied to the soil in each pot over a 6-wk period to yield ~2 L (~one pore volume) of leachate to assess potential total N and soluble reactive phosphorus (SRP) losses. Dry matter yields from the PBR treatment applied alone were significantly greater than yields from inorganic fertilizers, biosolids, and poultry manure treatments applied alone, and similar to yields obtained when the supplemental essential plant nutrients were added to the inorganic fertilizer, biosolids, and manure treatments. Leachate N and SRP concentrations from the PBR treatment were significantly lower than in the treatments with inorganic fertilizers, poultry manure, and biosolids. We conclude that PBR can substitute for inorganic fertilizers and other organic sources of plant nutrients to produce bioenergy biomass cheaply, without causing offsite N and P losses in vulnerable soils.
基金Supported by the National Natural Science Foundation of China (No. 41071159)the Cooperative Ecosystem Studies UnitNational Resources Conservation Service (NRCS), USA
文摘Overabundance of phosphorus (P) in soils and water is of great concern and has received much attention in Florida, USA. Therefore, it is essential to analyze and predict the distribution of P in soils across large areas. This study was undertaken to model the variation of soil total phosphorus (TP) in Florida. A total of 448 soil samples were collected from different soil types. Soil samples were analyzed by chemical reference method and scanned in the visible/near-infrared (VNIR) region of 350-2 500 nm. Partial least squares regression (PLSR) calibration model was developed between chemical reference values and VNIR values. The coefficient of determination (R2) and the root mean squares error (RMSE) of calibration and validation sets, and the residual prediction deviation (RPD) were used to evaluate the models. The R2in calibration and validation for log-transformed TP (log TP) were 0.69 and 0.65, respectively, indicating that VNIR calibration obtained in this study accounted for at least 65% of the variance in log TP using only VNIR spectra, and the high RPD of 2.82 obtained suggested that the spectral model derived in this study was suitable and robust to predict TP in a wide range of soil types, being representative of Florida soil conditions.
基金supported by the National Key Research and Development Program of China(2017YFD0800604)the National Natural Science Foundation of China(31301847,31301846) for financial support
文摘Dear Editor,The increased demand for economic and environmental benefits with the application of controlled release fertilizers(CRFs)has prompted the need for simple and viable prediction of controlled nitrogen release(CNR).Sigmoid pattern CRFs(SCRFs)has different release mechanisms and coating processes from parabolic pattern CRFs(PCRFs).The CNR rate of an SCRF can be very slow at low temperatures;much more time is needed to release the same quantity of nutrients as conventional fertilizers.However,the opposite is
基金sample collection and analysis was provided by the South Florida Water Management District(Contract#4600003031).
文摘Background:Evaluation of carbon(C),nitrogen(N),and phosphorus(P)ratios in aquatic and terrestrial ecosystems can advance our understanding of biological processes,nutrient cycling,and the fate of organic matter(OM)in these ecosystems.Eutrophication of aquatic ecosystems can change the accumulation and decomposition of OM which can alter biogeochemical cycling and alter the base of the aquatic food web.This study investigated nutrient stoichiometry within and among wetland ecosystem compartments(i.e.,water column,flocculent,soil,and aboveground vegetation biomass)of two subtropical treatment wetlands with distinct vegetation communities.Two flow-ways(FWs)within the network of Everglades Stormwater Treatment Areas in south Florida(USA)were selected for this study.We evaluated nutrient stoichiometry of these to understand biogeochemical cycling and controls of nutrient removal in a treatment wetland within an ecological stoichiometry context.Results:This study demonstrates that C,N,and P stoichiometry can be highly variable among ecosystem compartments and between FWs.Power law slopes of C,N,and P within surface water floc,soil,and vegetation were significantly different between and along FWs.Conclusions:Assessment of wetland nutrient stoichiometry between and within ecosystem compartments suggests unconstrained stoichiometry related to P that conforms with the notion of P limitation in the ecosystem.Differences in N:P ratios between floc and soil suggest different pathways of organic nutrient accumulation and retention between FWs.Surface nutrient stoichiometry was highly variable and decoupled(or close to decoupled as indicated by<25%explained variation between parameters),in particular with respect to P.We hypothesize that decoupling may be the imprint of variability in inflow nutrient stoichiometry.However,despite active biogeochemical cycles that could act to restore nutrient stoichiometry along the FW,there was little evidence that such balancing occurred,as the degree of stochiometric decoupling in the water column did change with distance downstream.This information is only the beginning of a larger journey to understand stoichiometric processes within wetland ecosystems and how they relate to ecosystem function.
