Showing papers in "Soil Science in 2010"
TL;DR: In this article, switchgrass (Panicum virgatum) and nonactivated recalcitrant pecan biochar was used to increase soil carbon content in the southeastern US Coastal Plain.
Abstract: Because the southeastern US Coastal Plain has high temperatures and abundant rainfall, its sandy soils have poor physical characteristics and low carbon (C) contents. To increase soil C, we added switchgrass (Panicum virgatum) and nonactivated recalcitrant pecan biochar. Biochar was develope
257 citations
TL;DR: The chemical interaction between soil organic matter and the orthophosphate anion (phosphate [P]) is important for reactions of P at the soil solid phase, in soil solution, and in natural waters.
Abstract: The chemical interaction between soil organic matter and the orthophosphate anion (phosphate [P]) is important for reactions of P at the soil solid phase, in soil solution, and in natural waters. Humic substances account for an important or dominant part of soil organic matter and of dissolv
196 citations
TL;DR: In this paper, an in situ field study was conducted during the summer and winter months to evaluate microbiological properties of three soil types that have evolved be the cause of different landscape positions in an agricultural field.
Abstract: Manure applications can benefit crop productivity by adding required nutrients and organic matter to soil. There is a paucity of infor mation on how soil microbial community dynamics will be altered by the application of manure to different landscape positions. Thus, an in situ field study was conducted during the summer and winter months to eval uate microbiological properties of three soil types that have evolved be cause of different landscape positions in an agricultural field. The three Coastal Plain soils investigated were Bama (sandy loam), Lynchburg (loam), and Goldsboro (loam) representing the landscape position of a summit, drainageway, and sideslope, respectively. Composted dairy manure was incorporated into in situ soil cores at a rate of 350 kg N ha j1 and com pared with unamended controls. Soil microbial biomass N and dehydro genase enzyme activity were determined to evaluate changes in the microbial biomass size and activity, whereas phospholipid fatty acid analy sis was used as an indicator of the microbial community structure. Ad dition of composted dairy manure increased microbial activity and N immobilization, representing a shift in microbial response resulting from changes in substrate availability. This was most evident during summer months, with the composted dairy manure increasing dehydrogenase en zyme activity 21% and microbial activity 20% compared with without manure, suggesting that seasonal timing of application will influence mi crobial activity. Microbial properties were also impacted by landscape position. The drainageway landscape position soil, a loam, had the highest microbial biomass and microbial activity. Changes in microbial commu nity structure using phospholipid fatty acid profiles were evaluated with canonical discriminate analysis. This analysis indicated that a shift in microbial community structure occurred between season, manure appli cation, and landscape position. Findings from this study suggest that changes in soil variability from landscape positions and season can impact the growth and dynamics of the microbial community when manure is applied to agricultural fields.
88 citations
TL;DR: An 8-year cover crop study was conducted in southern Illinois to evaluate the effects of conservation tillage systems on corn and soybean yields and for the maintenance and restoration of soil organic carbon (SOC) and soil productivity of previously eroded soils.
Abstract: An 8-year cover crop study was conducted in southern Illinois to evaluate the effects of conservation tillage systems on corn and soybean yields and for the maintenance and restoration of soil organic carbon (SOC) and soil productivity of previously eroded soils. In 2001, the no-till (NT), c
70 citations
TL;DR: In this paper, the temporal changes in soil physical and chemical properties were determined after conversion of native desert soils to irrigated croplands in a marginal oasis of the arid region, northwest China.
Abstract: Assessment of soil quality and its direction of change with time is a primary indicator of sustainable agricultural land management. In this study, the temporal changes in soil physical and chemical properties were determined after conversion of native desert soils to irrigated croplands in a marginal oasis of the arid region, northwest China. Soil samples were collected from seven closely located farm fields that had been cultivated for 3, 5, 10, 14, 23, 30, and 40 years after agricultural cultivation, from adjacent remnant uncultivated sandy land (0 year), and from farm fields in an old oasis cultivated for more than 50 years. All the soils in the study were Psamments that derived from the deposition of aeolian sand. After cultivation, significant changes in particle size distribution and aggregate size distribution and stability in the 0- to 20-cm surface soil only occurred in soils cultivated for more than 10 years, showing a consistently increasing pattern with increasing duration of cultivation. The result indicated that soil did not contain enough coarse aggregates to control wind erosion, suggesting the need to maintain residues on the soil surface to aid wind erosion control for these newly cultivated sandy soils. As cultivation time increased, soil organic carbon (SOC), total and available N and P, cation exchange capacity, and CaCO3 concentrations all increased. Soil organic carbon and total N concentrations increased by 6.4 times and 5.9 times, respectively, after 40 years of continuous cropping. The increased silt and clay content caused by irrigation with silt-laden river water plays an important role in the aggregate formation and SOC and nutrient accumulation and retention. The results also indicated that the evolution of desert soil toward the sustainable agricultural soil requires at least 50 years. The absolute amounts of soil aggregate, SOC, and nutrients are still low after 40 years of cropping and were insufficient to support sustaining crop production. Therefore, improved land management such as conservation tillage and crop and grass rotation is imperative to accelerate soil structure and fertility improvement and maintain long-term productivity of the farmlands.
61 citations
TL;DR: In this article, anion adsorption on the aluminum oxide, gibbsite, was investigated as a function of solution pH (3 − 11) and equilibrium solution Mo (3.13, 31.3, or 313 μmol/L), P (96.9 μmol /L), or S (156 μmol)/L) concentration.
Abstract: Anion adsorption on the aluminum oxide, gibbsite, was investigated as a function of solution pH (3―11) and equilibrium solution Mo (3.13, 31.3, or 313 μmol/L), P (96.9 μmol/L), or S (156 μmol/L) concentration. Adsorption of all three anions decreased with increasing pH. Electrophoretic mobility measurements indicated a downward shift in point of zero charge, indicative of an inner-sphere adsorption mechanism for all three anions. The constant capacitance model, having an inner-sphere adsorption mechanism, was able to describe Mo and P adsorption; whereas the triple-layer model with an outer-sphere adsorption mechanism was used to describe S adsorption. Competitive adsorption experiments showed a reduction of Mo adsorption at a Mo/P ratio of 1:30 and 1:300 but no reduction at a Mo/S ratio of 1 :52 and 1:520. These concentrations are realistic of natural systems where Mo is found in much lesser concentrations than P or S. Using surface complexation constants from single-ion systems, the triple-layer model predicted that even elevated S concentrations did not affect Mo adsorption. The constant capacitance model was able to predict the competitive effect of P on Mo adsorption semiquantitatively.
47 citations
TL;DR: In this article, the amount and rates of soil organic carbon storage and retention as a result of a conversion to no-till (NT) or chisel plow (CP) tillage systems were quantified.
Abstract: The objective of this 20-year tillage study was to quantify the amount and rates of soil organic carbon (SOC) storage and retention as a result of a conversion to no-till (NT) or chisel plow (CP) tillage systems using the comparison method with moldboard plow (MP) tillage SOC data as baselin
46 citations
TL;DR: Qualitative and quantitative changes of soil microbial communities in response to sustainable agricultural practices that stimulate soil microorganism activity and improve olive yield and fruit quality are revealed.
Abstract: The aim of the present work was to evaluate the effects of two soil management systems so called sustainable treatment (ST) and conventional treatment (CT) on the composition and on genetic, functional, and metabolic diversity of soil microbial communities in a Mediterranean olive orchard. The ST system included no-tillage, integrated chemical fertilization, and organic matter inputs from drip irrigation, spontaneous cover crops, and pruning material. Microbial analyses were carried out by an integrated approach of culture-dependent (microbial cultures and Biolog) and culture-independent methods (denaturing gradient gel electrophoresis [DGGE]). After 7 years of treatment, average olive yield was 8.4 and 3.1 t ha−1 year−1 in ST and CT, respectively. Conventional treatment had a significantly higher number of total culturable bacteria and actinomycetes compared with ST, whereas fungi were significantly lower. In ST, the number of ammonifying bacteria, proteolytic bacteria, and Azotobacter in the wetted areas under the drippers (ST-WET) was significantly higher than along interrows (ST-INTER). The DGGE analysis of microbial 16S/18S rDNA showed differences between ST and CT, whereas 16S/18S rRNA DGGE bands of ST-WET clustered differently from those of CT and ST-INTER. Some Biolog metabolic indexes were significantly different between ST and CT. The results revealed qualitative and quantitative changes of soil microbial communities in response to sustainable agricultural practices that stimulate soil microorganism activity and improve olive yield and fruit quality.
42 citations
TL;DR: In this article, the bioavailability of applied P in those waste materials is directly dependent on the presence of specific P forms in the waste materials and the type of the P forms.
Abstract: Land application of biosolids and poultry litter can benefit crop production by providing phosphorus (P) and other nutrients and organic matter However, the bioavailability of applied P in those waste materials is directly dependent on the presence of specific P forms In this study, we com
41 citations
TL;DR: In this article, the authors characterized and quantified the soil physical environment as affected by long-term fertilizer experiment application in a maize-wheat system on sandy loam soils of India using a unified soil physical quality index (S).
Abstract: Soil physical environment as affected by long-term fertilizer experiment application in a maize-wheat system on sandy loam soils of India was characterized and quantified using a unified soil physical quality index (S). Treatments were 100% and 150% of recommended nitrogen, phosphorus, and p
37 citations
TL;DR: In this article, an individual-based soil organic matter model, INDISIM-SOM, is proposed to model the dynamics and evolution of carbon and nitrogen associated with organic matter in soils.
Abstract: The fate of soil carbon and nitrogen compounds in soils in response to climate change is currently the object of significant research. In particular, there is much interest in the development of a new generation of micro-scale models of soil ecosystems processes. Crucial to the elaboration of such models is the ability to describe the growth and metabolism of small numbers of individual microorganisms, distributed in a highly heterogeneous environment. In this context, the key objective of the research described in this article was to further develop an individual-based soil organic matter model, INDISIM-SOM, first proposed a few years ago, and to assess its performance with a broader experimental data set than previously considered. INDISIM-SOM models the dynamics and evolution of carbon and nitrogen associated with organic matter in soils. The model involves a number of state variables and parameters related to soil organic matter and microbial activity, including growth and decay of microbial biomass, temporal evolutions of easily hydrolysable N, mineral N in ammonium and nitrate, CO2 and O2. The present article concentrates on the biotic components of the model. Simulation results demonstrate that the model can be calibrated to provide good fit to experimental data from laboratory incubation experiments performed on three different types of Mediterranean soils. In addition, analysis of the sensitivity toward its biotic parameters shows that the model is far more sensitive to some parameters, i.e., the microbial maintenance energy and the probability of random microbial death, than to others. These results suggest that, in the future, research should focus on securing better measurements of these parameters, on environmental determinants of the switch from active to dormant states, and on the causes of random cell death in soil ecosystems.
TL;DR: In this paper, a batch kinetic experiments were carried out to evaluate sorption and desorption of Zn for soils having distinctly different properties and the influence of P on increased Zn sorption was clearly manifested in the isotherms where similar trends were observed for two acidic and neutral soils.
Abstract: Transport of heavy metals such as zinc in soils may be affected by several rate limiting processes including kinetic sorption and release. Batch kinetic experiments were carried out to evaluate sorption and desorption of Zn for soils having distinctly different properties. A second objective was to test the hypothesis that phosphate additions to soils increases zinc adsorption. Sorption isotherms exhibited strong nonlinearity as well as kinetic behavior. Distinct differences in the amount of Zn sorbed among the different soils where highest sorption was observed for the neutral Webster soil. In contrast Windsor and Olivier (acidic) soils exhibited lower sorption capacities where Windsor soil showed least sorption. The influence of P on increased Zn sorption was clearly manifested in the isotherms where similar trends were observed for the two acidic and neutral soils. Distinct discrepancies between adsorption and successive desorption isotherms indicate considerable hysteresis for Zn release the extent of which varied among the three soils. For the two acidic soils Zn released ranged from 50%∼60% of that sorbed whereas for the neutral soil only 10%∼15% of sorbed Zn was released over time.
TL;DR: In this paper, the sodium tetraphenylboron (NaBPh 4 ) method was modified and compared with the conventional ammonium acetate (NH 4 OAc) method to evaluate K availability to perennial ryegrass (Lolium perenne L.) in soils with different K fertilities.
Abstract: Finding a uniform method to evaluate plant-available potassium (K) in a variety of soils has been a challenge. In this study, the sodium tetraphenylboron (NaBPh 4 ) method was modified and compared with the conventional ammonium acetate (NH 4 OAc) method to evaluate K availability to perennial ryegrass (Lolium perenne L.) in soils with different K fertilities. The amount of K extracted using NaBPh 4 was influenced by extraction time and concentrations of NaCl and NaBPh 4 . Without NaCl, the NaBPh 4 method with low concentrations of NaBPh 4 (0.001 and 0.003 mol L -1 ) could only extract soluble and exchangeable soil K, equivalent to three sequential extractions using the NE 4 OAc method, whereas the NaBPh 4 method with a high NaBPh 4 concentration (0.2 mol L -1 ) could extract all the NH 4 OAc-extractable K and some easily released nonexchangeable K (NEK) in soils. Easily released NEK contributed significantly to K uptake by ryegrass. Soil K availability estimated using the 60-min (r 2 = 0.83-0.92) and 120-min (r 2 = 0.84-0.94) modified NaBPh 4 methods correlated well to the K removed by one to eight crops of ryegrass. The 60-min modified NaBPh 4 method without NaCl (0.2 mol L -1 NaBPh 4 + 0.01 mol L -1 EDTA) was suitable for evaluating K availability to plants in a variety of soils, whereas the NH 4 OAc method was only suitable for evaluating K availability in soils of the same type or with similar K-buffering capacities, but not in soils with variable K buffer capacities or in which the NEK contribution to plant K uptake varied.
TL;DR: In this paper, the effect of gypsum on the solubility of 13 nutrients and how amending the soil with organic peat moss may mitigate the impact of the accumulation in gypsiferous soils on nutrients and soil fertility.
Abstract: It is widely accepted that the accumulation of gypsum in gypsiferous soils results in very low fertility, even with application of fertilizers and organic amendments. The objectives were to investigate, in laboratory experiments, the effect of gypsum on the solubility of 13 nutrients and how amending the soil with organic peat moss may mitigate the impact of gypsum on nutrients and soil fertility. A 100-g sample of gypsum-free soil (Sharpsburg Fine, montmorillonitic, mesic Typic Argiudolls) was treated with increasing amounts of gypsum (0, 1, 5, 10, 15, 20, 30, and 50 g), then water was added to the mixtures to reach 50% of the water saturation capacity. Another set of soil/gypsum mixtures received 5-g peat to study the effect of peat application. All mixtures were incubated at 32 degrees C for 15 weeks. After incubation, the concentration of water-soluble nutrients was measured. In general, the addition of gypsum increased the solubility of N, K, Ca, Mg, Mn, Cl, and S, whereas it decreased the solubility of P, Na, Fe, Cu, Zn, and B. The application of peat increased the solubility of all nutrients investigated, except for N and S. Chemical reactions and mechanisms were applied to interpret the effects of both gypsum and peat treatments on nutrient solubility and their relationship to soil fertility and crop production. The application of peat improved the solubility of most nutrients and proved to be useful as an amendment for gypsum-rich soils and increases its productivity.
TL;DR: In this paper, the authors used a complex empirical function with three constants to generate the transformed soil moisture profile by treating the whole process as an optimization problem, and the required conditions are that the constants of the empirical function are computed so that the analytically computed sorptivity agrees with the experimental one.
Abstract: Diffusivity is one of the main soil hydraulic properties. It is a critical parameter for the prediction of water transport within the vadose zone. The aim of this research was to generate the soil moisture profile from very simple measurements such as sorptivity, distance of the wetting font in transformed coordinates, and initial and final water contents. The objective was to use a complex empirical function with three constants to generate the transformed soil moisture profile by treating the whole process as an optimization problem. The required conditions are that the constants of the empirical function are computed so that the analytically computed sorptivity agrees with the experimental one, and at the beginning and at the end of the transformed soil moisture profile, the water content is the final and the initial correspondingly. Once an analytic function for the transformed soil moisture profile is determined, then diffusivity is calculated analytically. As an added verification of the accuracy of the analytic diffusivity function produced by this method, diffusivity results were used as input in Philip's semianalytic method to verify that the transformed soil moisture profiles can be regenerated. Integral continuity is preserved throughout the process.
TL;DR: In this article, a citrus grove was divided into five productivity zones based on tree canopy volume, and six random soil samples were collected from each zone at depths of 0 to 15, 15 to 30, 30 to 45, and 45 to 60 cm.
Abstract: Spatial variability of citrus yield is very common in Florida, but very little has been done to identify the responsible soil factors. Our objective was to characterize variations in soil physical properties in sandy soils where citrus is produced in Florida. A citrus grove was divided into five productivity zones defined as "very poor," "poor," "medium," "good," and "very good" based on tree canopy volume. Six random soil samples were collected from each zone at depths of 0 to 15, 15 to 30, 30 to 45, and 45 to 60 cm. Samples were analyzed for soil color, particle size and sand size distribution, and water retention parameters. Although the coefficients of variation (1%-60%) were large for color, texture, and water retention, the values were generally higher in areas with large trees and vice versa. The trend was opposite for soil lightness and sand content, which were lower in areas of greater growth. Most of the soil properties had a large spatial variation with semivariogram range of 100 to 250 m and varied greatly with increased productivity. Differences between the productivity zones were even more prominent at greater soil depth. Characterization and quantification of spatial soil variability in citrus groves would assist in planning future soil sampling in new fields showing soil and/or tree growth variability. The selection of soil sampling sites should be based on the sampling interval suggested by the variogram range (<75 m) and include the depth (45-60 cm) influencing productivity.
TL;DR: In this article, the authors investigated the mobility of imidacloprid applied to soils with different properties, using a modified miscible displacement approach, where soil columns under soil water-saturated conditions and constant flow velocity were maintained.
Abstract: Knowledge of the transport patterns of chemicals applied to soils is essential for environmental assessment of potential leaching to groundwater supplies. In this study, the mobility of imidacloprid applied to soils with different properties was investigated. The approach used was that of a modified miscible displacement, where soil columns under soil water-saturated conditions and constant flow velocity were maintained. The extent of imidacloprid mobility was measured by quantifying the concentration in the effluent solution versus time. All measured breakthrough curves (BTC) exhibited extensive asymmetry with sharp adsorption fronts. Imidacloprid exhibited high mobility in a silty kaolinitic (Mahan) soil, where 69% of the applied chemical was recovered in the effluent solution. In contrast, somewhat limited mobility was observed for Mhoon soil, with a high organic matter content (3.5%), where only 27% of applied imidacloprid was recovered. All BTC exhibited extensive tailing during leaching of the applied imidacloprid, indicative of the time-dependent release reactions of the adsorbed imidacloprid. A decrease in effluent concentration in response to flow interruption was also observed, which indicated kinetic retention of imidacloprid in all soils examined. The use of a linear model (CXTFIT) to simulate measured BTC showed good overall predictions. Concentration maxima and peak arrival time were well predicted by CXTFIT, but the slow release of imidacloprid during leaching was underestimated. The use of a multireaction and transport model proved successful in describing imidacloprid BTC for all soils. Based on measured BTC results, imidacloprid may be considered as a moderately mobile chemical that is susceptible to leaching from the soil profile.
TL;DR: In this paper, the authors evaluated the effects of crop management (conservation and conventional) and atmospheric CO 2 (ambient and twice ambient) on a Decatur silt loam (clayey, kaolinitic, thermic Rhodic Paleudults).
Abstract: To evaluate the contribution of agriculture to climate change, the flux of greenhouse gases from different cropping systems must be assessed. Soil greenhouse gas flux (CO 2 , N 2 O, and CH 4 ) was assessed during the final growing season in a long-term (10-year) study evaluating the effects of crop management (conservation and conventional) and atmospheric CO 2 (ambient and twice ambient) on a Decatur silt loam (clayey, kaolinitic, thermic Rhodic Paleudults). Seasonal soil CO 2 flux was significantly greater under elevated (4.39 Mg CO 2 -C ha -1 ) versus ambient CO 2 (3.34 Mg CO 2 -C ha -1 ) and was generally greater in the conventional (4.19 Mg CO 2 -C ha -1 ) compared with the conservation (3.53 Mg CO 2 -C ha -1 ) system. Soil flux ofboth N 2 O (range, -1.5 to 53.4 g N 2 O-N ha -1 day -1 ) and CH 4 (range, -7.9 to 24.4 g CH 4 -C ha -1 day -1 ) were low throughout the study and rarely exhibited differences caused by treatments. Global warming potential (calculated based on flux of individual gases) was increased by elevated CO 2 (33.4%) and by conventional management (17.1%); these increases were driven primarily by soil CO 2 flux. As atmospheric CO 2 continues to rise, our results suggest adoption of conservation management systems represents a viable means of reducing agriculture's potential contribution to global climate change.
TL;DR: In this paper, the authors investigated how elemental S amendment affects S dynamics in EAA soils and concluded that large-scale S application in the Everglades Agricultural Area (EAA) soils is likely to increase SO42- concentra- tions in soils, which poses a potential risk of SO 4 2- export to sensitive Everglade wetlands.
Abstract: Nutrient export from the Everglades Agricultural Area (EAA) has been implicated in causing sulfur (S) enrichment of Ever glades wetlands. However, quantification of the S budget and transfor mations in EAA soils is inadequate. The objective of this study was to quantify various S fractions and investigate how elemental S amendment affects S dynamics in EAA soils. Reduced S compounds were not detected in soil before elemental S application. Organic S was the major form of S, comprising 87% of total S, followed by extractable SO4-S (13%). Extractable SO4-S for soils receiving 448 kg S ha-1 was 36%, 131%, 201%, and 270% higher than for unamended soils at 2, 6, 9, and 13 months, respectively. Elemental S was significantly higher in soils receiving 448 kg S ha -1 (482 mg kg -1 ) than in soils receiving 224 (111 mg kg -1 ) and 112 kg S ha-1 (55 mg kg -1 ) and unamended soil (0 mg kg -1 ) at 2 months after S application. Similar to extractable SO4-S, elemental S significantly decreased during the growing season. Sulfur application did not affect the sulfatase activity, however, mineralizable S increased concurrently with S application rate, and the effects continued throughout the growing season. This result was largely attributed to the oxidation of the applied elemental S. Our results suggest that large-scale S application in the EAA soils is likely to increase SO42- concentra tions in soils, which poses a potential risk of SO 4 2- export to sensitive Everglades wetlands.
TL;DR: In this article, the effect of three commonly used surfactants applied to a sand-based root zone on turfgrass visual quality and drought symptoms, soil water content and uniformity, and soil water repellency was quantified.
Abstract: Water repellency and related localized dry spots are common problems on sand-based root zones often used for golf putting greens. The objective of this study was to quantify the effect of three commonly used surfactants applied to a sand-based root zone on turfgrass visual quality and drought symptoms, soil water content and uniformity, and soil water repellency. In 2007 and 2008, a study was conducted in Wisconsin on a creeping bentgrass golf putting green with a water-repellent sand soil. Prolonged periods of drought occurred in both years. Treatments included three surfactants and two controls, one irrigated at 30% of potential evapotranspiration (ETp) and a second irrigated at 100% of ETp. The surfactant treatments were irrigated at 30% of ETp. Soil moisture was measured weekly in each plot on a 5 × 5 30-cm grid pattern, along with visual estimates of area exhibiting drought symptoms and turfgrass visual quality. Soil water repellency was measured before and at the conclusion of each growing season. In 2007, the surfactant treatments maintained visual quality lower than the well-irrigated control treatment but greater than the reduced-irrigation control treatment. In 2008, substantial drought symptoms appeared on all surfactant treatments, which recovered faster than the reduced-irrigation control treatment. Soil water contents of surfactant treatments were similar to each other and the reduced-irrigation control on most testing dates. During periods of drought, surfactant-treated soils had the greatest uniformity of moisture content and lowest water repellency at the end of each growing season. These results indicate that use of these surfactants can reduce water use while improving visual quality compared with untreated areas, prevent localized dry-spot development, and increase moisture uniformity in sand-based golf putting green root zones.
TL;DR: In this article, the authors measured inorganic and organic carbon, bacterial biomass and structural community diversity in southern Idaho soils having long term land use histories that supported native sagebrush vegetation (NSB), irrigated moldboard plowed crops (IMP), irrigation conservation (chisel) tilled crops (ICT), and irrigated pasture systems (IP) organic carbon in soil decreased in the order IP>ICT>NSB>IMP.
Abstract: Sequestering carbon in soils may be one method to reduce the concentration of carbon dioxide in the atmosphere We measured inorganic and organic carbon, bacterial biomass and structural community diversity in southern Idaho soils having long term land use histories that supported native sagebrush vegetation (NSB), irrigated moldboard plowed crops (IMP), irrigated conservation (chisel) tilled crops (ICT) and irrigated pasture systems (IP) Organic carbon in soil decreased in the order IP>ICT>NSB>IMP We use our findings to estimate the organic carbon, potentially sequestered if the use of irrigated agriculture were increased We also use our findings to estimate inorganic and total carbon, potentially sequestered if the use of irrigated agriculture were increased If irrigated agricultural land was expanded by10 percent worldwide and NSB were converted to IMP, a possible 278 percent of the total carbon, emitted in the next 30 years could potentially be sequestered in soil If irrigated agricultural land was expanded by 10% worldwide and NSB were converted to ICT, a possible 187 percent of the total C emitted in the next 30 years could be sequestered in soil We used molecular methods to determine the bacterial diversity in all soils Bacterial diversity was the greatest in the NSB 5-15 cm soil and lowest in the IMP soil ICT and IP increased soil C and to some extent increased bacterial diversity relative to IMP Irrigated agricultural systems can produce twice the yield compared to non-irrigated land Irrigation also favors economic sustainability and increasing soil C relative to native semi arid or arid sites, but decreases bacterial diversity compared to native sagebrush soils Irrigation decreased soil bacterial diversity compared to native sagebrush soils, but because irrigated agriculture produces higher yields, less land needs to be put into production relative to rain-fed agriculture Altering land use practice to produce crops on high output irrigated agriculture, while returning less-productive rain-fed agricultural land to temperate forest or native grassland, could reduce atmospheric carbon dioxide
TL;DR: In this article, the univariate and the partial least square (PLS) techniques are used to analyze the LIBS spectra of 12 soil samples and to build calibration models predicting Cu and Zn concentrations.
Abstract: Laser-induced breakdown spectroscopy (LIBS) is a rapid quantitative analytical technique that can be used to determine the elemental composition of numerous sample matrices, and it has been successfully applied in many types of samples. However, for chemically and physically complex soil samples, its quantitative analytical ability is controversial. Multivariate analytical techniques have great potential for analyzing the complex LIBS spectra. To demonstrate the feasibility of LIBS as an alternative technique to quantitatively analyze soil samples, the univariate and the partial least square (PLS) techniques are used to analyze the LIBS spectra of 12 soil samples and to build calibration models predicting Cu and Zn concentrations. The results show that PLS can significantly improve the analytical results compared with the univariate technique. The normalized root mean square error (NRMSE) and r 2 of the univariate models are 16.60% and 0.71 in calibration and 18.80% and 0.62 in prediction for Cu and 18.97% and 0.62 in calibration and 22.81% and 0.45 in prediction for Zn. For the PLS models using the spectral range 300 to 350 nm, the NRMSE and r 2 are 1.94% and 0.99 for both Cu and Zn in calibration and 7.90% and 0.94 for Cu and 8.14% and 0.94 for Zn in prediction, respectively. Compared with the univariate technique, PLS improves the NRMSE 87.53% and 87.78% in calibration and 44.47% and 53.44% in prediction for Cu and Zn, respectively. The results indicate that PLS can improve the quantitative analytical ability of LIBS for soil sample analysis.
TL;DR: In this paper, a one-dimensional model with simultaneous production, decomposition, sorption/desorption, and transport of DOC to describe the behavior of DOC in the organic carbon (OC) layers above the mineral soils is presented.
Abstract: The movement of dissolved organic carbon (DOC) throughboreal ecosystems has drawn increased attention because of its poten-tial impact on the feedback of OC stocks to global environmentalchange in this region. Few models of boreal DOC exist. Herewe presenta one-dimensional modelwith simultaneous production, decomposition,sorption/desorption, and transport of DOC to describe the behavior ofDOC in the OC layers above the mineral soils. The field-observed con-centration profiles of DOC in two moderately well-drained black spruceforest sites (one with permafrost and one without permafrost), coupledwith hourly measured soil temperature and moisture, were used to in-versely estimate the unknown parameters associated with the sorption/desorption kinetics using a global optimization strategy. The model,along with the estimated parameters, reasonably reproduces the con-centration profiles of DOC and highlights some important potentialcontrols over DOC production and cycling in boreal settings. Thevaluesof estimated parameters suggest that humic OC has a larger potentialproduction capacity for DOC than fine OC, and most of the DOCproduced from fine OC was associated with instantaneous sorption/desorption whereas most of the DOC produced from humic OC wasassociated with time-dependent sorption/desorption. The simulatedDOC efflux at the bottom of soil OC layers was highly dependent onthe component and structure of the OC layers. The DOC efflux wascontrolled by advection at the site with no humic OC and moist con-ditions and controlled by diffusion at the sitewith the presence of humicOC and dry conditions.Key words: Black spruce, boreal, carbon, advection, diffusion,inversion.(Soil Science 2010;175: 223Y232)
TL;DR: In this paper, the effects of dissolved calcium (Ca) on arsenate (V)) reactivity and surface speciation at the kaolinite-water interface were studied as a function of pH using pseudo-equilibrium adsorption/ desorption experiments and extended X-ray absorption fine-structure spectroscopy (EXAFS) analyses.
Abstract: The effects of dissolved calcium (Ca) on arsenate (As(V)) reactivity and surface speciation at the kaolinite-water interface were studied as a function of pH using pseudo-equilibrium adsorption/ desorption experiments and extended X-ray absorption fine-structure spectroscopy (EXAFS) analyses. The EXAFS analyses indicated that As(V) tetrahedral molecules were coordinated on aluminum octahedral via bidentate binuclear (E3.11 A ˚ ) bonding at pH 4.5 to 6.75 and total As loading levels of 978 to 1,783 Kmol/L kg j1 . There was no evidence for As(V)-Ca ternary species when both As(V) and Ca were present (0.68Y1.3 mmol/L). In the adsorption experiments, As(V) adsorption gradually increased with increasing pH and decreased at pH above 6. Interestingly, As(V) sorption was suppressed when 1 mmol/L of Ca was added to the systems at pH 4 to 8. The As(V) desorption was also pronounced when the systems contained Ca. These macroscopic results indirectly suggest that the weakly sorbed As(V) surface species are outcompeted by the ion-exchange process of Ca at the broken edge site of kaolinite. Results of macroscopic data and EXAFS analysis suggest that both outer-sphere and inner-sphere surface As(V) species might coexist on kaolinite surfaces. In predicting the dissolved As(V) in subsurface environments, weakly sorbed As(V) species might be in- fluenced by not only anionic species, but also cationic species in soil solutions and in pore water. Quantifying the effects of various sorbed cations may be important in predicting arsenic transport processes in subsurface environments.
TL;DR: In this article, the authors examined corn grain yield and soil nutrient status under three nutrient sources (two rates of each) as follows: inorganic fertilizer, poultry litter, and dairy manure compared with a nontreated control under two tillage practices (no-till and incorporated).
Abstract: Large amounts of animal manure, particularly poultry litter and dairy manure, are generated in southeastern United States, where corn (Zea mays L.) is also extensively grown. Characterizations of management practices and long-term manure and soil nutrient dynamics are critical. This study examined corn grain yield and soil nutrient status under three nutrient sources (two rates of each) as follows: inorganic fertilizer, poultry litter, and dairy manure compared with a nontreated control under two tillage practices (no-till and incorporated). Treatments were replicated four times in a split-plot design from 2004 to 2007. Soil samples were taken annually in the spring before treatment application to evaluate the status of the residual nutrients in soil. Significant differences in corn grain yield between the two tillage practices (main effect) were observed in all 4 years. The high rate of poultry litter application produced similar grain yield as inorganic fertilizer. However, results from dairy manure were not as consistent as poultry litter. After 4 years of poultry litter application, Mehlich-3 (M-3) phosphorus (P) increased from an initial 31.4 to 63.0 mg kg−1 for the 4.5 Mg ha−1 year−1 rate and to 178 mg kg−1 for the 13.5 Mg ha−1 year−1 rate. More specifically, 5.2 kg ha−1 year−1 of P applied as poultry litter increased soil M-3 P by 1 mg kg−1 after 4 years of application. Results indicated that poultry litter is a primary fertilizer at the rate of 13.5 Mg ha−1 applied in four consecutive years on a silt loam soil-produced corn grain yields similar to inorganic fertilizer under both no-till and incorporated systems and did not result in residual soil test P, Cu, and zinc levels considered to be harmful to surface water or cropping systems.
TL;DR: In this article, the authors determined the concentration and composition of water-extractable organic carbon (EOC), water extractable organic N (EON), and water extraction organic P (EOP) before and after incubation of sand, peat, and clay grassland soils at different temperatures (1.5 °C, 10 °C and 20 °C) for 35 days.
Abstract: The release of dissolved organic matter (DOM) from agricultural land can have a large impact on the transport of N and phosphorus (P) to surface waters leading to water quality impairment. The speciation of DOM in agricultural grassland soils has received little attention thus far. Quantification of DOM speciation can improve our knowledge of its fate in these soils. Furthermore, the influence of temperature on DOM concentration and composition is still ambiguous. In this study, we determined the concentration and composition of water-extractable organic carbon (EOC), water-extractable organic N (EON), and water-extractable organic P (EOP) before and after incubation of sand, peat, and clay grassland soils at different temperatures (1.5 °C, 10 °C, and 20 °C) for 35 days. Extracted organic compounds were fractioned in three operationally defined fractions: humic acids (HA), fulvic acids (FA), and hydrophilic (Hy) compounds using a recently developed batch fractionation method. Both EON and EOP formed a major fraction of total N and P. Concentrations of EOC, EON, and EOP were different among the sand, peat, and clay soils, but their speciation was remarkably similar. The EOC and EON were mainly present in the hydrophobic form (HA and FA), whereas EOP was mainly present in the Hy fraction. An increase in temperature generally resulted in a decrease of the total EOC, EON, and EOP concentrations, whereas the speciation remained constant. The effect of temperature on the dynamics of DOM is not necessarily related to net changes in pool size of the HA, FA, and Hy fractions. Insight into the influence of incubation temperature on the dynamics of EOC, EON, and EOP can only be achieved when the processes responsible for the consumption and the production of dissolved organic nutrients are quantified
TL;DR: In this paper, the authors investigated the distribution of total and ammonium bicarbonateYDTPAYextractable (AB-DTPA) V in soil pro- files of representative Greek and Egyptian soils and their relationships to soil properties.
Abstract: Vanadium (V) is a trace element involved in soil pollution, originating from either soil parent material or anthropogenic sources. The aim of this study was to investigate the distribution of total and ammonium bicarbonateYDTPAYextractable (AB-DTPA) V in soil pro- files of representative Greek and Egyptian soils and their relationships to soil properties. Twenty-one soil profiles from Egypt and Greece (re- presenting the main soil orders, that is, Entisols (developed on fluvial, lacustrine, and marine deposits) and Aridisols for Egyptian soils and to the soil orders Entisols, Alfisols, Inceptisols, Vertisols, Mollisols, and Histosols for Greek soils) were sampled and analyzed for total and AB- DTPAYextractable V, and the relationship of V levels to soil properties were examined. Total V concentrations ranged from 23 mg kg j1 in the marine de- posits to 179 mg kg j1 in the lacustrine deposits. Total V levels signifi- cantly positively correlated to clay and silt content, cation exchange capacity, and free iron and manganese oxides and were negatively cor- related to sand, organic matter, and calcium carbonate content. The AB-DTPAYextractable V varied from 0.55 mg kg j1 in the Greek Entisol to 4.4 mg kg Y1 in the Egyptian lacustrine deposits and were signifi- cantly positively correlated with total V concentration, soil pH, clay and silt content, and cation exchange capacity (positively) and nega- tively correlated with sand content. Distribution of total and AB-DTPAY extractable V related mainly to particle size distribution, sesquioxides content, and soil pH. These results suggest that V could be a concern for many of the soils studied because in a large number of samples, V concentration values exceeded the international regulatory standards for remediation.
TL;DR: In this paper, the degree of spatial variability of soil properties was quantified by using geostatistical techniques to understand the spatial characteristics of soil property and to develop the development of site-specific management.
Abstract: Spatial variability in soil properties has long been observed within uniformly managed fields. Understanding the spatial characteristics of soil properties would be helpful in the development of site-specific management. Uniform management results in overapplication in areas with high nutrient levels and underapplication in areas with low nutrient levels. The objective of this study was to quantify the degree of spatial variability of soil properties. This is important to tobacco quality across flue-cured tobacco (Nicotiana tabacum) plantation fields. Fourteen soil properties were analyzed by geostatistical techniques. Soil organic matter (OM) had significantly positive correlations with active soil OM, total N (TN), available N, available phosphorus, available potassium, Cu, Fe, and Mn. Soil TN, Zn, cation exchange capacity, and silt showed strong spatial dependence, with nugget-sill ratios ranging from 3.39% to 23.43%. Other soil properties showed moderate dependence, with nugget-sill ratios of 30.87% to 49.99%. Spatial dependence ranged from 34.3 m (Zn) to 376.3 m (Mn). The OM contour map showed highest similarity with that of TN. Variography and kriging are useful tools for soil-sampling strategies and variable-rate application in site-specific farming.
TL;DR: In this article, the changes of soil pH, soil bulk density, soil aggregat and soil aggregation were investigated to find an effective way to overcome soil erosion in semiarid Loess Plateau.
Abstract: Because of overcultivation in the semiarid Loess Plateau during the past half century, soil erosion has become a serious problem in maintaining a sustainable ecosystem. To find an effective way to overcome soil erosion, we investigated the changes of soil pH, soil bulk density, soil aggregat
TL;DR: In this article, a field and laboratory study comparing CO 2 emission rates from the soil surface and β-glucosidase activity in Mediterranean Ultisols from the Canamero rana surface (continental detritic formations from southwest Spain) under different soil management conditions and vegetation cover was conducted.
Abstract: Soil respiration is the second-largest terrestrial carbon flux, and it has shown to be deeply affected by soil management. This article reports a field and laboratory study comparing CO 2 emission rates from the soil surface and β-glucosidase activity in Mediterranean Ultisols from the Canamero rana surface (continental detritic formations from southwest Spain) under different soil management conditions and vegetation cover: 1) soil in a cork oak grove, the climax vegetation of the studied rana surface; 2) soil in a Cistus scrubland with a 100% cover, uncultived for the past 45 years; 3) soil in a crop field that has been uncultivated for the past 35 years and with 55% of the shrub cover dominated by Cistus crispus L. and the rest covered by pasture; 4) soil in a degraded pastureland; and 5) soil in an olive grove that has been continuously cultivated for the past 65 years. We made a comparative assessment of aerobic activity in each of the soils at different times of the year. The level of degradation of natural vegetation, and therefore also the organic matter content, which decreased from Areas 1 to 5, affected the rate of CO 2 emission from the soil surface. This rate was also affected by soil water content, soil temperature, and the predominance of Cistus ladanifer L. in the soil vegetation cover. In the case of the Olea europaea L. grove soil, the CO 2 emission rate notably increased during autumn in years of high fruit production as a result of increased root respiration. β-Glucosidase activity was mostly, and positively, affected by organic matter content and also was negatively affected by the predominance of C. ladanifer in the vegetation soil cover.