bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimates of Residual Dairy Manure Nitrogen Availability Using Various Techniques
Authors: Cusick Paul R. , Kelling Keith A. , Powell J. Mark , Muñoz Gabriela R.
Published: October 2006

It is common practice to repeatedly apply dairy manure to the same fields. To accurately assess the total plant availability of manure nutrients, it is necessary to account for the nutrients remaining in soil from previous manure applications. A field experiment studying manure nitrogen (N) uptake by corn (Zea mays L.) was conducted from 1998 to 2003 on a Plano silt loam (fine‐silty, mixed, mesic, Typic Argiudolls). Plots received two rates of semisolid manure either every year, every 2 yr, or every 3 yr to estimate first‐, second‐, and third‐year dairy manure N residuals. Residual manure N availability was estimated from single and multiple manure applications using (i) the fertilizer N equivalence method, (ii) the apparent recovery (difference) method, (iii) relative effectiveness method, and (iv) recovery of 15N‐labeled manure. Second‐year availabilities after a single manure application using the fertilizer equivalence, difference, and relative effectiveness methods were estimated to be 12, 8, and 4% of total manure N applications, respectively. Estimates of third‐year availability by these methods were 3, 1, and 5%, respectively. Measurement of 15N recovered from labeled manure was 6 and 2% in the second and third year, respectively. Fertilizer equivalence, difference, and relative effectiveness methods showed great year to year variability, reducing the confidence in the residual manure N availability estimates by these methods, but using 15N‐labeled manures reduced variability substantially. Based on this and other studies, we suggest that second‐ and third‐year residual N availability from a single application of semisolid dairy manure would be 9 to 12%, and 3 to 5% of the original manure N application, respectively.
Compost, Manure, and Gypsum Application to Timothy/Red Clover Forage
Authors: Zheljazkov Valtcho D. , Astatkie Tess , Caldwell Claude D. , MacLeod John , Grimmett Mark
Published: October 2006

Some of the most fertile agricultural land in Atlantic Canada includes dykelands, which were developed from rich salt marshes along the Bay of Fundy through the construction of dykes. A 2‐yr field experiment was conducted on dykeland soil to evaluate the effect of fertility treatments: source‐separated municipal solid waste (SS‐MSW) compost, solid manure, commercial fertilizer, and gypsum on (1) timothy/red clover forage productivity, (2) N, S, and other nutrients uptake, and (3) residual NO3–N and NH4–N in the soil profile. All fertility treatments increased dry matter yields from the two cuts each year relative to the control. Residual soil NO3–N and NH4–N concentrations in the fall of the second year decreased with depth, and beyond 20‐cm depth were lower than 1 mg kg−1 Gypsum application equivalent to 40 kg S ha−1 increased dry matter yields and N uptake by forage, and increased soil Mehlich 3‐extractable S, tissue S, and uptake of S, Ca, P, Cu, Fe, and Mn relative to the control. High rates of compost can provide sufficient N, S, and perhaps other nutrients to a perennial forage system under the cool wet climate of Atlantic Canada with no heavy metal enrichment of forage. However, the chemical N provided greater total N uptake than organic sources, except the high rate of compost, suggesting that the N availability from organic sources was not well synchronized with forage N demand. Municipal solid waste compost may also increase soil and forage tissue Na, which might be of concern.
Antibiotic Transport via Runoff and Soil Loss
Authors: Davis J. G. , Truman C. C. , Kim S. C. , Ascough J. C. , Carlson K.
Published: October 2006

Research has verified the occurrence of veterinary antibiotics in manure, agricultural fields, and surface water bodies, yet little research has evaluated antibiotic runoff from agricultural fields. The objective of this study was to evaluate the potential for agricultural runoff to contribute antibiotics to surface water bodies in a worst‐case scenario. Our hypothesis was that there would be significant differences in antibiotic concentrations, partitioning of losses between runoff and sediment, and pseudo‐partitioning coefficients (ratio of sediment concentration to runoff concentration) among antibiotics. An antibiotic solution including tetracycline (TC), chlortetracycline (CTC), sulfathiazole (STZ), sulfamethazine (SMZ), erythromycin (ERY), tylosin (TYL), and monensin (MNS) was sprayed on the soil surface 1 h before rainfall simulation (average intensity = 60 mm h−1 for 1 h). Runoff samples were collected continuously and analyzed for aqueous and sediment antibiotic concentrations. MNS had the highest concentration in runoff, resulting in the highest absolute loss, although the amount of loss associated with sediment transport was <10%. ERY had the highest concentrations in sediment and had a relative loss associated with sediment >50%. TYL also had >50% relative loss associated with sediment, and its pseudo‐partitioning coefficient (P‐PC) was very high. The tetracyclines (TC and CTC) had very low aqueous concentrations and had the lowest absolute losses. If agricultural runoff is proven to result in development of resistance genes or toxicity to aquatic organisms, then erosion control practices could be used to reduce TC, ERY, and TYL losses leaving agricultural fields. Other methods will be needed to reduce transport of other antibiotics.
Ground Cover Impacts on Sediment and Phosphorus Export from Manured Riparian Pasture
Authors: Butler David M. , Franklin Dorcas H. , Ranells Noah N. , Poore Matthew H. , Green James T.
Published: October 2006

Maintaining pasture ground cover is important in preventing environmental degradation of grasslands and associated riparian areas. The objective of this work was to determine the effect of ground cover on sediment and P export from pastured riparian areas under simulated rainfall events. Plots were established on two sites in the North Carolina Piedmont: a 10% slope with Appling sandy loam soils (fine, kaolinitic, thermic Typic Kanhapludults) and a 20% slope with Wedowee sandy loam soils (fine, kaolinitic, thermic Typic Kanhapludults), both with mixed tall fescue (Festuca arundinacea Schreb.)–dallisgrass (Paspalum dilatatum Poir.) vegetation. Existing forage stands were modified to represent a range of ground cover levels: 0, 45, 70, and 95% (bare ground, low, medium, and high cover, respectively), and amended with beef steer (Bos taurus) feces and urine (about 10 kg P ha−1). Mean runoff volume from bare ground was generally twice that observed from low, medium, and high levels of cover, which were similar. For all rainfall events combined, export of dissolved reactive P was greatest (P < 0.1) at bare ground and was reduced 31% at low cover, which did not differ from medium or high cover. Mean total Kjeldahl P export was greater (P < 0.001) from bare ground than from other cover levels. Results indicate that riparian bare areas can contribute substantial sediment (>215 kg ha−1) and P (0.7 kg P ha−1) to surface waters during heavy rainfall, whereas export may be reduced equally well by low cover (45%) as by high cover.
The Effect of Land Use on Soil Health Indicators in Peri‐Urban Agriculture in the Humid Forest Zone of Southern Cameroon
Authors: Monkiedje Adolphe , Spiteller Michael , Fotio Daniel , Sukul Premasis
Published: October 2006

The objective of this study was to identify the effect of different land uses in peri‐urban agriculture on the soil properties. Soil health indicators were evaluated in the top 10 cm at five tilled agricultural sites involving different cropping systems and use of agrochemicals within the peri‐urban agricultural areas of Yaounde, Cameroon, and compared with a native forest land. The experimental data showed that the selected indicators were sensitive to cropping practice. Most cropped land had significantly higher total C, available N and P concentrations, soil pH, electrical conductivity, salinity, biomass C and P, dehydrogenase, β‐glucosidase, and acid phosphatase activities. Land producing corn (Zea maysL.) and sugarcane (Saccharum officinarumL.) differed from that producing tomatoes (Lycopersicon esculentumMill.), but cultivation of these crops has significantly impacted native soil quality. However, phenol oxidase, microbal biomass C/organic C (Cmic/Corg), and microbial biomass C/microbial biomass P (Cmic/Pmic) were negatively affected. These appeared to be more consistent indicators of negative management causing changes to soil health and may be suitable for an early appraisal of soil health.
Co‐composting of Acid Waste Bentonites and their Effects on Soil Properties and Crop Biomass
Authors: Soda Wannipa , Noble Andrew D. , Suzuki Shinji , Simmons Robert , Sindhusen La‐ait , Bhuthorndharaj Suwannee
Published: October 2006

Acid waste bentonite is a byproduct from vegetable oil bleaching that is acidic (pH < 3.0) and hydrophobic. These materials are currently disposed of in landfills and could potentially have a negative impact on the effective function of microbes that are intolerant of acidic conditions. A study was undertaken using three different sources of acid waste bentonites, namely soybean oil bentonite (SB), palm oil bentonite (PB), and rice bran oil bentonite (RB). These materials were co‐composted with rice husk, rice husk ash, and chicken litter to eliminate their acid reactivity and hydrophobic nature. The organic carbon (OC) content, pH, exchangeable cations, and cation exchange capacity (CEC) of the acid‐activated bentonites increased significantly after the co‐composting phase. In addition, the hydrophobic nature of these materials as measured using the water drop penetration time (WDPT) decreased from >10 800 s to 16 to 80 s after composting. Furthermore, these composted materials showed positive impacts on soil physical attributes including specific surface area, bulk density, and available water content for crop growth. Highly significant increases in maize biomass (Zea mays L.) production over two consecutive cropping cycles was observed in treatments receiving co‐composted bentonite. The study clearly demonstrates the potential for converting an environmentally hazardous material into a high‐quality soil conditioner using readily available agricultural byproducts. It is envisaged that the application of these composted acid waste bentonites to degraded soils will increase productivity and on‐farm income, thus contributing toward food security and poverty alleviation.
Cadmium Leaching from Micro‐Lysimeters Planted with the Hyperaccumulator Thlaspi caerulescens
Authors: Ingwersen Joachim , Bücherl Barbara , Neumann Günter , Streck Thilo
Published: October 2006

The use of heavy metal hyperaccumulating plants has the potential to become a promising new technique to remediate contaminated sites. We investigated the role of metal mobilization in the Cd hyperaccumulation of Thlaspi caerulescens (J. & C. Presl, ‘Ganges’). In a micro‐lysimeter experiment we investigated the dynamics of Cd concentration of leachate as well as Cd removal by plant uptake in four treatments: (i) Control (bare soil), (ii) T. caerulescens, (iii) nonhyperaccumulator Brassica juncea (L.) Czern. (‘PI 426308’), and (iv) co‐cropping of the hyperaccumulator and nonhyperaccumulator. The experimental findings were analyzed using one‐ and two‐site rate‐limited desorption models. Co‐cropping of T. caerulescens and B. juncea did not enhance metal uptake by B. juncea Although Cd uptake of T. caerulescens was 10 times higher than that of B. juncea, the Cd concentration of leachate of the T. caerulescens treatment did not decrease below that of the B. juncea treatment. The Cd depletion in leachate was well reproduced by the two‐site rate‐limited desorption model. The optimized desorption coefficient was three orders of magnitude higher in the rhizosphere than in the bulk soil. Our results indicate that T. caerulescens accelerates the resupply of Cd from soil pointing to an important role of kinetic desorption in the hyperaccumulation by T. caerulescens
Bioaccessibility of Lead Sequestered to Corundum and Ferrihydrite in a Simulated Gastrointestinal System
Authors: Beak Douglas G. , Basta Nicholas T. , Scheckel Kirk G. , Traina Samuel J.
Published: October 2006

Lead (Pb) sorption onto oxide surfaces in soils may strongly influence the risk posed from incidental ingestion of Pb‐contaminated soil. Lead was sorbed to model oxide minerals of corundum (α‐Al2O3) and ferrihydrite (Fe5HO8·4H2O). The Pb‐sorbed minerals were placed in a simulated gastrointestinal tract (in vitro) to simulate ingestion of Pb‐contaminated soil. The changes in Pb speciation were determined using extended X‐ray absorption fine structure (EXAFS) and X‐ray absorption near edge spectroscopy (XANES). Both corundum (sorption maximum of 2.13 g kg−1) and ferrihydrite (sorption maximum of 38.6 g kg−1) have been shown to sorb Pb, with ferrihydrite having a very high affinity for Pb. The gastric bioaccessible Pb for corundum was >85% for corundum when the concentration of Pb was >200 mg kg−1 Bioaccessible Pb was not detectable at ≤200 mg kg−1 Bioaccessible Pb ranged from 53 to 88% for ferrihydrite. The bioaccessible Pb was below detection limits for the intestinal phase in the ferrihydrite system. Solid phase speciation identified both inner‐ (mononuclear bidentate) and outer‐sphere species for Pb sorbed to corundum, while only an inner‐sphere (mononuclear bidentate) complex was found for ferrihydrite. Although corundum and ferrihydrite can bind Pb, they fail to significantly reduce gastric bioaccessible Pb but do reduce intestinal bioaccessible Pb. Treatment of Pb‐contaminated soil with corundum or ferrihydrite may reduce Pb solubility under field soil conditions of pH > 4. However, much of the sorbed Pb will become bioaccessible under gastric conditions (pH 1.5–2.5) if this soil is ingested. Caution should be used before using these materials to remediate a soil where soil ingestion is an important exposure pathway.
A Washing Procedure to Mobilize Mixed Contaminants from Soil
Authors: Ehsan Sadia , Prasher Shiv O. , Marshall William D.
Published: October 2006

We conducted a laboratory study to assess the feasibility of a washing process with nonionic and anionic surfactants in combination with ethylenediaminetetraacetate (EDTA) for the simultaneous mobilization of heavy metals and polychlorinated biphenyls (PCBs) from a field‐contaminated soil. Unit processes consisting of complexometric extraction and surfactant‐assisted mobilization were combined with reagent regeneration and detoxification steps to generate innocuous products. Ten minutes of ultrasonic mixing of the soil with a combination of 30 mL L−1surfactant suspension and a sparing quantity (2 mmol) of EDTA mobilized appreciable quantities of PCBs, virtually all of the available Cd, Cu, Mn, and Pb, and lesser amounts of the Zn, Ni, and Cr but only small quantities of Al and Fe. Relative to individual reagents, combinations of surfactant (Brij 98, Triton X‐301, or Triton XQS‐20) with EDTA did not influence PCB extraction efficiencies perceptibly. Of the three surfactants, the Brij 98 proved to be the most efficient for three successive extractions with a single charge, mobilizing 83% of the PCBs, whereas companion extractions that used fresh reagent each time mobilized 87% of the soil PCB content. The decreased PCB mobilization with the same quantity of anionic surfactant (71 or 68%) resulted from losses during the EDTA regeneration process with zero‐valent Mg. In toto, these studies demonstrate that PCB compounds and selected heavy metals can be coextracted efficiently from soil with three successive washes with the same washing suspension containing EDTA and a nonionic surfactant.
A Washing Procedure to Mobilize Mixed Contaminants from Soil
Authors: Ehsan Sadia , Prasher Shiv O. , Marshall William D.
Published: October 2006

We conducted a laboratory study to assess the efficiency of nonionic and anionic surfactants in combination with a sparing quantity of ethylenediaminetetraacetate (EDTA) to simultaneously extract heavy metals (HMs) and polychlorinated biphenyl (PCB) compounds from a field‐contaminated soil. A soil wash that mobilized both HMs and PCBs was combined with back‐extraction with hexane to remove PCBs from the aqueous wash. The aqueous washing suspension was then regenerated by precipitation of the HMs induced by corrosion and hydrolysis of zero‐valent Mg to provide a cleaned soil and innocuous extract. Finally, the washing suspension was recycled twice to mobilize more contaminants from the soil particulate fraction. After ultrasonic equilibration, EDTA in admixture with a nonionic surfactant did not appreciably change the efficiency of mobilization of most heavy metals (Al, Cd, Cr, Fe Mn, Ni, and Zn), but did increase the recovery of Cu and Pb. The release of EDTA from HM complexes was efficient for most metals (99%) but was influenced by the chemical characteristics of the surfactant. The EDTA recovery (62–65%) after three cycles of soil washing, hexane back‐extraction, and Mg0treatment was similar for all reagent combinations. In toto, these studies demonstrate that after treatment with ultrasound, selected heavy metals can be coextracted efficiently from soil with a single washing suspension containing EDTA and a nonionic surfactant.
Evaluation of Wetland Methyl Mercury Export as a Function of Experimental Manipulations
Authors: Gustin Mae Sexauer , Chavan Prithviraj V. , Dennett Keith E. , Marchand Eric A. , Donaldson Susan
Published: October 2006

Mercury associated with natural enrichment, historic mining, and ore processing is a contaminant of concern in watersheds of the western USA. In this region, water is a highly managed resource and wetlands, known to be important sites of methyl mercury production, are often an integral component of watersheds. This study applied controlled manipulations of four replicated experimental wetland designs with different water and soil mercury concentrations to determine the potential impacts on methyl mercury export. Wetlands were manipulated by drying and wetting, changing hydraulic retention time, and adding sulfate and nitrate to influent waters. In a summer drying and wetting manipulation, an immediate increase in total methyl mercury release was observed with rewetting, however, concentrations decreased quickly. Drying all wetlands over the winter and rewetting in the spring resulted in high net methyl mercury output relative to that observed before drying. Net methyl mercury output was not influenced by changes in hydraulic retention time from 4 to 8 h or to 30 min, or by increasing the nitrate concentration from 0.1 to 10 mg L−1 The addition of sulfate to the inlet waters of two mesocosms to increase concentrations from ∼100 to 250 mg L−1 did not result in a clear effect on methyl mercury output, most likely due to sulfate concentrations being higher than optimal for methyl mercury production. Despite the lack of response to sulfate amendments, the change in sulfate concentration between the inlet and outlet of the mesocosms and temperature were the parameters best correlated with methyl mercury outputs.
Nitrogen‐ vs. Phosphorus‐based Dairy Manure Applications to Field Crops
Authors: Toth John D. , Dou Zhengxia , Ferguson James D. , Galligan David T. , Ramberg Charles F.
Published: October 2006

Management of animal manures to provide nutrients for crop growth has generally been based on crop N needs. However, because manures have a lower N/P ratio than most harvested crops, N‐based manure management often oversupplies the crop‐soil system with P, which can be lost into the environment and contribute to eutrophication of water bodies. We examined the effects of N‐ vs. P‐based manure applications on N and P uptake by alfalfa (Medicago sativa L.), corn (Zea mays L.) for silage, and orchardgrass (Dactylis glomerata L.), leaching below the root zone, and accumulation of P in soil. Treatments included N‐ and P‐based manure rates, with no nutrient input controls and inorganically fertilized plots for comparison. Nitrate concentrations in leachate from inorganic fertilizer or manure treatments averaged 14 mg NO3–N L−1, and did not differ by nutrient treatment. Average annual total P losses in leachate did not exceed 1 kg ha−1 In the top 5 cm of soil in plots receiving the N‐based manure treatment, soil test P increased by 47%, from 85 to 125 mg kg−1 Nitrogen‐ and P‐based manure applications did not differ in ability to supply nutrients for crop growth, or in losses of nitrate and total P in leachate. However, the N‐based manure led to significantly greater accumulation of soil test P in the surface 5 cm of soil. Surface soil P accumulation has implications for increased risk of off‐field P movement.
Membrane Filtration Coupled with Chemical Precipitation to Treat Recirculating Aquaculture System Effluents
Authors: Yang Ling , Zhou Hongde , Moccia Richard
Published: October 2006

Effluents from recirculating aquaculture systems (RAS) contain high concentrations of nitrogen and phosphorous wastes and thus often require proper treatment to prevent potential detrimental impacts on receiving water bodies. The purpose of this study was to evaluate the feasibility of membrane filtration coupled with chemical precipitation as a pretreatment step with emphasis on phosphorus removal from RAS effluents. Chemical precipitation tests were conducted by adding magnesium chloride and alum at different chemical concentrations and pH values, respectively. Crossflow, flat‐sheet membrane filtration modules were used to examine the effects of transmembrane pressure and crossflow velocity in terms of solid/liquid separation efficiency and permeate flux decline. The results showed that membrane filtration can effectively separate the phosphorus precipitates after chemical precipitation. The total phosphorus in the treated effluent was reduced to less than 0.05 mg L−1 with a removal efficiency of more than 90%. However, much lower removal efficiencies were obtained for total organic carbon (TOC), total nitrogen, and turbidity. It was concluded that membrane filtration coupled with chemical precipitation can become an effective, compact treatment technology to meet the stringent regulatory requirements for RAS effluent discharge.
Dissolution and Transport of TNT, RDX, and Composition B in Saturated Soil Columns
Authors: Dontsova Katerina M. , Yost Sally L. , Šimunek Jiri , Pennington Judith C. , Williford Clint W.
Published: October 2006

Low‐order detonations and blow‐in‐place procedures on military training ranges can result in residual solid explosive formulations to serve as distributed point sources for ground water contamination. This study was conducted to determine if distribution coefficients from batch studies and transport parameters of pure compounds in solution adequately describe explosive transport where compounds are present as solid particles in formulations. Saturated column transport experiments were conducted with 2,4,6‐trinitrotoluene (TNT), hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX), and the explosive formulation, Composition B (Comp B) (59.5 ± 2.0% RDX, 39.5 ± 2.3% TNT, and 1% wax) in solid and dissolved forms. The two soils used were Plymouth loamy sand (mesic, coated Typic Quartzipsamments) from Camp Edwards, MA and Adler silt loam (coarse‐silty, mixed, superactive, thermic Fluvaquentic Eutrudepts) from Vicksburg, MS. Interrupted flow experiments were used to determine if explosives were at equilibrium distribution between soil and solution phases. The HYDRUS‐1D code was used to determine fate and transport parameters. Results indicated that sorption of high explosives was rate limited. The behavior of dissolved Comp B was similar to the behavior of pure TNT and RDX. Behavior of solid Comp B was controlled by dissolution that depended on physical properties of the Comp B sample. Adsorption coefficients determined by HYDRUS‐1D were different from those determined in batch tests for the same soils. Use of parameters specific to formulations will improve fate and transport predictions.
Emission of the Greenhouse Gases Nitrous Oxide and Methane from Constructed Wetlands in Europe
Authors: S⊘vik A. K. , Augustin J. , Heikkinen K. , Huttunen J. T. , Necki J. M. , Karjalainen S. M. , Kl⊘ve B. , Liikanen A. , Mander Ü. , Puustinen M. , Teiter S. , Wachniew P.
Published: October 2006

The potential atmospheric impact of constructed wetlands (CWs) should be examined as there is a worldwide increase in the development of these systems. Fluxes of N2O, CH4, and CO2 have been measured from CWs in Estonia, Finland, Norway, and Poland during winter and summer in horizontal and vertical subsurface flow (HSSF and VSSF), free surface water (FSW), and overland and groundwater flow (OGF) wetlands. The fluxes of N2O–N, CH4–C, and CO2–C ranged from −2.1 to 1000, −32 to 38 000, and −840 to 93 000 mg m−2 d−1, respectively. Emissions of N2O and CH4 were significantly higher during summer than during winter. The VSSF wetlands had the highest fluxes of N2O during both summer and winter. Methane emissions were highest from the FSW wetlands during wintertime. In the HSSF wetlands, the emissions of N2O and CH4 were in general highest in the inlet section. The vegetated ponds in the FSW wetlands released more N2O than the nonvegetated ponds. The global warming potential (GWP), summarizing the mean N2O and CH4 emissions, ranged from 5700 to 26000 and 830 to 5100 mg CO2 equivalents m−2 d−1 for the four CW types in summer and winter, respectively. The wintertime GWP was 8.5 to 89.5% of the corresponding summertime GWP, which highlights the importance of the cold season in the annual greenhouse gas release from north temperate and boreal CWs. However, due to their generally small area North European CWs were suggested to represent only a minor source for atmospheric N2O and CH4
Removal of Technetium from Solution by Algal Flagellate Euglena gracilis
Authors: Ishii Nobuyoshi , Uchida Shigeo
Published: October 2006

Based on limited data for the removal of radioactive 99Tc by freshwater phytoplankton, it has been thought that phytoplankton are unsuitable for remediation of 99Tc‐contaminated waters. This work sought to verify the validity of this assumption by studying the removal of 99TcO4− by freshwater and brackish water phytoplankton. The phytoplankton used were Euglena gracilis, Chlamydomonas pulsatilla, Chlorella vulgaris, and Spirulina platensis Each of them was incubated for 63 d, and the removal of 99Tc from solution was periodically determined. Significant removal of 99Tc was observed only for E. gracilis, and the maximum removal was 70% of the total 99Tc added. The killed cells of E. gracilis, however, removed hardly any 99Tc. When E. gracilis cells were washed with fresh culture medium, only 13% of the total 99Tc was desorbed. These results suggested that intracellular uptake of 99Tc by E. gracilis occurred. These results are the first documented example of significant removal of 99Tc by planktonic microalgae.
Evaluation of Extracted Organic Carbon and Microbial Biomass as Stability Parameters in Ligno‐Cellulosic Waste Composts
Authors: Mondini Claudio , Sánchez‐Monedero Miguel A. , Sinicco Tania , Leita Liviana
Published: October 2006

Extracted organic C and microbial biomass were evaluated as stability parameters in 3 different ligno‐cellulosic waste composts. Organic C was extracted by both water and alkali and further separated in humic‐like carbon (HLC) and nonhumic carbon (NHC). Conventional humification parameters, such as humification index and degree of humification were calculated from NHC and HLC. Microbial biomass carbon (BC) was determined as an indicator of the degree of biochemical transformation, whereas ninhydrin reactive N (BNIN) was measured to obtain the stability parameter BNIN/NTOT (NTOT, total N). The water‐extracted organic C did not provide reliable information on the transformations underwent by the ligno‐cellulosic wastes during composting, since its content remained almost unaltered during the whole process. In contrast, parameters based on the alkali‐extracted organic C and microbial biomass clearly reflected organic matter (OM) changes during the process. There was an increase in the net amount of HLC in the alkali extracts throughout composting, especially in the first 7 to 12 wk of the process, as well as a relative enrichment of HLC with respect to NHC. Values of humification index and degree of humification in end products were consistent with an adequate level of compost stability. The stability parameter BNIN/NTOT showed to be a reliable indicator of stability in ligno‐cellulosic wastes. Parameters based on the alkali‐extracted C and microbial biomass clearly reflected the transformation of the OM during composting and can be used as stability parameters in ligno‐cellulosic waste composts.
Estimating Plant‐Available Nitrogen Release from Manures, Composts, and Specialty Products
Authors: Gale Eric S. , Sullivan Dan M. , Cogger Craig G. , Bary Andy I. , Hemphill Delbert D. , Myhre Elizabeth A.
Published: October 2006

Recent adoption of national rules for organic crop production have stimulated greater interest in meeting crop N needs using manures, composts, and other organic materials. This study was designed to provide data to support Extension recommendations for organic amendments. Specifically, our objectives were to (i) measure decomposition and N released from fresh and composted amendments and (ii) evaluate the performance of the model DECOMPOSITION, a relatively simple N mineralization/immobilization model, as a predictor of N availability. Amendment samples were aerobically incubated in moist soil in the laboratory at 22°C for 70 d to determine decomposition and plant‐available nitrogen (PAN) (n = 44), and they were applied preplant to a sweet corn crop to determine PAN via fertilizer N equivalency (n = 37). Well‐composted materials (n = 14) had a single decomposition rate, averaging 0.003 d−1 For uncomposted materials, decomposition was rapid (>0.01 d−1) for the first 10 to 30 d. The laboratory incubation and the full‐season PAN determination in the field gave similar estimates of PAN across amendments. The linear regression equation for lab PAN vs. field PAN had a slope not different from one and a y‐intercept not different than zero. Much of the PAN released from amendments was recovered in the first 30 d. Field and laboratory measurements of PAN were strongly related to PAN estimated by DECOMPOSITION (r2 > 0.7). Modeled PAN values were typically higher than observed PAN, particularly for amendments exhibiting high initial NH4–N concentrations or rapid decomposition. Based on our findings, we recommend that guidance publications for manure and compost utilization include short‐term (28‐d) decomposition and PAN estimates that can be useful to both modelers and growers.
Influence of Geomorphological Variability in Channel Characteristics on Sediment Denitrification in Agricultural Streams
Authors: Opdyke Matthew R. , David Mark B. , Rhoads Bruce L.
Published: October 2006

Within fluvial systems, the spatial variability of geomorphological characteristics of stream channels and associated streambed properties can affect many biogeochemical processes. In agricultural streams of the midwestern USA, it is not known how geomorphological variability affects sediment denitrification rates, a potentially important loss mechanism for N. Sediment denitrification was measured at channelized and meandering headwater reaches in east‐central Illinois, a region dominated by intensive agriculture and high NO3–N stream export, between June 2003 and February 2005 using the chloramphenicol‐amended acetylene inhibition procedure. Sediment denitrification rates were greatest in separation zones, ranging from 0.6 to 76.4 mg N m−2h−1, compared with riffles, point bars, pools, and a run ranging from 0 to 36.5 mg N m−2h−1Differences in benthic organic matter (r= 0.70) and the percentage of fine‐grained sediments (r= 0.93) in the streambeds controlled much of the spatial variations in sediment denitrification among the geomorphological features. Although two meandering study reaches removed 390 and 99% more NO3–N by sediment denitrification than adjacent channelized reaches, NO3–N loss rates from all reaches were between 0.1 and 15.7% d−1, except in late summer. Regardless of geomorphological characteristics, streams in east‐central Illinois were not able to process the high NO3–N loads, making sediment denitrification in this region a limited sink for N.
Performance of Grass Barriers and Filter Strips under Interrill and Concentrated Flow
Authors: Blanco‐Canqui Humberto , Gantzer Clark J. , Anderson S. H.
Published: October 2006

Effectiveness of grass barriers and vegetative filter strips (FS) for reducing transport of sediment and nutrients in runoff may depend on runoff flow conditions. We assessed the performance of (1) switchgrass (Panicum virgatum L.) barriers (0.7 m) planted above fescue (Festuca arundinacea Schreb.) filter strips under interrill (B‐FS) and concentrated flow (CF‐B‐FS), and (2) fescue alone under interrill (FS) and concentrated flow (CF‐FS) for reducing runoff, sediment, nitrogen (N), and phosphorus (P) loss from fallow plots on a Mexico silt loam. We compared exclusively the performance of barriers and filter strips separately under interrill and concentrated flow. Runoff and sediment were sampled at 1 m above and at 0.7, 4, and 8 m below the downslope edge of the sediment source area. Filter strips under interrill flow reduced 80% and those under concentrated flow reduced 72% of sediment at 0.7 m (P < 0.01). With the addition of supplemental runoff simulating runoff from a larger sediment source area, FS reduced 80%, but CF‐FS reduced only 60% of sediment. The FS reduced organic N and NO3–N by an additional 50% (P < 0.01) more than CF‐FS at 0.7 m. Although the effectiveness of both treatments increased with increasing width, CF‐FS removed less sediment than FS alone at 8 m (P < 0.04). In contrast, barriers above filter strips under interrill and concentrated flow were equally effective at 8 m; decreasing runoff by 34%, sediment by 99%, and nutrients by 70%. Thus, barriers combined with FS can be an effective alternative to FS alone for sites where concentrated flows may occur.
Biosolids Affect Soil Barium in a Dryland Wheat Agroecosystem
Authors: Ippolito J. A. , Barbarick K. A.
Published: October 2006

In December 2003, the USEPA released an amended list of 15 “candidate pollutants for exposure and hazard screening” with regard to biosolids land application, including Ba. Therefore, we decided to monitor soil Ba concentrations from a dryland wheat (Triticum aestivum L.)–fallow agroecosystem experiment. This experiment received 10 biennial biosolids applications (1982–2003) at rates from 0 to 26.8 dry Mg ha−1 per application year. The study was conducted on a Platner loam (Aridic Paleustoll), ∼30 km east of Brighton, CO. Total soil Ba, as measured by 4 M HNO3, increased with increasing biosolids application rate. In the soil‐extraction data from 1988 to 2003, however, we observed significant (P < 0.10) linear or exponential declines in ammonium bicarbonate–diethylenetriaminepentaacetic acid (AB–DTPA) extractable Ba concentrations as a function of increasing biosolids application rates. This was observed in 6 of 7 and 3 of 7 yr for the 0‐ to 20‐ and 20‐ to 60‐cm soil depths, respectively. Results suggest that while total soil Ba increased as a result of biosolids application with time, the mineral form of Ba was present in forms not extractable with AB–DTPA. Scanning electron microscopy using energy dispersive spectroscopy verified soil Ba–S compounds in the soil surface, probably BaSO4 Wet chemistry sequential extraction suggested BaCO3 precipitation was increasing in the soil subsurface. Our research showed that biosolids application may increase total soil Ba, but soil Ba precipitates are insoluble and should not be an environmental concern in similar soils under similar climatic and management conditions.
Phosphorus Sorption by Sediments in a Southeastern Coastal Plain In‐Stream Wetland
Authors: Novak J. M. , Watts D. W.
Published: October 2006

A close relationship has been reported between sediment organic C (SedOC) content and its P sorption capacity (Pmax) and total P (TP) concentration. Phosphorus sorbed to organically complexed cations is a proposed explanation for this relationship. The objectives of this study were (i) to determine relationships between in‐stream wetland SedOC content and both the sediment's Pmax and TP concentrations, and (ii) to ascertain the role of both organically complexed and oxalate‐extractable cations on the sediment Pmax and TP values. The sediment's oxalate‐extractable Fe (Feox) and Al (Alox) contents were determined using acidified ammonium oxalate, while sodium pyrophosphate was used to extract organically complexed cations (Alpryo, Capyro, Fepyro, Mgpyro, and Mnpyro). Both the sediment's Pmax and TP contents were strongly correlated with its SedOC concentration (r2 > 0.90, P < 0.001). Only the Alox contents were significantly correlated with TP and Pmax, suggesting that amorphous Al forms have an important role in P sorption. All five pyrophosphate‐extracted cations were significantly correlated with SedOC contents. Regression analyses showed that the Alpyro accounted for 88% of the variation in sediment Pmax values, whereas a combination of Alpyro and Capyro accounted for 98% of the variation in sediment TP concentrations. Additionally, Al and Ca chelated by SedOC compounds also have an important role in P binding and indicate that a linkage exists between the wetlands SedOC and Pmax content and its ability to accumulate TP. This study identified that two different mechanisms have significant roles in regulating P sorption by sediments in a southeastern Coastal Plain in‐stream wetland.
Persistence of Fermentative Process to Phenolic Toxicity in Groundwater
Authors: Wu Youxian , Lerner David N. , Banwart Steven A. , Thornton Steven F. , Pickup Roger W.
Published: October 2006

The fermentation process is an important component in the biodegradation of organic compounds in natural and contaminated systems. Comparing with terminal electron‐accepting processes (TEAPs), however, research on fermentation processes has to some extent been ignored in the past decades, particularly on the persistence of fermentation process in the presence of toxic organic pollutants. Both field and laboratory studies, presented here, showed that microbial processes in a groundwater‐based system exhibited a differential inhibitory response to toxicity of phenolic compounds from coal tar distillation, thus resulting in the accumulation of volatile fatty acids (VFAs) and hydrogen. This indicated that fermentation processes could be more resistant to phenol toxicity than the subsequent TEAPs such as methanogenesis and sulfate reduction, thus providing us with more options for enhancing bioremediation processes.
Degree of Phosphorus Saturation Thresholds in Manure‐Amended Soils of Alberta
Authors: Casson Janna P. , Bennett D. Rodney , Nolan Sheilah C. , Olson Barry M. , Ontkean Gerald R.
Published: October 2006

The risk of P losses from agricultural land to surface and ground water generally increases as the degree of soil P saturation increases. A single‐point soil P sorption index (PSI) was validated with adsorption isotherm data for determination of the P sorption status of Alberta soils. Soil P thresholds (change points) were then examined for two agricultural soils after eight annual applications of different rates of cattle manure and for three agricultural soils after one application of different rates of cattle manure. Linear relationships were found between soil‐test P (STP) levels up to 1000 mg kg−1and desorbed P in the five Alberta soils. Weak linear relationships were also found between STP and runoff dissolved reactive phosphorus (DRP) in three of these soils. Change points for the degree of P saturation (DPS) were detected in four of the five soils at 3 to 44% for water‐extractable P (WEP) and at 11 to 51% for CaCl2–extractable P (CaCl2–P). Change points were not found for DPS or runoff DRP. Overall DPS thresholds for the five soils combined were 27% for WEP and 44% for CaCl2–P at a critical desorbable‐P value of 1 mg L−1The corresponding STP levels (44 mg kg−1for WEP and 71 mg kg−1for CaCl2–P) are similar to agronomic thresholds for crops grown on Alberta soils. Soluble P losses in overland flow and leaching may be greater in soils with DPS values that exceed these thresholds than in soils with lower DPS values.
Nitrogen Removal in Valley Bottom Wetlands
Authors: Montreuil Olivier , Merot Philippe
Published: October 2006

Although the reduction of nutrient loading between uplands and streams is sometimes considered evidence of the effect of wetlands acting as buffer zones, the influence of valley bottom wetlands (VBWs) on NO3− loading has seldom been assessed at the catchment scale. The objective of this study was to quantify the impact of VBWs on NO3− concentrations in streams in the Brittany region of France. We analyzed the spatial variation in NO3–N concentrations in 18 headwater catchments located in a 400‐km2 basin, with varying topographic, climatic, and agricultural intensity conditions. Approximately every 10 d, water was sampled during the high flow season. We investigated the relationships between the mean NO3− concentration and different characteristics of the catchments: (i) the amount of effective rainfall, i.e., the combined effect of precipitation and actual evapotranspiration on discharge and chemical dilution, (ii) the intensity of farming, i.e., the area used for farming in the catchments and the surplus of the agricultural N budget, and (iii) the relative area of VBWs. Although the first two characteristics were the main factors controlling N concentration variability, a step‐by‐step regression allowed us to attribute a significant part of the NO3− concentration decrease to the increase of VBW area in each catchment. For an increase of VBW area from 11 to 16%, the NO3–N concentration decreased from 5.3 to 4.2 mg L−1 Therefore in this basin, VBWs reduced the NO3− concentrations in streams with sources in agricultural fields by 30%. This work demonstrates the contribution of natural VBWs to NO3− removal at the catchment scale compared to other sources of variation, which is a current need for integrating water quality criteria into wetland management.
Soil Profile Distribution of Phosphorus and Other Nutrients following Wetland Conversion to Beef Cattle Pasture
Authors: Sigua Gilbert C. , Kang Woo‐Jun , Coleman Sam W.
Published: October 2006

Largely influenced by the passage of the Swamp Land Act of 1849, many wetlands were lost in the coastal plain region of the southeastern United States, primarily as a result of drainage for agricultural activities. To better understand the chemical response of soils during wetland conversion, soil core samples were collected from the converted beef cattle pastures and from the natural wetland at Plant City, FL in the summers of 2002 and 2003. Data collected from the natural wetland sites were used as reference data to detect potential changes in soil properties associated with the conversion of wetlands to improved beef cattle (Bos taurus) pastures from 1940 to 2003. The average concentration of total phosphorus (TP) in pasture soils (284 mg kg−1) was significantly (p ≤ 0.001) lower than its levels in natural wetland soils (688 mg kg−1). Compared with the adjoining natural wetlands, the beef cattle pasture soils, 63 yr after being drained exhibited: (1) a decrease in TOC (−172 g kg−1), TN (−10 g kg−1), K (−0.7 mg kg−1), and Al (−130 mg kg−1); (2) an increase in soil pH (+1.8), Ca (+88 mg kg−1), Mg (+7.5 mg kg−1), Mn (+0.3 mg kg−1), and Fe (+6.9 mg kg−1); and (3) no significant change in Na, Zn, and Cu. Wetland soils had higher concentrations (mg kg−1) of Al‐P (435), CaMg‐P (42), FeMn‐P (43), and Org‐P (162) than those of 172, 11, 11, and 84 mg kg−1, respectively, found in the pasture soils. The levels of water‐soluble P and KCl‐bound P were comparable between wetland and pasture soils in 2003. Results of this study therefore suggest that wetland conversion to beef cattle pastures did not function as a source of nutrients, especially P and N, even with manure and urine additions due to the presence of grazing cattle.
Characterization of Phosphorus Species in Biosolids and Manures Using XANES Spectroscopy
Authors: Shober Amy L. , Hesterberg Dean L. , Sims J. Thomas , Gardner Sheila
Published: October 2006

Identification of the chemical P species in biosolids or manures will improve our understanding of the long‐term potential for P loss when these materials are land applied. The objectives of this study were to determine the P species in dairy manures, poultry litters, and biosolids using X‐ray absorption near‐edge structure (XANES) spectroscopy and to determine if chemical fractionation techniques can provide useful information when interpreted based on the results of more definitive P speciation studies. Our XANES fitting results indicated that the predominant forms of P in organic P sources included hydroxylapatite, PO4 sorbed to Al hydroxides, and phytic acid in lime‐stabilized biosolids and manures; hydroxylapatite, PO4 sorbed on ferrihydrite, and phytic acid in lime‐ and Fe‐treated biosolids; and PO4 sorbed on ferrihydrite, hydroxylapatite, β‐tricalcium phosphate (β‐TCP), and often PO4 sorbed to Al hydroxides in Fe‐treated and digested biosolids. Strong relationships existed between the proportions of XANES PO4 sorbed to Al hydroxides and NH4Cl‐ + NH4F‐extractable P, XANES PO4 sorbed to ferrihydrite + phytic acid and NaOH‐extractable P, and XANES hydroxylapatite + β‐TCP and dithionite–citrate–bicarbonate (DCB)‐ + H2SO4‐extractable P (r2 = 0.67 [P = 0.01], 0.78 [P = 0.01], and 0.89 [P = 0.001], respectively). Our XANES fitting results can be used to make predictions about long‐term solubility of P when biosolids and manures are land applied. Fractionation techniques indicate that there are differences in the forms of P in these materials but should be interpreted based on P speciation data obtained using more advanced analytical tools.
Soil Electrical Conductivity and Water Content Affect Nitrous Oxide and Carbon Dioxide Emissions in Intensively Managed Soils
Authors: Adviento‐Borbe M. A. A. , Doran J. W. , Drijber R. A. , Dobermann A.
Published: October 2006

Accumulation of soluble salts resulting from fertilizer N may affect microbial production of N2O and CO2 in soils. This study was conducted to determine the effects of electrical conductivity (EC) and water content on N2O and CO2 production in five soils under intensive cropping. Surface soils from maize fields were washed, repacked and brought to 60% or 90% water‐filled pore space (WFPS). Salt mixtures were added to achieve an initial in situ soil EC of 0.5, 1.0, 1.5 and 2.0 dS m−1 The soil cores were incubated at 25°C for 10 d. Average CO2 production decreased with increasing EC at both soil water contents, indicating a general reduction in microbial respiration with increasing EC. Average cumulative N2O production at 60% WFPS decreased from 2.0 mg N2O‐N m−2 at an initial EC of 0.5 dS m−1 to 0.86 mg N2O‐N m−2 at 2.0 dS m−1 At 90% WFPS, N2O production was 2 to 40 times greater than that at 60% WFPS and maximum N2O losses occurred at the highest EC level of 2.0 dS m−1 Differences in the magnitude of gas emissions at varying WFPS were due to available substrate N and the predominance of nitrification under aerobic conditions (60% WFPS) and denitrification when oxygen was limited (90% WFPS). Differences in gas emissions at varying soil EC may be due to changes in mechanisms of adjustment to salt stress and ion toxicities by microbial communities. Direct effects of EC on microbial respiration and N2O emissions need to be accounted for in ecosystems models for predicting soil greenhouse gas emissions.