bluuebunny/crossref_metadata_2025 huggingface dataset:
In Situ Push–Pull Method to Determine Ground Water Denitrification in Riparian Zones
Authors: Addy Kelly , Kellogg D. Q. , Gold Arthur J. , Groffman Peter M. , Ferendo Gina , Sawyer Carl
Published: June 2010

To quantify ground water denitrification in discrete locations of riparian aquifers, we modified and evaluated an in situ method based on conservative tracers and15N‐enriched nitrate. Ground water was “pushed” (i.e., injected) into a mini‐piezometer and then “pulled” (i.e., extracted) from the same mini‐piezometer after an incubation period. This push–pull method was applied in replicate mini‐piezometers at two Rhode Island riparian sites, one fresh water and one brackish water. Conservative tracer pretests were conducted to determine incubation periods, ranging from 5 to 120 h, to optimize recovery of introduced plumes. For nitrate push–pull tests, we used two conservative tracers, sulfur hexafluoride and bromide, to provide insight into plume recovery. The two conservative tracers behaved similarly. The dosing solutions were amended with15N‐enriched nitrate that enabled us to quantify the mass of denitrification gases generated during the incubation period. The in situ push–pull method detected substantial denitrification rates at a site where we had previously observed high denitrification rates. At our brackish site, we found high rates of ground water denitrification in marsh locations and minimal denitrification in soils fringing the marsh. The push–pull method can provide useful insights into spatial and temporal patterns of denitrification in riparian zones. The method is robust and results are not seriously affected by dilution or degassing from ground water to soil air. In conjunction with measurements of ground water flowpaths, this method holds promise for evaluating the influence of site and management factors on the ground water nitrate removal capacity of riparian zones.
A Dynamic Two‐Dimensional System for Measuring Volatile Organic Compound Volatilization and Movement in Soils
Authors: Allaire S.E. , Yates S.R. , Ernst F.F. , Gan J.
Published: June 2010

There is an important need to develop instrumentation that allows better understanding of atmospheric emission of toxic volatile compounds associated with soil management. For this purpose, chemical movement and distribution in the soil profile should be simultaneously monitored with its volatilization. A two‐dimensional rectangular soil column was constructed and a dynamic sequential volatilization flux chamber was attached to the top of the column. The flux chamber was connected through a manifold valve to a gas chromatograph (GC) for real‐time concentration measurement. Gas distribution in the soil profile was sampled with gas‐tight syringes at selected times and analyzed with a GC. A pressure transducer was connected to a scanivalve to automatically measure the pressure distribution in the gas phase of the soil profile. The system application was demonstrated by packing the column with a sandy loam in a symmetrical bed–furrow system. A 5‐h furrow irrigation was started 24 h after the injection of a soil fumigant, propargyl bromide (3‐bromo‐1‐propyne; 3BP). The experience showed the importance of measuring lateral volatilization variability, pressure distribution in the gas phase, chemical distribution between the different phases (liquid, gas, and sorbed), and the effect of irrigation on the volatilization. Gas movement, volatilization, water infiltration, and distribution of degradation product (Br−) were symmetric around the bed within 10%. The system saves labor cost and time. This versatile system can be modified and used to compare management practices, estimate concentration–time indexes for pest control, study chemical movement, degradation, and emissions, and test mathematical models.
Adsorption of Arsenate and Arsenite on Ferrihydrite in the Presence and Absence of Dissolved Organic Carbon
Authors: Grafe Markus , Eick Matthew J. , Grossl Paul R. , Saunders Amy M.
Published: June 2010

The adsorption of As(V) and As(III) on synthetic two‐line ferrihydrite in the presence and absence of a peat humic acid (HAp), Suwannee River fulvic acid (FA), or citric acid (CA) was investigated. Previous work with goethite has demonstrated the ability of dissolved organic carbon (DOC) to decrease As(V) and As(III) adsorption. The results obtained demonstrate that As(V) adsorption on ferrihydrite was decreased only in the presence of CA. Arsenate decreased the adsorption of all organic acids except HAp Both FA and CA reduced As(III) adsorption on ferrihydrite, while HAp had no effect. Fulvic and citric acid adsorption on ferrihydrite was decreased in the presence of As(III); however, FA and CA adsorption increased at lower pH, which was consistent with decreased As(III) adsorption. Peat humic acid did not decrease As(III) adsorption, and we believe that the adsorption process of HAp and As(III) and As(V) on ferrihydrite are independent of each other. Previously, we observed that As(V) adsorption on goethite decreased in the presence of HAp > FA > CA, while As(III) adsorption on goethite was decreased similarly to that on ferrihydrite in the presence of CA > FA ≈ HAp, yet As(III) adsorption on ferrihydrite was greater than on goethite. The observed differences between this study and the earlier study on goethite are believed to be an intricate function of ferrihydrite's surface characteristics, which affect the mechanisms of adsorption and hence the affinity of organic acids such as HAp, FA, and CA for the ferrihydrite surface. As such, the adsorption of DOCs to ferrihydrite are assumed to be less favorable and to occur with a fewer number of ligands, resulting in lower surface coverage of weaker bond strength.
Adsorption–Desorption Behavior of Copper at Contaminated Levels in Red Soils from China
Authors: Yu S. , He Z.L. , Huang C.Y. , Chen G.C. , Calvert D.V.
Published: June 2010

Adsorption–desorption of copper (Cu2+) at contaminated levels in two red soils was investigated. The red soil derived from the Quaternary red earths (clayey, kaolinitic thermic plinthite Aquult) (REQ) adsorbed more Cu2+ than the red soil developed on the Arenaceous rock (clayey, mixed siliceous thermic typic Dystrochrept) (RAR). The maximum adsorption values (MA) that are obtained from the simple Langmuir model were 25.90 and 20.17 mmol Cu2+ kg−1 soil, respectively, for REQ and RAR. Adsorption of Cu2+ decreased soil pH, by 0.8 unit for the REQ soil and 0.6 unit for the RAR soil at the highest loadings. The number of protons released per Cu2+ adsorbed increased sigmoidally with increasing initial Cu2+ concentration for the RAR soil, but the relationship was almost linear for the REQ soil. The RAR soil released about 2.57 moles of proton per mole of Cu2+ adsorbed at the highest Cu2+ loading and the corresponding value for the REQ soil was 1.12. The distribution coefficient (Kd) decreased exponentially with increasing Cu2+ loading. Most of the adsorbed Cu2+ in the soils was readily desorbed in the NH4Ac. After five successive extractions with 1 mol L−1 NH4Ac (pH 5.0), 61 to 95% of the total adsorbed Cu2+ in the RAR soil was desorbed and the corresponding value for the REQ soil was 85 to 92%, indicating that the RAR soil had a greater affinity for Cu2+ than the REQ soil at low levels of adsorbed Cu2+
Carbon and Nitrogen Losses by Surface Runoff following Changes in Vegetation
Authors: Fierer Noah G. , Gabet Emmanuel J.
Published: June 2010

Rainfall simulation experiments were conducted on annual grassland and coastal sage scrub hillslopes to determine the quantities of C and N removed by surface runoff in sediment and solution. Undisturbed coastal sage scrub soils have very high infiltration capacities (>140 mm h−1), preventing the generation of surface runoff. Trampling disturbance to the sage scrub plots dramatically reduced infiltration capacities, increasing the potential for surface runoff and associated nutrient loss. Infiltration capacities in the grassland plots (30–50 mm h−1) were lower than in the sage scrub plots. Loss rates of dissolved C and N in surface runoff from grasslands were 0.5 and 0.025 mg m−2 s−1 respectively, with organic N accounting for more than 50% of the dissolved N. Total dissolved losses with simulated rainfall were higher than losses in simulations with just surface runoff, demonstrating the importance of raindrop impact in transferring solutes into the flow. Experimental data were incorporated into a numerical model of runoff and sediment transport to estimate hillslope‐scale sediment‐bound nutrient losses from grasslands. According to the model results, sediment‐bound nutrient losses are sensitive to the density of vegetation cover and rainfall intensity. The model estimates annual losses in surface runoff of 0.2 and 0.02 g m−2 for sediment‐bound C and N, respectively. The results of this study suggest that conversion of coastal sage scrub to annual grasslands increases hillslope nutrient losses and may affect stream water quality in the region.
Anionic Polyacrylamide Effects on Soil Sorption and Desorption of Metolachlor, Atrazine, 2,4‐D, and Picloram
Authors: Lu Jianhang , Wu Laosheng , Letey John , Farmer Walter J.
Published: June 2010

Polyacrylamide (PAM) treatment of irrigation water is a growing conservation technology in irrigated agriculture in recent years. There is a concern regarding the environmental impact of PAM after its application. The effects of anionic PAM on the sorption characteristics of four widely used herbicides (metolachlor, atrazine, 2,4‐D, and picloram) on two natural soils were assessed in batch equilibrium experiments. Results showed that PAM treatment kinetically reduced the sorption rate of all herbicides, possibly due to the slower diffusion of herbicide molecules into interior sorption sites of soil particles that were covered and/or cemented together by PAM. The equilibrium sorption and desorption amounts of nonionic herbicides (metolachlor and atrazine) were essentially unaffected by anionic PAM, even under a high PAM application rate, while the sorption amounts of anionic herbicides (2,4‐D and picloram) were slightly decreased and their desorption amounts increased little. The impact mechanisms of PAM were related to the molecular characteristics of PAM and herbicides. The negative effects of PAM on the sorption of anionic herbicides are possibly caused by the enhancement of electrostatic repulsion by presorbed anionic PAM and competition for sorption sites. However, steric hindrance of the large PAM molecule weakens its influence on herbicide sorption on interior sorption sites of soil particles, which probably leads to the small interference on herbicide sorption, even under high application rates.
Potential ofEnterococcus faecalisas a Human Fecal Indicator for Microbial Source Tracking
Authors: Wheeler Andrea L. , Hartel Peter G. , Godfrey Dominique G. , Hill Jennifer L. , Segars William I.
Published: June 2010

Regulatory agencies are interested in a fecal indicator bacterium with a host range limited to humans because human fecal contamination represents the greatest hazard to humans, yet is a relatively easy nonpoint source to remedy. Watersheds with human fecal contamination could be given first priority for cleanup. A fecal indicator bacterium with a host range limited to humans and a few other warm‐blooded animal species would also simplify microbial source tracking because only a few animal species would be required for any host origin database. The literature suggests that the fecal indicator bacteriumEnterococcus faecalishas a limited host range. On this basis, we selected this bacterium for study. Of 583 fecal streptococcal isolates obtained on Enterococcosel agar from Canada goose, cattle, deer, dog, human, chicken, and swine, 392 were considered presumptive enterococci and were subsequently speciated with the API 20 Strep system. Of these isolates, 22 wereEnt. durans(5.6%), 61 wereEnt. faecalis(15.6%), 98 wereEnt. faecium(25.0%), 86 wereEnt. gallinarum(21.9%), and 125 were unidentified (31.9%). The host range of theEnt. faecalisisolates was limited to dogs, humans, and chickens. Media were developed to isolate and identifyEnt. faecalisquickly from fecal samples and this scheme eliminatedEnt. faecalisisolates from dogs. When the remainingEnt. faecalisisolates were ribotyped, it was possible to differentiate clearly among the isolates from human and chicken. It may be that combining the potentially limited host range ofEnt. faecaliswith ribotyping is useful for prioritizing watersheds with fecal contamination.
Antibiotic Resistance Profiles to Determine Sources of Fecal Contamination in a Rural Virginia Watershed
Authors: Graves Alexandria K. , Hagedorn Charles , Teetor Alison , Mahal Michelle , Booth Amy M. , Reneau Raymond B.
Published: June 2010

Antibiotic resistance analysis (ARA) was used to determine if enterococci of human origin were present in a stream (Spout Run) that passes through a rural nonsewered community (Millwood, VA). Millwood consists of 82 homes, all served by individual septic systems, and Spout Run drains a 5800‐ha karst topography watershed that contains large populations of livestock and wildlife. Periodic monitoring by state regulatory officials had resulted in Spout Run being placed on the Virginia impaired stream list and Millwood being categorized as an at‐risk community. Stream samples were collected monthly and analyzed for fecal coliforms and enterococci (May 1999–May 2000); ARA was performed on enterococci stream isolates on a quarterly basis. All 117 stream samples were positive for fecal coliforms, and 32% exceeded the Virginia recreational water standard (1000 fecal coliforms/100 mL). A library of 1174 known source Enterococcus isolate antibiotic resistance profiles was constructed, and yielded correct classification rates of 94.6% for 203 human isolates, 93.7% for 734 livestock isolates, and 87.8% for 237 wildlife isolates. Antibiotic resistance analysis of 2012 enterococcal isolates recovered from stream samples indicated isolates of human origin appeared throughout the stream as it passed through Millwood, with a yearly average of approximately 10% human, 40% wildlife, and 50% livestock. There were no human origin isolates in samples collected upstream from Millwood, and the percent human origin isolates declined downstream from Millwood. While a human signature was found in Spout Run, it was small compared with the proportion of isolates from livestock and wildlife.
Management Factors Affecting Ammonia Volatilization from Land‐Applied Cattle Slurry in the Mid‐Atlantic USA
Authors: Thompson R. B. , Meisinger J. J.
Published: June 2010

Ammonia (NH3) volatilization commonly causes a substantial loss of crop‐available N from surface‐applied cattle slurry. Field studies were conducted with small wind tunnels to assess the effect of management factors on NH3 volatilization. Two studies compared NH3 volatilization from grass sward and bare soil. The average total NH3 loss was 1.5 times greater from slurry applied to grass sward. Two studies examined the effect of slurry dry matter (DM) content on NH3 loss under hot, summer conditions in Maryland, USA. Slurry DM contents were between 54 and 134 g kg−1 Dry matter content did not affect total NH3 loss, but did influence the time course of NH3 loss. Higher DM content slurries had relatively higher rates of NH3 volatilization during the first 12 to 24 h, but lower rates thereafter. Under the hot conditions, the higher DM content slurries appeared to dry and crust more rapidly causing smaller rates of NH3 volatilization after 12 to 24 h, which offset the earlier positive effects of DM content on NH3 volatilization. Three studies compared immediate incorporation with different tillage implements. Total NH3 loss from unincorporated slurry was 45% of applied slurry NH+4–N, while losses following immediate incorporation with a moldboard plow, tandem‐disk harrow, or chisel plow were, respectively, 0 to 3, 2 to 8, and 8 to 12%. These ground cover and DM content data can be used to improve predictions of NH3 loss under specific farming conditions. The immediate incorporation data demonstrate management practices that can reduce NH3 volatilization, which can improve slurry N utilization in crop–forage production.
Growth of Alfalfa in Sludge‐Amended Soils and Inoculated with Rhizobia Produced in Sludge
Authors: Rebah F. Ben , Prévost D. , Tyagi R.D.
Published: June 2010

The efficiency of rhizobial inoculants produced in wastewater sludge used as a growth medium and as a carrier was compared with that of inoculants produced in yeast mannitol broth (YMB) medium and by using peat as a carrier. Alfalfa (Medicago sativa L.) plants were inoculated with solid and liquid Sinorhizobium meliloti inoculants and grown in pots containing two soil types (Kamouraska clay soil and Saint‐André sandy soil). The effect of various levels of sludge amendment (60 and 120 kg N/ha) and nitrogen fertilizer (60 kg N/ha) was also studied. The sludge‐based inoculants showed the same symbiotic efficiency (nodulation and plant yield) as YMB‐based inoculants. The inoculation increased the nodulation indexes from 4–6 to 8–12, and the rhizobial number from 103 (uninoculated soils) to 106–107 cells/g in inoculated soils. However, the shoot dry weights and the nitrogen contents were not increased significantly by the inoculation. Applying sludge as an amendment enhanced the rhizobial number in soils from 103 to 104 cells/g and improved significantly the plant growth (shoot dry weights and nitrogen contents). This improvement increased with sludge rate and with the cut (three cuts). Compared with sludge, N fertilizer gave lower plant yields. The nodulation was not affected by sludge and N‐fertilizer application. The texture and physico–chemical properties of soil were found to affect the yield and nitrogen content of the plants. In this study, macroelements and heavy metals were at acceptable levels and were not considered to be negative factors.
Phosphorus Forms in Biosolids‐Amended Soils and Losses in Runoff
Authors: Penn Chad J. , Sims J. Thomas
Published: June 2010

Continuous addition of municipal biosolids to soils based on plant nitrogen (N) requirements can cause buildup of soil phosphorus (P) in excess of crop requirements; runoff from these soils can potentially contribute to nonpoint P pollution of surface waters. However, because biosolids are often produced using lime and/or metal salts, the potential for biosolids P to cause runoff P losses can vary with wastewater treatment plant (WWTP) process. This study was conducted to determine the effect of wastewater treatment process on the forms and amounts of P in biosolids, biosolids‐amended soils, and in runoff from biosolids‐amended soils. We amended two soil types with eight biosolids and a poultry litter (PL) at equal rates of total P (200 kg ha−1); unamended soils were used as controls. All biosolids and amended soils were analyzed for various types of extractable P, inorganic P fractions, and the degree of P saturation (acid ammonium oxalate method). Amended soils were placed under a simulated rainfall and all runoff was collected and analyzed for dissolved reactive phosphorus (DRP), iron‐oxide‐coated filter paper strip–extractable phosphorus (FeO‐P), and total phosphorus (EPA3050 P). Results showed that biosolids produced with a biological nutrient removal (BNR) process caused the highest increases in extractable soil P and runoff DRP. Alternatively, biosolids produced with iron only consistently had the lowest extractable P and caused the lowest increases in extractable soil P and runoff DRP when added to soils. Differences in soil and biosolids extractable P levels as well as P runoff losses were related to the inorganic P forms of the biosolids.
Relationship of Soil Test Phosphorus and Sampling Depth to Runoff Phosphorus in Calcareous and Noncalcareous Soils
Authors: Torbert H.A. , Daniel T.C. , Lemunyon J.L. , Jones R.M.
Published: June 2010

A study was initiated to investigate the relationship between soil test P and depth of soil sampling with runoff losses of dissolved molybdate reactive phosphorus (DMRP). Rainfall simulations were conducted on two noncalcareous soils, a Windthorst sandy loam (fine, mixed, thermic Udic Paleustalf) and a Blanket clay loam (fine, mixed, thermic Pachic Argiustoll), and two calcareous soils, a Purves clay (clayey, smectitic, thermic Lithic Calciustoll) and a Houston Black clay (fine, smectitic, thermic Udic Haplustert). Soil (0‐ to 2.5‐, 0‐ to 5‐, and 0‐ to 15‐cm depths) and runoff samples were collected from each of the four soils in permanent pasture exhibiting a wide range in soil test P levels (as determined by Mehlich III and distilled water extraction) due to prior manure applications. Simulated rain was used to produce runoff, which was collected for 30 min. Good regression equations were derived relating soil test P level to runoff DMRP for all four soil types, as indicated by relatively high r2 values (0.715 to 0.961, 0‐ to 5‐cm depth). Differences were observed for the depth of sampling, with the most consistent results observed with the 0‐ to 5‐cm sampling depth. Runoff DMRP losses as a function of the concentration of P in soil were lower in calcareous soils (maximum of 0.74 mg L−1) compared with noncalcareous soils (maximum of 1.73 mg L−1). The results indicate that a soil test for environmental P could be developed, but it would require establishing different soil test P level criteria for different soils or classes of soils.
Influence of Flooding on Phosphorus Mobility in Manure‐Impacted Soil
Authors: Pant H.K. , Nair V.D. , Reddy K.R. , Graetz D.A. , Villapando R.R.
Published: June 2010

Agricultural lands are often used for constructing stormwater treatment areas (STAs) to abate nutrient loading to adjacent aquatic systems. Flooding agricultural lands to create STAs could stimulate a significant release of phosphorus (P) from soil to the water column. To assess the suitability of agricultural lands, specifically those impacted by animal operations, for the construction of STAs, soils from different components of the New Palm–Newcomer dairies (Nubbin Slough Basin, Okeechobee, Florida, USA) were collected by horizon and their P retention and release capacities estimated. In general, P released from A‐horizon soil under flooded (anaerobic) conditions was greater than under drained (aerobic) conditions due to redox effect on iron (Fe) and consequent P releases. However, the P released from Bh‐horizon soil was greater under aerobic conditions than under anaerobic conditions, possibly due to excessive aluminum (Al) content in the horizon. Double acid–extractable calcium (Ca), magnesium (Mg), Al, and P explained 87% of the variability in P release under aerobic conditions, and 80% of that under anaerobic conditions. The P release maxima indicated a high solubility of P in A‐horizon soil from both active and abandoned dairies (13 and 8% of the total P, respectively), suggesting that these soils could function as potential sources of P to the overlying water column when used in STA construction. Preestablishment of vegetative communities or chemical amendment, however, could ameliorate high P flux from soil to the water column.
Differences in Microbial Biomass, Organic Carbon, and Dye Sorption between Flow and No‐Flow Regions of Unsaturated Soil
Authors: Gaston L.A. , Locke M.A.
Published: June 2010

Transport models in which the liquid phase is partitioned between conducting and nonconducting regions allow the possibility that degradation and sorption are different in these regions. However, there is little information on biological or chemical differences between conducting and nonconducting regions of the soil matrix. Previous work by the authors on Br− transport through unsaturated, intact soil cores of Dundee silty clay loam (fine‐silty, mixed, active, thermic Typic Endoaqualf) indicated non‐equilibrium conditions that could be well‐described by a two‐region model. Fitted parameters indicated little solute transfer between flow regions, suggesting that dye movement in unsaturated soil might delineate conducting and nonconducting regions of this soil. Steady‐state, unsaturated flow was established in intact cores (10 by 30 cm) of the Dundee soil, then Br− and erioglaucine dye were displaced through these cores. The soil cores were then sectioned into 5‐cm segments and stained soil was separated from unstained soil. Microbial biomass C, organic C, and dye sorption KD (= gsorbed kg−1soil/g L−1) values for stained and unstained soil were determined. Stained soil had higher microbial biomass C but generally lower organic C and lower affinity for dye sorption than unstained soil from the same depth increment. Fraction of immobile water, dispersion, and mass transfer between conducting and nonconducting regions were consistent with previous results.
Optical Properties of Intact Leaves for Estimating Chlorophyll Concentration
Authors: Carter Gregory A. , Spiering Bruce A.
Published: June 2010

Changes in leaf chlorophyll content can serve as relative indicators of plant vigor and environmental quality. This study identified reflectance, transmittance, and absorptance wavebands and band ratios within the 400‐ to 850‐nm range for intact leaves that could be used to estimate extracted leaf chlorophyll per unit leaf area (areal concentration) with minimal error. Leaf optical properties along with chlorophyll a, b, and a + b concentrations were measured for the planar‐leaved sweetgum (Liquidambar styraciflua L.), red maple (Acer rubrum L.), wild grape (Vitis rotundifolia Michx.), and switchcane [Arundinaria gigantea (Walter) Muhl.], and for needles of longleaf pine (Pinus palustris Miller). Generally, reflectance, transmittance, and absorptance corresponded most precisely with chlorophyll concentrations at wavelengths near 700 nm, although regressions were also strong in the 550‐ to 625‐nm range. A power function was superior to a simple linear function in yielding low standard deviations of the estimate (s). When data were combined among the planar‐leaved species, s values were low at approximately 50 μmol/m2 out of a 940 μmol/m2 range in chlorophyll a + b at best‐fit wavelengths of 707 to 709 nm. Minimal s values for chlorophyll a + b ranged from 32 to 62 μmol/m2 across species when band ratios having numerator wavelengths of 693 to 720 nm were used with the application of a power function. Optimal denominator wavelengths for the band ratios were 850 nm for reflectance and transmittance and 400 nm for absorptance. This information can be applied in designing field portable chlorophyll meters and in the landscape‐scale remote sensing of plant responses to the environment.
Vegetation Stress Detection through Chlorophyll a + b Estimation and Fluorescence Effects on Hyperspectral Imagery
Authors: Zarco‐Tejada P. J. , Miller J. R. , Mohammed G. H. , Noland T. L. , Sampson P. H.
Published: June 2010

Physical principles applied to remote sensing data are key to successfully quantifying vegetation physiological condition from the study of the light interaction with the canopy under observation. We used the fluorescence–reflectance–transmittance (FRT) and PROSPECT leaf models to simulate reflectance as a function of leaf biochemical and fluorescence variables. A series of laboratory measurements of spectral reflectance at leaf and canopy levels and a modeling study were conducted, demonstrating that effects of chlorophyll fluorescence (CF) can be detected by remote sensing. The coupled FRT and PROSPECT model enabled CF and chlorophyll a + b (Ca+b) content to be estimated by inversion. Laboratory measurements of leaf reflectance (r) and transmittance (t) from leaves with constant Ca+b allowed the study of CF effects on specific fluorescence‐sensitive indices calculated in the Photosystem I (PS‐I) and Photosystem II (PS‐II) optical region, such as the curvature index [CUR; R675·R690/R2683]. Dark‐adapted and steady‐state fluorescence measurements, such as the ratio of variable to maximal fluorescence (Fv/Fm), steady state maximal fluorescence (F′m), steady state fluorescence (Ft), and the effective quantum yield (ΔF/F′m) are accurately estimated by inverting the FRT–PROSPECT model. A double peak in the derivative reflectance (DR) was related to increased CF and Ca+b concentration. These results were consistent with imagery collected with a compact airborne spectrographic imager (CASI) sensor from sites of sugar maple (Acer saccharum Marshall) of high and low stress conditions, showing a double peak on canopy derivative reflectance in the red‐edge spectral region. We developed a derivative chlorophyll index (DCI; calculated as D705/D722), a function of the combined effects of CF and Ca+b content, and used it to detect vegetation stress.
Narrow‐Waveband Reflectance Ratios for Remote Estimation of Nitrogen Status in Cotton
Authors: Read J. J. , Tarpley L. , McKinion J. M. , Reddy K. R.
Published: June 2010

Tailoring nitrogen (N) fertilizer applications to cotton (Gossypium hirsutum L.) in response to leaf N status may optimize N use efficiency and reduce off‐site effects of excessive fertilizer use. This study compared leaf and canopy reflectance within the 350 to 950 nm range in order to identify reflectance ratios sensitive to leaf chlorophyll (Chl), and hence N status, in cotton. Plants were grown outdoors in large pots using half‐strength Hoagland's (control) solution until some three‐row plots received a restricted supply of N. Treatments comprised control, 20% of control N at first flower bud (square) onward; 0 and 20% of control N at first flower onward; and 0% of control N at fruit‐filling onward. Despite leaf N values ranging from 51 to 19 g kg−1 across treatments and sampling dates, a weak correlation was obtained between Chl and N (r2 = 0.32, df = 70). In general, N stress led to increased reflectance at 695 ± 2.5 nm (R695) and decreased reflectance at R410, and changes in leaf N were best correlated with either R695 or R755 in leaves and either R410 or R700 in canopies. The strongest associations between leaf constituent and canopy reflectance ratio were Chl vs. R415/R695 (r2 = 0.72), carotenoids vs. R415/R685 (r2 = 0.79), and N vs. R415/R710 (r2 = 0.70). The R415 measure appears to be a more stable spectral feature under N stress, as compared with more pronounced changes along the reflectance red edge (690–730 nm). Multiple regression identified a three‐waveband canopy reflectance model that explained 80% of the variability in leaf N. Results indicate that remote sensing of N status in cotton is feasible using narrow‐waveband reflectance ratios that involve the violet or blue region of the spectrum (400 to 450 nm) and the more commonly featured red‐edge region.
Spectral Properties of Salt Crusts Formed on Saline Soils
Authors: Howari F. M. , Goodell P. C. , Miyamoto S.
Published: June 2010

Rapid identification and large‐scale mapping of salt‐affected lands will help improve salinity management in watersheds and ecosystems. This study was conducted to examine spectral reflectance of soils treated with saline solutions containing NaCl, NaHCO3, Na2SO4, and CaSO4·2H2O. Spectral reflectance was measured upon salt crusts formed on two soils (Torrifluvents) subirrigated with saline solutions of 500, 1000, and 1500 mmolc L−1 with a spectroradiometer in the visible and near‐infrared region (400–2500 nm). Spectral analyses revealed that samples of gypsum crusts have diagnostic absorption features near 1023, 1225, 1457, 1757, 1800, and 2336 nm, whereas halite crusts have diagnostic absorption features near 1442, 1851, 1958, and 2226 nm. Several broad absorption features were seen in the spectra of the crusts of sodium bicarbonate at 1243, 1498, 1790, 1988, and 2356 nm. The spectrum of soils treated with sodium sulfate exhibited absorption features at 1243, 1472, 1677, 1774, 1851, 1968, and 2245 nm. Crystal size or salt concentrations did not affect the positions of the absorption bands of the salt crusts. However, reflectance increased as particle sizes decreased or with increasing presence of salt crusts. Spectroscopy can be used under certain conditions to identify the presence of primary diagnostic spectral features of gypsum, nahcolite, thenardite, and halite crusts.
Environmental Risks of Applying Sewage Sludge Compost to Vineyards
Authors: Korboulewsky Nathalie , Dupouyet Sylvie , Bonin Gilles
Published: June 2010

Biosolids are applied to vineyards to supply organic matter. However, there is concern that this practice can increase the concentration of macronutrients and heavy metals in the soil, some of which can leach. We evaluated the environmental hazard of sewage sludge compost applied in March 1999 at 10, 30, and 90 Mg ha−1 fresh weight in a vineyard in southeastern France. Soil organic matter increased in all plots by 3 g kg−1 18 mo after the amendment. Neither total nor available heavy metal concentrations increased in the soil. Mineral nitrogen (N) in the topsoil of amended plots of 10, 30, and 90 Mg ha−1 increased by 5, 14, and 26 kg (NO−3–N + NH+4–N) ha−1, respectively, the first summer and by 2, 5, and 10 kg NO−3–N + NH+4–N ha−1, respectively, the second summer compared with controls. At the recommended rate, risks of N leaching is very low, but phosphorus (P) appeared to be the limiting factor. Phosphorus significantly increased only in plots amended with the highest rate in the topsoil and subsoil. At lower rates, although no significant differences were observed, P added was greater than the quantities absorbed by vines. In the long run, P will accumulate in the soil and may reach concentrations that will pose a risk to surface waters and ground water. Therefore, although the current recommended rate (10 Mg ha−1) increased soil organic matter without the risk of N leaching, total sewage sludge loading rates on vineyards should be based on P concentrations.
Application of Classification‐Tree Methods to Identify Nitrate Sources in Ground Water
Authors: Spruill Timothy B. , Showers William J. , Howe Stephen S.
Published: June 2010

A study was conducted to determine if nitrate sources in ground water (fertilizer on crops, fertilizer on golf courses, irrigation spray from hog (Sus scrofa) wastes, and leachate from poultry litter and septic systems) could be classified with 80% or greater success. Two statistical classification‐tree models were devised from 48 water samples containing nitrate from five source categories. Model 1 was constructed by evaluating 32 variables and selecting four primary predictor variables (δ15N, nitrate to ammonia ratio, sodium to potassium ratio, and zinc) to identify nitrate sources. A δ15N value of nitrate plus potassium >18.2 indicated animal sources; a value <18.2 indicated inorganic or soil organic N. A nitrate to ammonia ratio >575 indicated inorganic fertilizer on agricultural crops; a ratio <575 indicated nitrate from golf courses. A sodium to potassium ratio >3.2 indicated septic‐system wastes; a ratio <3.2 indicated spray or poultry wastes. A value for zinc >2.8 indicated spray wastes from hog lagoons; a value <2.8 indicated poultry wastes. Model 2 was devised by using all variables except δ15N. This model also included four variables (sodium plus potassium, nitrate to ammonia ratio, calcium to magnesium ratio, and sodium to potassium ratio) to distinguish categories. Both models were able to distinguish all five source categories with better than 80% overall success and with 71 to 100% success in individual categories using the learning samples. Seventeen water samples that were not used in model development were tested using Model 2 for three categories, and all were correctly classified. Classification‐tree models show great potential in identifying sources of contamination and variables important in the source‐identification process.
Relating Net Nitrogen Input in the Mississippi River Basin to Nitrate Flux in the Lower Mississippi River
Authors: McIsaac Gregory F. , David Mark B. , Gertner George Z. , Goolsby Donald A.
Published: June 2010

A quantitative understanding of the relationship between terrestrial N inputs and riverine N flux can help guide conservation, policy, and adaptive management efforts aimed at preserving or restoring water quality. The objective of this study was to compare recently published approaches for relating terrestrial N inputs to the Mississippi River basin (MRB) with measured nitrate flux in the lower Mississippi River. Nitrogen inputs to and outputs from the MRB (1951 to 1996) were estimated from state‐level annual agricultural production statistics and NOy (inorganic oxides of N) deposition estimates for 20 states that comprise 90% of the MRB. A model with water yield and gross N inputs accounted for 85% of the variation in observed annual nitrate flux in the lower Mississippi River, from 1960 to 1998, but tended to underestimate high nitrate flux and overestimate low nitrate flux. A model that used water yield and net anthropogenic nitrogen inputs (NANI) accounted for 95% of the variation in riverine N flux. The NANI approach accounted for N harvested in crops and assumed that crop harvest in excess of the nutritional needs of the humans and livestock in the basin would be exported from the basin. The U.S. White House Committee on Natural Resources and Environment (CENR) developed a more comprehensive N budget that included estimates of ammonia volatilization, denitrification, and exchanges with soil organic matter. The residual N in the CENR budget was weakly and negatively correlated with observed riverine nitrate flux. The CENR estimates of soil N mineralization and immobilization suggested that there were large (2000 kg N ha−1) net losses of soil organic N between 1951 and 1996. When the CENR N budget was modified by assuming that soil organic N levels have been relatively constant after 1950, and ammonia volatilization losses are redeposited within the basin, the trend of residual N closely matched temporal variation in NANI and was positively correlated with riverine nitrate flux in the lower Mississippi River. Based on results from applying these three modeling approaches, we conclude that although the NANI approach does not address several processes that influence the N cycle, it appears to focus on the terms that can be estimated with reasonable certainty and that are correlated with riverine N flux.
Secondary Metabolite Concentrations and Terpene Emissions of Scots Pine Xylem after Long‐Term Forest Fertilization
Authors: Turtola S. , Manninen A.‐M. , Holopainen J. K. , Levula T. , Raitio H. , Kainulainen P.
Published: June 2010

Secondary compounds are known to be associated with the resistance of conifer xylem against insects and fungi. The effects of long‐term forest fertilization with nitrogen (N) or with N, calcium (Ca), and phosphorus (P) on secondary compounds in the xylem of 50‐yr‐old Scots pine (Pinus sylvestris L.) trees were examined. Xylem samples were collected from trees growing in three locations in southern Finland: Vilppula, Padasjoki, and Punkaharju. Forests were fertilized every fifth (Vilppula and Padasjoki) or tenth (Punkaharju) year since the 1950s. We compared concentrations of individual and total monoterpenes and resin acids in the heartwood and sapwood of Scots pine. Terpene emissions were analyzed from the sapwood and total phenolics from the heartwood. Fertilization did not have any significant effect on the concentrations and emissions of xylem monoterpenes. Concentrations of several individual terpenes in sapwood were positively correlated with the corresponding terpene emission. The concentrations of individual resin acids (i.e., abietic and dehydroabietic) decreased significantly in Punkaharju, but increased in the sapwood of N‐fertilized trees compared with control ones at Padasjoki and Vilppula. The concentrations of resin acids in the heartwood were not significantly affected by fertilization. Both fertilization treatments decreased the total phenolic concentration in the heartwood of trees growing in Padasjoki. There was a significant positive correlation between the total phenolics and total resin acid concentration. Overall, resin acids and phenolics seemed be more responsive than monoterpenes to N treatment. These results suggest that forest fertilization might cause slight changes in secondary compound concentrations of xylem, and thus might have significance in the decay resistance of wood.
Bioavailability of Organic Phosphorus in a Submerged Aquatic Vegetation–Dominated Treatment Wetland
Authors: Pant H. K. , Reddy K. R. , Dierberg F. E.
Published: June 2010

Enzymatic hydrolysis and mineralization of organic phosphorus (P) were determined in surface water samples collected from inflow and outflow of a submerged aquatic vegetation (SAV)–dominated treatment wetland of the Florida Everglades. Water samples were fractionated into three size fractions (>0.4 μm, <0.4 to >0.05 μm, and <0.05 μm) with a sequential flow filtration technique. The fractionated water samples were incubated to hydrolyze with alkaline phosphatase (APase) and phosphodiesterase (PDEase), and to mineralize at different redox and pH. Unlike APase, which hydrolyzed ≤10% of organic P, PDEase hydrolyzed ≥71% of organic P in unfiltered water from both inflow and outflow waters, suggesting the domination of bioavailable diester P in the water. Phosphodiesterase completely hydrolyzed organic P in the <0.4‐ to >0.05‐μm and <0.05‐μm fractions, as compared with ≤35% in the >0.4‐μm fraction. However, the P mineralization in inflow and outflow waters at different redox and pH showed that P associated with particulate > 0.4 μm had been mineralized the most. Phosphorus‐31 nuclear magnetic resonance (NMR) spectroscopy showed that surficial sediments from the inflow region contained a high proportion of polynucleotides, nucleoside monophosphates, and previously unreported glycerophosphoethanolamine and phosphoenolpyruvates. However, at the outflow, the relative proportion of polynucleotides and nucleoside monophosphates was reduced substantially. This suggests that the SAV wetland may sequester P via accretion of organic matter.
Hydrogen Sulfide Effects on Ammonia Removal by a Biofilter Seeded with Earthworm Casts
Authors: Lee E. Y. , Cho K. S. , Han H. D. , Ryu H.W.
Published: June 2010

Ammonia (NH3) removal efficiencies were evaluated when hydrogen sulfide (H2S) and NH3 in binary mixture gases were supplied to a ceramic biofilter seeded with earthworm (Lumbricus terrestris) casts. The effect of inlet H2S concentration and space velocity (SV) on the removal of NH3 was investigated after the acclimation of the biofilter with NH3 gas. When NH3 was singly supplied to the biofilter, NH3 removal was maintained at almost 100% until inlet NH3 concentration was increased up to 600 μL L−1 and SV up to 330 h−1, at which the elimination capacity of NH3 was 148 g N m−3 h−1 When H2S was supplied simultaneously, however, the accumulation of toxic sulfide ions showed dual effects on NH3 removal efficiencies. First, no effects were observed at inlet H2S loading below 60 g S m−3 h−1; however, inhibition by H2S at higher loading was observed above 60 g S m−3 h−1 The point at which loading achieved a maximum of more than 99% NH3 removal efficiency was 139 g N m−3 h−1, when inlet H2S concentration was held under 100 μL L−1, but it dropped to 76 and 30 g N m−3 h−1 when the inlet H2S concentration increased to 220 and 460 μL L−1, respectively. The critical points of inlet H2S loading that guaranteed over 99% NH3 removal were determined as 100, 100, 60, and 40 g S m−3 h−1 at inlet NH3 concentrations of 100, 200, 400, and 600 μL L−1, respectively. Inlet NH3 loading had synergic effects of increasing the inhibition of inlet H2S loading on the NH3 removability of the biofilter.
Application Technique and Slurry Co‐Fermentation Effects on Ammonia, Nitrous Oxide, and Methane Emissions after Spreading
Authors: Wulf S. , Maeting M. , Clemens J.
Published: June 2010

The aim of this study was to investigate the effect of different application techniques on greenhouse gas emission from co‐fermented slurry. Ammonia (NH3), nitrous oxide (N2O), and methane (CH4) emissions were measured in two field experiments with four different application techniques on arable and grassland sites. To gather information about fermentation effects, unfermented slurry was also tested, but with trail hose application only. Co‐fermented slurry was applied in April at a rate of 30 m3 ha−1 Measurements were made every 4 h on the first day after application and were continued for 6 wk with gradually decreasing sampling frequency. Methane emissions were <150 g C ha−1 from co‐fermentation products and seemed to result from dissolved CH4 Only in the grassland experiment were emissions from unfermented slurry significantly higher, with wetter weather conditions probably promoting CH4 production. Nitrous oxide emission was significantly increased by injection on arable and grassland sites two‐ and threefold, respectively. Ammonia emissions were smallest after injection or trail shoe application and are discussed in the preceding paper. We evaluated the climatic relevance of the measured gas emissions from the different application techniques based on the comparison of CO2 equivalents. It was evident that NH3 emission reduction, which can be achieved by injection, is at least compensated by increased N2O emissions. Our results indicate that on arable land, trail hose application with immediate shallow incorporation, and on grassland, trail shoe application, bear the smallest risks of high greenhouse gas emissions when fertilizing with co‐fermented slurry.
Irrigation of Broccoli and Canola with Boron‐ and Selenium‐Laden Effluent
Authors: Bañuelos G. S.
Published: June 2010

Selenium (Se), boron (B), and salinity contamination of agricultural drainage water is potentially hazardous for water reuse strategies in central California. To demonstrate the feasibility of using plants to extract Se from drainage water, Se accumulation was determined in canola (Brassica napus L.) and broccoli (Brassica oleracea L.) irrigated with drainage effluent in the San Joaquin Valley, California. In the 2‐yr field study, both crops were irrigated with a typical drainage water containing Se (150 μg L−1), B (5 mg L−1), and a sulfate dominated salinity (EC of 7 dS m−1). Total dry matter yields were at least 11 Mg ha−1 for both canola and broccoli, and plant tissue Se concentrations did not exceed 7 mg kg−1 DM for either crop. Based on the amount of soluble Se applied to crops with drainage water and the estimated amount of soluble Se remaining in soil to a depth of 90 cm at harvest, both canola and broccoli accumulated at least 40% of the estimated soluble Se lost from the soil for both years. Applied Se not accounted for in plant tissue or as soluble Se in the soil was presumably lost by biological volatilization. This study suggests that irrigating two high value crops such as canola and broccoli with Se‐laden effluent helps manage Se‐laden effluent requiring treatment, and also produces economically viable Se‐enriched crops. Future research should focus on managing residual salt and B in the soil for sustaining long time water reuse strategies.