| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||
Phosphatic clay, a by-product of phosphate mining industry, could be cost effective in the remediation of heavy metal–contaminated soils and sediments, according to a report by Singh et al. Metals were sorbed onto phosphatic clay in the order Pb2+ > Cd2+ > Zn2+. Desorption data suggested that a large fraction of metals sorbed onto phosphatic clay remained intact when extracting solution pH ranged from 3 to 10. The phosphatic clay is high in apatite, smectite, kaolinite, illite, attapugite, and polygorskite with lesser amounts of other minerals, making it an excellent binding agent for in situ immobilization of heavy metals in contaminated soils and sediments.
L.Q. Ma (lqma{at}ufl.edu)
Heavy Metal Interactions with Phosphatic Clay: Sorption and Desorption Behavior. J. Environ. Qual. 30:1961–1968.
Phytosiderophores Inadequate as Cadmium Mediators
Synthetic chelates have been used to increase metal mobilization and facilitate phytoextraction as a means for the remediation of metal polluted soils. Plant-produced chelators, called phytosiderophores, are excreted directly to the rhizosphere. Shenker et al. now show that phytosiderophores efficiently extract cadmium (Cd) from a solid phase, even in the presence of iron and other competing metals. However, their results also show that in situ–released phytosiderophores had little effect on Cd uptake by barley and wheat plants. Results suggest that plants that are highly efficient in phytosiderophore release may not necessarily accumulate more Cd from contaminated soils than iron-inefficient plants, nor are they likely to provide any advantage for phytoremediation of Cd-contaminated soils. Since roots occupy only a small portion of the bulk soil, most of the chelate-extracted metal might be quite far from the uptake sites and may be leached rather than being mobilized to plant roots.
M. Shenker (shenker{at}agri.huji.ac.il)
Phytosiderophores Influence on Cadmium Mobilization and Uptake by Wheat and Barley Plants. J. Environ. Qual. 30:2091–2098.
Environmental Risks of Pig Slurry Application
The recycling of pig slurry in agricultural soils is practiced in many countries. Diez et al. report that the application of high doses of pig slurry led to nitrate contamination of ground water and increased soil salinity. Two and five months after application of pig slurry, no unwanted phenols, indols, or PCBs were detected in the soil, but there were indications of copper contamination. Nitrate leaching was proportional to fertilizer dose and drainage volume. The authors recommend that the dose of pig slurry should be calculated before application, taking into account available soil nitrogen. Results are based on field experiments where normal and threefold pig slurry doses were applied.
J.A. Diez Lopez
(jadiez{at}ccma.csic.es)
Evaluation of the Application of Pig Slurry to an Experimental Crop Using Agronomic and Ecotoxicological Approaches. J. Environ. Qual. 30:2165–2172.
Farming System Reduces Nitrate in Water
Farming systems are a package of activities involving growing crops. The package will vary from farm to farm due to availability of labor, capitol, equipment, managerial skills, crop production goals, landlord–tenant relationships, and various social pressures. A review by Power et al. suggests that the key to reducing the movement of nitrate into surface and ground water resources is selection of the best package of farming activities. A five-year, five-state comprehensive research program showed that at most field locations a combination package of corn–soybean rotations, ridge-till, soil-testing, and appropriate nitrogen fertilizer practice resulted in the lowest nitrate degradation of water resources and near maximum economic return.
R.A. Wiese (dw53434{at}alltel.net)
Managing Farming Systems for Nitrate Control: A Research Review from Management Systems Evaluation Areas. J. Environ. Qual. 30:1866–1880.
Chlorobenzene Degraded with Advanced Oxidation Processes
Oxidation in water can convert organic pollutants into innocuous materials like carbon dioxide and water, but the process is too slow at ambient conditions. Therefore, Dilmeghani and Zahir studied the kinetics and mechanism of chlorobenzene degradation using UV, UV–H2O2, UV–O3, and UV–H2O2–O3. Using HPLC and GC–MS, they found that the degradation rate was fastest for the UV–H2O2 system and slowest for the UV system. For the UV–H2O2 system, the rates varied linearly with H2O2 concentration. More than 90% of 2 mM chlorobenzene was degraded in two minutes using 0.03 M H2O2. Depending on the time of photolysis and the method used, different intermediates were formed during photolysis. These were also degraded at longer times, leading to the formation of carbon dioxide and water as the possible final products.
K. Omar Zahir
(omar.zahir{at}csun.edu)
Kinetics and Mechanism of Chlorobenzene Degradation in Aqueous Samples Using Advanced Oxidation Processes. J. Environ. Qual. 30:2062–2070.
Natural Accumulator Wins Phytoremediation Test
Which is the better way to remove heavy metals from contaminated soils—use a plant that naturally accumulates metals, or enhance metal uptake by treating a plant with EDTA? Lombi et al. now report that three crops of the hyperaccumulator Thlaspi caerulescens removed >43 and 7% of the total cadmium (Cd) and zinc (Zn) from an industrially contaminated soil. The EDTA treatment greatly increased the solubility of heavy metals in the two soils investigated, but this did not result in a large increase in metal concentrations in maize shoots. Phytoextraction of Cd and Zn by maize + EDTA was much lower than that by T. caerulescens from the industrially contaminated soil, and was either smaller (Cd) or similar (Zn) from the agricultural soil. After EDTA treatment, soluble heavy metals in soil pore water occurred mainly as metal–EDTA complexes, which were persistent for several weeks.
S. McGrath
(steve.mcgrath{at}bbsrc.ac.uk)
Phytoremediation of Heavy Metal–Contaminated Soils: Natural Hyperaccumulation versus Chemically Enhanced Phytoextraction. J. Environ. Qual. 30:1919–1926.
Runoff and Soil Loss in Effluent-Irrigated Soils
Stability of soil surface aggregates and irrigation water quality can affect runoff and soil erosion. Aggregate stability depends strongly on rate of aggregate wetting. Fast wetting may enhance soil susceptibility to runoff and erosion under rain, especially in effluent irrigated soils. Mamedov et al. show that for soils taken from fields irrigated with fresh water or effluents for >15 years, runoff and soil loss decreased with decreasing rate of aggregate wetting. In addition, long-term irrigation with effluents in soils containing >20% clay did not adversely affect soil susceptibility to runoff and soil loss in soils exposed to simulated rainfall beyond that observed in fresh water–irrigated soils. Results are from laboratory studies on effects of prewetting rate on runoff and inter-rill erosion from five Israeli soils exposed to simulated rain.
G.J. Levy
(vwguy{at}volcani.agri.gov.il)
Irrigation with Effluents: Effects of Prewetting Rate and Clay Content on Runoff and Soil Loss. J. Environ. Qual. 30:2149–2156.
Redox Reaction Determines Methane Production, Oxidation
Methane formation in flooded rice soils occurs under anaerobic and reduced soil conditions. Redox reactions involving oxidized inorganic species like NO-3, Mn+4, Fe+3, and SO2-4 inhibit methane formation. Microbially mediated methane consumption in these soils may also be regulated by the soil reduction characteristics. Kumaraswamy et al. now show that addition of rice straw as a carbon source to increase the electron donor/electron acceptor ratio does not completely alleviate the inhibitory effects of oxidized redox species on methane production. Addition of MnO2 and K2SO4 enhanced aerobic methane oxidation. Sulfate stimulated oxidation under aerobic and anaerobic conditions, nitrate and ferric ion stimulated oxidation under aerobic conditions, and manganese(IV) ion stimulated oxidation under anaerobic conditions. Results suggest that different redox reactions exert differential effects on aerobic and anaerobic methane consuming activities in soils.
B. Ramakrishnan (crrictc{at}ori.nic.in or ramakrishnanbala{at}yahoo.com)
Methane Production and Oxidation in an Anoxic Rice Soil as Influenced by Inorganic Redox Species. J. Environ. Qual. 30:2195–2201.
Sorption in Norwegian Soils Questioned
As a main recipient of pesticides, the soil plays an important role in the environmental fate and protection of surface and ground waters. Soils from Nordic countries differ from soils in other countries in their genesis and in quality and quantity of clay minerals and organic matter. These attributes likely affect pesticide sorption. Thorstensen et al. report that the pesticides bentazone, dichlorprop, and MCPA are relatively weakly bound, whereas propiconazole is strongly sorbed. Despite differences in Nordic soils, the sorption indices were within the range of those from other countries. Results suggest that bentazone, dichlorprop, and MCPA are more prone to leach to the aquatic environment than is the less mobile propiconazole.
C.W. Thorstensen
(christian.thorstensen{at}planteforsk.no)
Sorption of Bentazone, Dichlorprop, MCPA, and Propiconazole in Reference Soils from Norway. J. Environ. Qual. 30:2046–2052.
Global Warming Increases Soil Thaw Depth
In response to global climate change, regional temperatures are warming most rapidly at high latitudes. Stottlemyer et al. describe a study begun in 1990 to measure effects of changes in temperature and moisture on a treeline ecosystem in the Noatak National Preserve, Northwest Alaska. One effect of increased temperatures is an increase in soil thaw depth, which will increase available nitrogen from previously unavailable organic pools. Increased nitrogen—a limiting nutrient—will likely alter ecosystem biodiversity, a policy concern for this legally protected national park. Warming temperatures will also increase soil respiration rates, as measured by carbon dioxide flux, which could add further to greenhouse gases.
R. Stottlemyer
(Robert_Stottlemyer{at}usgs.gov)
Biogeochemistry of a Treeline Watershed, Northwestern Alaska. J. Environ. Qual. 30:1990–1998.
Soils Leak Microbes
Animal or human waste applied to soil can result in chemical and microbial contamination of shallow ground water and waterways. McLeod et al. show that bromide moves uniformly through pumice and allophanic soils with peak concentrations at about one pore volume, whereas a bacteriophage was detected only at trace levels or not at all. Both bromide and bacteriophage tracers moved rapidly through Gley and recent soils, appearing early in the leachate and then tailing off. Results suggest that vertical movement of viruses varies significantly with soil type. They followed the fate of a host-specific Salmonella bacteriophage and a nonreactive chemical (Br-) tracer applied to large intact lysimeter soil cores. Resulting leachates, collected continuously over at least one pore volume, were analyzed for the bacteriophage and bromide tracers.
M. McLeod
(mcleodm{at}landcare.cri.nz)
Viral and Chemical Tracer Movement through Contrasting Soils. J. Environ. Qual. 30:2134–2140.
Estrogens Labile in Soils
Livestock manures can contain excreted estrogenic hormones that might be a risk to ground or surface waters. Colucci and Topp show that two hormones (17ß-estradiol and estrone) were rapidly removed over a wide range of soil moistures and temperatures. Both [4-14C]–17ß-estradiol and [4-14C]-estrone formed nonextractable residues, and soil-bound residues were only slowly mineralized, suggesting that their bioavailability was low. There were no other estrogenic compounds produced during 17ß-estradiol dissipation, and total estrogenicity was rapidly dissipated below the detection limit. They used laboratory microcosms to establish the persistence and pathways of dissipation of the hormones and a recombinant yeast assay to measure total estrogenicity in soil extracts.
E. Topp (toppe{at}em.agr.ca)
Persistence of Estrogenic Hormones in Agricultural Soils: I. 17ß-Estradiol and Estrone. J. Environ. Qual. 30:2070–2076.
Synthetic Estrogen Unstable in Soils
Some synthetic compounds with hormone-like action could pose a threat to surface or ground water if applied to agricultural land in sewage sludge. Colucci and Topp report that the synthetic hormone 17
-ethynylestradiol, found in oral contraceptives, was rapidly removed in loam, sandy loam, and silt loam soils under a range of moisture and temperature conditions. Removal of 17-ethynylestradiol correlated closely with removal of total estrogenicity determined with a recombinant yeast bioassay, indicating that extractable estrogenic transformation products did not accumulate. They conclude that 17-ethynylestradiol is rapidly dissipated in agricultural soils under a range of conditions typical of a temperate growing season.
E. Topp (toppe{at}em.agr.ca)
Persistence of Estrogenic Hormones in Agricultural Soils: II. 17-Ethynylestradiol. J. Environ. Qual. 30:2077–2080.
Rapid, Sensitive, Microscale Phosphate Determination
A new rapid, sensitive, and accurate method to measure phosphate in a wide range of soil and water samples is described by D'Angelo et al. The method is based on the complexation of malachite green with phosphomolybdate and is adapted to a 96-well microtiter plate format. They tested for matrix interferences using 15 soils and some common extractants, including water, KCl, CaCl2, NaOH, and HCl. Absorbance was not affected when background concentrations of these constituents were <0.1 M. Recovery of added inorganic P to different types of soils and extracts in this range averaged 102%, and the method detection limit at the 99% confidence limit was 0.006 mg P L-1. The method measures inorganic and organic phosphorus at submicromolar concentrations in water and soil extracts.
E. D'Angelo (edangelo{at}ca.uky.edu)
Rapid, Sensitive, Microscale Determination of Phosphate in Water and Soil. J. Environ. Qual. 30:2206–2209.
Soil Surface Structure Alters Herbicides Loss in Runoff
The transport of chemicals beyond a cultivated field by runoff can contribute to the contamination of surface waters. Lecomte et al. report that degradation of the structural state of the soil surface increases the ratio of pesticide loss to application rate. The structural state of the soil surface influences the rapidity at which runoff begins after the onset of rain, and the runoff coefficient at steady state. Development of a surface seal limits the depth of soil–runoff interaction and thus influences the dynamics of herbicide mobilization. They evaluated the effect of degraded soil surface structures on herbicide loss in runoff, and used the experimental data to test the uniform mixing zone concept and two-site sorption kinetics for modeling herbicide transfer to runoff. The experiments were done with simulated rainfall on field and laboratory plots.
V. Lecomte
(Lecomte-Morel{at}exchange.brgm.fr)
Soil Surface Structure Effect on Isoproturon and Diflufenican Loss in Runoff. J. Environ. Qual. 30:2113–2119.
Incidental Phosphorus Transfer from Grassland
Hydrologically driven exports of phosphorus (P) from agricultural watersheds are the primary cause of eutrophication for many surface waters. The high frequency of rainfall in the UK means that any recent application of fertilizer or manure to the soil surface may be vulnerable to direct (incidental) transfer in runoff. Preedy et al. investigated mechanisms of accelerated P transfer following applications of triple superphosphate fertilizer and dairy slurry to grassland plots. Forty-nine millimeters of rainfall in the seven days following application resulted in P transfers that were equivalent to annual P exports from carefully managed grassland. Phosphorus concentrations in subsurface and surface hydrological pathways were 50 to 110 times higher than those considered eutrophic in surface waters. They suggest that highlighting the risk associated with incidental P transfers and targeting short-term decision making is perhaps the most immediately viable method for mitigating P loss.
N. Preedy (Neil.preedy{at}bbsrc.ac.uk)
Rapid Incidental Phosphorus Transfers from Grassland. J. Environ. Qual. 30:2105–2112.
Model Predicts Heavy Metal Balances
Heavy-metal inputs into agricultural soils take place at a rather slow rate but on large areas, originating from atmospheric deposition and applied fertilizers and pesticides. Keller et al. describe the empirical stochastic model PROTERRA-S, which takes into account agricultural characteristics in balances and to provide preventive strategies against heavy-metal accumulation in regional agroecosystems. The basic units of these balances are land use systems defined by livestock production and cultivated crops. In a case study in Switzerland they assessed the phosphorus, cadmium, and zinc balances and compared the results with reported metal balances of experimental farms. Results indicate that identification of agricultural land with high risks of heavy metal accumulation benefits from stratification of heavy metal balances according to land use systems.
A. Keller
(armin.keller{at}ito.umnw.ethz.ch)
A Stochastic Empirical Model for Regional Heavy-Metal Balances in Agroecosystems. J. Environ. Qual. 30:1976–1989.
Spatial Variability Critical for Soil Phosphorus Management
In a phosphorus (P)-based nutrient management strategy, exceeding an established soil P threshold would prohibit manure applications. Following soil sampling recommendations is critical to obtaining trustworthy measures of soil P, especially when implementing threshold strategies for nutrient management, according to a report by Daniels et al. They characterized studied soil P variability in 12 pastures amended with animal waste using grid soil sampling and kriging. Reliability of soil P estimates from pastures for comparison to a threshold was influenced by spatial variability.
M. Daniels (mdaniels{at}uaex.edu)
Soil Phosphorus Variability in Pastures: Implications for Sampling and Environmental Management Strategies. J. Environ. Qual. 30:2157–2165.
Benefits of Organochlorine Pesticide Prohibition
In 1985, soil applications of organochlorine compounds were forbidden in Brazil, but some compounds were kept on the market for other purposes—lindane for animal ectoparasites, and heptachlor for termites in wood. Sparovek et al. report that, in spite of many previously applied organochlorine compounds, only lindane and heptachlor metabolites were detected in soils, colluviums, sediments, and organisms in a watershed where sugarcane is cultivated at the southeastern part of Brazil. Since many organochlorine pesticides were applied to sugarcane before the ban, these results suggest that detected pesticides were applied after the prohibition in 1985. The authors suggest that regulation could avoid undesirable dispersion of pesticides.
G. Sparovek
(Sparovek.PB.FAL{at}kepler.dv.fal.de)
Organochlorine Compounds in a Brazilian Watershed with Sugarcane and Intense Sediment Redistribution. J. Environ. Qual. 30:2006–2010.
Regional Scale Phosphorus Loss
Agricultural losses of phosphorus (P) in runoff are a primary cause of eutrophication in many freshwater systems. Mulla et al. describe a modified version of the P Index to prioritize P loss vulnerability at the regional scale from 60 watersheds in Minnesota. They validated the P Index rating using long-term water quality monitoring data for total P concentrations in watersheds and lakes. Results suggest that, with certain limitations, the P Index can be used at the regional scale to characterize P loss vulnerability using state and national databases.
D.J. Mulla (dmulla{at}soils.umn.edu)
Evaluation of the Phosphorus Index in Watersheds at the Regional Scale. J. Environ. Qual. 30:2018–2025.
Regulation of Nitrous Oxide Emissions
Applying animal slurries and effluents to soil often increases nitrous oxide emissions. It is not always apparent if this increase is due to increased N availability, increased soil water content, increased C availability, or a combination of these factors. Barton and Schipper report that applying dairy farm effluent generally increased soil nitrous oxide emissions more than applying inorganic fertilizer with water at the same N and hydraulic loading as dairy farm effluent. Enhanced nitrous oxide emissions from effluent irrigation were attributed to increased denitrification activity due to increased C availability. These findings suggest that the proportion of applied N emitted as nitrous oxide might be greater for organic N fertilizers than inorganic N fertilizers.
L. Barton
(lbarton{at}agric.uwa.edu.au)
Regulation of Nitrous Oxide Emissions from Soils Irrigated with Dairy Farm Effluent. J. Environ. Qual. 30:1881–1887.
Bioavailability Determines Contamination
A two-compartment plant model has been developed by Sung et al. to study plant contamination by organic pollutants in phytoremediation. They describe numerical experiments conducted to investigate model behavior and to determine important parameters affecting plant contamination. The most important factor affecting plant contamination is bioavailability. Microbial activities and plant contamination are closely related, suggesting that plants and microorganisms can have complementary roles in phytoremediation.
K. Sung (ksung{at}civil1.tamu.edu)
Plant Contamination by Organic Pollutants in Phytoremediation. J. Environ. Qual. 30:2081–2090.
Blast Furnace Sludge Cyanide Secrets Revealed
During blast furnace operation for the production of pig iron, a cyanide-containing muddy waste—referred to as sludge—is generated in large amounts. There has been no information about the type of cyanide occurring in blast furnace sludge deposits. Mansfeldt and Dohrmann have now identified by powder x-ray diffraction the crystalline cyanide-containing compound potassium zinc hexacyanoferrate(II) nonahydrate, K2Zn3[Fe(CN)6]2 9H2O, as the cyanide-bearing compound. Their study is the first to identify potassium zinc hexacyanoferrate(II) nonahydrate in the environment. Because the iron–cyanide complex [Fe(CN)6] is not acutely toxic, any direct hazard comes from cyanide occurring in the investigated wastes.
T. Mansfeldt
(Tim.Mansfeldt{at}ruhr-uni-bochum.de)
Identification of a Crystalline Cyanide-Containing Compound in Blast Furnace Sludge Deposits. J. Environ. Qual. 30:1927–1932.
Hunting for Mercury in Soil, Water, Vegetation
Sloan et al. detected elevated levels of mercury (Hg) in the surface soil and snowmelt runoff of soils that received biosolids, although total concentrations were low. They measured Hg levels in soil, runoff water, and vegetation from a cultivated agricultural watershed that previously received annual applications of wastewater biosolids for a period of 20 years. They also found elevated levels of mercury in vegetation growing adjacent to a lagoon that retained runoff water and sediments from the biosolids-treated areas. Total Hg concentrations in runoff water from biosolids-treated soils were much lower than the current maximum contaminant level established by the USEPA.
J. Sloan (j-sloan{at}tamu.edu)
Distribution of Mercury in Soil and its Concentration in Runoff from a Biosolids-Amended Agricultural Watershed. J. Environ. Qual. 30:2173–2179.
To Spike or Not to Spike
Spiking sewage sludge with heavy metals is a widely used but controversial technique used in experiments on the fate of sludge metals. McLaren and Clucas now describe the degree of incorporation of Cu, Ni, and Zn into sewage sludge samples spiked with these metals compared with nonspiked samples. Using a sequential fractionation scheme, they found substantial proportions of all three metals incorporated into the sludge matrix, particularly as evidenced by their occurrence in the oxide-bound, organic-bound, and residual fractions. At lower levels of metal addition there was little difference in the fractional distribution of metals between spiked and nonspiked sludges, but for Ni and Zn at higher rates of addition, greater proportions of these metals occurred in the most soluble fractions compared with nonspiked sludge. The drying of sewage sludge before analysis increased metal solubility. Even when sewage sludge is spiked following digestion, restricting the concentrations of metals added produced sludges with metal distributions similar to those in nonspiked sludges.
R.G. McLaren
(Mclaren{at}lincoln.ac.nz)
Fractionation of Copper, Nickel, and Zinc in Metal-Spiked Sewage Sludge. J. Environ. Qual. 30:1968–1975.
Floyd's Flood Fumes
Hurricane Floyd induced flooding along the Neuse River basin in North Carolina, which damaged and disabled hog lagoons and municipal wastewater treatment plants. Tabachow et al. now report that hurricane-loaded soils produced >30 times greater nitric oxide (NO) emissions than nonflooded soils, with NO fluxes ranging from 0.1 to 102.5 ng N/(m2 s). They studied NO flux from eastern North Carolina soils subjected to flooding from hurricanes in laboratory experiments and examined three sites along the Neuse River basin that sustained different intensities of flooding in September 1999.
R. Tabachow (rmt{at}duke.edu)
Hurricane-Loaded Soil: Effects on Nitric Oxide Emissions from Soil. J. Environ. Qual. 30:1904–1910.
Organic Matter Bonding with TNT
Transport, retention, and bioavailability of organic contaminants in soil depend on the reactivity with soil organic matter (SOM). Eriksson and Skyllberg show that trinitrotoluene (TNT) and its degradation products bind more strongly to dissolved SOM than to particulate SOM. On the other hand, particulate SOM shows a much higher binding capacity. Results show that SOM stimulates the degradation of TNT, which in turn results in a stronger bonding to SOM.
J. Eriksson
(Johan.Eriksson{at}sek.slu.se)
Binding of 2,4,6-Trinitrotoluene and its Degradation Products in a Soil Organic Matter Two-Phase System. J. Environ. Qual. 30:2053–2061.
Peat-Burning Precedes Plant Invasion
Everglades regions are being invaded by alien cattail (Typha domingensis Pers.) plants following severe fire events. Smith et al. report that peat fires result in losses of total carbon, nitrogen, and organic phosphorus, while inorganic phosphorus is elevated. Surface fire has a limited impact on these constituents. They studied effects of surface- and peat-fire on a number of soil constituents within a Florida Everglades marsh, using calcium profiles to evaluate chemical vs. physical mechanisms of change. The observed transformations appear to be a basis for cattail invasion.
S.M. Smith (smsmith{at}sfwmd.gov)
Differential Effects of Surface and Peat Fire on Soil Constituents in a Degraded Wetland of the Northern Florida Everglades. J. Environ. Qual. 30:1998–2005.
Spent Mushroom Substrate Weathering Alters Soil Chemistry
Leachate from field-based weathering of spent mushroom substrate (SMS) percolates into the unsaturated zone and alters soil chemistry. Guo et al. report that SMS weathering did not raise soil total organic carbon content, but it did increase water soluble organic matter, soil pH, soluble salts, and altered the composition of adsorbed ions. Concentration profiles in the impacted soils show that following two years of SMS weathering, leachate solutes have migrated to depths that correspond to their respective affinities for the solid phase. Results suggest that field weathering of SMS piles >0.9 m in depth can adversely impact ground water quality.
J. Chorover (jdc7{at}psu.edu)
Effects of Spent Mushroom Substrate Weathering on the Chemistry of Underlying Soils. J. Environ. Qual. 30:2127–2134.
Spatial–Temporal Dynamics of Manure
Pasture-based systems could reduce manure handling and storage requirements proportional to the time cattle are on pastures, according to a report by White et al. They found that manure on pasture was evenly distributed, except around the water tank during warm-weather grazings. Percentages of defecations and urinations on the pasture, feeding, and milking areas were highly correlated with time spent in those areas. Results are from a study of the distribution of feces and urine from 36 lactating dairy cattle managed in a rotationally grazed endophyte-free tall fescue–white clover pasture.
S. Washburn
(Steve_Washburn{at}ncsu.edu)
Spatial and Time Distribution of Dairy Cattle Excreta in an Intensive Pasture System. J. Environ. Qual. 30:2180–2187.
Management Practices Reduce Herbicides in Runoff
The contamination of surface waters by herbicides is an issue of public concern. Two management practices that affect the transport of herbicides in runoff are tillage and herbicide application rate. Hansen et al. show that applying herbicides in a band resulted in less herbicide in runoff than for broadcast applications, but mostly for tillage systems with little residue cover. When conservation tillage was used, herbicide transport was low due to low overall runoff.
N.C. Hansen
(hansennc{at}mrs.umn.edu)
Herbicide Banding and Tillage System Interactions on Runoff Losses of Alachlor and Cyanazine. J. Environ. Qual. 30:2120–2126.
Nutrients, Not Metals, Determine Biosolids Sustainability
Recycling biosolids onto cropland can turn a major human waste stream into a valuable fertilizer for crops. The benefits of this recycling may diminish if biosolids are applied repeatedly to the same piece of land. Cogger et al. applied biosolids from two urban sources to irrigated tall fescue for seven years. Beginning in the fourth year, unused available N accumulated in the soil profile, where it was subject to winter leaching. Available P also accumulated in the soil. Since only small amounts of heavy metals accumulated in the soil and crop, they conclude that nutrients rather than metals will control sustainable site management for repeated biosolids applications. Managers will need to adjust rates or cease applications as appropriate to avoid excess N or P accumulation at long-term application sites.
C. Cogger (cogger{at}wsu.edu)
Seven Years of Biosolids versus Inorganic Nitrogen Applications to Tall Fescue. J. Environ. Qual. 30:2188–2194.
| ||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
