Column Leaching Using Dry Soil to Estimate Solid-Solution Partitioning Observed in Zero-Tension Lysimeters. 1. Method Development

In order to understand the reactions taking place between the soil solid phase and the soil solution, we require knowledge of the chemistry of the soil solution as it occurs in the field. This knowledge allows us to conduct experiments with environmentally relevant concentrations of macro and microelements in solution. Zero-tension lysimeters directly sample the mobile fraction of soil solutions. Unfortunately, they are expensive to sample and require long equilibration periods. Other solution extraction methods do not provide solutions similar in concentration to lysimeters, either because they sample a different fraction of the soil solution or due to the impacts of the sampling process. The processes that produce lysimeter solutions cannot be emulated; however, to estimate lysimeter solution chemistry, we developed a standard protocol to produce solutions that resemble lysimeter solutions from podzolic soils using air-dried samples. We washed air-dried soil columns sequentially with de-ionized water until the electrical conductivity (EC) of the leachates stabilized and then leached the columns using an environmentally relevant concentration of a weak salt solution. We hypothesize that the stabilization point of the EC of the soil solution is indicative of the point at which soluble salts and organic material precipitated during sampling and storage are removed from the soil surface. Solutions produced by leaching, once the EC of wash solutions had stabilized, were comparable to lysimeter solutions from the area where samples were collected with respect to the concentrations of divalent cations, pH, EC and DOC.     

Environmental fate of the triazole fungicide propiconazole in a rice-paddy-soil lysimeter

Environmental fate of the triazole fungicide propiconazole, 1-[[2(2,4-dichlorophenyl)-4-propyl-1,3-diox olane-2-yl]methyl]1H-1,2,4-triazole, in soil was investigated using lysimeters simulating a rice-paddy-soil conditions. Two lysimeters composed of different soil types, a sandy loam (lysimeter A) and silty clay (lysimeter B), were used. Propiconazole (Tilt 250^R EC) plus [U-¹⁴C]-propiconazole was applied over a two-year period to the soil surface of the lysimeters. Propiconazole fate in the lysimeters was assessed by measuring total radioactivity in the leachate, evolved ¹⁴CO₂, and ¹⁴C-residues in the soil and rice plants. The amounts of applied ¹⁴C in the leachate from lysimeter A were 4.4 and 5.2% in the first and second year, respectively. A background level of (0.00005% of applied) ¹⁴C in the leachate from lysimeter B was detected, suggesting negligible movement of the fungicide to groundwater in the silty clay soil. The amount of ¹⁴CO₂ evolved from lysimeter A accounted for 7.8 and 12.2% of applied ¹⁴C in the first and second year, respectively, whereas those from lysimeter B were 5.7 and 7.1%. Total ¹⁴C detected in the rice plants grown in lysimeter A were 7.3 and 9.8% of applied ¹⁴C in the first and second year, respectively, which compared to 3.0 and 7.6% in lysimeter B. Most of the applied ¹⁴C was detected in the top 10 cm soil layer, suggesting that propiconazole remains close to the soil surface after application in soil. Degradation products of propiconazole identified in the lysimeter soils were 1-[[2(2,4-dichlorophenyl)-2-(1,2,4-triazole -1-yl) ketone (DP-1), 1-(2,4-dichlorophenyl)-2-(1,2,4-triazole-1- yl) ethanol (DP-2) and 1-[[2(2,4-dichlorophenyl)-4-hydroxypropyl-1,3-dioxolane-2-yl]methyl]1H-1,2,4-triazole (DP-3 and DP-4).     

A comparison of the effects of subsoiling on plant uptake and leaching losses of sulphur and nitrogen from a simulated urine patch

Synthetic cow urine labelled with ³⁵S and ¹⁵N was applied to large, undisturbed, monolith lysimeters sampled from subsoiled and non-subsoiled areas of a grass/clover pasture. For one year following the urine application, the lysimeters were subjected to a combination of natural rainfall, simulated rainfall and simulated flood irrigations. Drainage from the lysimeters was sampled regularly and monthly (approx.) pasture cuts taken. At the end of the year, the lysimeters were destructively sampled in 50 mm depth increments for soil analysis. Leachates, plant samples and soil samples were analysed for ³⁵S and ¹⁵N.There were no significant differences in plant uptake of ³⁵S and ¹⁵N between the subsoiled and nonsubsoiled lysimeters. Initially grass showed a higher degree of labelling than clover. Total amounts of ³⁵S and ¹⁵N leached from the subsoiled lysimeters were approximately twice that leached from the nonsubsoiled ones. Leaching patterns differed substantially between the two nutrients.Total recoveries of ³⁵S (in plants, leachates and soil extracts) accounted for 82% of the applied ³⁵S for the subsoiled lysimeters and 72% for non-subsoiled ones. The unrecovered ³⁵S is considered to have been incorporated into soil organic matter. Total recoveries of ¹⁵N (in plants, soil and leachates) were similar to those for ³⁵S, but unrecovered ¹⁵N is attributed to loss by denitrification.     

Optimization of methods for detecting Mycobacterium avium subsp. paratuberculosis in environmental samples using quantitative, real-time PCR

Detection of Johne's disease, an enteric infection of cattle caused by Mycobacterium avium subsp. paratuberculosis (M. paratuberculosis), has been impeded by the lack of rapid, reliable detection methods. The goal of this study was to optimize methodologies for detecting M. paratuberculosis in manure from an infected dairy cow or in contaminated soil samples using a quantitative, real-time PCR (QRT-PCR) based analysis. Three different nucleic acid extraction techniques, the efficiency of direct versus indirect sample extraction, and sample pooling were assessed. The limit of detection was investigated by adding dilutions of M. paratuberculosis to soil. Results show that the highest yield (19.4+/-2.3 microg(-1) DNA extract) and the highest copy number of the targeted M. paratuberculosis IS900 sequence (1.3+/-0.2x10(8) copies g(-1) manure) were obtained with DNA extracted from manure using Qbiogene's Fast DNA Spin kit for soil. Pooling ten samples of M. paratuberculosis-contaminated soil improved the limit of detection ten fold (between 20 and 115 M. paratuberculosis cells g(-1) soil). Detection was between 65% and 95% higher when samples were extracted directly using bead-beating than when using pre-treatment with cell extraction buffers. The final soil-sampling and extraction regime was applied for detection of M. paratuberculosis in pasture soil after the removal of a M. paratuberculosis culture positive dairy cow. M. paratuberculosis remained in the pasture soil for more than 200 days. Results from these studies suggest that DNA extraction method, sampling protocol and PCR conditions each critically influence the outcome and validity of the QRT-PCR analysis of M. paratuberculosis concentrations in environmental samples.     

Multi-Species Ecotoxicity Assessment of Petroleum-Contaminated Soil

In 1992, a study was begun to compare the effect of landfarming vs. natural attenuation on the restoration of soil that had been contaminated with crude oil. Each of three lysimeters was filled with a sandy loam topsoil, and crude oil was applied to two of the lysimeters. One of the contaminated lysimeters was tilled, watered, and received a one-time application of fertilizer (N, P, K). No amendments were added to the second contaminated lysimeter, and the third was left uncontaminated. The lysimeters were monitored for 6 months and then left unattended. In 1995 and again in 1997 we sampled these lysimeters to evaluate the long-term effects of contamination and bioremediation. In 1995 we found marked effects on soil chemistry, bacterial, fungal, nematode, and plant populations and a higher rate of bioremediation in the fertilized-contaminated lysimeter (Lawlor et al., 1997). Data from 1997 and previously unreported data from 1995 are the subject of the current report. In 1997, low densities of hydrocarbon-degrading bacteria were found in all the lysimeters and little loss of TPH from the two contaminated lysimeters, suggesting a decreased rate of bioremediation. Nevertheless, there were increases in diversity and number of functional groups of bacteria, nematodes, and native plant species. However, molecular analyses revealed marked differences remained in the composition of dominant eubacterial species, and tests of soybeans indicated field conditions remained unsuitable for these plants.     

Fate of aluminium and nickel in soil. Evaluation through lysimeters under laboratory conditions

ABSTRACT

Nanomaterials (Nms) applications and environmental deposition are continuously increasing. Aluminum (Al) and nickel (Ni) fate in soil, both from gamma alumina-based Nms and as chloride salts were evaluted through lysimeters. After 85 days of treatment, which included irrigation and collection of eluates, the soil of each lysimeter was divided into four sections. The metal concentration was analyzed in eluates, soil samples, and extracts. Al and iron (Fe) present in soil eluted from Control lysimeter. Al from Nms suspension treatment was quantified in the eluates since 30 days on. Ni eluted upon solid salt deposition on top of one device. These results indicate that Al and Ni applied under certain conditions on soil, could leach and reach groundwater. The total concentration and bioavailability (extractable metals) of Al and Fe in soils showed similar patterns. Ni was retained only in the soil of devices treated with chloride salts. Bioavailability % results were of concern for Ni under certain conditions of treatment: 15.57% and 11.08% in two chloride salt-treated lysimeters versus 0.55% and 0.47% of those in control and treated with Nms lysimeters. Conducting studies with different kinds of soil and longer treatment periods should be useful to understand Nms-metals fate in the environment. The results presented here constitute important evidences both for significant metal release from Nms and elution and for considerable Ni bioavailability, after deposition on soil in the form of Nms or as a chloride salt, respectively. Then, possible toxic effects could occur through exposure of aquatic and terrestrial organisms.     

Effects of cattle feeding regimen and soil management type on the fate of Escherichia coli O157:H7 and salmonella enterica serovar typhimurium in manure, manure-amended soil, and lettuce

Survival of the green fluorescent protein-transformed human pathogens Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium was studied in a laboratory-simulated lettuce production chain. Dairy cows were fed three different roughage types: high-digestible grass silage plus maize silage (6:4), low-digestible grass silage, and straw. Each was adjusted with supplemental concentrates to high and low crude protein levels. The pathogens were added to manure, which was subsequently mixed (after 56 and 28 days for E. coli O157:H7 and Salmonella serovar Typhimurium, respectively) with two pairs of organically and conventionally managed loamy and sandy soil. After another 14 days, iceberg lettuce seedlings were planted and then checked for pathogens after 21 days of growth. Survival data were fitted to a logistic decline function (exponential for E. coli O157:H7 in soil). Roughage type significantly influenced the rate of decline of E. coli O157:H7 in manure, with the fastest decline in manure from the pure straw diet and the slowest in manure from the diet of grass silage plus maize silage. Roughage type showed no effect on the rate of decline of Salmonella serovar Typhimurium, although decline was significantly faster in the manure derived from straw than in the manure from the diet of grass silage plus maize silage. The pH and fiber content of the manure were significant explanatory factors and were positively correlated with the rate of decline. With E. coli O157:H7 there was a trend of faster decline in organic than in conventional soils. No pathogens were detected in the edible lettuce parts. The results indicate that cattle diet and soil management are important factors with respect to the survival of human pathogens in the environment.     

Persistence of Mycobacterium avium subsp. paratuberculosis and other zoonotic pathogens during simulated composting, manure packing, and liquid storage of dairy manure

Livestock manures contain numerous microorganisms which can infect humans and/or animals, such as Escherichia coli O157:H7, Listeria monocytogenes, Salmonella spp., and Mycobacterium avium subsp. paratuberculosis (Mycobacterium paratuberculosis). The effects of commonly used manure treatments on the persistence of these pathogens have rarely been compared. The objective of this study was to compare the persistence of artificially inoculated M. paratuberculosis, as well as other naturally occurring pathogens, during the treatment of dairy manure under conditions that simulate three commonly used manure management methods: thermophilic composting at 55 degrees C, manure packing at 25 degrees C (or low-temperature composting), and liquid lagoon storage. Straw and sawdust amendments used for composting and packing were also compared. Manure was obtained from a large Ohio free-stall dairy herd and was inoculated with M. paratuberculosis at 10(6) CFU/g in the final mixes. For compost and pack treatments, this manure was amended with sawdust or straw to provide an optimal moisture content (60%) for composting for 56 days. To simulate liquid storage, water was added to the manure (to simulate liquid flushing and storage) and the slurry was placed in triplicate covered 4-liter Erlenmeyer flasks, incubated under ambient conditions for 175 days. The treatments were sampled on days 0, 3, 7, 14, 28, and 56 for the detection of pathogens. The persistence of M. paratuberculosis was also assessed by a PCR hybridization assay. After 56 days of composting, from 45 to 60% of the carbon in the compost treatments was converted to CO2, while no significant change in carbon content was observed in the liquid slurry. Escherichia coli, Salmonella, and Listeria were all detected in the manure and all of the treatments on day 0. After 3 days of composting at 55 degrees C, none of these organisms were detectable. In liquid manure and pack treatments, some of these microorganisms were detectable up to 28 days. M. paratuberculosis was detected by standard culture only on day 0 in all the treatments, but was undetectable in any treatment at 3 and 7 days. On days 14, 28, and 56, M. paratuberculosis was detected in the liquid storage treatment but remained undetectable in the compost and pack treatments. However, M. paratuberculosis DNA was detectable through day 56 in all treatments and up to day 175 in liquid storage treatments. Taken together, the results indicate that high-temperature composting is more effective than pack storage or liquid storage of manure in reducing these pathogens in dairy manure. Therefore, thermophilic composting is recommended for treatment of manures destined for pathogen-sensitive environments such as those for vegetable production, residential gardening, or application to rapidly draining fields.     

两种外源抗生素在农业土壤中的吸附与迁移特性

长期施用禽畜排泄物可导致抗生素在土壤中的积累,对生态环境产生不良影响.为了解长江三角洲和珠江三角洲农业土壤中长期施用含抗生素的有机肥可能产生的环境影响,选择了7个典型农业土壤,用室内模拟方法研究了我国常用的2种抗生素(泰乐菌素和土霉素)在这些土壤中吸附和迁移行为.研究表明,抗生素在土壤中的吸附、迁移行为与抗生素种类和土壤性质有关,土壤对土霉素的吸附能力明显高于泰乐菌素.土壤对抗生素的吸附能力主要与土壤粘粒含量、有机质和氧化铁呈正相关,与其它土壤性质的相关性较小.这2类抗生素在粘质农业土壤剖面中的迁移能力较弱;但泰乐菌素在砂质土壤中较易迁移,有较大的环境风险.     

The effect of leachates from grass trash on establishment of ryegrass

These experiments have shown that whilst leachates from grass trash produced by killing grass with glyphosate can significantly affect germination and seedling growth of both perennial and Italian ryegrass on germination paper and on inert media, they had no effect when added to seeds on soil. This suggests that these leachates are unlikely to inhibit germination in direct drilled sowings in the field unless seeds are sown in direct contact with grass trash and in conditions of sufficient moisture availability to enable production of the leachates. Comparisons of the effect of leachates from grass killed with herbicides or by drying, both before and after passing through a soil column further confirmed this and suggested that the effect of these leachates could partly though not wholly be attributed to herbicide residues on the trash. Glyphosate was less toxic to germination than paraquat. However on sandy soils, glyphosate residues could still cause a reduction in germination. Surface trash produced by spraying with glyphosate had no effect when seeds were sown at a depth of 1 cm, again confirming that seeds must be in close proximity to grass trash before germination and establishment is reduced.     

Effects of Cattle Feeding Regimen and Soil Management Type on the Fate of Escherichia coli O157:H7 and Salmonella enterica Serovar Typhimurium in Manure, Manure-Amended Soil, and Lettuce

Survival of the green fluorescent protein-transformed human pathogens Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium was studied in a laboratory-simulated lettuce production chain. Dairy cows were fed three different roughage types: high-digestible grass silage plus maize silage (6:4), low-digestible grass silage, and straw. Each was adjusted with supplemental concentrates to high and low crude protein levels. The pathogens were added to manure, which was subsequently mixed (after 56 and 28 days for E. coli O157:H7 and Salmonella serovar Typhimurium, respectively) with two pairs of organically and conventionally managed loamy and sandy soil. After another 14 days, iceberg lettuce seedlings were planted and then checked for pathogens after 21 days of growth. Survival data were fitted to a logistic decline function (exponential for E. coli O157:H7 in soil). Roughage type significantly influenced the rate of decline of E. coli O157:H7 in manure, with the fastest decline in manure from the pure straw diet and the slowest in manure from the diet of grass silage plus maize silage. Roughage type showed no effect on the rate of decline of Salmonella serovar Typhimurium, although decline was significantly faster in the manure derived from straw than in the manure from the diet of grass silage plus maize silage. The pH and fiber content of the manure were significant explanatory factors and were positively correlated with the rate of decline. With E. coli O157:H7 there was a trend of faster decline in organic than in conventional soils. No pathogens were detected in the edible lettuce parts. The results indicate that cattle diet and soil management are important factors with respect to the survival of human pathogens in the environment.     

Integrated Field Lysimetry and Porewater Sampling for Evaluation of Chemical Mobility in Soils and Established Vegetation

Potentially toxic chemicals are routinely applied to land to meet growing demands on waste management and food production, but the fate of these chemicals is often not well understood. Here we demonstrate an integrated field lysimetry and porewater sampling method for evaluating the mobility of chemicals applied to soils and established vegetation. Lysimeters, open columns made of metal or plastic, are driven into bareground or vegetated soils. Porewater samplers, which are commercially available and use vacuum to collect percolating soil water, are installed at predetermined depths within the lysimeters. At prearranged times following chemical application to experimental plots, porewater is collected, and lysimeters, containing soil and vegetation, are exhumed. By analyzing chemical concentrations in the lysimeter soil, vegetation, and porewater, downward leaching rates, soil retention capacities, and plant uptake for the chemical of interest may be quantified. Because field lysimetry and porewater sampling are conducted under natural environmental conditions and with minimal soil disturbance, derived results project real-case scenarios and provide valuable information for chemical management. As chemicals are increasingly applied to land worldwide, the described techniques may be utilized to determine whether applied chemicals pose adverse effects to human health or the environment.     

Studies on the Survival and Fate of Enteroviruses in an Experimental Model of a Municipal Solid Waste Landfill and Leachate

In laboratory scale municipal solid waste lysimeters containing simulated refuse, and seeded with either laboratory or field strains of poliovirus type 1 and echovirus type 7, viruses were not detected in the lysimeter leachate produced over a 4-month period. In addition, viruses were detected in the lysimeter refuse contents after termination of lysimeter operation. These results appeared to be due to virus retention in the lysimeter caused by virus adsorption and virus inactivation. Evidence for virus inactivation was provided by the results of experiments on virus inactivation in composite leachate samples. Evidence for virus adsorption was supported by the rapid adsorption of viruses to various municipal solid waste components in the presence of a salt similar in composition to the major inorganic salts of leachates.     

Assessing the performance of a cold region evapotranspiration landfill cover using lysimetry and electrical resistivity tomography

In order to test the efficacy ofa cold-region evapotranspiration (ET) landfill cover against a conventional compacted clay (CCL) landfill cover, two pilot scale covers were constructed in side-by-side basin lysimeters (20m x 10m x 2m) at a site in Anchorage, Alaska. The primary basis of comparison between the two lysimeters was the percolation of moisture from the bottom of each lysimeter. Between 30 April 2005 and 16 May 2006, 51.5 mm of water percolated from the ET lysimeter, compared to 50.6 mm for the the CCL lysimeter. This difference was not found to be significant at the 95% confidence level. As part of the project, electrical resistivity tomography (ERT) was utilized to measure and map soil moisture in ET lysimeter cross sections. The ERT-generated cross sections were found to accurately predict the onset and duration of lysimeter percolation. Moreover, ERT-generated soil moisture values demonstrated a strong linear relationship to lysimeter percolation rates (R-Squared = 0.92). Consequently, ERT is proposed as a reliable tool for assessing the function of field scale ET covers in the absence of drainage measurement devices.     

Impacts of Environmental Colloids on the Transport of 17 β-estradiol in Intact Soil Cores

Estrogens such as 17-β estradiol (E2) are endocrine-disrupting compounds and can affect the reproductive systems of aquatic organisms. Therefore, it is important to understand the mechanisms of their transport in the environment. E2 and its daughter product estrone (E1) are both strongly adsorbed by soil organic matter and have relatively short half-lives. Reduced contact time with soil makes transport of E2 and E1 in soil more likely. In this study, intact soil cores from three soils representing a range of particle size distribution, structure, and organic matter content were used to compare the transport of E2 with and without the presence of colloidal material fractionated from soil or swine manure. In chemical transport experiments conducted with undisturbed soil columns, E2 and E1 were measured both in solution and attached to suspended solids in column effluent. During the transport experiments, colloids carrying E2 passed through all soils, with the exception of the sandy soil. The presence of colloids decreased the first detection time of E2 in the aqueous phase, was correlated with greater peak E2 concentrations in the effluent of both loamy and clayey soils, but not through the sandy soil, and increased mass fractions of the E2 that was transported.     

Persistence of Mycobacterium avium subsp. paratuberculosis at a farm-scale biogas plant supplied with manure from paratuberculosis-affected dairy cattle

In this study, products from all steps of anaerobic digestion at a farm-scale biogas plant supplied with manure from paratuberculosis-affected dairy cattle were examined and quantified for the presence of the causal agent of paratuberculosis, Mycobacterium avium subsp. paratuberculosis, using culture and quantitative real-time PCR (qPCR). Viable M. avium subsp. paratuberculosis cells were detected using culture in fermentors for up to 2 months; the presence of M. avium subsp. paratuberculosis DNA (10(1) cells/g) was demonstrated in all anaerobic fermentors and digestate 16 months after initiation of work at a biogas plant, using IS900 qPCR. F57 qPCR was able to detect M. avium subsp. paratuberculosis DNA (10(2) cells/g) at up to 12 months. According to these results, a fermentation process that extended beyond 2 months removed all viable M. avium subsp. paratuberculosis cells and therefore rendered its product M. avium subsp. paratuberculosis free. However, M. avium subsp. paratuberculosis DNA was found during all the examined periods (more than 1 year), which could be explained by either residual DNA being released from dead cells or by the presence of viable cells whose amount was under the limit of cultivability. As the latter hypothesis cannot be excluded, the safety of the final products of digestion used for fertilization or animal bedding cannot be defined, and further investigation is necessary to confirm or refute this risk.     

Commercially available plant growth regulators and promoters modify bulk tissue abscisic acid concentrations in spring barley, but not root growth and yield response to drought

Field and lysimeter experiments were conducted in 2002 to investigate the effects of an antigibberellin growth regulator (Moddus, active ingredient trinexapac‐ethyl, Syngenta Crop Protection UK Ltd, Whittlesford, Cambridge, UK) and an auxin‐stimulating (Route, active ingredient zinc ammonium acetate, De Sangosse Ltd, Swaffham Bulbeck, Cambridge, UK) growth promoter on root growth, soil water extraction and the drought response of spring barley. The effects on root growth and distribution were investigated in the field. The effects on the drought response were studied in 1.2‐m‐deep lysimeters packed with a loamy sand subsoil and sandy loam topsoil. Lysimeters were located under a fixed rain shelter, and drought was imposed by withholding irrigation. In both field and lysimeter experiments, growth regulator/promoters were applied to cv. Optic at early tillering according to the manufacturers’ recommendations. After withholding irrigation from lysimeters at Zadoks growth stage (GS) 21 (37 days after sowing), 50% of the profile available water had been depleted by flag leaf emergence (GS 37/39; 62 days after sowing). Drought significantly reduced stem biomass at ear emergence (GS 59; 78 days after sowing) but not leaf or ear dry weight; this was before there was any significant reduction in leaf water potential or stomatal conductance to water vapour. The reduction in stem biomass may reflect a change in partitioning between shoot and root in response to soil drying. When averaged over growth regulator/promoter treatments, drought reduced grain yield by approximately 1 t ha^?1. This was associated with a reduction in both ears per m² and grains per ear. The mean grain weight was not reduced by drought, in spite of significant reductions in stomatal conductance and canopy lifespan post‐anthesis. Route, and to a lesser extent Moddus, significantly increased abscisic acid accumulation in the stem base of droughted plants, and there was some indication of a possible delay in stomatal closure in Route‐treated plants as the soil moisture deficit developed. However, there was no significant effect on the amount of soil water extracted or grain yield under drought. Similarly, in field experiments, neither Route nor Moddus significantly altered total root length, biomass or distribution. There is little evidence from these experiments or in the literature to support the use of antigibberellin or auxin‐simulating growth regulator/promoters to modify root growth and drought avoidance of spring barley.     

Land use and hydrologic flowpaths interact to affect dissolved organic matter and nitrate dynamics

The transport and transformation of dissolved organic matter (DOM) and dissolved inorganic nitrogen (DIN) through the soil profile impact down-gradient ecosystems and are increasingly recognized as important factors affecting the balance between accumulation and mineralization of subsoil organic matter. Using zero tension and tension lysimeters at three soil depths (20, 40, 60 cm) in paired forest and maize/soybean land uses, we compared dissolved organic C (DOC), dissolved organic N (DON) and DIN concentrations as well as DOM properties including hydrophilic-C (HPI-C), UV absorption (SUVA₂₅₄), humification index and C/N ratio. Soil moisture data collected at lysimeter locations suggest zero tension lysimeters sampled relatively rapid hydrologic flowpaths that included downward saturated flow through the soil matrix and/or rapid macropore flow that is not in equilibrium with bulk soil solution whereas tension lysimeters sampled relatively immobile soil matrix solution during unsaturated conditions. The effect of land use on DOC and DON concentrations was largely limited to the most shallow (20 cm) sampling depth where DOC concentrations were greater in the forest (only zero tension lysimeters) and DON concentrations were greater in the cropland (both lysimeter types). In contrast to DOC and DON concentrations, the effect of land use on DOM properties persisted to the deepest sampling depth (60 cm), suggesting that DOM in the cropland was more decomposed regardless of lysimeter type. DOC concentrations and DOM properties differed between lysimeter types only in the forest at 20 cm where soil solutions collected with zero tension lysimeters had greater DOC concentrations, greater SUVA₂₅₄, greater humification index and lower HPI-C. Our data highlight the importance of considering DOM quality in addition to DOC quantity, and indicate long-term cultivation reduced the delivery of relatively less decomposed DOM to all soil depths.     

Nitrogen and phosphorus content of flow from drains fertilized with cow manure slurry

Summary The rate of flow and nitrate and phosphorus content of the water from four drained sandy and clayey plots of size 12×60 m cropped to continuous corn were determined following two annual applications of different rates (0, 260, 390 and 520 kg N/ha) of cow manure slurry. The drain flow was directly related to the rainfall and was greatly influenced by soil texture. The N losses were greater in 1972 (7.8 to 19.1 kg N/ha) than in 1971 (0.4 to 7.8 kg N/ha) because of more summer rainfall. Nitrogen and phosphorus losses were larger from the sandy plots than from the clayey plots. The manure application rates had no apparent effect on nitrogen losses in the drain water.