Soil Extraction Methods Research Articles

Evaluation of arsenic in soils and plant uptake using various chemical extraction methods in soils affected by old mining activities

The aims of this study were to assess arsenic concentrations and solubility in soils, and its uptake by plant species growing in an area strongly affected by mining activities in Murcia (SE, Spain) paying attention to the mineralogical composition of the soils and the relation of the same with the bioavailability of this element. For this, extractions were made with several chemical reagents, to determine the bioavailability of the element in different environmental conditions (natural or potential) and, especially, the arsenic bioavailable for the plant uptake. Maximum extraction was achieved using the Mehra and Jackson procedure, while the least effective extractant was an ammonium sulphate solution. The strongest relationship between the As determined by soil chemical extractions and the As measured in plant biomass was found using the oxidisable-organic matter extraction procedure.

Development of Methods for Multiresidue Analysis of Rice Post-Emergence Herbicides in Loam Soil and Their Possible Applications to Soils of Different Composition

Two simple and straightforward sample preparation methods were developed for the multiresidue analysis of post-emergence herbicides in loam soil that are commonly used in rice crop cultivation. A number of strategic soil extraction and cleanup methods were evaluated. The instrumental analysis was performed by HPLC with a diode array detector. The best compromise between the recoveries (69-98%) and good repeatability (RSD < 15%) was obtained using either methanol or methanol-ethyl acetate (70 + 30, v/v) as extraction solvents without any further cleanup. For the first time, residues of metsulfuron methyl, bensulfuron ethyl, bentazone, cyhalofop butyl, pyrazosulfuron ethyl, propanil, and clomazone were analyzed simultaneously. Quinclorac and bispyribac sodium were also assayed, but their recoveries were below 50%. Both methods had an LOD of 0.7 microg/kg and could accurately determine the residues at the 2 microg/kg level. These two methods could not be applied directly to other soil types as the recoveries strongly depended on the soil composition. The developed methodologies were successfully applied in monitoring 87 real-world soil samples, in which only propanil (6 to 12 microg/kg) and clomazone (15 to 20 microg/kg) residues could be detected.

Boron Fertilization and Evaluation of Four Soil Extractants: Russet Burbank Potato

Yield‐response correlations with old and improved soil extraction methods for boron (B) are needed. Russet Burbank potato (Solanum tuberosum L.) was grown with two, four, and six B treatments applied in 2004, 2005, and 2006, respectively. Zero and 1.1, 2.2, or 3.4 kg B ha−1 soil and 0.22 or 0.28 kg B ha−1 foliar treatments were applied. Boron fertilization did not significantly increase tuber yield or quality despite initially low hot‐water‐extractable B (0.34–0.50 mg kg−1), although postseason B for unfertilized treatments increased (0.51–0.57 mg kg−1). Soil‐applied B generally reflected B application relative to the untreated control and the low foliar rates in all three years for the four soil extractions utilized [hot water, pressurized hot water, diethylenetriaminepentaacetic acid (DTPA)–sorbitol, and Mehlich III]. Boron content of potato petiole did reflect application of B in 2 years, but tuber and peel tissues did not consistently reflect application of B.

Fertilizer Recommendation : Correlation and Calibration Study of Soil P Test for Yard Long Bean (Vigna unguilata L) on Ultisols in Nanggung-Bogor

Yar d long bean (Vigna unguilata L.) 777 was grown in Ultisols, which typically have low pH and high P-fi xation, to determine the best correlation of soil extraction methods for soil P with yields, and to develop soil P response categories. The research was conducted at SANREM base camp in Hambaro Village, Nanggung, Bogor, Indonesia from April to August 2008. Treatments were arranged in a Split Plot Design with three replications. The main plots were treatments with soil P status of 0X, ¼X, ½X, ¾X and X, where is X = 1,590.5 kg SP-36 ha -1 (36% P 2 O 5 ) applied once a month before planting. The subplots were P application rate of 0, 75, 150, 225 and 300 kg P 2 O 5 ha -1 . Yard long beans were planted in double rows per bed, 60 cm between rows and 25 cm within rows, 2 seeds per hole, with plot size of 1.5 m x 5 m. Coeffi cient correlation (r) of extraction reagents Olsen, Bray-1, HCl 25%, and Mechlich-1 were 0.772, 0.765, 0.755, and 0.732, respectively. Based on Olsen soil testing methods, soil response categories of very low, low, medium, and high were (ppm P 2 O 5 ) # 18.40, 18.40 < P < 117.27, 117.27 < P < 267.04, and $ 267.04 extracted-P, respectively. Based on Bray-1 soil testing methods, soil response categories for low, medium, and high were # 87.81, 87.81 < P < 233.78, and $ 233.78 extracted-P (ppm P 2 O 5 ), respectively. Fertilizer recommendation based on the Olsen soil test for low response category was 185.75 kg P 2 O 5 ha -1 , and for the medium soil category was 175.97 kg P 2 O 5 ha -1 . The Bray-1 soil test for the low response category was 184.31 kg P 2 O 5 ha -1 , and for the medium soil category was 161.39 kg P 2 O 5 ha -1 .

Mobility of arsenic and its compounds in soil and soil solution: The effect of soil pretreatment and extraction methods

The effect of soil extraction procedures and/or sample pretreatment (drying, freezing of the soil sample) on the extractability of arsenic and its compounds was tested. In the first part, five extraction procedures were compared with following order of extractable arsenic portions: 2 M HNO 3 ≫ 0.43 M CH 3COOH ≥ 0.05 M EDTA ≥ Mehlich III (0.2 M CH 3COOH + 0.25 M NH 4NO 3 + 0.013 M HNO 3 + 0.015 M NH 4F + 0.001 M EDTA) extraction ≫ water). Additionally, two methods of soil solution sampling were compared, centrifugation of saturated soil and the use of suction cups. The results showed that different sample pretreatments including soil solution sampling could lead to different absolute values of mobile arsenic content in soils. However, the interpretation of the data can lead to similar conclusions as apparent from the comparison of the soil solution sampling methods ( r = 0.79). For determination of arsenic compounds mild extraction procedures (0.05 M (NH 4) 2SO 4, 0.01 M CaCl 2, and water) and soil solution sampling using suction cups were compared. Regarding the real soil conditions the extraction of fresh samples and/or in situ collection of soil solution are preferred among the sample pretreatments and/or soil extraction procedures. However, chemical stabilization of the solutions should be allowed and included in the analytical procedures for determination of individual arsenic compounds.

A COMPARISON OF TESTS FOR EXTRACTABLE COPPER AND ZINC IN METAL-SPIKED AND FIELD-CONTAMINATED SOIL

Common soil test methods were compared with 0.01 M CaCl2 extraction to determine their relative abilities to extract and estimate phytoavailability of Cu and Zn. In aged metal-spiked soils, all soil tests evaluated (Mehlich 3, diethylenetriaminepentaacetic acid [DTPA], Morgan, modified Morgan, CaCl2) showed a linear relationship of extractable to total Cu and Zn for both soil types studied. The fraction of total Cu and Zn extracted by aggressive tests (Mehlich 3, DTPA) was much higher than the fraction extracted by CaCl2, with the Morgan tests being intermediate. Although all extraction methods revealed Cu and Zn to be more available in the coarse-textured soil than the fine-textured soil, this texture effect was greatest for the least aggressive test (CaCl2) and least for Mehlich 3. The texture effect on soil test Cu and Zn was also reflected in bioavailability, with greater plant tissue concentrations of both metals from the coarse-textured soil in a soybean assay. Although all soil test methods provided similarly strong correlations to plant tissue concentrations of Zn for soybeans grown in the two soils, the less aggressive soil tests seemed more reliable as predictors of Cu uptake. The efficiency of Cu and Zn extraction from field-contaminated soils was much lower than that from laboratory-spiked aged soils. For Mehlich 3 and DTPA tests, Cu and Zn in field-contaminated soils were less extractable by a factor of about 2 compared with the spiked soils. For less aggressive tests, the difference in extractability was even greater. This study suggests that soil extraction methods removing smaller pools of Cu and Zn are more responsive to soil properties affecting chemical lability of the metals. Therefore, chemically nonaggressive neutral salts may be the most appropriate extractants where phytotoxicity is the concern in metal-contaminated soils.

Metal availability in heavy metal-contaminated open burning and open detonation soil: Assessment using soil enzymes, earthworms, and chemical extractions

The effects of heavy metal contamination on soil enzyme activity and earthworm health (bioaccumulation and condition) were studied in contaminated soils collected from an formerly open burning and open detonation (OBOD) site. Soil extraction methods were also evaluated using CaCl 2 and DTPA solutions as surrogate measures of metal bioavailability and ecotoxicity. Total heavy metal content of the soils ranged from 0.45 to 9.68 mg Cd kg −1, 8.96 to 5103 mg Cu kg −1, 40.21 to 328 mg Pb kg −1, and 56.61 to 10,890 mg Zn kg −1. Elevated metal concentrations are assumed to be primarily responsible for the reduction in enzyme activities and earthworm health indices. We found significant negative relationships between CaCl 2- and DTPA-extractable metal content (Cd, Cu, and Zn) and soil enzyme activity ( P < 0.01). Therefore, it could be concluded that soil enzyme activity and metal bioaccumulation by earthworms can be used as an ecological indicator of metal availability. Furthermore, CaCl 2 and DTPA extraction methods are proved as promising, precise, and inexpensive surrogate measures of Cd, Cu, Pb, and Zn bioavailability from heavy metal-contaminated soils.

Comparability of Electroultrafiltration and Ammonium Acetate–Lactate Extraction Data for Phosphorus and Potassium in Pseudogley Soils

The aim of this research was to compare two standardized soil extraction methods [electroultrafiltration (EUF) and ammonium acetate–lactate (AL)] regarding potassium (K) and phosphorus (P) availability in pseudogley soils. In total, 60 pseudogley soil samples from 12 agricultural sites in eastern Croatia (each represented by five soil samples—replicates) were simultaneously analyzed by both methods. The relations of K and P with other important soil traits [pH, selective mineral clay content (SMC), humus content] were established by multiple regression analyses. Furthermore, a highly significant regression equation (P ⩽ 0.01) was established for AL–phosphorus pentoxide (P2O5), using EUF‐P‐I and EUF‐P‐II separately as well as soil pH value determined in 1 M KCl as independent variables. The actual P amount extracted by AL differed by 9% from the value predicted by the regression function. According to the highly significant multiple regression function (P ⩽ 0.01), AL‐extractable dipotassium oxide (K2O) can be approximated using EUF‐K (sum of EUF‐K‐I and EUF‐K‐II fraction), SMC, and the EUF‐K‐Q (ratio of EUF‐K‐II and EUF‐K‐I) as the independent variables. A deviation of calculated AL‐K2O value from the extracted amount of K was 4%. These results point out the possibility of the comparison of EUF and AL extraction data in the evaluation of K and P availability in pseudogley soils. The necessity of more comprehensive research regarding the comparison of the EUF and AL method, taking into account plant nutrient acquisition specificity and a great number of interrelated soil and climate factors, was suggested.

Effects of different soil weights, storage times and extraction methods on soil phospholipid fatty acid analyses

Phospholipid fatty acid (PLFA) analysis has become a popular and powerful method for characterizing soil microbial communities. However, little work has been done to compare different extraction procedures. In this study, the effects of single or consecutive extractions, varying soil weights, alternative solid phase extraction (SPE) tubes and a comparison of extractions from fresh soil and that from soil previously stored freeze-dried at − 70 °C for 1 year were determined. About 90–95% of PLFAs were extracted by the method used in this paper. More individual PLFAs and changes in PLFA peak distributions (profiles) were found with increasing soil sample weights, which suggests that for each set of experiments, the soil weight should be constant. Home-made SPE tubes used in this study can give almost as good results as the commercial standard ones, which significantly decreased costs. The total PLFA concentrations decreased by more than 28% following storage of the freeze-dried soils for 1 year at − 70 °C. The PLFA profiles also changed during storage over this period, suggesting that PLFA analyses are best done as soon as possible after sampling.

Sensitivity of soil phosphorus tests in predicting the potential risk of phosphorus loss from pasture soil

The objective of this study was to examine the effects of urine and dung additions on the phosphorus (P) chemistry of pasture land and to compare the sensitivity of two soil extraction methods in assessing the P-loading risk. In a field experiment, urine and dung were added to soil in amounts corresponding to single excrement portions and the soil samples, taken at certain intervals, were analysed for pHH2O, acid ammonium acetate extractable P (PAc) and water extractable total P (TPw), and molybdate reactive P (MRPw). Urine additions immediately increased soil pH and MRPw, but no such response was observed in PAc extraction due to the low pH (4.65) of the extractant enhancing the resorption of P. The PAc responded to the dunginduced increase in soil total P similarly as did Pw, which suggests that both tests can serve to detect areas of high P concentration. However, water extraction was a more sensitive method for estimating short-term changes in P solubility. In pasture soils, the risk of P loss increases as a result of the interaction of urination and high P concentration in the topsoil resulting from continuous dung excretion.;

Agri-environmental models using Mehlich-III soil phospho rus saturation index for corn in Quebec

Soil phosphorus (P), which is potentially a risk for environmental contamination, is currently interpreted using soil P saturation in North America. Our objective was to assess the ratio of P to aluminum (Al) in the Mehlich-III (M-III) soil test to build P requirement models for corn and soybean. We analyzed 129 corn and 19 soybean P fertilizer trials. For corn, the (P/Al)M-III ratio improved soil fertility classification compared with PM-III alone. The critical PM-III value as determined by the Cate-Nelson procedure was found to be 31.5 mg PM-III kg-1, close to published values. The critical (P/Al)M-III ratios of 0.025 for &gt; 300 g clay kg-1 soils and 0.040 for ≤ 300 g clay kg-1 soils differed significantly between the two soil groups. For (P/Al)M-III ratios above 0.214, there was no positive response to added P for all soils regardless of texture. Using published critical environmental (P/Al)M-III ratios of 0.076 for &gt; 300 g clay kg-1soils and 0.131 for ≤ 300 g clay kg-1 soils as benchmarks values, agri-environmental P requirement models were built using conditional expectations of 50 to 80% of computed optimum P values within a soil class. A validation study supported the low critical (P/Al)M-III ratios and the 50% conditional expectation model except for a high carbon soil which was outside the application range of the models. However, banded P decreased corn yield at four validation sites although the model predicted positive response to P. Soybean did not respond to P except at extremely low fertility levels ((P/Al)M-III ≤ 0.02) and behaved as a P-mining crop even in low-P soils. Corn-soybean rotations can reduce soil P to low (P/Al)M-III ratios with minimal agronomic risk. Key words: Soil phosphorus saturation, Mehlich-III soil extraction method, soil fertility classification, soil texture, fertilizer P requirement model, corn, soybean

Environmental Mehlich-III soil phosphorus saturation indices for Quebec acid to near neutral mineral soils varying in texture and genesis

The Mehlich-III method (M-III) (Mehlich 1984) is a multinutrient agri-environmental routine soil-testing procedure used in many jurisdictions in North America, but one that is affected by soil texture. The PW determined by the Sissingh (1971) method is an index of surface water contamination and desorbed P that is not influenced by soil texture and that can be used to define specific M-III critical environmental indices by soil texture group. Our objective was to define critical environmental indices by relating (P/Al)M-III to PW. We analyzed 275 soil samples from surface, and 175 from subsurface layers, varying in genesis, texture, and pH. The relationship between PW and (P/Al)M-III was influenced by soil properties, particularly soil texture and genesis. Fine-textured (&gt; 300 g clay kg-1) and gleyed soils tended to release more PW at a given (P/Al)M-III compared with coarse-textured (≤ 300 g clay kg-1) and podzolized soils. Using a critical value of 9.7 mg PW L-1 derived from the literature, critical environmental (P/Al)M-III ratios were found to be 0.131 for coarse-, and 0.076 for fine-textured soils. Subsurface PW increased significantly with (P/Al)M-III above 0.131 in the plough layer of coarse-textured soils, but was independent of (P/Al)M-III in fine-textured soils, indicating contrasting mechanisms of P accumulation in subsurface layers (matrix vs. preferential flow). After accounting for soil texture, (P/Al)M-III appeared to be a useful index of P accumulation in Quebec mineral soils. Key words: Soil phosphorus saturation, Mehlich-III soil extraction method, water-extractable phosphorus, soil environmental phosphorus threshold, soil texture

Determination of selected polychlorinated biphenyls in soil by miniaturised ultrasonic solvent extraction and gas chromatography-mass-selective detection

Miniaturised ultrasonic solvent extraction procedure was developed for the determination of selected polychlorinated biphenyls (PCBs) in soil samples by gas chromatography-mass-selective detection by using 2 3 factorial experimental design. Recoveries of PCBs from fortified soil samples are over 90% for three different fortification levels between 40 and 120 μg kg −1, and relative standard deviations of the recoveries are below 7%. The limits of detection (LODs) ranged from 0.003 to 0.006 μg kg −1. The performance of the proposed method was compared to traditional shake flask extraction method on the spiked real soil sample and extraction methods showed comparable efficiencies. Proposed miniaturised ultrasonic solvent extraction offers several advantages, i.e., reducing sample requirement for measurement of target compound, less solvent consumption and reducing the costs associated with solvent purchase and waste disposal.

Quantification of changes in decomposable N fractions caused by atmospheric N inputs - A 15N balance study

In a field experiment we analysed the 15N/14N ratios in hot- and coldwater soil extracts, salt extracts (KCl), leachates as well as in the soil vegetation for quantifying the impacts of atmospheric N inputs on soil N dynamics. We simulated moderate and chronically high N inputs and determined the forms, contents, and atom% from December 2001 to November 2002 in a German Scots pine forest stand. A maximum of 90% of the total 15N in the soil was extractable by the KCl, hot- and coldwater soil extraction methods in strongly dependence of the soil horizon. The highest 15N recovery was calculated for the organic layer and the Ah horizon. After one year, only 2% of the added 15N was leached below the C2 horizon (−100 cm), whereas up to 11% were found in the soil vegetation. About 70% of the added 15N was lost by nitrification and denitrification processes during the experiment.

Determination of micronutrients and heavy metals in soils using electro–ultrafiltration (EUF) technique by addition of DTPA

AbstractWith the electro–ultrafiltration (EUF) technique, the plant availability of several plant nutrients in soils can be characterized. The basic principle of EUF is that an electric field is induced using platinum electrodes. Ions in the soil suspension move either to the cathode or to the anode and are filtrated through ultra‐membrane filters. In the standard EUF procedure, two extractions steps are used: 30 min at 20°C and 5 min at 80°C. However, the determination of micronutrients and heavy metals with the standard EUF procedure is not possible, because the solubility of these elements in water is low and most of the watersoluble elements are precipitated when passing the platinum electrodes.The addition of DTPA, a well known complexing agent, during a third EUF fraction (5 min at 80°C) enables extraction of micronutrients and heavy metals. Highest concentrations in the 33 soils of the study were found for iron, followed by zinc, manganese, lead, copper, and nickel. Lower concentrations were obtained for cobalt, chromium, cadmium, and molybdenum. For two soils, the EUF/DTPA procedure was compared to CaCl2/DTPA and EDTA soil extraction methods, showing that higher or comparable amounts were found with CaCl2/DTPA and much higher amounts with the EDTA method.These results reveal that the EUF/DTPA technique in principle can be used for the determination of plant‐available micronutrients and heavy metals. However, in a next step the relationship between EUF/DTPA‐extractable elements and their availability for plants needs to be quantified.

Development of PCR-based Detection Methods for the Quarantine Phytopathogen Synchytrium endobioticum, Causal Agent of Potato Wart Disease

PCR-based methods were developed for the detection and quantification of the potato pathogen Synchytrium endobioticum in soil extracts and in planta. PCR primers, based on the internal transcribed spacer region of the multi-copy gene rDNA were tested for specificity, sensitivity and reproducibility in conventional and real-time PCR assays. Soil extraction procedures compared included the Hendrickx centrifugation (HC) procedure, nested wet sieving (NWS) and a method used by the Plant Protection Service (PPS). The primers amplified a 472 bp product from S. endobioticum DNA, but did not amplify DNA from other potato pathogens, other plant pathogens, and related species. Standard cell disruption and DNA extraction and purification methods were optimized for amplification of S. endobioticum DNA from resting sporangia. DNA was successfully amplified from a single sporangium and equivalent DNA preparations from soil extracts. Low levels of target DNA in water did not amplify, possibly due to DNA loss during final purification steps. A real-time PCR assay, developed for soil-based extracts using primers and probe based on the rDNA gene sequences, involved co-amplification of target DNA along with an internal DNA fragment. Both conventional and real-time PCR methods performed well with HC- and NWS-extracts having a threshold sensitivity of 10 sporangia per PCR assay. Of the three soil extraction methods, only with the HC method could 100 g soil samples be efficiently processed in one single PCR assay. Such a high capacity assay could be useful for routine soil analysis in respect to disease risk assessments and to secure de-scheduling according to EPPO guidelines.

Ability of different soil extraction methods to predict potassium release from soil in ley over three consecutive years

AbstractTo avoid over‐fertilization of potassium (K) and thereby a mineral composition in the grass crop not optimal for animal health, estimation of K release from soil is important. The analytical methods should therefore predict the total K release. Furthermore, to minimize costs for the farmers they should provide information which remains valid over a period of several years.The relationship between different soil extraction procedures for K and K uptake in ley for three subsequent years after soil sampling was studied in 19 field experiments on a range of mineral soil types in Norway. Potassium determined with solutions that extracted exchangeable K or parts of exchangeable K (0.01 M CaCl2, 0.5 M NaHCO3, 1 M NH4oAc, or ammonium acetate lactate) was significantly (p &lt; 0.05) related to the K yield only in the 1st yr after soil sampling. Potassium extracted with boiling in 1 M or 2 M HNO3 was significantly related to the K yield only in the 2nd and 3rd yr. Potassium extracted with cold 2 M HCl, boiling 0.1 M HNO3 or 0.5 M HNO3 was significantly related to the K yield in all 3 yr after soil sampling. Among these extractants, 0.1 M and 0.5 M HNO3‐extractable K were better predictors of K uptake than 2 M HCl‐extractable K. These three extractants release some non‐exchangeable K in addition to exchangeable K. The fraction of 1 M HNO3‐K extractable with 0.1 M HNO3 varied from 4% to 45%, whereas from 15% to 78% of 1 M HNO3‐K was extractable with 0.5 M HNO3. Consequently, the more easily releasable fraction of K extracted by boiling with 1 M HNO3 varied considerably between different sites.

Trace Element Chemistry in Residual‐Treated Soil: Key Concepts and Metal Bioavailability

Trace element solubility and availability in land-applied residuals is governed by fundamental chemical reactions between metal constituents, soil, and residual components. Iron, aluminum, and manganese oxides; organic matter; and phosphates, carbonates, and sulfides are important sinks for trace elements in soil-residual systems. The pH of the soil-residual system is often the most important chemical property governing trace element sorption, precipitation, solubility, and availability. Trace element phytoavailability in residual-treated soils is often estimated using soil extraction methods. However, spectroscopic studies show that sequential extraction methods may not be accurate in perturbed soil-residual systems. Plant bioassay is the best method to measure the effect of residuals on phytoavailability. Key concepts used to describe phytoavailability are (i) the salt effect, (ii) the plateau effect, and (iii) the soil-plant barrier. Metal availability in soil from metal-salt addition is greater than availability in soil from addition of metal-containing residuals. Plant metal content displays plateaus at high residual loadings corresponding to the residual's metal concentration and sorption capacity. The soil-plant barrier limits transmission of many trace elements through the food chain, although Cd (an important human health concern) can bypass the soil-plant barrier. Results from many studies that support these key concepts provide a basis of our understanding of the relationship between trace element chemistry and phytoavailability in residual-treated soils. Research is needed to (i) determine mechanisms for trace element retention of soil-residual systems, (ii) determine the effect of residuals on ecological receptors and the ability of residuals to reduce ecotoxicity in metal-contaminated soil, and (iii) predict the long-term bioavailability of trace elements in soil-residual systems.

Simultaneous extraction of tetracycline, macrolide and sulfonamide antibiotics from agricultural soils using pressurised liquid extraction, followed by solid-phase extraction and liquid chromatography–tandem mass spectrometry

The veterinary antibacterial agents chlortetracycline (CTC), oxytetracycline (OTC), sulfadiazine (SDZ), erythromycin (ERY) and tylosin (TYL A, B, C and D) were extracted from soil using pressurized liquid extraction (PLE). Citric acid (pH 4.7) and methanol was used as extraction buffer, followed by tandem-solid-phase extraction (SPE) clean-up (SAX+HLB) for all compounds. For quantification two slightly different methods were employed using LC–MS–MS with MRM detection. The soil extraction method was validated using a loamy sand soil and a sandy soil, representing two typical Danish agricultural soils. Recoveries were 50–80% for the tetracyclines (CTC and OTC) and sulfadiazine (SDZ) and 60–100% for the macrolides (TYL and ERY). Limits of detection for the soil extraction method (LOD soil) were 0.6–5.6 μg kg −1 soil for CTC and OTC, 0.9–2.9 μg kg −1 soil for SDZ and 2.4–5.5 μg kg −1 soil for TYL A and ERY. Furthermore, the method was applied to field samples taken from two agricultural fields fertilised with liquid manure containing CTC and TYL A. These results showed a decline in the content of antibacterial agents throughout the sampling period of 155 days from 10 to 15 μg CTC kg −1 soil and 20–55 μg TYL A kg −1 soil to below or near the LOD soil listed above. Finally, the method was applied to barley grains harvested from the fields. None of the antibacterial agents were measured in grain samples, but recoveries for spiked grain samples were similar to soil recoveries.

Phosphorus runoff relationships for Louisiana Coastal Plain soils amended with poultry litter.

Long-term application of poultry (Gallus gallus domesticus) litter has built high levels of P in certain Coastal Plain soils of north Louisiana. However, soil P/runoff P relationships for soil and environmental conditions of the area have not been examined. This study measured soil P (total, Bray 1, Bray 2, Mehlich 3, resin-exchangeable, and water-extractable) and runoff P (dissolved P, DP; and total P, TP) at four pasture sites previously amended with poultry litter. Sites varied in soil P due to annual litter applications ranging from 1 to more than 20. Three replicated plots at each site were subjected to simulated rainfalls over 2 yr, and concentrations of DP and TP in runoff were measured and related to soil P. This allowed examination of soil P/runoff P relationships and their changes over time. Runoff DP was also related to DP desorbed from surface soil in a miscible displacement experiment. Among measures of soil P, only resin-exchangeable and water-extractable P showed significant decreases over 2 yr. These measures of soil P explained 54 to 64% of the variability in runoff DP data. However, the miscible displacement technique proved the best indicator of runoff DP, explaining 70% of the variability. Runoff varied among sites (decreasing with increasing years of litter application), limiting the predictive capability of the soil extraction methods. Linking runoff characteristics with miscible displacement data may be a useful predictive tool and warrants further examination.