A rapid procedure for estimating nitrogen mineralization in manured soil

 A routine soil testing procedure for soil N mineralization is needed that is rapid and precise. Not accounting for N mineralization can result in the over-application of N, especially in soils with a history of manure application. Our objectives were to compare results from a recently proposed rapid laboratory procedure with: (1) long-term N mineralization under standard laboratory conditions, and (2) actual forage N uptake from soil receiving dairy cattle (Bos taurus) manure in a 2-year field study. The rapid procedure is based on the quantity of CO₂-C evolved during 24 h under optimum laboratory conditions following the rewetting of dried soil. Dairy cattle manure was surface applied beginning in 1992 at annual rates of 0, 112, 224, or 448 kg N ha^–1 to field plots on a Windthorst fine sandy loam soil (fine, mixed, thermic Udic Paleustalf) near Stephenville, Texas (32°N, 98°W). Results of the one-day CO₂ procedure were highly correlated with soil N mineralized from samples collected in March of 1995 (P=0.004) and 1996 (P<0.001) and with forage N uptake (P<0.001) both years of the study. Residual inorganic N in the same soil samples was poorly correlated with soil N mineralization and forage N uptake. Received: 23 February 2000     

Simple and rapid spectrophotometric method for determination of adrenaline and isoprenaline

A simple, rapid, and specific method for determination of adrenaline bitartrate and isoprenaline sulfate was developed. The method is based on the oxidation reaction in aqueous solution of either adrenaline bitartrate or isoprenaline sulfate in the presence of silver oxide to give a red aminochrome measurable at 490 nm. The color is stable for 2 h. Beer's law is valid within a concentration range of 5-80 micrograms/mL for each drug. All variables were studied to optimize the reaction conditions. The method is specific for catecholamine drugs having a secondary amine in the side chain. Other catecholamines such as orciprenaline and noradrenaline do not interfere, and no interference was observed in the presence of common pharmaceutical adjuvants. Interference due to sodium metabisulfite and sodium chloride was circumvented. The validity of the method was tested by analyzing adrenaline injections and isoprenaline tablets. Good recoveries were obtained for these preparations. The results were comparable to those obtained by official procedures. The proposed method is also recommended as a stability indicating assay for oxidative degradation of both drugs.     

A rapid dichromate procedure for routine estimation of total nitrogen in soils

Abstract

A simple procedure for routine estimation of total nitrogen (N) in soils is described. It involves (a) digestion of the soil sample with an acidified dichromate (K₂Cr₂O₇‐H2SO₄) solution for 45 minutes in a Pyrex digestion tube in a 40‐tube block digester preheated to 170°C, (b) titrimetric determination of the ammonia‐N liberated by direct steam distillation of the digest with alkali (NaOH), and (c) calculation of the total‐N value by application of a correction factor (1.1) to the measured NH₃‐N value. Studies using 14 soils selected to obtain a wide range in total N content and other properties showed that the uncorrected recovery of N by the procedure described ranged from 88.5% to 92.3% and averaged 90.5%. When a correction factor of 1.1 was applied to the results, the recovery of N ranged from 97.4% to 101.5% and averaged 99.6%.

The dichromate procedure described is rapid and precise, and it permits at least 80 analyses in a normal working day. The only equipment required for its use is equipment commonly used for total N analysis of soils by the Kjeldahl method (40‐tube block digester and steam distillation unit), and the acidified dichromate solution used for digestion of the soil is, the reagent commonly used for determination of organic carbon in soil by a modified Mebius procedure. Besides being simpler and more rapid than the Kjeldahl method, the procedure described has the advantage that it does not require the expensive fume disposal system needed for Kjeldahl digestion.     

Simple, rapid method for determination of total extractable fat in canned pet foods

The rapid column method described, unlike AOAC method 7.056, determines both neutral ("crude") and total fat in canned pet foods, and uses nonflammable solvent mixtures and simple laboratory equipment. Neutral fat values are obtained by eluting the column with dichloromethane, whereas total fat values are determined by using dichloromethane-methanol (9 + 1). For 7 samples analyzed in triplicate, fat ranged from 2.9 to 10.8%. Neutral fat values by the dry column method were significantly lower (P less than 0.05) than were those by 7.056 (6.29 vs 6.49), although these differences were practically unimportant. Total fat determinations by the dry column method and by 7.056 yielded overall means of 7.40 and 6.49%, respectively. The 0.91% mean difference is significant (P less than 0.01) and represents a more complete extraction of polar lipids by the proposed method.     

Simple, rapid cleanup method for analysis of aflatoxins and comparison with various methods

A method is described for simple and rapid determination of aflatoxins in corn, buckwheat, peanuts, and cheese. Aflatoxins were extracted with chloroform-water and were purified by a Florisil column chromatographic procedure. Column eluates were concentrated and spotted on a high performance thin layer chromatographic (HPTLC) plate, which was then developed in chloroform-acetone (9 + 1) and/or ether-methanol-water (94 + 4.5 + 1.5) or chloroform-isopropanol-acetone (85 + 5 + 10). Each aflatoxin was quantitated by densitometry. The minimum detectable aflatoxin concentrations (micrograms/kg) in various test materials were 0.2, B1; 0.1, B2; 0.2, G1; 0.1, G2; and 0.1, M1. Recoveries of the aflatoxins added to corn, peanut, and cheese samples at 10-30 micrograms/kg were greater than 69% (aflatoxin G2) and averaged 91%, B1; 89%, B2; 91%, G1; 78%, G2; and 92%, M1. The simple method described was compared with the AOAC CB method, AOAC BF method, and AOAC milk and cheese method. These methods were applied to corn, peanut, and cheese composites spiked with known amounts of aflatoxins, and to naturally contaminated buckwheat and cheese. Recoveries were much lower for the BF method compared with our simple method and the CB method.     

Simple and rapid method for the analysis of phenolic compounds in beverages and grains

A new method for the detection of phenolics in food systems was developed. This method is based on interactions of phenolics with Fast Blue BB diazonium salt in alkali pH, forming azo complexes, with the absorbance measured at 420 nm after 60 min. The linear regression correlations (R(2)) of gallic acid calibration standards were >0.99. The phenolic content (gallic acid equivalent) of samples analyzed yielded higher ratios (1.7-6.6) of the total phenolics by Fast Blue BB to Folin-Ciocalteu methods in most beverages and grain samples, but in flaxseed and some juice blends, the ratios were <1. The lower ratios suggest the presence of non-phenolic reducing constituents measured with the Folin-Ciocalteu method as "total phenolics". This method is simple and inexpensive and can be used to rapidly assess the total phenolics of foods and beverages.     

Accounting for habitat loss rates in sequential reserve selection: Simple methods for large problems

We develop reserve selection methods for maximizing either species retention in the landscape or species representation in reserve areas. These methods are developed in the context of sequential reserve selection, where site acquisition is done over a number of years, yearly budgets are limited and habitat loss may cause some sites to become unavailable during the planning period. The main methodological development of this study is what we call a site-ordering algorithm, which maximizes representation within selected sites at the end of the planning period, while accounting for habitat loss rates in optimization. Like stochastic dynamic programming, which is an approach that guarantees a globally optimal solution, the ordering algorithm generates a sequence in which sites are ideally acquired. As a distinction from stochastic dynamic programming, the ordering is generated via a relatively fast approximate process, which involves hierarchic application of the principle of maximization of marginal gain. In our comparisons, the ordering algorithm emerges a clear winner, it does well in terms of retention and is superior to simple heuristics in terms of representation within reserves. Unlike stochastic dynamic programming, the ordering algorithm is applicable to relatively large problem sizes, with reasonable computation times expected for problems involving thousands of sites.     

A rapid, inexpensive and quantitative procedure for assessing soil structure with respect to cropping

Abstract. The essential factors dependent on soil structure that influence plant growth are soil/root contact, adequate air and water, and low mechanical impedance. Bulk density, shear strength and texture arc interrelated closely and permit quantification of these factors. A general relationship between clay content and vane shear strength of soil at field capacity and non-limiting bulk density provides a rapid means of quantitatively estimating structure. We propose a procedure utilizing vane shear strength and a tactile assessment of clay content as criteria for judging soil structure in the field.     

Simple and rapid method for the differentiation of Lens culinaris Medik. from false lentil species

The practice of using both common vetch (Vicia sativa L.) and single-flower vetch (Vicia articulata Hornem.) seeds as food or feed is encouraged by the very high resemblance of their seeds with those of small-seeded lentil cultivars. Among the Vicieae, antinutritional and toxic factors are particularly important, because many species, containing high levels of these compounds, are not safe. A simple and fast capillary electrophoresis (CE) method was proposed for the differentiation of lentil cultivars from false lentil species (i.e., single-flour vetch and common vetch). Proteins were extracted from defatted milled seeds with an alcoholic/saline solution. Extracts were separated in an uncoated fused-silica capillary with iminodiacetic acid (IDA) isolectric buffer containing 0.05% hydroxypropylmethylcellulose (HPMC) and 20% acetonitrile. The presented method is useful also for the detection of contamination of whole or split seeds of lentil by vetch species. With respect to alternative techniques, such as DNA-based markers or thin-layer chromatography (TLC), CE has the advantages of being less expensive, faster, and fully automated.     

A simple procedure for 15N determinations in relatively large samples by emission spectrometry

Abstract

Discharge tubes containing argon, and NH₃ separated from atmospheric N₂ by condensation in a liquid‐nitrogen—cooled trap, are used to determine ¹⁵N: ¹⁴N ratios in ammonium solutions. Reduction of NH₃ to N₂ during sample preparation is not required; the dissociation of NH₃ in the discharge tube produces sufficiently intense N₂ band spectra for the isotope analysis. The method can be readily applied to the analysis of ammonium solutions derived from Kjeldahl digests of plant material.     

Modelling long‐term carbon dynamics in soils reconstituted with large quantities of organic matter

In urban conditions, the widescale availability of organic matter to be recycled and the necessity for soil reconstitution (Technosol) has led to the input of very large quantities of organic matter (up to 50% v/v). The long‐term degradation of these large quantities of organic matter in the soil is not well known. We monitored, over a 60‐month period, the total carbon (C) content and the particulate and biochemical fractions of reconstituted soils placed in 600‐litre boxes under natural conditions. The top layer was a sandy loam amended with 20 or 40% of sphagnum peat or organic compost (sewage sludge, wood chip compost or green waste compost) lying on a layer of sandy loam. We measured C mineralization over time under controlled conditions and built a long‐term model to simulate carbon dynamics where exogenous organic carbon (EOC) was divided into two biodegradable compartments. The model yielded the proportions of EOC that either resisted degradation or contributed to soil organic C storage by mineralization and/or humification. Organic matter degradation was linked to its maturity and to its contents in certain particulate and biochemical fractions but was independent of how much of a given organic matter was introduced. We found a good correlation between the degradable organic compartment and the lignin and cutin‐like, hemicellulose and cellulose‐like fractions larger than 1 mm. The model showed that a large part of initial EOC was still present in the soil after 5 years in a potentially biodegradable but resistant compartment. The degradation of that compartment by mineralization or humification is therefore expected to take longer.     

Simple and rapid portable chromatographic method for separation and detection of phenylmercuric acetate in seeds and water

Phenylmercuric acetate can be detected by horse liver acetone powder succinate dehydrogenase inhibition, using a mixture of 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl tetrazolium chloride (INT), sodium succinate, and N-methylphenazonium methosulfate as the chromogenic reagent. The simple cleanup involves extraction of phenylmercuric acetate in chloroform and concentration by evaporation. In the extract, the compounds in seeds or water could be separated and identified by paper chromatography in the field or laboratory at microgram levels with an acetone-water (70 + 30) solvent system.     

Characterization of anti-irradiation-denatured ovalbumin monoclonal antibodies. Immunochemical and structural analysis of irradiation-denatured ovalbumin

Five monoclonal antibodies (OVA-01, -02, -03, -04, -06) produced against irradiated ovalbumin were investigated in relation to the conformational change in the ovalbumin molecule induced by irradiation with Cobalt-60 gamma-rays. Four antibodies (OVA-01, -02, -04, -06) recognized both native and irradiated ovalbumin, but OVA-03 reacted only with irradiated ovalbumin. These antibodies were classified by modified competitive ELISA, and their K(d) values were determined by the Klotz equation. Epitope analyses were also performed on OVA-03 using CNBr-cleaved peptide fragments from ovalbumin, and it was confirmed that OVA-03 bound to the fragment corresponding to residues Val173-Met196 of the ovalbumin molecule that consists of internal beta-sheet strand 3A and helix F1 containing one open turn. These results demonstrate that dramatic conformational changes in proteins can be induced or that some tertiary or secondary structures can be broken down by gamma-ray irradiation, producing new antigenic sites.     

Simple, rapid, and inexpensive cleanup method for quantitation of aflatoxins in important agricultural products by HPLC

A chemical cleanup procedure for low-level quantitative determination of aflatoxins in major economically important agricultural commodities using HPLC has been developed. Aflatoxins were extracted from a ground sample with MeOH/H2O (80:20, v/v), and after a cleanup step on a minicolumn packed with Florisil, aflatoxins were quantified by HPLC equipped with a C18 column, a photochemical reactor, and a fluorescence detector. Water/MeOH (63:37, v/v) served as the mobile phase. Recoveries of aflatoxins B1, B2, G1, and G2 from peanuts spiked at 5, 1.7, 5, and 1.7 ng/g were 89.5+/-2.2, 94.7+/-2.5, 90.4+/-1.0, and 98.2+/-1.1, respectively (mean+/-SD, %, n=3). Similar recoveries, precision, and accuracy were achieved for corn, brown and white rice, cottonseed, almonds, Brazil nuts, pistachios, walnuts, and hazelnuts. The quantitation limits for aflatoxins in peanuts were 50 pg/g for aflatoxin B1 and 17 pg/g for aflatoxin B2. The minimal cost of the minicolumn allows for substantial savings compared with available commercial aflatoxin cleanup devices.     

Characterization and optimization of the preparation procedure for solution P-31 NMR analysis of organic phosphorus in sediments

Purpose

The single-step sodium hydroxide?Cethylenediaminetetraacetic acid (NaOH?CEDTA) extraction is currently the most common preparation technique for the measurement of organic phosphorus (P) composition in sediments using solution ³¹P nuclear magnetic resonance (NMR). In this study, detailed investigations were conducted to evaluate the performance of this technique, with an objective of finding an optimal procedure for the measurement of sediment organic P.

Materials and methods

A single-step extraction with NaOH?CEDTA was investigated on two types of sediment, i.e., Fe/Al-rich sediment and calcareous sediment. The influence of different sediment preparation methods, NaOH?CEDTA compositions, solid:solution ratios, extraction time, pre-concentration techniques, and NMR sample frozen storage time on P extraction and solution ³¹P NMR analysis were investigated.

Results and discussion

Both air- and freeze-drying increased organic P extraction for the calcareous sediment. An extraction time of 16?h was sufficient for quantitative recovery of extracted organic P for both Fe/Al-rich and calcareous sediments. The use of a 1:8 solid:solution ratio achieved stronger NMR signals and greater P diversity than the use of a 1:20 ratio. Extraction of the two sediments with 0.25 NaOH?C50?mM EDTA favored ³¹P NMR detection by reducing the relaxation times required and the risk of organic P degradation compared to the use of stronger NaOH?CEDTA solutions. Rotary evaporation was a better technique for pre-concentration of the NaOH?CEDTA extracts than freeze drying. The concentrated extracts could be preserved by freezing (?20?°C) for at least 2?months.

Conclusions

An optimized procedure was developed based on these investigations, including freeze-drying of fresh sediments, extraction with 0.25?M NaOH?C50?mM EDTA for 16?h using a solid:solution ratio of 1:8, pre-concentration of the extract to the level of ??10 times of its original concentration using rotary evaporation, and storage of the NMR sample at ?20?°C until ³¹P NMR analysis.