Variability of hydrolysis of β-, αs1-, and αs2-caseins by 10 strains of Streptococcus thermophilus and resulting bioactive peptides

Milk proteins contain numerous potential bioactive peptides, which may be released by digestive proteases or by the proteolytic system of lactic acid bacteria during food processing. The capacity of Streptococcus thermophilus to generate peptides, especially bioactive peptides, from bovine caseins was investigated. Strains expressing various levels of the cell envelope proteinase, PrtS, were incubated with α(s1)-, α(s2)-, or β-casein. Analysis of the supernatants by LC-ESI-MS/MS showed that the β-casein was preferentially hydrolyzed, followed by α(s2)-casein and then α(s1)-casein. Numbers and types of peptides released were strain-dependent. Hydrolysis appeared to be linked with the accessibility of different casein regions by protease. Analysis of bonds hydrolyzed in the region 1-23 of α(s1)-casein suggests that PrtS is at least in part responsible for the peptide production. Finally, among the generated peptides, 13 peptides from β-casein, 5 from α(s2)-casein, and 2 from α(s1)-casein have been reported as bioactive, 15 of them being angiotensin-converting enzyme inhibitors.     

Design, synthesis, and insecticidal activity of novel pyrazole derivatives containing α-hydroxymethyl-N-benzyl carboxamide, α-chloromethyl-N-benzyl carboxamide, and 4,5-dihydrooxazole moieties

On the basis of commercial insecticides tebufenpyrad and tolfenpyrad, two series of novel pyrazole-5-carboxamides containing α-hydroxymethyl-N-benzyl or α-chloromethyl-N-benzyl and pyrazoles containing 4,5-dihydrooxazole moieties were designed and synthesized via the key intermediate 2-amino-1-(4-substituted) phenyl ethanol. The structures of target compounds were confirmed by (1)H NMR and elemental analysis or high-resolution mass spectrum (HRMS), and their activities against cotton bollworm (Helicoverpa armigera), diamondback moth (Plutella xylostella), bean aphid (Aphis craccivora), mosquito (Culex pipiens pallens), and spider mite (Tetranychus cinnabarinus) were tested. The results of bioassays indicated that compounds containing α-chloromethyl-N-benzyl and compounds containing 4,5-dihydrooxazole showed high insecticidal activity against cotton bollworm. Especially, stomach activities of compounds Ij, Il, and IIe were 60% at 5 mg kg(-1). Moreover, the target compounds exhibited high selectivity between cotton bollworm and diamondback moth, although both of them belong to the order Lepidoptera. Although the activities against diamondback moth were at a low level, some of the target compounds exhibited antifeedant activity. The compounds also had good activities against bean aphid, mosquito, and spider mite. The foliar contact activity of compounds Ic, Id, Ie, and IIf against bean aphid were 95, 95, 100, and 95%, respectively, at 200 mg kg(-1). The miticidal and ovicidal activities of compound IIi against spider mite were both 95% at 200 mg kg(-1). Furthermore, a trivial change at 4-position of pyrazole ring would lead to great changes in properties and activities, which can easily be deduced by comparing the activities of compounds in series I (4-chloro-pyrazole compounds) with corresponding compounds in series II (4-hydro-pyrazole compounds), especially from the miticidal and ovicidal activities of Ii and IIi against spider mite.     

Effect of Protease Treatment Before Hydrolysis with α-Amylase on the Rate of Starch and Protein Hydrolysis of Maize,Whole Sorghum,and Decorticated Sorghum

We studied the effect of sorghum decortication and protease treatment on starch hydrolysis before liquefaction with thermoresistant α-amylase and the generation of free amino nitrogen (FAN) in preparation for subsequent steps of ethanol production. A bifactorial experiment with a level of confidence of P < 0.05 was designed to study differences among maize, whole sorghum, and decorticated sorghum and the effectiveness of the protease treatment before starch liquefaction. Sorghum was decorticated 9.7% to remove most of the pericarp and part of the germ and increase starch concentration. Starch concentration increased in decorticated kernels, whereas total phenols, fiber, and fat decreased. The decorticated sorghum had significantly higher starch and protein hydrolysis compared with the whole kernel. Protease treatment before liquefaction improved the rate of starch hydrolysis, especially in mashes from whole and decorticated sorghums. Whole and decorticated sorghum hydrolyzates treated with protease contained ≈50% more reducing sugars than the untreated counterparts. Maize yielded hydrolyzates with the the highest amount of FAN, followed by decorticated and whole sorghums. The maize and both sorghum hydrolyzates treated with protease contained ≈60 and 30% more FAN compared with the untreated counterparts. Both sorghum decortication and protease treatments before hydrolysis with α-amylase are recommended to increase ethanol yields, save processing time (and therefore energy), and to produce mashes with higher FAN content, which is considered as an important yeast substrate.     

Grape Seed and Tea Extracts and Catechin 3-Gallates Are Potent Inhibitors of α-Amylase and α-Glucosidase Activity

This study evaluated the inhibitory effects of plant-based extracts (grape seed, green tea, and white tea) and their constituent flavan-3-ol monomers (catechins) on α-amylase and α-glucosidase activity, two key glucosidases required for starch digestion in humans. To evaluate the relative potency of extracts and catechins, their concentrations required for 50 and 90% inhibition of enzyme activity were determined and compared to the widely used pharmacological glucosidase inhibitor, acarbose. Maximum enzyme inhibition was used to assess relative inhibitory efficacy. Results showed that grape seed extract strongly inhibited both α-amylase and α-glucosidase activity, with equal and much higher potency, respectively, than acarbose. Whereas tea extracts and catechin 3-gallates were less effective inhibitors of α-amylase, they were potent inhibitors of α-glucosidase. Nongallated catechins were ineffective. The data show that plant extracts containing catechin 3-gallates, in particular epigallocatechin gallate, are potent inhibitors of α-glucosidase activity and suggest that procyanidins in grape seed extract strongly inhibit α-amylase activity.     

Lipid stability and antioxidant profile of microsomal fraction of broiler meat enriched with α-lipoic acid and α-tocopherol acetate

The importance of the linkage between nutrition and health is a hot issue. Like other food-related sectors, the meat industry is undergoing foremost transformations, driven among other things by changes in consumer requirements. The present study was designed to evaluate the lipid stability and antioxidative potential of leg and breast microsomal fraction of broiler meat fed on ALA and ATA. For the first 3 weeks of growth, broilers were fed on feed supplemented with ATA (200 mg/kg of feed) and during the last 3 weeks broilers were fed on feed supplemented with ALA (25, 75, 150 mg/kg of feed) and a constant level of ATA (200 mg/kg of feed). The body weight of the carcass was measured after every week of growth until 6 weeks. Positive correlation between the antioxidant activity and the TPC was observed. Higher values of TBARS were detected in leg muscles than in breast muscles. HPLC data revealed ALA and ATA contents were higher in T(4) (leg, 5.55 ± 0.19 and 3.87 ± 0.15 μg/mg of protein; breast, 5.63 ± 0.20 and 2.03 ± 0.10 μg/mg of protein, respectively) and lowest in T(5) (ALA, leg, 1.40 ± 0.06 μg/mg of protein; breast, 1.54 ± 0.05 μg/mg of protein; ATA, leg, 1.25 ± 0.06 μg/mg of protein; breast, 0.63 ± 0.008 μg/mg of protein), in which the only oxidized oil was used. Oxidized oil in feed reduced weight gain and increased TBARS, whereas TPC, DPPH, ALA, and ATA values decreased in both leg and breast meat.     

Application of the Weng’s ratio for the identification of Zn, Cu, and Pb contamination in soils and sediments

Purpose

This work explores the application of the use of Zn, Cu, and Pb relative contents as a new type of normalization method for geochemical properties of soils and sediments in an Atlantic Basin (Anllóns River, NW Spain). The method is based on the conservative behavior of these elements, which exhibit a certain concentration ratio that remains stable as long as there are no human disturbances.

Materials and methods

The average relative contents of Zn, Cu, and Pb were calculated by dividing the concentration of each metal in soils or sediments, in the <63-μm fraction, by the sum of Zn, Cu, and Pb, expressed as a percentage. The evaluation of the sum of the average relative concentrations of Zn, Cu, and Pb (Ri), together with three standard deviations for each element, namely, Ri ± 3Si, allows a hexagon to be constructed, represented in ternary diagrams of Zn:Cu:Pb. Following the method proposed by Weng et al. (Environ Geol 45:79–85, 2003), those samples falling outside the hexagon must be considered outliers.

Results and discussion

Results obtained confimed the conservative behavior between the relative contents of Zn, Cu, and Pb in surficial samples (soils, bed, and suspended sediments). Only sediment cores displayed nonconservative behavior, showing a marked Pb enrichment, with respect to the surficial samples. When Zn, Cu, and Pb relative contents were plotted in ternary diagrams, outliers were best classified when the hexagon was drawn with standard deviations of samples from the study area. The hexagon drawn with an international database of soils and sediments showed a poorer classification of outliers.

Conclusions

The results showed that total Zn, Cu, and Pb relative contents may be employed to investigate anthropogenic disturbances of these elements in soils and sediments of the Anllóns River Basin, thus corroborating that this type of normalization may be employed as a tool to assess outliers in a contaminated area.     

Cultivar evaluation and effect of fermentation on antioxidant capacity and in vitro inhibition of α-amylase and α-glucosidase by highbush blueberry (Vaccinium corombosum)

The berry fruits of highbush blueberry (Vaccinium corymbosum) contain bioactive compounds with potential health benefits. The objective was to evaluate blueberries grown in southern Illinois as well as the effect of fermentation, at two different temperatures, on chemical and physical parameters. Fruits from fifteen blueberry cultivars were analyzed. Fruit diameter ranged from 12.8 mm to 18.7 mm, pH from 2.6 to 3.7, reducing sugars from 6.4% to 15.2%, total sugars from 13.9% to 21.6%, total polyphenols from 0.39 to 1.00 mg gallic acid equivalents (GAE)/g blueberry and antioxidant capacity from 5.8 to 10.9 μM Trolox equivalents (TE)/g. In vitro α-amylase and α-glucosidase inhibitory capacity relative to the positive control acarbose, a known anti-diabetic drug, showed a range from 91.8 to 103.3% for α-amylase and from 103.2% to 190.8% for α-glucosidase. Wines prepared from several of these blueberry cultivars were analyzed throughout fermentation and compared at room temperature and cold temperature fermentation for pH (3.5 to 6.3), °Brix (13.6 to 29.7), total polyphenols (375.4 to 657.1 μg GAE/mL wine), and antioxidant capacity (4.5 to 25.1 mM TE). The wines were also tested for their in vitro capacity to inhibit α-amylase and α-glucosidase and maintained similar inhibitory action as the berries. Highbush blueberry cultivars and their fermented beverages are good natural sources of antioxidants and starch-degrading enzyme inhibitors important for type 2 diabetes management.     

In vitro digestibility of α-casozepine, a benzodiazepine-like peptide from bovine casein, and biological activity of its main proteolytic fragment

α-Casozepine is a peptide, corresponding to the sequence 91-100 of the bovine α(s1)-casein, displaying anxiolytic activity in the rat. The α(s1)-casein tryptic hydrolysate containing this peptide decreases stress effects after oral administration in various species including man. Therefore, the stability of this peptide toward gastric and pancreatic proteases has been assessed by using pepsin, chymotrypsin/trypsin, Corolase PP, pepsin followed by chymotrypsin/trypsin or pepsin followed by Corolase PP. α-Casozepine was slowly degraded by chymotrypsin, much more sensitive to pepsin and Corolase PP but not completely destroyed after 4 h kinetics. The bonds in the region 91 to 95 of the α-casozepine were totally resistant to hydrolysis by all studied proteases. Surprisingly, a fragment, corresponding to the sequence 91-97 and found in all the hydrolysis media in significant amount, possessed an anxiolytic activity in three behavioral tests measuring this parameter. This peptide could participate in the in vivo activity of α-casozepine.     

Recovery and characterization of α-zein from corn fermentation coproducts

Zeins were isolated from corn ethanol coproduct distiller's dried grains (DDG) and fractionated into α- and β γ-rich fractions. The effects of the ethanol production process, such as fermentation type, protease addition, and DDG drying temperature on zein recovery, were evaluated. Yield, purity, and molecular properties of recovered zein fractions were determined and compared with zein isolated from corn gluten meal (CGM). Around 29-34% of the total zein was recovered from DDG, whereas 83% of total zein was recovered from CGM. Process variations of cooked and raw starch hydrolysis and fermentation did not affect the recovery, purity, and molecular profile of the isolated zeins; however, zein isolated from DDG of raw starch fermentation showed superior solubility and film forming characteristics to those from conventional 2-stage cooked fermentation DDG. Protease addition during fermentation also did not affect the zein yield or molecular profile. The high drying temperature of DDG decreased the purity of isolated zein. SDS-PAGE indicated that all the isolated α-zein fractions contained α-zein of high purity (92%) and trace amounts of β and γ-zeins cross-contamination. Circular dichroism (CD) spectra confirmed notable changes in the secondary structure of α-zeins of DDG produced from cooked and raw starch fermentation; however, all the α-zeins isolated from DDG and CGM showed a remarkably high order of α-helix structure. Compared to the α-zein of CGM, the α-zein of DDG showed lower recovery and purity but retained its solubility, structure, and film forming characteristics, indicating the potential of producing functional zein from a low-value coproduct for uses as industrial biobased product.     

Similarity of fine specificity of IgA anti-gliadin antibodies between patients with celiac disease and humanized α1KI mice

Gliadins, and primarily α-gliadins containing several sequences such as aa 31-49, aa 56-88 (33-mer), aa 57-68, and aa 69-82, are critical in the induction of immune response or toxic reaction leading to the development of celiac disease (CLD). The role of IgA anti-gliadin antibodies (IgA AGA) is unknown. To this end, we prepared several humanized monoclonal IgA AGA using transgenic α1KI mice. Employing Pepscan with overlapping decapeptides of α-gliadin we observed a robust similarity between the specificity of humanized mouse monoclonal IgA AGA and IgA AGA from patients with florid CLD. The common immunodominant region included several sequential epitopes localized in the N-terminal part of α-gliadin (QFQGQQQPFPPQQPYPQPQPFP, aa 29-50, and QPFPSQQPYLQL, aa 47-58). Notably, IgA AGA produced by clones 8D12, 15B9, 9D12, and 18E2 had significant reactivity against sequences localized in the 33-mer, LQLQPFPQPQ (aa 56-65) and PQLPYPQPQPFL (aa 69-80). Humanized mouse monoclonal IgA AGA that have a known specificity are suitable as standard in ELISAs to detect serum IgA AGA of CLD patients and for studying the AGA pathogenic role in CLD, especially for analyzing the translocation of complex of specific IgA antibodies and individual gliadin peptides through enterocyte barrier.     

In silico structural characteristics and α-amylase inhibitory properties of Ric c 1 and Ric c 3, allergenic 2S albumins from Ricinus communis seeds

The major Ricinus communis allergens are the 2S albumins, Ric c 1 and Ric c 3. These proteins contain a trypsin/α-amylase inhibitor family domain, suggesting that they have a role in insect resistance. In this study, we verified that Ric c 1 and Ric c 3 inhibited the α-amylase activity of Callosobruchus maculatus, Zabrotes subfasciatus, and Tenebrio molitor (TMA) larvae as well as mammalian α-amylase. The toxicity of 2S albumin was determined through its incorporation in C. maculatus larvae as part of an artificial diet. Bioassays revealed that 2S albumin reduced larval growth by 20%. We also analyzed the tridimensional structures of Ric c 1 and Ric c 3 by (a) constructing a comparative model of Ric c 1 based on Ric c 3 NMR structure and (b) constructing the theoretical structure of the Ric c 1-TMA and Ric c 3-TMA complexes. Our biological and theoretical results revealed that Ric c 1 and Ric c 3 are a new class of α-amylase inhibitors. They could potentially be used to help design inhibitors that would be useful in diverse fields, ranging from diabetes treatment to crop protection.     

Effect of calcium sprays,time of harvest,cold storage,and ripeness on fruit quality of ‘anjou’ pears 1

Calcium chloride (CaCl₂), increased Ca concentrations in fruit cortex and peel of ‘Anjou’ pears (Pyrus communis L.). Calcium sprays reduced the fruit disorders: brown core, cork spot and superficial scald. Fruit size (weight) increased while fruit Ca concentrations decreased with fruit at the later harvest dates. The earliest harvest date was associated with a lower incidence of fruit disorders. Superficial scald increased in fruit held longer in cold storage and in ripened fruit. Shelf‐life and fruit quality of Ca‐sprayed fruit was improved due to higher Ca concentrations in fruit peel and cortex resulting in overall enhancement of fruit appearance, and in improvement in the control of the incidences of cork spot, scald, brown core, and external and internal rots, and in amelioration of fruit juiciness and fruit color.     

Removal of Chromium, Copper, and Nickel from an Electroplating Effluent Using a Flocculent Brewer’s Yeast Strain of Saccharomyces cerevisiae

The release of heavy metals in aquatic systems due to the discharge of industrial wastewaters is a matter of environmental concern. Heat-inactivated cells of a flocculent strain of Saccharomyces cerevisiae were used in the bioremediation, in a batch mode, of a real electroplating effluent containing Cu, Ni, and Cr. In this approach, no previous reduction of Cr(VI) to Cr(III) was required. Cr(VI) was selectively removed (98%) by yeast biomass at pH 2.3. At this pH, Cr(VI) is mainly in the form of HCrO ₄ ^? and yeast surface is surrounded by H⁺ ions, which enhance the Cr(VI) interaction with biomass binding sites by electrostatic forces. Subsequently, pH of the effluent was raised up to 6.0; this pH maximizes the efficiency of cations removal since at this pH the main binding groups of yeast cells are totally or partially deprotonated. The passage of effluent through a series of sequential batches, at pH 6.0, allowed, after the third batch, the removal of Cu(II), Ni (II), Cr total, and Cr(VI) in the effluent to values below the legal limit of discharge. The strategy proposed in the present work can be used in plants for the treatment of heavy metals rich industrial effluents containing simultaneously Cr(VI) and Cr(III).     

Genetic resources collections of leafy vegetables (lettuce, spinach, chicory, artichoke, asparagus, lamb’s lettuce, rhubarb and rocket salad): composition and gaps

Lettuce, spinach and chicory are generally considered the main leafy vegetables, while a fourth group denoted by ‘minor leafy vegetables’ includes, amongst others, rocket salad, lamb’s lettuce, asparagus, artichoke and rhubarb. Except in the case of lettuce, central crop databases of leafy vegetables were lacking until recently. Here we report on the update of the international Lactuca database and the development of three new central crop databases for each of the other leafy vegetable crop groups. Requests for passport data of accessions available to the user community were addressed to all known European collection holders and to the main collection holders located outside Europe. Altogether, passport data of 17,530 accessions from a total of 129 collections were collected. The four separate databases were made available on line via a common entry page accessible at http://documents.plant.wur.nl/cgn/pgr/LVintro/. Based on a literature study, an analysis of the gene pool structure of the crops was performed and an inventory was made of the distribution areas of the species involved. The results of these surveys were related to the contents of the newly established databases in order to identify the main collection gaps. Priorities are presented for future germplasm acquisition aimed at improving the coverage of the crop gene pools in ex situ collections.     

Distribution of Total and DTPA‐Extractable Zinc,Copper, Manganese,and Iron in Vertisols of India

Abstract

Vertisols of India are developed over isohyets of 600 to 1500 mm, and their chemical cycles are set by drainage, landforms, and particle size, which results in variable pedogenic development within the otherwise homogeneous soils. The purpose of this study was to identify pedogenic processes in the distribution of total and DTPA‐extractable zinc (Zn), copper (Cu), manganese (Mn), and iron (Fe). The soils are developed over basaltic parent material of Cretaceous age. Soil samples were drawn from genetic horizons of the 13 benchmark profiles and analyzed by using HF–HClO₄ acid for total and DTPA extraction. Correlation coefficients were calculated taking all samples together. The total concentration varied from 24 to 102 mg kg^?1 for Zn, 21 to 148 mg kg^?1 for Cu, 387 to 1396 mg kg^?1 for Mn, and 2.36 to 9.50% for Fe. Their variability was proisotropic and haplodized, and their concentrations increased with advancing isohyets. Within the isohyets, hindrance in drainage caused retention of Zn and Cu but loss of Fe. The piedmont soils had more Fe than alluvium soils. The spatial distribution of total contents of Zn, Cu, and Fe was influenced by the pedogenic processes associated with Haplusterts but not with provenance materials. Surface concentrations of the elements by biotic lifting and/or harvest removal were negated by the pedoturbation that further contributed to the irregular distribution of the elements in the profiles. Total Zn and total Cu had positive coefficients of correlations with coarse clay, whereas total Mn and total Fe were positively correlated with fine clay. The DTPA‐extractable forms were functions of isohyets and drainage and showed association with organic carbon content and coarse clay.     

Inhibitory effects of muscadine anthocyanins on α-glucosidase and pancreatic lipase activities

Inhibitory effects of the Noble muscadine grape extracts and the representative phytochemicals for anthocyanins (i.e., cyanidin and cyanidin-3,5-diglucoside) on two enzymes, that is, α-glucosidase and pancreatic lipase, were investigated regarding their antidiabetic activities. The study demonstrated that the anthocyanin extracts and the selected chemicals obeyed the competitive mode against the enzymes. The methanolic extracts of whole fruit and skin of the muscadine showed inhibitory activities against the α-glucosidase with their IC(50) values at 1.50 and 2.73 mg/mL, and those against the lipase at 16.90 and 11.15 mg/mL, respectively, which indicated that the muscadine extracts possessed strong antidiabetic activities. Particularly, the ethyl acetate (EtoAc) extract and the butanol (BuOH) extract exhibited much higher inhibitory activities against both enzymes than the CHCl(3) and water extracts, while the majority of anthocyanins existed in the BuOH fractions. Moreover, cyanidin exhibited a much stronger antidiabetic activity than cyanidin-3,5-diglucoside, suggesting that anthocyanins may have higher inhibitory activities after being digested. Further chromatographic analysis by high-performance liquid chromatography-mass spectrometry identified five individual anthocyanins, including cyanidin, delphinidin, petunidin, peonidin, and malvidin glycosides.     

Structure-activity relationships of α-, β(1)-, γ-, and δ-tomatine and tomatidine against human breast (MDA-MB-231), gastric (KATO-III), and prostate (PC3) cancer cells

Partial acid hydrolysis of the tetrasaccharide (lycotetraose) side chain of the tomato glycoalkaloid α-tomatine resulted in the formation of four products with three, two, one, and zero carbohydrate side chains, which were separated by high-performance liquid chromatography (HPLC) and identified by thin-layer chromatography (TLC) and liquid chromatography ion-trap time-of-flight mass spectrometry (LCMS-IT-TOF). The inhibitory activities in terms of IC(50) values (concentration that inhibits 50% of the cells under the test conditions) of the parent compound and the hydrolysates, isolated by preparative HPLC, against normal human liver and lung cells and human breast, gastric, and prostate cancer cells indicate that (a) the removal of sugars significantly reduced the concentration-dependent cell-inhibiting effects of the test compounds, (b) PC3 prostate cancer cells were about 10 times more susceptible to inhibition by α-tomatine than the breast and gastric cancer cells or the normal cells, (c) the activity of α-tomatine against the prostate cancer cells was 200 times greater than that of the aglycone tomatidine, and (d) the activity increased as the number of sugars on the aglycone increased, but this was only statistically significant at p < 0.05 for the normal lung Hel299 cell line. The effect of the alkaloids on tumor necrosis factor α (TNF-α) was measured in RAW264.7 macrophage cells. There was a statistically significant negative correlation between the dosage of γ- and α-tomatine and the level of TNF-α. α-Tomatine was the most effective compound at reducing TNF-α. The dietary significance of the results and future research needs are discussed.     

Effect of saccharide structure and size on the degree of substitution and product dispersity of α-lactalbumin glycated via the Maillard reaction

The course of the Maillard reaction between α-lactalbumin and various mono- and oligosaccharides in the solid state was studied using UPLC-ESI-TOF-MS. Individual reaction products were monitored for their degree of substitution per protein molecule (DSP). The Maillard reaction rate depended on the saccharide type and decreased when the saccharide size increased. Conjugation with charged saccharides was hindered when a specific average DSP was reached, probably resulting from electrostatic repulsion. The DSP varied between 0 and 15, and the standard deviation of the average DSP, which is a measure for product dispersity, increased to 1.9. Similar experiments were performed with a dipeptide. Relative reaction rates in these experiments were 1 for glucose, 0.28 for maltose, and 0.16 for maltotriose. Comparison of the results obtained using α-lactalbumin and the dipeptide made clear that the Maillard reaction rate is determined by a number of factors, including saccharide reactivity and lysine accessibility.     

Comparison of mehlich 3, mehlich 1, ammonium bicarbonate‐DTPA, 1.0M ammonium acetate,and 0.2M ammonium chloride for extraction of calcium,magnesium, phosphorus,and potassium for a wide range of soils

Abstract

Extractants employed for routine soil analysis vary from one laboratory to another. Lack of a universal soil extractant is a serious limitation for interpretation of analytical results from various laboratories on nutritional status of a given soil. This limitation can be overcome by developing functional relationships for concentrations of a given nutrient extractable by various extradants. In this study, extractability of Ca, Mg, P, and K in a wide range of soils (0–15 cm) from citrus groves in Florida representing 21 soil series, with varying cultural operations, were compared using Mehlich 3 (M3), Mehlich 1 (M1), ammonium acetate (NH₄AOc), pH = 7.0 (AA), 0.2M ammonium chloride (NH₄Cl), and ammonium bicarbonate‐DTPA (AB‐DTPA) extractants. Soil pH (0.01M CaCl₂) varied from 3.57 to 7.28. The concentrations of Ca or Mg extractable by M3, M1, AA, and NH₄Cl were strongly correlated with soil pH (r² = 0.381–0.482). Weak but significant correlations were also found between AB‐DTPA extractable Ca or Mg and soil pH (r² = 0.235–0.278). Soil pH relationships with extractable K were rather weak (r² = < 0.131) for M1 and NH₄Cl but non‐significant for M3, AB‐DTPA, and AA. Concentrations of Ca, Mg, and K extractable by M3 were significantly correlated with those by either M1, AA, or NH₄Cl extractants. Mehlich 3‐P was significantly correlated with P extractable by M1 extractant only. Mehlich 3 versus AB‐DTPA relationship was strong for K (r² = 0.964), weaker for Mg and P (r² = 0.180–0.319), and non‐significant for Ca. With the increasing emphasis on possible use of M3 as an universal soil extractant, data from this study support the hypothesis that M3 can be adapted as a suitable extractant for routine soil analysis.