Protein from red cabbage (Brassica oleracea) seeds with antifungal, antibacterial, and anticancer activities

A 30 kDa antifungal protein was purified from red cabbage ( Brassica oleracea ) seeds. It exhibited a molecular mass and N-terminal amino acid sequence disinct from those of previously isolated Brassica antifungal proteins. The protocol used entailed ion exchange chromatography on Q-Sepharose and SP-Sepharose followed by fast protein liquid chromatography on Mono S. The protein hindered mycelial growth in Mycosphaerella arachidicola (with an IC50=5 μM), Setospaeria turcica, and Bipolaris maydis. It also inhibited the yeast Candida albicans with an IC50=96 μM. It exerted its antifungal action by permeabilizing the fungal membrane as evidenced by staining with Sytox green. The antifungal activity was stable from pH 3 to 11 and from 0 to 65 °C. It manifested antibacterial activity against Pseudomonas aeruginosa (IC50=53 μM). Furthermore, after 48 h of culture, it suppressed proliferation of nasopharyngeal cancer and hepatoma cells with IC50=50 and 90 μM, respectively.     

Hypotin, a novel antipathogenic and antiproliferative protein from peanuts with a sequence similar to those of chitinase precursors

A protein designated Hypotin, with both antifungal and antibacterial activity, was isolated from peanut (Arachis hypogaea) seeds. The isolation procedure included extraction, ammonium sulfate precipitation, affinity chromatography on Affi-gel blue gel, ion chromatography, and gel filtration. The protein exhibited a molecular mass of 30.4 kDa in SDS-polyacrylamide gel electrophoresis under both reducing and nonreducing conditions, indicating that it is a monomeric protein. Its N-terminal sequence was highly homologous to those of chitinases and chitinase precursors from plants. It exerted potent antifungal action toward a variety of fungal species, including Pythium aphanidermatum, Fusarium solani, Physalospora piricola, Alternaria alternata, Botrytis cinerea, and Fusarium oxysporum. In addition, this novel protein exhibited antiproliferative activity against tumor cells. These findings further the progress in the research of leguminous plants.     

Chelating resin method for estimation of sludge‐cadmium bioavailability

Abstract

A chelating resin procedure was developed to predict the plant uptake of Cd by municipal sewage sludges applied to land. Seventeen anaerobically digested sludges were sampled to give a range of total Cd content of 0.07 to 2.02 mmol/kg. Sludge suspensions [20 g in 100 mL 0.05 M Ca(NO₃)₂] were equilibrated with 1 g Chelex 100 resin placed in dialysis tubing and shaken at 200 rpm for 16 h. Resin‐extractable Cd was compared with sludge solution Cd (CdT and Cd²⁺) in equilibrium with 0.05 M Ca(NO₃)₂, and 0.05 M Ca(NO₃)₂ containing 50 (μM Na‐EDTA (ethylenediaminetetraacetate). Resin extractable Cd was correlated with Cd uptake by sudax, a sorghum/sudangrass hybrid (Sorghum bicolar), grown in Spinks loamy sand (Typic Udipsamment) amended with each of the sludges to give a constant Cd concentration of 22 μmol/kg soil.

Resin extractable Cd ranged from < 0.1 to 48 μmol/kg. Resin extracted between zero and 5.3% of total sludge Cd. Resin extractable Cd was highly correlated with CdT and Cd²⁺ in 0.05 M Ca(NO₃)₂ (R² = 0.97 and 0.98, respectively), and with 0.05 M Ca(NO₃)₂ containing 50 μM NaEDTA (R² = 0.97 and 0.98, respectively). There was a lower correlation with total sludge Cd and soil solution Cd (R² = 0.53 and 0.63, respectively). Cadmium concentration in sudax was highly correlated with resin extractable sludge Cd (R² = 0.92). When the two sludges with highest total sludge Cd were dropped, the correlation dropped (R² = 0.57), but resin extractable Cd predicted Cd uptake as effectively as CdT and Cd²⁺ in Ca(NO₃)₂ or Ca(NO₃)₂/EDTA. Resin extraction appears to be a promising method of assessing the potential bioavailability of sludge Cd.     

Functional Properties of 7s Globulin Extracted from Cowpea Vicilins

The seed of cowpea (Vigna unguiculata L.) is rich in protein and the amino acid profiles of the meal are suitable for human dietary products, but little is known about the structure and chemical properties of the protein extracted from this legume. This study determined the functional properties of two selected cowpea cultivars and their solubility, emulsifying capacity, surface hydrophobicity, and thermal stability. Seeds of red and black cowpea were surface sterilized and the 7s globulin was isolated and purified using column chromatography with Sephacryl S‐300 (Hi‐Prep 26/60) gel column. Also, SDS‐PAGE and protein structure were analyzed using biochemical procedures. At high ionic strength (μ = 0.5), cowpea 7s globulin fraction exhibited better solubility for a wide range of pH levels, higher emulsifying capacities, and greater thermal stability than those obtained at low ionic strength (μ = 0.08). The lowest solubility was observed at pH 5.3–6.4 at the low ionic strength. Emulsifying capacities at high protein concentration were greater when compared with low protein concentration. T_m values of black cowpea globulin fraction were higher than those of red cowpea globulin fraction, whereas the surface hydrophobicity of the globulin fraction in red cowpea was larger than that in black cowpea.     

Characteristics of membrane filters in relation to aluminium studies in soil solutions and natural waters

Potential vitiative effects of Millipore 0.45-, 0.22-, 0.05- and 0.025-pm filter elements on aqueous samples were investigated. All the filter elements evaluated exhibited a cation exchange capacity (CEC); in the case of 0.025-pm filter elements, the CEC increased with pH. Filtration of 20 μM AlCl₃/1.65 mM CaCl₂, solutions (I～0.005 M) to 0.45, 0.22 and 0.05 pm resulted in no significant change in solution A1 concentration. Filtration through 0.025-μm filter elements significantly reduced the total A1 present in solutions adjusted to pH 4.5 and 5.0; the A1 concentration of solution adjusted to pH 4.0 was not altered. The removal of A1 from pH 4.5 and pH 5.0 solutions was attributed to the retention of A1 hydroxide micro-particulates formed during pH adjustment of the AlCl₃/CaCI₂, solution. Adsorption of A1 by the filter element was not significant. Soil solutions were analysed without filtering and after filtration to 0.45,0.22,0.05 and 0.025 pm. Filtration had no effect on the concentration of the major anions (Cl^?, SO²₄ -, NO¹₃) or cations (Ca⁺⁺, Mg⁺⁺, Na⁺, K⁺). However, filtration to 0.05 and 0.025 pm resulted in significant reductions in the concentration of Al, Fe, Si and organic C in some samples. In soil solutions for which filtration resulted in the removal of large amounts of particulate material, the solution appeared less coloured after filtration and exhibited lower absorbance in the visible spectrum (4O(MOO nm). However, the absence of colour did not preclude the presence of colloidal particles.     

Aerobic biodegradation kinetics and pathway of the novel herbicide ZJ0273 in soils

Degradation of ZJ0273, a recently developed pyrimidynyloxybenzoic‐based herbicide, was investigated in five different soils under aerobic conditions. ZJ0273 degradation rate was strongly affected by soil physico‐chemical characteristics and the inoculation of ZJ0273‐degrading bacteria. Greater organic matter (OM) content, neutral pH and inoculation of ZJ0273‐degrading bacteria can increase degradation rate and decrease the half‐life value (DT50). At 30°C the biodegradation rate of ZJ0273 reached 41–85% in natural (unsterilized) soils. It ranged from 69 to 96% at 90 days after treatment (DAT) in five different types of soils after re‐inoculation of Amycolatopsis sp. M3‐1 and DT50 decreased by 34 , 81, 16, 20 and 32 days, respectively, in soils S1, S2, S3, S4 and S5. Furthermore, using the six metabolites (M1–M6) identified six metabolites (M1–M6) by liquid chromatography‐mass spectrometry (LC‐MS) and their behaviour, a biodegradation pathway of ZJ0273 in soils was proposed. New metabolites, M5 and M6, were found in soils. Biodegradation of ZJ0273 involved continuous biocatalytic reactions, such as de‐estering, hydrolysis, acylation, C‐N cleavage, de‐methyl and ether cleavage reactions. Finally, ZJ0273 was bio‐transformed into M4 and M6, which could be degraded and oxidized into CO₂ and H₂O through the tricarboxylic acid (TCA) cycle.     

Rhizodeposition of maize: Short‐term carbon budget and composition

The aim of this study was to assess differences in rhizodeposition quantity and composition from maize cropped on soil or on 1:1 (w/w) soil–sand mixture and distribution of recently assimilated C between roots, shoots, soil, soil solution, and CO₂ from root respiration. Maize was labeled in ¹⁴CO₂ atmosphere followed by subsequent simultaneous leaching and air flushing from soil. ¹⁴C was traced after 7.5 h in roots and shoots, soil, soil solution, and soil‐borne CO₂. Rhizodeposits in the leachate of the first 2 h after labeling were identified by high‐pressure liquid chromatography (HPLC) and pyrolysis–field ionization mass spectrometry (Py‐FIMS). Leachate from soil–sand contained more ¹⁴C than from soil (0.6% vs. 0.4%) and more HPLC‐detectable carboxylates (4.36 vs. 2.69 μM), especially acetate and lactate. This is either because of root response to lower nutrient concentrations in the soil–sand mixture or decreasing structural integrity of the root cells during the leaching process, or because carboxylates were more strongly sorbed to the soil compared to carbohydrates and amino acids. In contrast, Py‐FIMS total ion intensity was more than 2 times higher in leachate from soil than from soil–sand, mainly due to signals from lignin monomers. HPLC‐measured concentrations of total amino acids (1.33 μM [soil] vs. 1.03 μM [soil–sand]) and total carbohydrates (0.73 vs. 0.34 μM) and ¹⁴CO₂ from soil agreed with this pattern. Higher leachate concentrations from soil than from soil–sand for HPLC‐measured carbohydrates and amino acids and for the sum of substances detected by Py‐FIMS overcompensated the higher sorption in soil than in sand‐soil. A parallel treatment with blow‐out of the soil air but without leaching indicated that nearly all of the rhizodeposits in the treatment with leaching face decomposition to CO₂. Simultaneous application of three methods—¹⁴C‐labeling and tracing, HPLC, and Py‐FIMS—enabled us to present the budget of rhizodeposition (¹⁴C) and to analyze individual carbohydrates, carboxylates, and amino acids (HPLC) and to scan all dissolved organic substances in soil solution (Py‐FIMS) as dependent on nutrient status.     

Effect of ammonium and phosphorus supply on h+ production in gel by two tropical forage grasses

The effect of the supply of ammonium (NH₄ ⁺) and phosphorus (P) in gel on the amounts of hydrogen ion (H⁺) excreted from plant roots was studied with Brachiaria humidicola (a highly acid‐soil tolerant tropical grass) and B. brizantha (less acid‐soil tolerant) grown in soil in a glasshouse. The H⁺ production was measured over 24 h in agar gel containing full nutrient solution with a range of NH/‐N levels (0, 0.25, 0.5, and 5.0 mM NH₄ ⁺‐N). Highly soluble P, K₂HPO₄, or relatively insoluble P, rock P, was supplied at four concentrations (0, 11.5, 34.5, or 115 μM p) in the gel. Increasing NH₄ ⁺ concentration in the gel increased H⁺ production for both grasses, but there was some inhibition of growth for B. brizantha at the highest N concentration. For B. humidicola, but not B. brizantha H⁺ production was greater with 34.5 μM K₂HPO₄ than 11.5 μM K₂HPO₄. At 34.5 μM P for both grasses there was no difference in H⁺ production when P was supplied as rock P or K₂HPO₄. With 11.5 μM P both grasses produced less acid in the gel with the rock P compared with K₂HPO₄. The reduced H⁺ production is probably due to a lower availability of P in the rock P compared with K₂HPO₄. This effect was greater with B. brizantha than B. humidicola, implying that 11.5 μM rock P was not able to supply sufficient P for the growth of B. brizantha. Brachiaria humidicola was able to dissolve more rock P than B. brizantha or alternatively, the growth of B. humidicola was less adversely affected by the low P supply from rock P than B. brizantha. Plant‐induced acidity does not seem to occur as a response to a lack of available P, but rather these grasses only produce acid if there are enough nutrients for growth, i.e., both NH₄ ⁺ and P. If either N or P is limiting, growth is limited as is NH₄ ⁺ uptake, so that H⁺ production is curtailed.     

No‐tillage with half‐amount residue retention enhances microbial functional diversity,enzyme activity and glomalin‐related soil protein content within soil aggregates

A 3‐year field tillage and residue management experiment established in North China was used to analyse topsoil (0–15 cm) aggregation, and microbial functional diversity, enzyme activity and glomalin‐related soil protein (GRSP) content within aggregates. Compared with conventional tillage (CT), no‐tillage (NT) alone significantly (P < 0.05) increased organic C contents in 50–250 and <2 μm aggregates and decreased the proportion of C accumulated by 2–50 μm aggregates and microbial functional diversity indices in <2 μm aggregates. Regardless of tillage practice, both half‐amount (C50) and full (C100) residue retention tended to increase organic C and GRSP contents, or dehydrogenase and invertase activities, in certain aggregates. Under CT, a poorer performance of C50 than C100 was observed in maintaining Shannon index (H′) and Simpson index (D) in >250 and <2 μm aggregates, and also McIntosh index (U) in <2 μm aggregates, owing to insufficient residue and possible decreases in the distribution of decomposer micro‐organisms. Under NT, however, C50 was more effective than C100 in maintaining/elevating H′, D and U in all soil aggregates except for 50–250 μm, suggesting that surplus residue may induce worse soil conditions, decreasing heterotrophic microbial activities. Thus, NT with half‐amount residue retention improved soil physical–chemical–biological properties and could be a useful management practice in North China.     

Purification and characterization of phytase induced in tomato roots under phosphorus-deficient conditions

Phytase (myo-inositol hexakisphosphate phosphohydrolase; EC 3.1.3.8) was purified from roots of tomato plants grown under phosphorus-deficient conditions using five purification schemes. The phytase was successfully separated from the major acid phosphatase to an electrophoretic homogeneity. The native molecular weight of this enzyme was estimated to be about 164 kD by Bio-Gel P-200 gel filtration. The molecular weight of the subunit on SDS-PAGE was approximately 82 kD, indicating that the native form of the enzyme was a homodimer. The isoelectric point of tomato phytase was about 5.5. The enzyme exhibited a high affinity for phytic acid (K _m = 38 μM), and was strongly inhibited by phosphate, molybdate and fluoride. Among other characteristics of tomato phytase, the pH and temperature optima were 4.3 and 45°C, respectively. Tomato phytase contained a fairly high concentration of aspartic, glutamic acid and glycine residues.     

Salinity risk assessment using fuzzy multiple criteria evaluation

For agricultural productivity, primary salinity constitutes a hazard. Understanding the risk of secondary salinization is also important and it is necessary to map all these hazards and the overall risk. One approach is digital soil mapping. We have developed hazard maps of root zone (0–2 m) and subsurface (6–12 m) salinity, as well as groundwater height, using empirical best linear unbiased prediction using proximal and remotely sensed ancillary data. To convert the hazards into salinity risk maps and account for some uncertainty, fuzzy membership functions (FMF) were used in conjunction with semantic import models that consider the vulnerability of agricultural crops. Therefore, we developed memberships (μ) to three salinity risk classes and created maps of each, including root zone (μ_RSR) and subsurface (μ_SSR) salinity, and depth to groundwater (μ_GTR). To estimate groundwater (μ_GSR) and overall salinity risk (μ_OSR), fuzzy multiple criteria evaluation was undertaken. To account for μ_GSR, the μ_SSR and μ_GTR were combined using a t‐norm operator, and μ_OSR was accounted for by combining μ_RSR and μ_GSR using a t‐conorm operator. The approach was applied to an area growing irrigated cotton. Cross‐validation shows predicted μ_OSR was good, with an agreement rate of 70.6%. The predicted μ_OSR was consistent with that of many areas affected by point‐source salinity. The method provides an effective way of mapping salinity hazard and risk. Incorporation of FMF provides a meaningful continuum of membership and allows the incorporation of uncertainty. Salinity risk can be calculated relative to any vegetation community and locations where management actions to moderate soil salinization can be identified.     

The Influence of Cadmium Toxicity on Some Physiological Parameters as Affected by Iron in Rice (Oryza Sativa L.) Plant

The effects of interaction between cadmium chloride (CdCl₂) and iron (Fe)- ethylenediaminetetraacetic acid (EDTA) were studied in rice plant. The seedlings of rice were treated with 0, 50, and 100 μM CdCl₂ supplemented with 5, 10 and 20 ppm Fe as Fe-EDTA for 30 days. Plants were grown under controlled condition. In all the plants treated with CdCl_2, growth parameters [relative leaf growth rate (RLGR), specific leaf area (SLA), and leaf water content area (LWCA)], soluble, and unsoluble sugars contents decreased. Addition of Fe-EDTA moderated cadmium effects. Under CdCl₂ stress without Fe, malondialdehyde (MDA) content, proline content, catalase (CAT) and peroxidase (POD) activity increased, however, in solutions containing both CdCl₂ and Fe-EDTA, MDA content, proline content and activities of antioxidant enzymes decreased. In 50 μM CdCl₂, total protein content increased but in 100 μM decreased. With increasing Fe in solutions containing CdCl₂, protein content decreased. The results indicated that with increasing Fe-EDTA in CdCl₂ treated plants, the effects of toxicity of Cd decreased.     

Antioxidant Capacity of Water‐Extractable Arabinoxylan from Commercial Barley,Wheat, and Wheat Fractions

The objective of this research was to analyze the antioxidant capacity directly of water‐extractable nonstarch polysaccharides (NSP) and feruloylated arabinoxylans (WEAX) following their characterization. NSP were isolated from barley, wheat, and wheat fractions (germ, bran, and aleurone). WEAX were extracted only from wheat fractions. Antioxidant capacity of NSP measured with the 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH), 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid (ABTS), and oxygen radical absorbance capacity (ORAC) assays was 24.0–99.0, 40.0–122.0, and 140.0–286.0μM Trolox equivalents (TE)/g, respectively. The antioxidant capacity of WEAX was 75.7–84.0, 58.0–105.0, and 110.0–235.0μM TE/g for those three assays. DPPH and ABTS were highly correlated to xylose content (R² = 0.85), degree of substitution (R² = −0.99), total phenolic acids (R² = >0.73), total phenolic content (TPC) (R² = >0.78), and ferulic acid content (R² = >0.86). ORAC was only influenced by TPC (R² = 0.63). By taking yield and antioxidant capacity into account, NSP would provide about 0.4–4.2, 0.6–5.1, and 2.8–12.0μM TE/g of flour of radical scavenging activity as measured by DPPH, ABTS, and ORAC, respectively, compared with WEAX (0.4–1.0, 0.3–1.3, and 0.6–2.8μM TE/g). Our results suggest that NSP or WEAX may play a role in protection against free radicals in a food matrix and likely in the gastrointestinal tract.     

Isolation and characterization of a bioactive mannose-binding protein from the Chinese chive Allium tuberosum

A mannose-binding protein was isolated from two different cultivars of the Chinese chive Allium tuberosum by extraction with 0.2 M NaCl, ammonium sulfate precipitation, and affinity chromatography on mannose agarose and fetuin agarose. It exhibited hemagglutinating activity toward rabbit erythrocytes. The lectin (agglutinin) was adsorbed on the mannose-agarose column, but not on the fetuin-agarose column. This A. tuberosum lectin (ATL) is unglycosylated, and not sialic acid binding. Lectins isolated from the two cultivars exhibited the same molecular mass of 25 kDa on gel filtration (Superose 12) and 12.5 kDa on SDS-polyacrylamide gel electrophoresis, indicating that they might be a dimeric protein composed of two identical subunits. The N-terminal amino acid sequence analysis of the lectin of various cultivars of A. tuberosum revealed that they were identical and showed 50%, or more, homology to the lectins from Galanthus nivalis (family Amaryllidaceae), Narcissus tazetta (family Amaryllidaceae), and Aloe arborescenes (family Liliaceae).     

Fractionation of hydrolase-humus complexes by gel chromatography

Summary Purification of soil phosphatase-, urease-, casein- and benzoylarginamide-hydrolysing proteases was obtained by exhaustively ultrafiltering a soil extract using 0.1M pyrophosphate solution at pH 7.1, separating the retained material into fractions of molecular weight higher (A_I) and lower (A_II) than 10⁵ and eluting the fractions on gel chromatography.Three peaks of phosphatase and urease activity were obtained after gel chromatography of fraction A_I on Sephadex G200 using 0.1M pyrophosphate solution as eluant. Only one distinct activity peak was observed when casein- and benzoylarginamide-hydrolysing proteases were assayed in the eluted fractions. Elution diagrams obtained by gel chromatography of fraction A_II on Sephadex G100, using a water as eluant, were characterized by one peak each of phosphatase-, casein- and benzoylarginamide-hydrolysing activity and by two peaks of urease activity.Gel chromatography of both A_I and A_II, generally, but not always, increased specific activity on a C and N basis of derivative fractions. Both proteases showed the highest increase in specific activity due to a marked decrease in organic C and N and an increase in total activity.     

Influence of Starch and Gluten Characteristics on Rheological Properties of Wheat Flour Gel at Small and Large Deformation

Starch and gluten were isolated from 10 wheat cultivars or lines with varied amylose content. The rheological properties of 30% wheat flour gel, starch gel, and the gel of isolated gluten mixed with common starch were determined in dynamic mechanical testing under shear deformation, creep‐recovery, and compression tests under uniaxial compression. Variation of wheat samples measured as storage shear modulus (G′), loss shear modulus (G″), and loss tangent (tan δ = G″/G′) was similar between flour and starch gels and correlated significantly between flour and starch gel. The proportion of acetic acid soluble glutenin exhibited a significant relationship with tan δ of gluten‐starch mixture gel. The small difference in amylose content strongly affected the rheological parameters of flour gels in creep‐recovery measurement. Wheat flour gel with lower amylose content showed higher creep and recovery compliance that corresponded to the trend in starch gel. Compressive force of flour gel at 50 and 95% strain correlated significantly with that of starch gel. Gel mixed with the isolated gluten from waxy wheat lines appeared to have a weaker gel structure in dynamic viscoelasticity, creep‐recovery, and compression tests. Starch properties of were primarily responsible for rheological changes in wheat flour gel.     

Air Drying Affects Extractable Sulfate in Soils of Variable Charge: Test of Two Extraction and Two Quantification Methods

Abstract

Fertilizer recommendations need to be based on reliable soil sulfate determinations. Airdrying samples changes irreversibly many properties of soils with variable charge and might affect the extractable sulfate. In this study, sulfate extracted from air‐dry and field‐moist samples was compared. Two extracting solutions [water and 00.1 M Ca(H₂PO₄) ₂] and two quantification methods (turbidimetry and ion chromatography) were assayed on A and B horizon samples of five Humic Acrisols from southeast Mexico. Air drying increased water‐extractable sulfate in Ah horizons, whereas in Bt horizons, it increased the 00.1 M Ca(H₂PO₄)₂‐extractable sulfate. Airdrying increased dissolved organic carbon contents in all samples and increased soil acidity and oxalate extractable iron in 70 and 60% of the samples, respectively. Results showed larger coefficients of variation in air‐dried samples. Turbidimetry resulted less sensible than ion chromatography. To enhance sensitivity and reproducibility, particularly organic soil samples should be analyzed field‐moist and by ion chromatography.     

Ion chromatography in nutrient depletion studies: Measurement of very low nitrate concentrations

Abstract

Determination of the extent to which plants can deplete nitrate from nutrient solutions (C_min) has been hindered in the past by insufficiently sensitive assay techniques. Now ion chromatography on a Dionex AS4A column can be used to separate and quantitate as little as 5 pmoles nitrate (a sensitivity of 0.02 + 0.005 μM NO₃ ^‐[0.3 ppb NO₃ ^‐N]) in nutrient medium containing other anions in more than 10⁵molar excess. To obtain this precision in actual depletion experiments, however, certain important precautions must be observed, including the avoidance of membrane filters with interfering extractables, i.e. all types tested. Under these conditions, other components of the medium do not interfere, nor apparently do root exudates. The sensitivity and absence of interference is compared with that of existing methods for nitrate estimation (nitrate electrode, salicylate, phenoldisulfonate, nitrate reductase/ nitrite diazotization, and ultraviolet absorption, alone, or coupled with high pressure liquid chromatography). The technique is used to demonstrate that pumpkins (Cucurbita moschataPoir.) growing in nutrient solutions can deplete nitrate at least to 0.16 μM, a concentration probably not measurable by any non‐chromatographic method, and measurable accurately at present only by the ion chromatography technique described here. Chloride uptake, and efflux, has also been measured simultaneously from the same chromatography profiles     

Evaluating the influence of surface soil moisture and soil surface roughness on optical directional reflectance factors

Fine‐scale information on soil surface roughness (SSR) is needed for calculating heat budgets, monitoring soil degradation and parameterizing surface runoff and sediment transfer models. Previous work has demonstrated the potential of using hyperspectral, hemispherical conical reflectance factors (HCRFs) to retrieve the SSR of different soil crusting states. However, this was achieved by using dry soil surfaces, generated in controlled laboratory conditions. The primary aim of this study was therefore to test the impact that in situ variations in surface soil moisture (SSM) content had on the ability of directional reflectance factors to characterize SSR conditions. Five soil plots (20 cm × 20 cm in area) representing different agricultural conditions were subjected to different durations of natural rainfall to produce a range of different levels of SSR. The values of SSM varied from 8.7 to 20.1% across all soil plots. Point laser data (4‐mm sample spacing) were geostatistically analysed to give a spatially‐distributed measure of SSR, giving sill variance values from 3.2 to 23.0. The HCRFs from each soil state were measured using a ground‐based hyperspectral spectroradiometer for a range of viewing zenith angles from extreme forward‐scatter (θ_r = ?60°) to extreme back‐scatter (θ_r = +60°) at a 10° sampling resolution in the solar principal plane. The results showed that despite a large range of SSM values, forward‐scattered reflectance factors exhibited a very strong relationship with SSR (R² = 0.84 at θ_r = ?60°). Our findings demonstrate the operational potential of HCRFs for providing spatially‐distributed SSR measurements, across spatial extents containing spatio‐temporal variations in SSM content.     

A new soil test method for the determination of plant‐available cadmium in soils

Abstract

A new soil test procedure using 1M NH₄Cl was developed for the extraction of plant‐available cadmium (Cd) from soils. Five grams of soil is weighed into a 50‐mL polyethylene vial to which 30 mL of 1M NH₄Cl solution is added. The soil suspension is then shaken on a horizontal shaker for 16 h at 25°C at 180 cycles per min. The suspension is then centrifuged at 2,500g for 5 min and the supernatant filtered through a 0.45 μm nitrocellulose filter under vacuum. Cadmium in the extract is then determined at 228.8 nm on a graphite furnace equipped atomic absorption spectrophotometer. A highly significant correlation was observed between the natural logarithm (In) of 1M NH₄Cl‐extractable Cd in soils and the Cd content in the grain of durum wheat (Triticum turgidum var. durutn L.) grown on the same soils (r = 0.974, p = 3.8 x 10^‐7). In comparison with several commonly used extradants, such as ABDTPA, CaCl₂, NH₄OAc, and NH₄NO₃, the 1M NH₄Cl‐extracted Cd from soils was found to be a better index of Cd availability.