1,4-Dimethoxyglucobrassicin in Barbarea and 4-hydroxyglucobrassicin in Arabidopsis and Brassica

A novel indole glucosinolate, 1,4-dimethoxyglucobrassicin (1,4-dimethoxyindol-3-ylmethylglucosinolate), was isolated as the desulfo derivative from roots of the P-type of Barbarea vulgaris ssp. arcuata, and its structure was determined by spectroscopy including 2D NMR spectroscopy. 4-Hydroxyglucobrassicin (4-hydroxyindol-3-ylmethylglucosinolate) was isolated as the desulfo derivative from green siliques (fruits) of Arabidopsis thaliana and identified by comparison of its (1)H NMR spectrum with the spectrum of the known desulfoglucosinolate from Brassica napus. The delayed elution of desulfo indole glucosinolates from the DEAE Sephadex column used in sample preparation was examined, and the diode-array UV spectra of desulfo indole glucosinolates were measured, to ensure a reliable determination of 1,4-dimethoxyglucobrassicin and 4-hydroxyglucobrassicin with the existing analysis method based on the HPLC of desulfoglucosinolates. 1,4-Dimethoxyglucobrassicin was not detected in 10 other Arabidopsis, Brassica, and Barbarea species, indicating an evolutionarily recent mutation in the indole glucosinolate biosynthesis in B. vulgaris ssp. arcuata type P.     

Glucosinolates in members of the family brassicaceae: separation and identification by LC/ESI-MS-MS

Seeds of 14 different members of the family Brassicaceae were investigated with regard to their content and composition of glucosinolates by HPLC-UV/ESI-MS-MS coupling. The seeds were extracted with hot methanol/water (70:30 v/v) and the desulfoglucosinolates isolated by anion-exchange chromatography with solid-phase extraction columns. The desulfoglucosinolates were detected by UV and identified by ESI-MS/MS with the neutral loss method. Nineteen different glucosinolates were detected in the seeds with a wide range of contents (10-200 micromol/g) and a great variation in the composition.     

How Stable Are Soils for the Determination of Available N?

When potassium chloride (KCl) is used to extract “available” mineral nitrogen (N) species from field-moist soils, samples are usually transferred to the laboratory in a cool box prior to extraction and stored in a fridge until being prepared for extraction. This study shows that significant changes, especially in nitrate concentration, occur under refrigerated conditions for 16 h, especially in grassland subsoils, and these are reflected in total mineral N levels. Surprisingly, storage at room temperature for the same time caused no significant additional net nitrate production. Extractable ammonium concentrations often fell significantly during storage, especially in woodland soil samples, probably via microbial immobilization as well as nitrification. In the present study, 12 pairs of students were used to perform all extractions within 30 min of sampling in the field, which would not be generally practical. It is suggested that volumetric subsampling in the field and immediate addition to a known volume of KCl solution may be more reliable than methodology currently employed by many soil scientists.     

Analysis of intact glucosinolates by MALDI-TOF mass spectrometry

Glucosinolates are naturally occurring plant compounds that may be important in the dietary prevention of cancer. This study shows that they can be detected in their intact form by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) with a high degree of sensitivity. The methodology was used to characterize a number of individual glucosinolates either produced by synthetic chemistry or isolated from plants. The method was used for crude plant extracts to rapidly examine the glucosinolate profile of the plant. The results for a range of plant extracts showed good agreement with previous LC-MS analysis of the desulfoglucosinolates from the same samples.     

Effects of Vermicompost Tea (Aqueous Extract) on Pak Choi Yield,Quality, and on Soil Biological Properties

This study investigated the effects of vermicompost tea (aqueous extract) on yield and chemical quality of pak choi (Brassica rapa cv Bonsai, Chinensis group) grown in three media (two soils and a peat-perlite medium) under two fertilizer regimes (compost and synthetic fertilizer). The impacts of tea application on the chemical and biological properties of the growth media were also investigated. Vermicompost teas were prepared using various extraction methods (non-aerated, aerated, aerated with additives) with 1:10 (v:v) chicken manure-based vermicompost to water dilution and applied weekly at the rate of 200 mL plant^?1 for 4 weeks. Application of vermicompost tea increased plant production, total carotenoids and total glucosinolates in plant tissue. This effect was most prominent under compost fertilization. Total phenolic was lower in vermicompost tea treated plants compared to those treated with only mineral nutrient solution and the water control. Vermicompost tea improved mineral nutrient status of plants and media, and enhanced the biological activity of the media. Variability in yield and chemical quality of plants across treatments was explained largely by variability in tissue N uptake and dry matter accumulation. Dehydrogenase activity and soil respiration of vermicompost tea-treated growth media were approximately 50% higher than untreated media. This study confirmed that vermicompost tea can positively influence plant yield and quality and increase soil biological activity in multiple soil types.     

Air-drying changes the distribution of Hedley phosphorus pools in forest soils

Hedley labile phosphorus(P)pools in soil tend to be several times larger than annual forest requirements,even in highly weathered soils characterized by P limitation.The discrepancy between plant and soil P status could be partly attributable to the frequently adopted air-drying pretreatment that tends to increase soil P solubility.In this study,the effects of air-drying on the distribution of Hedley P fractions were examined using soils collected under 4 forest types at Gongga Mountain,southwestern China.The results showed that the microbial biomass P(Pmic)in the organic horizon decreased markedly after air-drying.The concentrations of Hedley labile P in the air-dried samples were 31%–73%more than those in the field-moist samples.Consequently,the air-drying-induced increments of Hedley labile P pools in the surface soil horizons were 0.8–3.8 times the annual plant P requirements.The organic horizon was more susceptible to the air-drying-induced increases in Hedley labile P than the mineral horizon,probably because of the stronger release of Pmicand disruption of soil organic matter.The quality of P,indexed by the ratio of Hedley labile P to slowly cycling P,shifted in favor of the Hedley labile fractions after air-drying,further revealing that air-drying changed the distribution of Hedley P pools in forest soils.These indicated that the effects of air-drying could not be ignored when interpreting the discrepancy between the P status of plants and the Hedley labile P pools in forest soils.To more efficiently evaluate the P status in forest soils via the Hedley fractionation procedure,the use of field-moist soils is recommended.     

石灰土地区几种作物根际与非根际土壤养分特征对比研究——以重庆市中梁山为例

以重庆市中梁山石灰土地区为研究区,选择莴笋、红菜苔、白菜、瓢儿菜和桔子5种不同的作物,通过野外采样和室内实验分析的方法,分别测定了5种作物的根际与非根际土壤的全氮、全磷、全钾、水解氮、速效磷、速效钾、有机质的含量以及土壤pH值,并进行了对比分析。结果表明,根际与非根际土壤的全氮、全磷、全钾、水解氮、速效磷、速效钾、有机质和pH值之间均表现出显著的差异性（p<0.05）。这5种作物的养分含量除了桔子树的根际土壤速效磷出现亏缺外,其余4种作物根际土壤的全氮、全磷、全钾、水解氮、速效磷以及速效钾都高于非根际土壤,不同作物出现了不同程度的富集现象。另外,根际土壤的pH值均低于非根际土壤;根际土壤有机质含量均高于于非根际土壤。     

Stability of urease in soils

Studies with surface samples of Iowa soils selected to obtain a wide range in properties showed that the following treatments of field-moist soils had no effect on urease activity: leaching with water ; drying for 24 h at temperatures ranging from 30 to 60°C ; storage for 6 months at temperatures ranging from ?20 to 40°C; incubation under aerobic or waterlogged conditions at 30 or 40°C for 6 months. No loss of urease activity could be detected when field-moist soils were air-dried and stored at 21–23°C for 2yr, but complete loss of urease activity was observed when they were dried at 105°C for 24 h or autoclaved (120°C) for 2h. Inactivation of urease in moist soils was detected at temperatures above 60°C.Treatment of field-moist soils with proteolytic enzymes which cause rapid destruction of jackbean urease did not decrease urease activity, but jackbean urease was destroyed or inactivated when added to sterilized or unsterilized soils.Although no decrease in urease activity could be detected when field-moist soils were air-dried, an appreciable (9–33%) decrease in urease activity was observed when air-dried soils were incubated under aerobic or waterlogged conditions. This decrease occurred within a few days, and prolonged incubation or repetition of the drying-incubation treatment did not lead to a further decrease in urease activity. Treatment of incubated air-dried soil with urease or glucose initially increased urease activity to a level exceeding that of the undried soil, but this activity decreased with time and eventually stabilized at the level observed for the undried soil.The work reported supports the conclusions from previous work that the native urease in Iowa soils is remarkably stable and that different soils have different levels of urease activity determined by the ability of their constituents to protect urease against microbial degradation and other processes leading to inactivation of enzymes.     

Effects of drying and wetting on extractable aluminum in strongly acid soils and in aluminum-saturated clays

A number of field-moist strongly acid soils, NaObr-treated soils, and Al-saturated clays were subjected to drying and wetting treatments in the laboratory. Oven drying of samples resulted in decreases in extractable Al and increases in extractable H from field-moist soils containing more than 12 mequiv./100 g exchange acidity and from Al-saturated clays, and wetting the samples resulted in the reverse. However, when field-moist soil samples containing less than 7 mequiv./100 g exchange acidity were oven dried, both the extractable Al and extractable H tended to increase. Removing organic matter with NaOBr from a soil sample low in exchange acidity resulted in a change from an increase to a decrease in extractable Al upon oven drying. In all cases, the extractable Al and extractable H contents fluctuated cyclically with repeated drying and wetting. The cause for the observed changes was attributed to Al hydrolysis, with additional influence from soil acidity buffering, Al interlayer formation, and inorganic and organic matter dissolution.     

Assessing air-drying and rewetting pre-treatment effect on some soil enzyme activities under Mediterranean conditions

Soil enzyme activities are useful indicators of soil quality as they are very sensitive to disturbance. Sample storage or pre-treatments could affect the results in these assays, which are normally determined in fresh samples, kept cold or frozen. The objectives of this study were to (i) evaluate the effect of air-drying or air-drying and rewetting on β-glucosidase, acid phosphatase and urease activities in soils from different locations, degradation status and sampling seasons, and (ii) assess if air-drying or air-drying and rewetting is an accurate sample storage and pre-treatment procedure for enzyme activities in soil quality evaluations under semiarid Mediterranean conditions. Our results showed that urease, phosphatase and β-glucosidase activities were hardly affected by air-drying of degraded and non-degraded soils from the two locations studied in all seasons. Short incubations (4, 8 and 12 d at 23 °C) of rewetted air-dried soil at 55% of water-holding capacity showed different patterns depending on the enzyme studied. Urease and β-glucosidase activities were relatively stable during incubation, with several significant (P<0.05) shifts up and down in some soils and samplings. However, acid phosphatase showed an increase in activity with incubation, of between 5% and 50% relative to air-dried samples. These increases followed no pattern and were unrelated to soil characteristics or sampling date. Hence, urease, phosphatase and β-glucosidase activities determined in air-dried soil samples seem to be representative of those obtained under field-moist conditions. In contrast, short incubations of rewetted soil samples can produce fluctuations in these enzyme activities, mainly of acid phosphatase, and estimations in these conditions are not so representative of field-moist soil values.     

Correlation of glucosinolate content to myrosinase activity in horseradish (Armoracia rusticana)

Fully developed horseradish (Armoracia rusticana Gaertn., Mey., & Scherb.) roots from 27 accessions and leaves from a subset of 9 accessions were evaluated for glucosinolates and myrosinase enzyme activity. Eight different glucosinolates were detected (based on HPLC retention times as desulfoglucosinolates) in both root and leaf tissues. The sum of these glucosinolates, referred to as total, ranged from 2 to 296 micromol g(-1) of dry weight (DW) in both tissues. Four glucosinolates (sinigrin, glucobrassicin, neoglucobrassicin, and gluconasturtiin) were detected in major quantities. In fully developed roots, sinigrin concentration represented approximately 83%, gluconasturtiin approximately 11%, and glucobrassicin approximately 1% of the total glucosinolates. Approximately the same proportions of individual glucosinolates appeared in fully developed leaves, except that glucobrassicin was substituted by neoglucobrassicin and gluconasturtiin concentration was significantly lower (<1%). At least four other glucosinolates were detected in very small quantities (<1%) in both roots and leaves. Myrosinase (beta-thioglucoside glucohydrolase, EC 3.2.3.1) is the enzyme responsible for the hydrolysis of the parent glucosinolates into biologically active products. Very little is known about myrosinase activity and the correlation of its activity to total and individual glucosinolates in plant tissues. Significant differences in myrosinase activity were detected between the roots and leaves, ranging from 1.2 to 57.1 units g(-1) of DW. Data showed no correlation between myrosinase activity and total and/or individual glucosinolates in the roots. However, in the leaves, significant correlations were found between myrosinase activity and total glucosinolates (0.78 at P = 0.01) and between myrosinase activity and sinigrin (0.80 at P = 0.01). Glucosinolates content and myrosinase activity were also correlated in young and fully developed roots and leaves and during tissue crushing. Glucobrassicin concentration in the roots and neoglucobrassicin concentration in the leaves were significantly higher in young than in fully developed tissue. Crushing of the tissue resulted in rapid hydrolysis of sinigrin and glucobrassicin, as expected, from the presence of myrosinase. Likewise, myrosinase activity declined rapidly after crushing, perhaps due to inactivation by the reaction products and/or the depletion of its substrates.     

Factors affecting the availability of organic carbon for denitrification of nitrate in subsoils

Summary Recent work in our laboratory indicated that the slow rate of denitrification in Iowa subsoils is not due to a lack of denitrifying microorganisms, but to a lack of organic C that can be utilized by these microorganisms for reduction of nitrate. To identify factors affecting the availability of leachable organic C in surface soils capable of promoting denitrification in subsoils, we studied the effects of freezing and drying and of plants and plant residues on the amounts of water-soluble organic C in surface soils and the ability of this organic C to promote denitrification in subsoils. We found that aqueous extracts of field-moist, frozen, and air-dried surface soils promoted denitrification in subsoils and that their stimulatory effects on denitrification were highly correlated (r=0.93) with their organic C contents and decreased in the order air-dried soils frozen soils >field-moist soils. But a detailed study of the effect of drying a surface soil to different water tensions indicated that drying of soils under natural conditions is not likely to lead to a substantial increase in their content of water-soluble organic C. Amendment of surface soils with corn or soybean residues led to a marked increase in the amount of organic C in aqueous extracts of the soils and in the ability of these extracts to promote denitrification in subsoils. These effects of plant residues could not be detected after incubation of residue-treated soils for a few days under aerobic conditions, but they increased markedly with an increase in the time of incubation from 1 to 10 days when residue-treated soils were incubated under anaerobic conditions. Analyses for organic acids indicated that this increase was largely due to fermentative production of acetic, propionic, and butyric acids by soil microorganisms. Growth chamber studies showed that growth of corn, soybean, wheat, and sorghum plants on surface soil did not significantly increase the organic C content of leachates of the soil or the ability of these leachates to promote denitrification in subsois. We conclude that plant residues are a major source of the leachable organic C in surface soils that is capable of promoting denitrification in subsoils.     

Short-term assay of soil urease activity using colorimetric determination of ammonium

Summary A rapid assay for soil urease in the absence of bacteriostatic agents has been developed. The method comprises incubation of soil with an aqueous or buffered urea solution, extraction of ammonium with 1 N KCl and 0.01 NHCl and colorimetric NH₄ ⁺ determination by a modified indophenol reaction. The method is characterized by high sensitivity and stability of the coloured complex formed. Measurements obtained by this method showed that no change in urease activity occurred when field-moist samples of soils were stored at –20°C for as long as 5 months. Air-drying of field-moist soil samples may lead to an increase in urease activity.     

Allelochemicals released in soil following incorporation of rapeseed (Brassica napus) green manures.

Plant-derived allelochemicals such as those produced by glucosinolate hydrolysis in Brassica napus, or rapeseed, are viable alternatives to synthetic compounds for the control of soil-borne plant pests. However, allelochemical production and residence times in field soils have not been determined. Soil samples were taken at 0-7.5 and 7.5-15 cm during a period of 3 weeks following plow-down of two winter rapeseed cultivars (Humus and Dwarf Essex). Soil samples were extracted with dichloromethane and analyzed using gas chromatography. Nine glucosinolate degradation products were identified-five isothiocyanates, three nitriles, and one oxazolidinethione. Maximum concentrations were observed 30 h after plow-down. Compounds derived from 2-phenylethyl glucosinolate, the principal glucosinolate in rapeseed roots, dominated the profile of degradation products. Shoot glucosinolates left few traces. This indicates that rapeseed roots may be a more important source of toxic fumigants than above-ground parts of the plant.     

Phytoextractability of Cd from Soil by Some Oilseed Species as Affected by Sewage Sludge and Farmyard Manure

A pot experiment was conducted on cadmium (Cd)–enriched (0, 40, 80, 120, 160 mg Cd kg^?1 soil, using CdCl₂), untreated (Unamended), 3% sewage sludge–treated (SS-amended), and 3% farmyard manure–treated (FYM-amended) soils to evaluate the phytoextractibility of Cd by three oilseed crop species (viz., Brassica juncea, Brassica napus, and Eruca sativa). Visual observation showed that at or above 40 ppm Cd, some light chlorotic symptoms, resembling iron (Fe) chlorosis, appeared after 2 to 3 weeks of germination. The extent of chlorosis followed the order Eruca sativa > Brassica napus > Brassica juncea, and for amendment treatments Unamended > SS-amended > FYM-amended soils. Both the amendments resulted in an increased biomass production in comparison to the Unamended soil, with the effect being more pronounced for FYM. The dry-matter yield of different plant parts followed the order FYM-amended > SS-amended > Unamended soils. For plant species, it followed the order Brassica juncea > Brassica napus > Eruca sativa. The Cd concentration in different plant parts followed the order leaf > stem > seed in all the three species. Amongst the species, the concentration followed the order Brassica napus > Brassica juncea > Eruca sativa, and for amendment treatments SS-amended > Unamended > FYM-amended soils. The mean Cd uptake by different plant species followed the order Brassica juncea > Brassica napus > Eruca sativa, and for amendment treatments SS-amended soil > Unamended soil > FYM-amended soil. The amounts of exchangeable, carbonate bound, Fe-Mn oxide bound, and organic-matter-bound fractions of Cd in the postharvest soil samples increased with the addition of Cd in soil. However, the residual fraction did not change much. At comparable levels of Cd additions, application of sewage sludge as well as FYM resulted in decreases in the exchangeable and Fe-Mn oxide–bound fractions and an increase in the organic-matter-bound fraction. The beneficial effect of sewage sludge and FYM on biomass production was attributed to (i) improvement in the physicochemical and biological environment of the growth medium, (ii) additional supply of essential nutrients, and (iii) possible decrease in toxic effect of added Cd through organo-metallic complexation reactions.     

Dynamics of dissolved and extractable organic nitrogen upon soil amendment with crop residues

Dissolved organic nitrogen (DON) is increasingly recognized as a pivotal pool in the soil nitrogen (N) cycle. Numerous devices and sampling procedures have been used to estimate its size, varying from in situ collection of soil solution to extraction of dried soil with salt solutions. Extractable organic N (EON) not only consists of DON but contains also compounds released from soil biomass and desorbed organic matter. There is no consensus whether DON or EON primarily regulates N mineralisation in soil, and their contribution to N mineralisation has not been quantified simultaneously. We evaluated three sampling procedures on their ability to determine the dynamic of dissolved organic N pools. The three procedures were the determination of DON in 1) soil solution collected by centrifugation, and the determination of EON in 2) a 0.01 M CaCl₂ extract of field moist or 3) dried soil. We added unlabeled leek and ¹⁵N-labeled ryegrass residues to a loamy sandy soil to create a temporarily increase in DON and EON, to stimulate microbial activity, and to test whether the source and dynamics of the three pools differ. We also tested whether the flow of N through DON or EON was associated with the production of inorganic N using ¹⁵N isotope tracing. Sampling procedures significantly affected the amount, but not the dynamics and origin of the three organic N pools. DON and EON (determined on field-moist and dried soils) showed all a significant increase upon crop amendment and returned to their background concentrations within 10 to 30 days. The fraction of DON and EON originating from the crop residue slightly decreased over 138 days and was not different for DON and EON. Field moist extraction of a loamy sandy soil with 0.01 M CaCl₂ gave a reliable estimate of the concentration of in situ dissolved organic N. In contrast, extraction of dried soil significantly increased EON compared to DON. The agreement in dynamics, ¹⁵N enrichment and C-to-N ratio’s indicate that dissolved and extracted organic N have a similar role in N mineralisation. Our results also suggest that they make a minor contribution to N mineralisation; changes in the turnover rate of EON were not associated with changes in the net N mineralisation rate.     

Ionic thiocyanate (SCN(-)) production, fate, and phytotoxicity in soil amended with Brassicaceae seed meals

Brassicaceae seed meals produce ionic thiocyanate (SCN (-)), a bioherbicidal compound. This study determined the fate of SCN (-) in a field soil amended with seed meals of Sinapis alba, Brassica juncea, and Brassica napus and quantified crop phytotoxicity by monitoring carrot ( Daucus carota) emergence. Meals were applied at 1 or 2 t ha (-1), and soils were sampled to 35 cm for SCN (-). Maximum SCN (-) (211 micromol kg (-1) of soil) was measured at 5 days in 0-5 cm samples from plots amended with S. alba meal at 2 t ha (-1). Less than 30 micromol of SCN (-) kg (-1) of soil was measured at soil depths below 15 cm. At 44 days, SCN (-) was <15 micromol kg (-1) of soil in all treatments. Emergence inhibition of carrots seeded 15-36 days after meal amendment was found only in S. alba treatments. The rapid decrease of SCN (-) concentrations in Brassicaceae meal-amended soil indicates limited potential for off-site environmental impacts.     

Usefulness of near-infrared spectroscopy to determine biological and chemical soil properties: Importance of sample pre-treatment

Near-infrared reflectance spectroscopy (NIRS) is known for its inexpensiveness, rapidity and accuracy and may become a useful tool for the assessment of soil quality. Objectives were (i) to evaluate the ability of NIRS to predict several chemical and biological properties of organically managed arable soils as well as the properties of grain yield from winter cereals for a closed population and (ii) to test whether the use of field-moist and pre-treated (quick-freezing followed by freeze-drying and grinding) samples will generate similar results. One hundred and sixteen soil samples from nine organically managed farms from Germany sampled in 2005 and 2006 were used for this investigation. Spectra of the near-infrared region (including the visible range, 400–2500 nm) from field-moist (<2 mm) or pre-treated soil samples were recorded. A modified partial least-square regression method and cross-validation were used to develop an equation over the whole spectrum (first–third derivation). For the pre-treated soils, good predictions were obtained for pH, contents of organic C, total N, plant-available P (Olsen) and exchangeable K (calcium-acetate-lactate (CAL)), contents of microbial biomass C and N (C_mic and N_mic) and ergosterol, basal respiration, metabolic quotient, the ratio of organic C/total N, the grain yield of winter cereals and grain nitrogen uptake. The RSC (the ratio of standard deviation of laboratory results to standard error of cross-validation) was greater than 2.0, the correlation coefficients (r) of a linear regression (measured against predicted values) were greater than or equal to 0.9 and the regression coefficients (a) ranged from 0.9 to 1.1. Similar good predictions were obtained if field-moist samples were used, with the exception of P (Olsen), K (CAL), metabolic quotient, grain yield of winter cereals and grain nitrogen uptake (satisfactory predictions) and ergosterol content (unsatisfactory prediction). Good predictions of the contents of Mg (CaCl₂) and microbial biomass P (P_mic) were achieved for field-moist but not for pre-treated samples. Despite sample preparation, only satisfactory predictions were obtained for the ratios of C_mic/N_mic and ergosterol/C_mic and grain nitrogen content (1.4RSC2.0, r0.8 and 0.8a1.2). However, unsatisfactory predictions for field-moist and pre-treated samples were achieved for the content of P (CAL), the nitrogen mineralisation rate and the ratios of C_mic/P_mic and basal respiration/nitrogen mineralisation rate. Our results demonstrate that biological soil properties can be predicted with NIRS for closed populations in both sample states. The pre-treatment should be used if samples have to be stored prior to infrared measurements for periods longer than a month.     

Pressurized Hot Water and DTPA‐Sorbitol as Viable Alternatives for Soil Boron Extraction. II. Correlation of Soil Extraction to Responses of Boron‐Fertilized Alfalfa

Abstract

Pressurized hot water and DTPA‐Sorbitol are two relatively new, proposed alternative soil boron (B) extraction methods for which no data on yield or plant nutrient uptake have been reported for validation. Both methods initially have shown significant correlation with the hot water extraction method in untreated soils as well as soils incubated with various levels of B. The objective of the research was to extract samples of B‐treated soils by using all three extraction methods and correlate the B values obtained to yield, B tissue concentration, and total B removal of alfalfa (Medicago sativa). Greenhouse and field experiments on alkaline and limed acid soils naturally low in hot water‐extractable B were conducted to test alfalfa response to B fertilizer. In the greenhouse, highly significant relationships exist between plant uptake and extractable B with all three methods at varying levels of applied B, but no alfalfa yield response was observed. All three methods result in accurate predictions of plant B tissue concentrations and total B removal. The field experiment exhibited a significant positive relationship between total alfalfa yield and extractable B using hot water and pressurized hot water extractions. Extractable B using DTPA‐Sorbitol was not related to total alfalfa yield in the field experiment. This work, coupled with the earlier incubation studies, supports the pressurized hot water extraction method as an improvement over hot water in diverse soil types. The lack of relationship in the acid soil supports DTPA‐Sorbitol as an improvement over hot water in alkaline soils.     

Comparison of EDTA and ammonium Bicarbonate-DTPA for the extraction of phosphorus in calcareous soils from Kerman,Iran

Developing a fast and reliable soil testing method is critical for improving soil testing efficiency and ensuring reliable fertilizer recommendation. The objectives of this study were to evaluate sodium ethylene diamine tetra acetic acid (Na₂-EDTA) as a replacement for ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA) to extract phosphorus (P) to determinate the relationships between extractable P and its uptake by crop in calcareous soils. Na₂-EDTA and AB-DTPA was compared by the amounts of extracted P by analyzing soil samples collected from agricultural production areas. There were significant correlations between Na₂-EDTA and AB-DTPA for soil test P based on soils collected from the agricultural field. Soil test P by both extractants was significantly correlated with plant P concentration. Na₂-EDTA was identified as an alternate improved extraction method instead of AB-DTPA in calcareous soils based on this study. However, more work will be needed to identify the correlation of the two extractants and crop responses under a field condition.