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.     

Predicting Maize Yield,Nutrient Concentration,and Uptake in Phosphorus- and Potassium-Fertilized Soils: Pressurized Hot Water and Other Alternatives to Mehlich I Extraction in Guatemala Soils

Abstract

Poor accessibility and cost of soil testing reduce effectiveness of fertilizer use on small‐scale subsistence farms, and inadequate funding promotes adoption of soil tests in developing countries with minimal validation. For example, Mehlich I extraction of phosphorus (P) currently used extensively in Guatemala may not be suitable for Guatemala's broad range of soils. At least four alternatives are available but relatively untested [Bray 1, Mehlich III, Olsen, and pressurized hot water (PHW)]. Pressurized hot water is relatively simple and inexpensive but is not yet tested against other extraction methods under variable P or potassium (K) fertilization levels. To determine whether PHW‐extracted nutrients could be used to predict maize yield and nutrient concentration and uptake, soil, plant tissue and grain samples were obtained from a multiple‐site field study, and calibration studies were conducted using five rates of P and three rates of K on soils incubated without plants or cropped with maize in greenhouse and field conditions. In the multiple‐site field study, maize yield related significantly to PHW‐extractable P (r²=0.36) and to leaf P concentration (r²=0.23), but Mehlich I–extractable P did not. In the two soils used in the greenhouse study, maize yield, vegetative P concentration, and total P uptake by maize were predicted by PHW‐extractable P (R²=0.72, 0.75, and 0.90, respectively). In the field experiment, grain yield was not improved by P or K application, but P concentration of maize leaf tissue did relate significantly with PHW‐extracted P (R²=0.40). Mehlich I did not. There were no yield responses to K application in any experiment, but relationships defined between extractable K for all five K‐extraction procedures and soil‐applied K were similarly significant. In comparison, PHW was as good as or better than Olsen whereas Bray 1 and Mehlich III were less consistent. Mehlich I was overall the poorest P extractant. Mehlich I extraction of P should be replaced by one of the four alternatives tested. PHW is the least expensive and, therefore, most viable for use in Guatemala soils.     

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

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

Pressurized Hot Water and DTPA‐Sorbitol as Viable Alternatives for Soil Boron Extraction. I. Boron‐Treated Soil Incubation and Efficiency of Extraction

Abstract

Serious challenges associated with hot water extraction, the standard extraction method for water‐soluble boron (B), limit its use in commercial soil‐testing laboratories. Several alternatives to make B testing more practical have been proposed and studied; none of the alternatives have readily replaced the hot water method. Two relatively new, promising B extraction methods are pressurized hot water and DTPA‐Sorbitol. Very little reported work compares B extraction values obtained from the standard hot water extraction method and these two alternative methods. This study was conducted to complete an initial step in validating new procedures—extracting the designated nutrient from fertilized, incubated soils by using standard and alternative extraction methods and comparing the resulting values. The three extraction methods were used to extract B from samples of calcareous sand and silt loam soils and limed, loamy fine sand, all which had been treated with 10 levels of B (0–8 mg kg^?1) and incubated for 7 and 28 days. The amount of B extracted increased as the rate of B application increased with all three soil‐extraction methods. High correlations (r 0.977–0.999) were observed between extractable B and rate of B application with all three procedures. Correlations between the amount of extractable B using hot water extraction and the value obtained with an alternative extraction method were similar for both methods (r=0.89). Hot water generally extracted the least and pressurized hot water the most B regardless of soil type, rate of application, or duration of incubation. This study suggests the more easily used methods of pressurized hot water and DTPA‐Sorbitol could be recommended as replacements to the cumbersome hot water extraction.     

Pressurized Hot Water Procedures for Use on Small Farms in Developing Countries

Abstract

Soil analysis for small farms in developing countries is often inconvenient and prohibitively expensive, yet the information gained from these soil tests could result in significant benefits. Based on tests done on a limited range of soils, the pressurized hot water (PHW) extraction coupled with colorimetric or turbidimetric analysis is a promising alternative. Before this extraction and analysis can be used in developing countries, testing is needed across the range of soils found in these countries. At Brigham Young University (BYU), 228 soils from Guatemala and Morocco were analyzed for NO₃‐N, phosphorus (P), and potassium (K) using standard methods (water–CTA, Olsen–molybdic acid and ammonium acetate–atomic absorption, respectively). Results were correlated to values obtained from the PHW extraction coupled with colorimetric or turbidimetric analytical procedures. The relationships between these tests were good (r² values of 0.96, 0.71, and 0.52 for NO₃‐N, P, and K, respectively). In an additional study comparing several P extraction methods for Guatemala soils, relationships between PHW‐extractable P and Olsen‐, Bray I–, and Mehlich I–extractable P (r² values of 0.75, 0.67, and 0.46, respectively) suggest that PHW is a promising P‐extraction procedure for use in Guatemala. Overall, PHW extraction and accompanying analyses are a less expensive alternative to current soil nutrient extraction and analysis procedures for the soils of Morocco and Guatemala.     

Mehlich‐1‐ and DTPA‐extractable lead in soils in relation to soil properties

Abstract

Mehlich‐1 and DTPA extractants are frequently used to predict metal availability in soils. Metal extractability by the acid or chelate extractant reflects the metal characteristics and metal‐soil interactions. In this study, samples of eight topsoils from the southeastern United States were incubated with added lead (Pb) at the rate of 40 mg#lbkg^‐1. After five months in the greenhouse, Mehlich‐1 and DTPA extractants were employed to extract Pb in both metal‐amended and natural soils. For the natural soils, Pb concentration in the DTPA extractant was always higher than that in the Mehlich‐1 extractant. This indicates that the DTPA chelate extractant is able to dissolve some Pb in soils which is not solubilized by protons. The negative correlation found between Mehlich‐1‐extractable Pb and soil clay content might result from two mechanisms: i) strong association between Pb and soil surfaces, or ii) readsorption of Pb during extraction. None of the correlations between DTPA‐extractable Pb and soil properties was significant, suggesting that the DTPA‐extractable Pb is not heavily dependent on soil properties. The DTPA extractant showed a high ability to solubilize Pb in the natural soils possibly due to a high affinity of Pb for soil organic matter.     

Simplified Soil Analysis Procedure for Use in Small‐Scale Agriculture

Abstract

Soil analysis for small‐scale farms in developing countries is often inconvenient and prohibitively expensive using currently available procedures, yet the information gained from these soil tests could result in economical and environmental benefits. The pressurized hot water (PHW) extraction coupled with colorimetric or turbidimetric analysis shows promise as a viable alternative based on tests done on a limited range of soils. Before this extraction and analysis can be used in developing countries, testing is needed across the range of soils found in these countries. At Brigham Young University (BYU), 228 soils from different areas of Guatemala and Morocco were analyzed for NO₃‐N, phosphorus (P), and potassium (K) using standard methods (water–CTA, Olsen–molybdic acid, and ammonium acetate–atomic absorption, respectively). Results were correlated to values obtained from the PHW extraction coupled with colorimetric or turbidimetric analytical procedures. The relationships between the values for these tests were good (r² of 0.96, 0.71, and 0.52 for NO₃‐N, P, and K, respectively). Soils from each country were concurrently analyzed for NO₃‐N and P in laboratories in Guatemala and Morocco, and these results were correlated with those from BYU. Positive correlations between BYU values and those from other laboratories were obtained, with the data from the Guatemalan laboratory showing overall closer correlation than the Moroccan laboratory. In an additional study comparing several P extraction methods for Guatemalan soils, relationships between PHW‐extracted P and Olsen‐, Bray I‐, and Mehlich I‐extracted P and measured at BYU (r² of 0.75, 0.67, and 0.46, respectively) indicate that PHW is a promising alternative P extraction for use even with the highly variable soils of Guatemala. Overall, the data support PHW extraction and accompanying analyses as a less expensive alternative to current soil nutrient extraction and analysis procedures for the soils of Morocco and Guatemala.     

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.     

Evaluation of the NH4HCO3‐DTPA soil test for assessing boron availability to wheat

Abstract

The NH₄HCO₃‐DTPA (AB‐DTPA), 1 MNH₄HCO₃, 0.005 M DTPA, pH=7.6, was proposed as a multi‐element extractant, for evaluating macro and micronutrients availability to plants. AB‐DTPA was also evaluated as a soil test, for assessing boron availability and toxicity to alfalfa. In a pot experiment, ten soils of Northern Greece were used to assess AB‐DTPA as an extractant of available boron to wheat (Triticum aestivum L., cv. Yecora), in comparison with hot water and saturation extract. Boron (B) was added as borax (Na₂B₄O₇*10H₂O) to the ten soils, at rates equal to 0, 3, and 5 mg B kg^‐1. Wheat was grown in pots containing the boron amended soils to the stage of tillering, and dry aboveground biomass, B concentration and B uptake by wheat were determined. AB‐DTPA extractable B was significantly greater than saturation extract and similar to hot water at each B application rate, and was correlated significantly with hot water (r=0.84), or with saturation extract (r=0.48). Extractable boron by all extractants, boron concentration in wheat and boron uptake were significantly affected by the soil x B application rate interaction. In assessing B availability to wheat using AB‐DTPA as a soil test, CEC should be included in the regression equation for B concentration, or pH for B uptake. However, the corresponding adjusted coefficients of determination for B concentration (adjusted R²=0.46) and B uptake (adjusted R²=0.48) were similar or lower to those of hot water (adjusted R²=0.45 and 0.60, respectively) and the saturation extract (adjusted R²=0.70 and 0.49, respectively), when the latter two soil tests were used in the regression equations without the inclusion of any soil property.     

Use of NH4 HCO3‐DTPA soil test to assess availability and toxicity of selenium to alfalfa plants

Abstract

This study was carried out to determine if ammonium bicarbonate‐DTPA soil test (AB‐DTPA) of Soltanpour and Schwab for simultaneous extraction of P, K, Zn, Fe, Cu and Mn can be used to determine the availability index for Se. Five Mollisols from North Dakota were treated with sodium selenate and were subjected to several wetting and drying cycles. These soils were extracted with hot water and with ammonium bicarbonate‐DTPA (AB‐DTPA) solution for Se analysis. Alfalfa plants were grown in these soils in a growth chamber to determine plant uptake of Se. In addition to the above experiment, coal mine soil and overburden materials from Western Colorado were extracted and analyzed as mentioned above.

It was found that hot water and AB‐DTPA extracted approximately equal amounts of Se from Mollisols. A high degree of correlation (r =0.96) was found between Se uptake by plants and AB‐DTPA extractable Se. Extractable level of Se in treated soils was decreased with time due to change of selenate to less soluble Se forms and plant uptake of Se. An AB‐DTPA extractable Se level of over 100 ppb produced alfalfa plants containing 5 ppm or higher levels of Se that can be considered toxic to animals. Soils with about 2000 ppb of extractable Se were highly toxic to alfalfa plants and resulted in plant concentrations of over 1000 ppm of Se. The high rate of selenate (4ppm Se) was less toxic to alfalfa plants in soils of high organic matter content. This lower toxicity was accompanied with lower extractable levels of Se.

The AB‐DTPA solution extracted on the average about 31% more Se than hot water from the mine and overburden samples and was highly correlated with the latter (r =0.92). The results indicated the presence of bicarbonate‐exchangeable Se in these materials.     

Evaluation of certain Ni soil tests for an initial estimation of Ni sufficiency critical levels

Although Ni is officially recognized as an essential micronutrient for all higher plants, the majority of the published research on soil availability of Ni focuses on its hazardous role as a heavy metal. The objective of the study was to evaluate certain Ni soil tests in uncontaminated soils for an initial estimation of its sufficiency critical levels. Nickel was extracted from 30 cultivated soils employing the following extraction methods: DTPA, AB‐DTPA, AAAc‐EDTA, Mehlich‐3, 0.1 M HCl, and 0.1 M HNO₃. Ryegrass (Lolium perenne L.) was grown in pots containing the soils, harvested five times, certain plant parameters were determined, and the Cate–Nelson procedures were used for Ni critical levels determination. Among the six methods, HCl was the least reliable extractant for the evaluation of soil available Ni, whereas the most significant (p ≤ 5%) relationships between Ni concentration or Ni uptake by ryegrass and Ni soil tests were consistently obtained for AAAc‐EDTA or Mehlich‐3 extractable Ni. In many cases, > 80% of the variability of Ni concentration or uptake by ryegrass was explained by these two soil tests without the inclusion of other soil properties that affect Ni bioavailability. Sufficiency critical levels of Ni in soil were ≈ 2 mg kg^–1 for both methods. Consequently, as an initial approach, concentrations of AAAc‐EDTA or Mehlich‐3 extractable Ni < 2 mg kg^–1 are probably a good guide to indicate soils that will respond to Ni fertilization.     

Comparison of Three Micronutrient Soil-Test Extractants in Three Greek Soil Types

The purpose of the present study was to compare the ability of three micronutrient soil-test extractants [diethylenetriaminepentaacetic acid (DTPA), Mehlich 3, and Soltanpour and Schwab] to determine plant-available concentrations of manganese (Mn), iron (Fe), and zinc (Zn) in three soils (from parent material Marl, Gneiss schist, and Peridotite) from central Macedonia, northern Greece. In black plastic bags containing 3 kg of air-dried soil, self-rooted olive plants (cv. Chondrolia Chalkidikis) were grown for about 5 months and irrigated with distilled water during the experimental period. At the end of the experimental period, the three extractants were evaluated, based on correlation analysis among leaf micronutrient concentrations, total plant micronutrient content of olive plants, and soil micronutrient concentrations determined by each extractant. The largest extractable concentrations of Mn, Fe, and Zn were determined by Mehlich 3, compared to the other two soil-test extractants. However, for the correlation analysis, the greatest correlation coefficient between leaf Mn (and total plant Mn content) and soil extractable Mn was achieved when DTPA was used (varying from 0.76 to 0.88, depending on soil type). Therefore, it is concluded that DTPA was a better extractant to determine plant-available Mn than the other extractants for the three soils studied. For correlations between leaf Fe and Zn concentrations and also for total plant Fe and Zn content, and soil extractable concentrations, the type of extractant and soil type play a very important role in determining the best correlation. This means that in each soil type the greatest correlation was achieved with the use of other extractant. For example, for Fe in the Marl and Peridotite soils the best correlation was found for Mehlich 3, whereas in the Gneiss schist the best correlation was achieved for DTPA (R = 0.72–0.94). For Zn, in the Gneiss schist soil the best extractant in determining plant available concentration was Soltanpour and Schwab (R = 0.49–0.60), whereas in the other two soil types DTPA was found to be the most reliable extractant (R = 0.51–0.78). Therefore, soil type should be carefully and thoroughly studied by the researchers in similar future experiments.     

Evaluation of Mehlich 3 extractant for estimating phosphorus deficiency and phosphorus sorption of Zimbabwean soils

Abstract

The Mehlich 3 extractant was compared with the resin method for its ability to predict the phosphorus (P) status of Zimbabwean soils. Correlation of P extraction between the two methods and with plant growth was found to vary with soil texture. Because the Mehlich 3 extractant was less influenced by texture, it was better able to predict the P status over a wide range of soil types. The Mehlich 3 extractant correctly predicted P deficiency for all Zimbabwean soils, except for those that contained visible calcium carbonate. Mehlich 3‐extractable aluminum (Al) was very highly correlated with the maximum P‐sorption capacity of a wide range of soils, excluding those with calcium carbonate. Adoption of the Mehlich 3 extractant for multiple elemental analysis of soils in Zimbabwe is recommended, particularly if routine Al measurement is included as an indicator of soil P requirements.     

Availability of extractable boron in some acid soils,west Bengal,India

Abstract

A relatively small range between deficiency and toxic limits of boron (B) necessitates precise evaluation of the availability of extractable boron before applying B in deficient soils. Keeping this in view, laboratory and greenhouse experiments were conducted to assess the availability of native B in soils. For this purpose, 25 acid soils with diverse properties and varying hot water extractable B content, were selected from lateritic and alluvial tracts of Southern West Bengal. A greenhouse pot experiment with four rates of B (0, 0.5, 1.0, and 2.0 mg kg^‐1) was conducted in completely randomized design to study the response of soybean (Glycine max L.) to native and applied B in all 25 soils. The suitability of nine extractants for determining available soil B was assessed by correlating the amount of extractable B in untreated soils with Bray's percent yield, uptake, and tissue B concentration of soybean plants. Optimization of salicylic acid concentration is described and the advantages of this extractant are discussed. The interference of amethyst color (produced by iron and salicylic acid) with the colorimetric estimation of B is studied. Hot CaCl₂ was found to be the most suitable extractant for the determination of available B in these soils, followed by hot water, salicylic acid, and ammonium acetate. However, salicylic acid appeared to be the most efficient extractant for routine soil analysis for available B, where a large number of samples are analyzed. The critical values in respect to sufficiency of extractable B for soybean plants were 0.51 for hot water, 0.61 for hot CaCl₂, 0.27 for ammonium acetate and 0.45 mg kg^‐1 for salicylic acid. The critical B concentration in soybean plants was 18 mg kg^‐1 on dry weight basis. Multiple regression equations relating soil properties to native soil B extracted by various extractante were developed. It was observed that organic carbon and clay contributed positively to B extracted by hot water, hot CaCl₂, and ammonium acetate, while salicylic acid extractable B showed positive relationships with cation exchange capacity (CEC) and clay. The CEC and Fe₂O₃ were found to have positive influence on tartaric acid extractable B. Implications of the influences of soil properties on the extractable B content of soils are discussed.     

Comparison of soil zinc extractants for detection of applied zinc and prediction of leaf zinc concentration

Abstract

Many soil extractants have been developed for determination of zinc (Zn) availability to plants. The optimum soil Zn extractant should be useful not only for prediction of plant Zn concentration but also for detection of applied Zn levels. The objectives of this study were: i) to compare soil Zn extradants for detecting applied Zn and for predicting peanut leaf Zn over a range of soil pH levels, and ii) to correlate other soil‐extractable Zn levels with Mehlich‐1. Soil and peanut leaf samples were taken from a field study testing pH levels as the main plots and Zn application rates in the sub‐plots. Extractable Zn was determined on soil samples using Mehlich‐1, Mehlich‐3, DTPA, MgNO₃, and many dilute salt extradants of varied strength and pH. Correlation of extractable soil Zn to cumulative applied Zn levels revealed Mehlich‐1, Mehlich‐3, DTPA, and AlCl₃ extradants to be among the best indicators of applied Zn. Leaf Zn concentration was best correlated with soil Zn extracted by dilute salts, such as KCl, CaCl₂, NH₄Cl, CaSO₄, and MgCl₂. Including soil pH as an independent variable in the regression to predict leaf Zn considerably improved R‐square values. The DTPA‐extractable soil Zn levels were very well correlated with Mehlich‐1‐extractable Zn. Mehlich‐3 extracted about 20% more soil Zn than Mehlich‐1, but Mehlich‐3 soil Zn was not as well correlated to Mehlich‐1 soil Zn as DTPA soil Zn. Lower pH solutions extracted more of the applied Zn, but more neutral solutions extracted Zn amounts which were better correlated with Zn uptake. On the other hand, Mehlich‐1, which had a lower pH, had better correlations with both applied Zn and leaf Zn than did Mehlich‐3. Shortening the DTPA extraction time to 30 minutes resulted in better correlations than the standard two hour extraction time. Chloride (Cl) was the best anion tested in relation to soil applied Zn recovery in combination with potassium (K), calcium (Ca), and aluminum (Al), and Cl optimized leaf Zn correlations for ammonium (NH₄), K, Ca, and magnesium (Mg). The larger the valence of the cation, the better the correlation with applied Zn and the poorer the correlation with leaf Zn.     

Evaluation of Mehlich 3 for Extraction of Copper and Zinc from Irish Grassland Soils and for Prediction of Herbage Content

Abstract: The objective of this study was to determine how the extractant Mehlich 3 (M3) compared with other methods currently used in Ireland for determination of copper (Cu) and zinc (Zn) in soils. Samples from eight different mineral soil types, four of sandstone/shale and four of limestone origin, were analyzed for copper and zinc using M3 and conventional extractants. Herbage samples were taken from the soils and analyzed for Cu and Zn. Mehlich 3 results showed good correlation with ethylenediamine‐tetraacetic acid (EDTA)– and diethylenetriamine‐pentaacetic acid (DTPA)–extractable Cu and Zn. Inclusion of soil properties in multiple regression models improved the coefficients of determination. All extractants were equal in their ability to predict Cu and Zn herbage content. Differences between sandstone/shale and limestone soils in relation to herbage content were also found, with the better relationship found in sandstone/shale soils.     

Evaluation of Agro Services International Soil Test Method for Phosphorus and Potassium

Soil testing is widely adopted as an essential diagnostic tool for identifying soil nutrient factors that limit sustained crop production. A systematic approach for rapid soil testing and fertilizer recommendation has been introduced and widely used in China by Agro Services International (ASI), USA. To verify the usefulness and reliability of the ASI method in soil testing and fertilizer recommendation in comparison with other commonly used traditional soil testing methods, 294 soil samples from major agricultural regions and soil types in China with a wide range of soil pH, from 5.1 to 8.9, were taken and analyzed for available phosphorus (P) and potassium (K) by the ASI multielement extraction solution and selected traditional methods, Olsen extractant for P, ammonium acetate (NH₄OAc) extractant for K, and multielement extractant Mehlich 3 for P and K. Also, 46 soils were selected from northern China regions for a greenhouse trial with sorghum seedlings to determine if the soil testing values correlate well with plant response. Results indicated that the amount of soil P extracted by the ASI method (ASI P) was correlated to both soil extractable P tested by the Olsen extractant (Olsen P) and Mehlich 3 extractant (Mehlich 3 P). The correlation coefficient of ASI P with Mehlich 3 P (R² = 0.86) was greater than that of ASI P with Olsen P (R² = 0.74) across all selected soils. A good correlation was also found between the exchangeable K from the ASI method with the traditional ammonium acetate method (R² = 0.81) and the Mehlich 3 method (R² = 0.85). The results from the greenhouse trial showed that the extractable P and exchangeable K by the ASI multielement extraction solution could be used to represent the fertility status of soil P and K for the selected soils. Regression analysis indicated that the relative dry-matter yield of the sorghum plants can be predicted with either ASI P and ASI K values with the correlation coefficients (R²) values of 0.78 and 0.72 respectively and could be a good measure for soil testing and fertilizer recommendation in the selected soils and regions in China.     

Effects of Boron Application on Yield,Foliar Boron Concentration,and Efficiency of Soil Boron Extracting Solutions in a Xanthic Ferralsol Cultivated with Banana in Central Amazon

Boron (B) is known to play important roles in the structures of cell walls and membranes and in the integrity and functions of membranes in plants. Under the conditions in the central Amazon region, there are few studies about this nutrient. In Brazilian soils, the hot-water B extraction method has been extensively used for evaluation of soil B status. However, difficulties with this method result in poor accuracy and precision of extraction of available B in soil. The objective of this study was to evaluate the yield, foliar concentration, and efficiency of B extracting solutions and the effect of B fertilization on B uptake in banana (Musa spp.) leaves and fruits, subgroup Cavendish (AAA), cultivated in a Xanthic Ferralsol (dystrophic Yellow Latosol) located in Amazonas State, Brazil. The experimental design was a completely randomized split plot, with four B rates (0, 4, 8, and 12 kg ha^?1), two harvest cycles (subtreatments), and four replicates. Available B was determined with seven extractant solutions: Mehlich 1, Mehlich 3, hot water, hydrochloric acid (HCl) 0.05 mol L^?1, HCl 0.1 mol L^?1, HCl 5.0 mol L^?1, and potassium chloride (KCl 1.0 mol L^?1). The application of B fertilizer increased the yield and B concentration in leaves and fruits. Hot water and KCl 1.0 mol L^?1 were the most efficient extracting solutions for the determination of available B in soil. The application of 3.4 kg B ha^?1 in the first cycle and 1.3 kg B ha^?1 in the second cycle guarantees an adequate nutritional status in banana plants.     

Development of a New Soil Extractant for Simultaneous Phosphorus,Ammonium, and Nitrate Analysis

Abstract

A new soil extractant (H³A) with the ability to extract NH₄, NO₃, and P from soil was developed and tested against 32 soils, which varied greatly in clay content, organic carbon (C), and soil pH. The extractant (H³A) eliminates the need for separate phosphorus (P) extractants for acid and calcareous soils and maintains the extract pH, on average, within one unit of the soil pH. The extractant is composed of organic root exudates, lithium citrate, and two synthetic chelators (DTPA, EDTA). The new soil extractant was tested against Mehlich 3, Olsen, and water for extractable P, and 1 M KCl and water‐extractable NH₄ and NO₂/NO₃. The pH of the extractant after adding soil, shaking, and filtration was measured for each soil sample (5 extractants×2 reps×32 soils=320 samples) and was shown to be highly influential on extractable P but has no effect on extractable NH₄ or NO₂/NO₃. H³A was highly correlated with soil‐extractable inorganic N (NH₄, NO₂/NO₃) from both water (r=0.98) and 1 M KCl (r=0.97), as well as being significantly correlated with water (r=0.71), Mehlich 3 (r=0.83), and Olsen (r=0.84) for extractable P.     

Extraction of Soil Boron for Predicting Its Availability to Plants

Field and greenhouse studies were conducted in Prince Edward Island (P.E.I.) on soybean (Glycine max(L.) Merr.), red clover (Trifolium pratense L.),alfalfa (Medicago sativa L.), and rutabaga (Brassica napobrassica,Mill).Plant B concentrations were compared to soil B extracted by hot-water,0.05 M HC1,1.5 M CH3COOH and 0.01 M CaCl2.The r values for extractable soil B vs.plant B were:hot water (0.67),0.05 M HCl(0.82),1.5M CH3COOH(0.78) and hot 0.01 M CaCl2(0.61).Results of soil B from the 0.05 M HCl extracts were generally found to give the best correlation and linear regression among the four extractants tested for predicting the availability of B to the plants.Overall,the 0.05 M HCl proved to be superior to hot water extraction and is recommended for predicting the available B status of the acid soils of P.E.I.The probability of error with 0.05 M HCL is less since it is shaken for a fixed period of time as opposed to subjective error which could be caused in monitoring the boiling time using hot water.