Ammonium Bicarbonate-diethylenetriaminepentaacetic Acid Research Articles

Assessing Micronutrients in Soil with a New Chemical Extractant Using Isotopic Dilution Techniques: Linkages to Labile Fractions in Soil

ABSTRACT With the purpose of economizing the routine soil testing for micronutrients and avoiding the use of multiple soil extraction procedures, a laboratory investigation was attempted to evaluate a new chemical extractant for assessing the availability of common micronutrients (Fe, Cu, Mn, Zn, Mo, and B) in soils of widely varying properties (n = 32). The new extractant designated as OM-MES-VERA# contained 0.01 M oxalic acid, 0.02 M maleic acid, 0.02 M 2-(N-Morpholino) ethane sulfonic acid (MES), 0.0025 M ethylene diamine tetraacetic acid di-sodium salt, 0.02 M acetic acid, and 0.1% polyacrylamide (final pH adjusted to 6.0). OM-MES-VERA extracted significantly higher amounts of micronutrient cations and B from soils compared to the conventional diethylene triamine pentaacetic acid (DTPA, pH 7.3) extractable micronutrient cations and hot water soluble B, respectively, but lesser amount of Mo compared to Mehlich-3 universal extractant. Soil test values by both OM-MES-VERA- and conventional extractants were correlated with soil properties. The labile (E and L) values of micronutrient cations and Mo estimated by isotopic dilution method, ammonium bicarbonate-DTPA, pH 7.6 extractable soil B (as an estimate of E for B) and B concentration in maize (as an estimate of L for B) were successfully regressed on soil test values of micronutrients by OM-MES-VERA and conventional soil extractants except in the case of DTPA (pH 7.3) for E-value of Fe and L-value of Mn. The OM-MES-VERA extractant can be considered to assess the availability of common micronutrients in soils of diverse soil properties.

Comparative Analysis of Soil Phosphorus Determination Methods and Their Correlation with Plant Phosphorus in Standing Wheat Crops

This study compared the accuracy of various soil phosphorus assessment methods to measure the soil's ability to supply plants with phosphorus over a brief period in the field. Twenty individual soil samples were collected from a standing wheat (Triticum aestivum L) crop at depths ranging from zero to twenty centimeters. An equivalent plant spike sample was also procured from the soil sampling fields. In comparison to the wet acid digestion method used to detect phosphorus in plants, several methods were utilized to assess phosphorus in the soil, including resin extractable phosphorus, AB-DTPA extractable phosphorus, NaHCO3 extractable phosphorus, water-soluble phosphorus in suspension, and paste. The levels of variation and deficiency of phosphorus, which were found by different methods followed different patterns as shown by the fact that, AB-DTPA method finds phosphorus deficiency in 20% of samples while on the other hand, Olsen method finds phosphorus deficiency in 80% of samples. Even with such a small sampling area, none of the procedures showed a significant correlation with any other method that might account for uneven variation among the samples when determined by distinct procedures. However, corrections were observed to a certain degree between ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA) extractable and resin, as well as between other procedures and the plant P scale. Both resin and ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA) had a strong relationship with plant phosphorus, with the former showing a significant correlation of 0.48 and 0.21, respectively. Hence Resin and AB-DTPA methods are recommended for the determination of phosphorus under certain soil and plant conditions.

Evaluation of Extractants for Determination of Micronutrients in Soils of South Gujarat, India

An experiment was conducted at Department of Soil Science and Agricultural Chemistry, Navsari Agricultural University during the year 2018-19. The methods of micronutrients determination were (i) extracted through diethylene triamine penta acetic acid (DTPA) (ii) extracted through ammonium bicarbonate- diethylene triamine penta acetic acid (AB-DTPA) (iii) extracted through Neubauer. The methods of micronutrients were evaluated through method validation parameters like linearity, sensitivity of instruments, precision and predictability. The available micronutrients determined from the sample soils were correlated with soil physico-chemical properties to know the relationship of these properties with available micronutrients. The linearity study of the series of micronutrients standard were measured through different methods of micronutrient determination. These measured values showed linear relationship with reference values. The coefficient of determination (R2) for all the methods was > 0.90. The precision was determined by relative standard deviation (RSD) (%) of different micronutrient methods which were in the range of 1.834 to 19.11 %. All the studied methods of copper, iron, zinc and manganese determination, AB-DTPA extractant method has highly significant and positive correlation with nutrient uptake by wheat on Microwave Plasma Atomic Emission Spectroscopy (MP-AES) instrument. Organic C and sand content of soil have positive correlation with micronutrients availability. While pH, EC, CEC, CaCO3, silt and clay content of soil have negative correlation with available micronutrients.

Assessing Suitability of Different Extractants for Estimating Plant Available Boron in Lateritic Soils (Alfisols)

ABSTRACT The depth-wise distribution of plant available boron (B) extracted by dilute HCl (HCl), tartaric acid (TA), hot calcium chloride (HCC), hot water (HW), ammonium acetate (AA), Ammonium Bicarbonate-Diethylene Triamine Penta Acetic acid (AB-DTPA) and mannitol calcium chloride (MCC) in some acidic lateritic soils (Alfisols) of Birbhum, West Bengal, India, was examined in relation to their physicochemical properties and grain yield, concentration and removal of B by rice grain to screen out the most suitable extractant for lateritic soils. The highest overall mean B concentration of surface soils (0.325 mg kg−1) was obtained by 0.05 M HCl, whereas its lowest content was obtained by MCC (0.145 mg kg−1) and with increasing depth its content was decreased for all the extractants used. The sequence of B extraction by various extractants was as follows: HCl > TA > HCC > HW > AA > AB-DTPA > MCC. Higher extractability of HCl is due to lower pH and attendant dissolution of soil minerals. Most often, decrease in organic carbon, clay, CEC, amorphous iron and aluminum oxides or increase in manganese oxide contributed to the observed drop in B along soil depth. The B extracted by different extractants showed significant positive correlations among themselves. The HCl extracted B showed the highest correlation with grain yield, concentration, and removal of B by rice grain. The HCl extractable B enhanced adjusted R2 value in multiple regression equation, boosting the predictability of the model. Thus, in acidic lateritic soils (Alfisols), the 0.05 M HCl is the best extract for estimating plant available B.

Changes in land use practices influence soil sulfur fractions and their bioavailability

Changes in land use practices may affect the distribution of soil sulfur (S) fractions and their bioavailability. Therefore, this study was undertaken to assess the influence of different land use changes on the distribution of soil S fractions and their bioavailability for plant nutrition. Soil samples from farmers’ fields with different land use practices such as rice-mustard-jute (R-M-J), rice-lentil-jute (R-L-J), rice-lentil-sesame (R-L-S), rice-vegetable-jute (R-V-J), and rice-potato-green gram (R-P-G) were collected and analyzed for different fractions of S. The bioavailability of S was assessed by extracting the soil with six different extractants (acidic, neutral, and alkaline) with different extraction modes and chemistry. The results showed that changes in land use practices could influence the distribution of soil S fractions and their bioavailability. Organic S was the dominant fraction, accounting for 93.5% of total S across land use practices. The inorganic S fraction (water-soluble, sorbed, and occluded) varied significantly among the land use practices. Among the inorganic fractions, the water-soluble fraction was the dominant fraction across the land use practices. The bioavailability of S, as assessed by different chemical extractants, was in the following order: sodium hydrogen carbonate (NaHCO3) > mehlich-3 > ammonium bicarbonate-diethylenetriamine penta-acetic acid (AB-DTPA) > ammonium acetate-acetic acid (NH4Ac-HOAc) > calcium dihydrogen phosphate {Ca(H2PO4)2} > calcium chloride (CaCl2). By establishing relationships between extractable S and soil S fractions, it was observed that all the extractants could obtain S from the water-soluble, sorbed, and organic S fractions, with little extractability from the occluded fraction. Among the extractants tested, mehlich-3 extracted a similar amount of S corresponding to the inorganic fraction across the land use practices. It also maintained positive relationships with different fractions of S, and as a multi-nutrient extractant, its use in routine soil testing can be recommended.

Need to revisit potassium soil test methods: ammonium acetate method does not correlate with tuber yield and potassium uptake in potato

The study was driven by concerns regarding lack of response to K applied as per existing soil test based fertilizer recommendations in case of the potato crop in northwest India. Geo-tagged surface soil (0-15 cm) samples 180 were collected from three (60 each) different fields (named A, B and C) followed by pot experiment involving potato planted to 30 different surface (0-15 cm) soils using two K levels (0 and 60 kg K2O ha−1). Cate-Nelson (CN) model, and non-linear segmented linear-plateau (LP) and quadratic-plateau (QP) models were used to compute critical K levels by relating relative yield with soil test K using five different methods: 1 M ammonium acetate (AA K), ammonium bicarbonate-diethylenetriamine pentaacetic acid (AB-DTPA), Mehlich-3, sodium tetraphenylboron (STPB) and 1 M boiling nitric acid. These were validated by conducting fertilizer response trials (six K fertilizer levels- 0, 15, 30, 45, 60 and 90 kg K2O ha−1) at four sites. AA K correlated with other soil K extractants in the order: AB-DTPA (r = 0.93**, 0.27* and 0.67**)> STPB K (r = 0.71**, 0.27* and 0.39**) whereas AA K generally did not show any correlation with HNO3 K. AAK method was poorly correlated with yield and plant K uptake (r = 0.15, 0.24, respectively) in comparison to AB-DTPA (r = 0.75**, 0.64**), Mehlich-3 (r = 0.78**, 0.72**), STPB (0.58**, 0.76**) and nitric acid method (0.55**, 0.44*). Thus, multi-nutrient extractants like AB-DTPA and Mehlich-3 are better (than AAK) indices of plant available K.

English

Phytoavailable cadmium (Cd) refers to the fraction of total cadmium in soil that is easily taken up by plants, which degrades the environmental quality and can cause contamination in the food chain. Cd contamination causes high carcinogenicity and toxicities, which harm both the environment and human health, including damage to the kidneys, bones, and respiratory system. In this study, seven extracting agents like ammonium bicarbonate diethylene triamine penta acetic acid (ABDTPA) and neutral salts having low and higher concentrations were used for the determination of phytoavailable Cd in sandy clay loam (SCL) and clay loam (CL) soils contaminated with Cd at naturally-Cd, Cd-20, Cd-40, and Cd-60 mg kg-1 and correlate it with Cd contents in roots, shoots, and grains of maize crop. Extraction efficiency of extractants remains in order: 10 M NH4AOc > ABDTPA > 1 M NH4AOc > 0.1 M CaCl2 > 0.01 M CaCl2 > 1 M NaNO3 > 0.1 M NaNO3. ABDTPA showed significantly the highest positive correlation with maize roots, shoots, and grains Cd contents in naturally Cd contaminated SCL and CL soils. While for artificially contaminated SCL and CL soils contaminated with Cd at Cd-20, Cd-40, and Cd-60 contamination levels, 0.1 M CaCl2 extractable Cd showed a stronger positive significant correlation with Cd contents in roots, shoots, and grains of maize crop. Overall results concluded that 10 M NH4AOc has the highest efficiency to extract Cd and 0.1 M NaNO3 has the lowest Cd extraction efficiency. Correlation results showed that ABDTPA and 0.1 M CaCl2 were found to be the most suitable extractants for predicting the bioavailability of Cd. Highly concentrated extractants give a stronger positive correlation as compared to low concentrated extractants. SCL soil showed stronger positive correlations as compared to CL soil

Comparing distinct soil test methods for available nitrogen, phosphorus and potassium for groundnut (Arachis hypogaea L.) and wheat (Triticum aestivum L.) grown in North Western India

An experiment was conducted during 2020-21 and 2021-22 in the tarai region of Uttarakhand in order to find simple, economical, effective, and plant uptake correlated soil test methods for determining the available nitrogen, phosphorous, and potassium. Before sowing of groundnut and wheat, soil samples were collected to evaluate available nitrogen, phosphorus, and potassium soil test methods. Wet oxidation was used for organic carbon, alkaline potassium permanganate (KMnO4) was used for mineralizable nitrogen, Olsen's-P, ammonium bicarbonate-diethylene triamine penta acetic acid (AB-DTPA), Mehlich-1 and Morgan-P were used to extract phosphorus (P), and ammonium acetate (NH4OAc), ammonium bicarbonate-diethylene triamine penta acetic acid (AB-DTPA), Mehlich-1 and Morgan-K were used to extract potassium (K). The suitability of these methods for various soil nutrients was assessed by comparing R2 values (coefficients of determination) derived through regression analysis. The results showed that the R2 values of the derived equations by using different combinations of soil test methods to determine available N, P, and K in soil were highly significant in both crops. Superior R2 value for groundnut (0.853**) was observed with the combination of alkaline KMnO4, Olsen’s P, Mehlich-K and for wheat (0.515**) the combination of alkaline KMnO4, Mehlich-P, NH4OAc–K. It found that these combinations are more superior to other methods and more promising.

Comparison of agri-environmental phosphorus tests for boreal agricultural and natural Podzols

Over a dozen soil phosphorus (P) extraction procedures have been designed for agri-environmental purposes (P-tests). Sustainable expansion of agriculture into boreal regions dominated by Podzols requires further insights into P extractability. We extracted P from Podzol samples ( n = 96) using nine P-tests followed by both colorimetric (PCol) and inductively coupled plasma (PICP) quantifications and assessed the relationships between P-tests. Samples were collected by depth or horizon from agricultural fields and reference sites in eastern, central, and western Newfoundland, Canada. The soil P was extracted with water, citric acid, ammonium bicarbonate diethylenetriaminepentaacetic acid (AB-DTPA), Morgan, Olsen, Bray-1, Bray-2, Mehlich-1, and Mehlich-3 solutions, thus targeting a wide range of extractable P pools in managed and natural Podzols. The soils had a pH of 3.4–6.9, organic matter of 0.5%–47.2%, and Al-M3 of 977–2561 mg kg−1. On average, water extracted the lowest PCol (1.0) and PICP (5.7) mg kg−1, while citric acid extracted the highest PCol (151) and PICP (290) mg kg−1. For the managed podzolic soils, the extractability of P followed the sequence water < Morgan < AB-DTPA < Mehlich-1 < Bray-1 < Mehlich-3 ≤ Olsen ≤ Bray-2 < citric acid; this varied slightly by quantification techniques and soil groups. The differences between PICP and PCol were most significant for the citric acid extracts. Most P-tests measurements were moderately to strongly correlated to P-M3ICP measurements ( r2 > 0.50) but variable with quantification techniques and soil depths. Given the diversity in extractable P pools across management-induced soil conditions, it is evident that a fully informed P management for the Newfoundland Podzols will require calibration of P-tests against crop P uptake.

Different Indices as Indicators of Phosphorus Availability to Wheat on Vertisols in Central Highlands of Ethiopia

ABSTRACT Vertisols are important soils in the agricultural activity of Ethiopia. Their wide distribution and erratic crop responses to recommended phosphorus (P) fertilizer application justify the attempt for determining the P status and most suitable P availability estimation on these soils. In the present study, the forms of soil P and their relationship with different indices of available P and P uptake by wheat grown under greenhouse were evaluated. Total P, organic P, seven indices of available soil P, and fractions of soil inorganic P were determined from surface soil samples of ten Ethiopian central highland Vertisols. The amount of active inorganic P fractions i.e. water-soluble and loosely bound P, Al-phosphates (Al-P), Fe-phosphates (Fe-P) and Ca-phosphates (Ca-P) found to contain; < 0.5, 4–33, 4–66, and 15–73 mg P kg−1, respectively. As for the different indices of soil available P, the extraction efficiency of the tested methods was found to decrease in the order: ammonium oxalate > Olsen > Mehlich3 > Bray1 > ammonium acetate > ammonium bicarbonate-diethylene triamine pentaacetic acid (AB-DTPA) > 0.01 M calcium chloride (CaCl2). Olsen-P (r = 0.83) and AB-DTPA-P (r = 0.83) showed significant (P < .001) correlation with the P uptake by wheat and the active inorganic P fractions (Al-P and Fe-P). Moreover, multiple regression analysis indicated that the variation of P extracted by Olsen and AB-DTPA methods were best predicted by Fe-P (84%) and Al-P (68%), respectively. Consequently, Olsen and AB-DTPA methods were found to be most suitable for determining wheat available P on vertisols of central highlands of Ethiopia.

Multinutrient Extraction – Need of the Hour – A Review

A Multi nutrient extractant is a standardized reagent which is capable of extracting several elements or ions simultaneously to facilitate quick estimation of soil macro and micronutrients saving time, labour and resources. The procedure for extraction should be rapid, consistent, less expensive, reliable and considerate of the soil physico-chemical properties. Progressive research on developing such an extractant and an extracting procedure has resulted in various extractants such as Morgan reagents, Mehlich reagents, Diethylene Triamine Pentaacetic Acid (DTPA), ammonium bicarbonate- DTPA(AB-DTPA) and various other formulations. This article presents a comprehensive review of all the multinutrient extractants developed so far and their advantages and limitations in the extraction of soil macro and micronutrients, their efficiency in the extraction of nutrients and correlation with standard extraction procedures. Also, the potential utility of multi nutrient analysers such as Inductively Coupled Plasma – Optical Emission Spectrometry and Atomic Absorption Spectrometers can be achieved by employing appropriate multi nutrient extractants in the estimation of soil nutrients which could establish significant relationship between estimated nutrients and crop response. The selection of an appropriate multi nutrient extractant and the standard extracting procedure is commendable and is the need of the hour to support the fertilization schedule for crop cultivation and sustainable maintenance of soil health which has direct implication on food and nutrition security and ecological sustainability.

Predicting the response of soil potassium to broccoli (Brassica oleracea var. italica) in a Gangetic Inceptisol of West Bengal, India through suitable chemical extractants

Finding a suitable method for estimating soil and crop specific potassium (K) bioavailability under variable range of soil fertility has been a mighty challenge. To undermine this, a field experiment was conducted under varying levels of fertilizer application on pre-established fertility gradient strips in the Indo-Gangetic plains of West Bengal, India for predicting crop response and to assess the K availability in winter growing broccoli by employing six acclaimed chemical extractants viz. ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA), calcium chloride (CaCl2), Kelowna, Mehlich-III, ammonium acetate (NH4OAc), and sodium tetraphenylborate (NaTPB4). The availability study of K followed the pattern as, CaCl2 < AB-DTPA < Kelowna < NH4OAc < Mehlich-III < sodium tetraphenylborate (NaTPB4). A higher extractability of K was envisaged under the conjoint application of higher doses of K fertilizers along with the organics. Among the extractants, NaTPB4 showed the highest correlation sum (3.98) and also yielded a significant relationship with plant tissue K concentration (0.858) and uptake (0.715). The NaTPB4, Mehlich-III, and NH4OAc extractants were found to be significantly related to most of plant indices. The Euclidean distance based cluster analysis and linear regression study further proved the relatively higher efficiency of NaTPB4 extractant followed by Mehlich-III and NH4OAc to estimate plant K response in broccoli under the Gangetic alluvial soils of West Bengal, India.

Acid-Modified and Unmodified Natural Clay Deposits for In Situ Immobilization and Reducing Phytoavailability of Molybdenum in a Sandy Loam Calcareous Soil

Molybdenum (Mo) in basic soils has high bioavailability and plant toxicity. This study aimed to investigate the effect of increasing Mo concentration on its availability and toxicity threshold in alfalfa plants grown in sandy loam calcareous soils, and the potential use of raw and acid- modified clay deposits as soil additives to immobilize Mo and reduce its phytoavailability. Raw clay deposits (RCD) were treated with H2SO4 to produce acid-modified clay deposits (AMCD). The first experiment was performed using soils treated with 0, 0.1, 1, 10, 50, and 100 mg Mo kg−1. The second experiment was conducted with soils treated with 10 or 50 mg Mo kg−1 and amended with RCD and AMCD at application rates of 0, 2.5, 5, and 10% (w/w). After harvesting, water-soluble Mo, ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA)-extractable Mo, and shoot Mo content as well as dry matter were measured. The results showed that water-soluble Mo, AB-DTPA-extractable Mo, and shoot Mo concentration increased at higher Mo soil addition. AMCD had a stronger influence on Mo immobilization and reduction effect on plant shoots compared to RCD, depending on soil Mo concentration and application rate. Applying AMCD decreased soil pH but increased salinity levels. The shoot dry matter significantly increased in soils amended with RCD and/or AMCD compared to control soils; with the highest improvement recorded for RCD at 10%. It was concluded that AMCD is an efficient immobilizing agent to reduce Mo mobility and its phytoavailability in calcareous soils. Additionally, both AMCD and especially RCD were able to create favorable conditions for plant growth.

Dynamics of AB-DTPA-extractable Zn in high and low limed calcareous soils amended with biochar and farmyard and poultry manures

Zinc (Zn) deficiency is widespread in the calcareous soils which needs correction in a sustainable way. An open-air incubation study was conducted to observe the effects of biochar (BC), farmyard manure (FYM) and poultry manure (PM) on ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA)-extractable Zn in high-limed (16.6% CCE) and low-limed (6.6% CCE) calcareous soils. Both soils were treated with10 g kg−1 (equivalent to 20 t ha−1) of BC, FYM and PM and three levels of Zn (as ZnSO4), i.e. 0, 1.5 and 3 mg kg−1 soil. The AB-DTPA-extractable Zn and soil pH was determined at 0, 7, 14, 28, 56 and 84 days of incubation. Results revealed that more extractable Zn was recorded in the low-limed soil as compared with high-limed soil. Further, more extractable Zn was detected in both soils when treated with PM (84.62%), followed by FYM (69.23%) and BC (52.56%) during 0–28 days as compared with control. But after 56 days and later, BC alone or in combination with external Zn produced more extractable Zn. Increase in extractable Zn, upon Zn external application, was dose dependent (highest with 3 mg Zn kg−1 soil) in both soils. Moreover, high-limed soil (0.73–1.28 mg kg−1) had significantly lower AB-DTPA-extractable Zn than low-limed soil (1.28–1.45 mg kg−1) at each incubation interval, irrespective of applied Zn levels. Data of combined application of organic amendments with external Zn showed that PM + Zn treatment had more extractable Zn (1.23–1.44 mg kg−1) than FYM + Zn treatment (1.08–1.32 mg kg−1) in both soils in earlier incubation intervals, but later, more extractable Zn was recorded in BC + Zn treatment (1.39–1.49 mg kg−1) at 84th day of incubation. Further, pH of high- and low-limed soils was decreased with PM, FYM and BC, applied either alone or in combination with external Zn. Thus, organic amendments applied with mineral Zn may improve Zn pools and productivity of calcareous soils in a sustainable way.

Alleviating Soil Acidity: Optimization of Lime and Zinc Use in Maize (Zea mays L.) Grown on Alfisols

ABSTRACTSoil acidity, one of the causes of soil degradation, adversely affects phytoavailability of soil nutrients and crop growth in 50% of arable land of the world. There is a persistent need for alleviating the effect of soil acidity for adequate nutrient availability and proper crop growth. Addition of ameliorants like farmyard manure (FYM) and lime to acid soils affects the crop growth and nutrient availability, especially zinc (Zn) availability, by moderating soil acidity. However, the information regarding optimum quantities of lime and zinc requirement for alleviating soil acidity, proper crop growth, and Zn nutrition in acid soil is limited. Therefore, the present greenhouse pot experiments were carried out at ICAR-Indian Institute of Soil Science, Bhopal, India, in kharif season of 2015 using two acid soils (representing Alfisol order) to optimize lime and Zn application and to understand the impact of FYM and lime application on soil properties, phytoavailable Zn, biomass yield of maize, and Zn uptake, for better growth and Zn nutrition of maize. Maize was raised for 60 days with two levels of FYM (0 and 4,500 mg kg−1), five levels of lime requirement (LR) (0, 1/10th, 1/3rd, 2/3rd, and 1.0), and three Zn levels (0, 2.5, and 5.0 mg kg−1). Results revealed that FYM and lime addition significantly influenced soil properties, biomass yield, and postharvest soil extractable Zn. Lime addition at 1/3rd LR was found optimum as biomass yield enhanced up to this level of liming. FYM addition augmented biomass yield. A higher amount of lime (2/3rd and 1.0 LR) led to a reduction in crop Zn concentration and its uptake. The phytoavailable Zn extracted by different extractants in soils declined with increasing lime rates. Zn addition enhanced biomass yield and crop Zn concentration. The lowest and the highest amount of Zn were extracted from the soil at all levels of lime addition by diethylenetriaminepentaaceticacid (DTPA) and 0.1 M HCl, respectively. The extractable Zn was correlated significantly with biomass yield, crop Zn concentration, and its uptake. Ammonium bicarbonate DTPA (ABDTPA) proved promising extractant for estimation of Zn availability in these acid soils. This knowledge will be of use for alleviation of acid soils by the addition of the required quantity of lime and effective Zn management in acid soils for proper Zn nutrition and crop growth.

Comparison of Extractants for Calibrating Phosphorus Application Rates in a Calcareous Soil

Preplant soil testing is essential for optimizing phosphorus (P) fertilization and minimizing the potential for soil P losses. Currently, there is no effective soil P extractant for calcareous soils in Florida. This study was conducted to compare Mehlich-3, ammonium bicarbonate–diethylenetriaminepentaacetic acid (AB-DTPA), and Olsen for evaluating P availability, estimating soil-test P (STP) critical levels, and calibrating P application rates for fresh-market tomato (Solanum lycopersicum L.) production in a calcareous soil. Tomatoes were grown during Winter 2014 and 2015 with P application rates of 0, 29, 49, 78, 98, and 118 kg·ha‒1 P. Water-extractable P (water-P) and dissolved reactive P (DRP) in leachate were used to determine the STP change point of leaching potential. Results showed the greatest correlation occurred between Mehlich-3 and Olsen of the three STP extractants. For Mehlich-3-P, the medium STP level (producing 75% to 90% relative yield) was predicted from 76 to 89 mg·kg‒1 and the change point was predicted at 88 or 104 mg·kg‒1 by split-line models. The P requirement was calculated from 52 to 112 kg·ha‒1 when Mehlich-3-P was rated as low level (producing 50% to 75% relative yield), which was from 42 to 76 mg·kg‒1. The multiple regression models using AB-DTPA-P and Olsen-P could not predict either the medium STP level or the practical P application rates for the low level. Consequently, based on 2 years of data, Mehlich-3 was the most effective extractant for estimating soil P availability and calibrating P rates in calcareous soils with an extremely high calcium carbonate (CaCO3) content.

Influence of Pyrolyzed Grape-Seeds/Sewage Sludge Blends on the Availability of P, Fe, Cu, As and Cd to Maize

Current intensive agricultural practices, although highly successful in terms of production, have been found to be environmentally unsustainable. One of the crucial approaches to increase agricultural sustainability is the recycling of organic wastes, since these materials often contain many beneficial nutrients for soil and agriculture. Recently, pyrolytic conversion of biodegradable waste into charred material has gained global attention as an amendment to recycle nutrients while improving soil health. Increasing interest in the beneficial applications of pyrolyzed biomass has expanded multidisciplinary areas for science and engineering. The fertilizers used in this study were prepared by pyrolyzing mixtures of two abundant residues in Mediterranean areas: grape seeds and sewage sludge, in different proportions (100% GS, 75% GS-25% SS, 50% GS-50% SS, 25% GS-75% SS, 100% SS). In addition, fresh sludge was mixed with pyrolyzed grape seeds and included as an additional treatment. In this study, the positives and negatives of the application of biochars on agronomic potential and environmental risk have been addressed, taking into account P, Zn, Cu, Fe, As and Cd. In order to choose the best mixture, it is necessary to find a compromise between maximizing the beneficial elements that are translocated to the plant crop, as well as reducing the elements that are leached. Results of a 6-week greenhouse study indicated that the unpyrolyzed sludge mixture contained the largest amount of available nutrients Fe, Cu and P. In agreement, this treatment mixed with a Chromic Luvisol soil (40 ton/ha) increased the uptake of these elements in corn (Zea mays L.—LG ambitious). The yield also increased by 60% in this treatment. However, this mixture also contained more contaminants (As, Cd) which were extracted with Ammonium Bicarbonate-DTPA. According to our results, the treatments where grape seeds and sewage sludge were mixed at 50% and then pyrolyzed exhibited the optimal compromise between efficiency (nutrients uptake) and tolerable levels of potentially toxic elements in leachates.

Assessing the uptake of selenium from naturally enriched soils by maize (Zea mays L.) using diffusive gradients in thin-films technique (DGT) and traditional extractions

A generally accepted method to predict selenium (Se) bioavailability of long-term contaminated soils has not yet been established, even if risk assessments in selenosis areas are crucial. In this study, a set of methods were tested to assess the bioavailability of Se to field maize. Fifty maize (Zea mays L.) samples and corresponding soils were collected from a selenosis area (Ziyang, China). The diffusive gradients in thin-films (DGT) technique and the traditional chemical extraction methods, including seven single-step extraction procedures and a five-step sequential extraction were used to predict the bioaccumulation of Se in plant. The result verified the presence of 50% of total Se in the form of residual Se fraction, followed by organic-bound and Fe-Mn oxide-bound Se fractions in soil. In addition, Se6+, Se4+, and Se2− were all detected in the solution extracted by H2O, KCl, phosphate-buffered solution (PBS), NaHCO3, ethylenediaminetetraacetic acid-2Na (EDTA-2Na) and ammonium bicarbonate–diethylenetriaminepentaacetic acid (AB-DTPA), but Se6+ was not extracted by NaOH. The Se extracted by single-step extraction methods was weakly correlated with the Se uptake by plants with relatively high Se concentration (>3 mg·kg−1). The abilities of the tested methods to predict Se bioavailability in naturally Se-enriched soils declined in the following order: DGT > soil solution > PBS > KCl > H2O > NaHCO3 > EDTA > DTPA > NaOH. The ratio of CDGT to soil solution Se (Csoln) totaled 0.13, indicating an extremely low Se supply from the soil solid phase to the soil solution. Se measured by DGT was mainly derived from the soluble and exchangeable Se fractions that can accurately reflect the plant-absorbed Se pool. Therefore, the DGT technique is highly applicable in the simultaneous prediction of Se bioavailability in naturally Se-enriched 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.

Potassium fractions and availability for chickpea (Cicer arietinum) in Vertisols of north-west Ethiopia

For a critical appraisal of the supplying power of potassium (K) and to predict bioavailable K, it is necessary to have knowledge on the fractions of K and evaluate soil test methods for plant nutrition. This research aimed to assess the forms of K and select a suitable extractant for chickpea (Cicer arietinum L.) nutrition on Vertisols of East Gojjam, north-west Ethiopia. Potassium fractions and bioavailable K extracted by chemical solutions was measured using flame photometry. The mineralogy of Vertisols was assessed by X-ray diffraction. The results showed that the fractions of K were significantly correlated to each other and regression analysis showed that 97.6% of the variability of NH4OAc-K was accounted by the HNO3-K and total K fractions, signifying their existence in dynamic equilibrium. The forms of K were correlated to K uptake by chickpea, suggesting the contribution of the fractions of K to plant nutrition. The high level of K in each form was associated with the illite-smectite clay mineral. The availability of K by ammonium bicarbonate-DTPA was best predicted (R2 = 0.61, p < 0.05) by chickpea uptake in comparison with Mehlich 3 and NH4OAc (R2 = 0.48 and 0.47, respectively). The weaker prediction of NH4OAc-K may be due to the presence of high fixing clays. Further research is necessary on a wide variety of soils and crop types to verify this result and select a suitable extractant for crops in local conditions.