Soil science
Z. Movahedi Rad; M. Hamidpour; A. Tajabadipour
Abstract
Introduction
Recently, layered double hydroxides (LDHs) with a unique structure and unbeatable characteristics have been widely studied and investigated in various fields. One of these fields is the investigating the potential of these compounds to supply essential nutrients for plants. Several studies ...
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Introduction
Recently, layered double hydroxides (LDHs) with a unique structure and unbeatable characteristics have been widely studied and investigated in various fields. One of these fields is the investigating the potential of these compounds to supply essential nutrients for plants. Several studies have reported the application of LDHs as fertilizers for macronutrients and micronutrients. These compounds have a very high potential as fertilizers and can increase agricultural productivity. Micronutrients such as Zn, Cu and Mn can be structurally incorporated in the metal hydroxide layer. According to recent research, LDHs have shown a suitable potential to release micronutrients. However, more studies are needed to enhance our understanding of the mechanism and reaction of layered double hydroxides in different conditions. Although various studies have explored the potential of LDHs as slow-release fertilizers, our research focuses on the role of citric acid and tartaric acid and as well as the ratio of divalent to trivalent cations on the kinetics of Zn, Mn and Mg release from Mg-Zn-Mn-Al-LDH intercalated with nitrate.
Materials and Methods
All chemicals used in this study including citric acid (C6H8O7.H2O), tartaric acid (C4H6O6) KCl, Zn (NO3)2.6H2O, Mn(NO3)2.4H2O Mg(NO3)2.6H2O and Al(NO3).9H2O were of analytical grades, purchased from Chem-Lab or Merck Chemical Corporations. Solutions were prepared using decarbonated ultrapure water (electrical resistivity = 18 MΩcm). The LDHs were synthesized by co-precipitation method at constant pH = 9.2-9.6. Two types of LDHs were synthesized by varying the M+2(Zn+Mn+Mg)/M+3(Al) ratios of 3:1 and 4:1 in the precursor solution while stirring vigorously in a nitrogen atmosphere. The pH was kept at 9.2-9.6 by adding volumes of 3 M NaOH. The LDH crystals were allowed to ripen in the mixture for 2 hours, after which the precipitates were centrifuged at 3000 rpm for 20 min and washed several times with distilled water and placed in an oven at 70°C for 8 hours to dry.
The chemical composition of the synthesized layered double hydroxides (LDHs) was analyzed using furnace atomic absorption spectrophotometry (SavantAA, GBC) following acid digestion. The physical, chemical, and morphological characteristics of the LDHs were assessed through several techniques, including X-ray diffraction (Panalytical X Pert Pro X-ray diffractometer), field emission scanning electron microscopy (FE-SEM, Sigma VP), Fourier-transform infrared spectroscopy (FT-IR, Nicolet iS10 spectrometer), and Brunauer-Emmett-Teller (BET, BELSORP Mini II) analysis.
A batch study was conducted to evaluate the effects of varying M²⁺/M³⁺ ratios in LDHs and the influence of citric acid and tartaric acid on the release of Zn, Mn, and Mg from LDH (3:1) and LDH (4:1). In brief, 0.01 g of synthesized LDH was placed in a centrifuge tube and mixed with 10 ml of background electrolyte (0.01 M KCl) and 1.25 mM of citric acid or tartaric acid, maintaining an initial pH of 6–7 at a constant temperature of 25 ± 0.5 °C. Blank samples (without ligands) were also included for comparison. The suspensions were shaken for time periods ranging from 5 to 720 minutes at an agitation speed of 180 rpm. After shaking, the supernatant was separated by centrifugation at 4000 rpm for 20 minutes. The concentrations of Zn, Mn, and Mg in the supernatant solutions were determined using graphite furnace atomic absorption spectrophotometry.
To describe the time-dependent release of Zn, Mn, and Mg, several kinetic models were tested. Among the five models evaluated, the pseudo-second-order and power function models provided the best fit for the kinetic data. Additionally, the chemical species present in the initial solution and the saturation index (SI) of various minerals were predicted using the Visual MINTEQ 3.1 computer code.
Results and Discussion
The results indicated that the calculated molar ratio of divalent cations to trivalent cations closely matched the molar ratios used in the synthesis of the layered double hydroxide (LDH) samples. The X-ray diffraction (XRD) patterns for both LDH (3:1) and LDH (4:1) samples exhibited strong and sharp peaks corresponding to the 003 and 006 reflections, confirming the layered structure of the synthesized materials. Fourier-transform infrared (FT-IR) spectroscopy revealed two significant absorption bands around 3480 cm⁻¹ and 1620 cm⁻¹ in all synthesized LDH materials, which are indicative of stretching vibrations associated with the O-H groups in the hydroxide layers and the interlayer water molecules. Additionally, a sharp band at approximately 1382 cm⁻¹ in LDH (3:1) and a band at around 1354 cm⁻¹ in LDH (4:1) were attributed to the antisymmetric stretching mode of the nitrate anion present in the LDH structure. The specific surface areas of LDH (3:1) and LDH (4:1) were measured at 5.50 m²/g and 16.54 m²/g, respectively. Correspondingly, the average pore diameters were found to be 1.92 nm for LDH (3:1) and 2.55 nm for LDH (4:1), indicating differences in porosity between the two samples. The time-dependent cumulative release of Zn, Mn, and Mg from LDH (3:1) and LDH (4:1) in the presence and absence of citric acid and tartaric acid was investigated. The release of these micronutrients was accelerated in the presence of both organic acids. The release process appeared to occur in two stages: during the initial stage (0 to 50 minutes), the release rate of Zn, Mn, and Mg was rapid, followed by a period from 50 to 720 minutes where the release rate either fixed or slightly increased.
In this research, among the non-linear models which were used to determine the release kinetics of Zn, Mn, and Mg, the one with the highest R2 values was chosen. The R² values ranged from 0.81 to 0.99 for the pseudo-first-order model, 0.89 to 0.93 for the pseudo-second-order model, 0.97 to 0.99 for the Elovich model, 0.89 to 0.99 for the power function model, and 0.55 to 0.86 for the parabolic diffusion model. Ultimately, the pseudo-second-order and power function models were chosen to analyze the kinetic data. The amount of Zn, Mn and Mg released at equilibrium (qe) were higher in the presence of citric acid (42%) compared to tartaric acid. Additionally, the release of these elements was greater from LDH (4:1) than from LDH (3:1). This suggests that increasing the ratio of divalent cations to trivalent cations reduces the stability of LDH, enhancing the release of micronutrients.
Conclusion
The results of this study demonstrated that the release of Zn, Mn, and Mg from layered double hydroxides (LDHs) was influenced by time, the type of low molecular weight organic acid, and the ratio of divalent to trivalent cations in the LDH structure. Kinetic modeling revealed that the release rates of Zn, Mn, and Mg from LDH with a 4:1 ratio were higher than those from LDH with a 3:1 ratio. Additionally, the dissolution rates of LDHs were faster in the presence of citric acid compared to tartaric acid. To further assess the potential of LDHs as slow-release micronutrient fertilizers in calcareous soils, additional greenhouse and soil experiments are recommended.
T. Poorbafrani; A. Tajabadi Pour; V. Mozafari; A.R. Akhgar
Abstract
Introduction: Pistachio is one of the most important crops in many regions of Iran with respect of production and export. There are more than 470000 ha of nonbearing and bearing pistachio trees mainly in Kerman province. Despite the economic importance of this crop, very little information is available ...
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Introduction: Pistachio is one of the most important crops in many regions of Iran with respect of production and export. There are more than 470000 ha of nonbearing and bearing pistachio trees mainly in Kerman province. Despite the economic importance of this crop, very little information is available on its nutritional requirements. Pistachio trees like other crops need to macro and micro nutrients. one of these elements is manganese (Mn). Manganese is an essential mineral nutrient, playing a key role in several physiological processes, particularly photosynthesis, respiration and nitrogen assimilation. This element is normally supplied to the plants by soil. Therefore, soil conditions affect its availability to plants. Soils with high pH, calcareous soils, especially those with poor drainage and high organic matter, are among the soils which produce Mn-deficient plants. Calcium carbonate is the major inactivation factor of Mn in calcareous soils. The soils of Iran are predominantly calcareous in which micronutrients deficiency, including Mn, is observed due to the high pH and nutrient fixation. The objective of this research was to examine the effect of manganese application on growth and chemical composition of pistachio seedlings in some calcareous soils with different chemical and physical properties.
Materials and Methods: For this purpose a greenhouse experiment was carried out as factorial (two factors including soil type and Mn levels) experiment in completely randomized design with three replications. Treatments were consisted of three levels of Mn (0, 10 and 20 mg Mn Kg-1 soil as Manganese sulfate) and 12 different soils from Rafsanjan region in Southern Iran. Soil samples were air dried and crushed to pass through a 2-mm sieve, and some physical and chemical properties of soils such as texture, electrical conductivity, pH, organic matter content, calcium carbonate equivalent, cation exchange capacity and iron, manganese, copper and zinc availability were determined. Then plastic pots were filled with 5 kg of these soils. Pistachio seeds (cv Badami Zarand) were placed in muslin sacks and pretreated for 24 h with Benomyl solution. The germinated seeds were planted in each pot, and each pot was irrigated with distilled water. Nitrogen and phosphorous were applied uniformly to all pots at the rate of 50 mg kg−1 soil as ammonium nitrate and potassium dihydrogen phosphate forms, respectively. Zinc, iron and copper also were added to treatments at level of 5 mg kg−1 soil as zinc sulfate, iron sequestrine138 and copper sulfate. After 24 weeks, the seedlings were cut at the soil surface, and the roots were washed free of soil. Leaves, stems and roots were dried at 70 oC for 48 h in an oven. The total leaf, stem, and root dry weights were recorded. The ground plant samples were dry- ashed at 550oC, dissolved in 2 N HCl, and made to volume with hot distilled water. Plant Mn, Cu, Zn and Fe concentrations determined by atomic absorption spectrophotometry. All data were statistically analyzed according to the technique of analysis variance (ANOVA) by MSTATC.
Results and Discussion: Results indicated that the application of manganese increased leaf, stem and root dry weight of pistachio seedlings so that the maximum amount of the dry weight of roots stems and leaves of pistachio seedlings were observed at 10 mg Mn kg-1soil. Application of 10 mg Mn kg-1 soil increased leaf, stem and root dry weight by 19.2%, 25.2% and 23.9% in comparison to control, respectively. Chemical composition (concentration and uptake) of shoot of pistachio seedlings was also affected by Mn application. Mn application decreased the concentration and uptake of iron, concentrations of copper and zinc in Pistachio seedling shoots so that the highest concentrations of these elements were observed in control treatment. Reductions in concentrations of zinc and copper elements in 10 mg Mn kg-1 treatment were not statistically significant but in 20 mg Mn kg-1 treatment they were significant.
Conclusions: The results of this research showed that the application of 10 mg Mn kg-1soilto highly calcareous soils significantly increased most of growth parameters of pistachio seedlings in comparison to control. Although higher amounts of manganese (20 mg Mn kg-1 soil) reduced the growth parameters than the previous level. In overall, the results of this study indicated that for optimum growth and chemical composition of pistachio seedlings in calcareous soils, application of 10 mg Mn kg-1 sol is necessary.
S. Eskandari; V. Mozafari; A. Tajabadi
Abstract
Abstract
A greenhouse experiment was conducted to study the effects of soil copper (Cu) and salinity application on photosynthesis parameters, enzyme activity and anatomical structure of two pistachio cultivars. A factorial greenhouse experiment was carried out as completely randomized design with three ...
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Abstract
A greenhouse experiment was conducted to study the effects of soil copper (Cu) and salinity application on photosynthesis parameters, enzyme activity and anatomical structure of two pistachio cultivars. A factorial greenhouse experiment was carried out as completely randomized design with three replications. Treatments consisted of four Cu levels (0, 2.5, 5, and 7.5 mg Kg-1soil as CuSO4.2H2O), five salinity levels (0, 800, 1600, 2400, and 3200 mg NaCl Kg-1 soil) and two pistachio cultivars (Badami-e-Zarand and Ghazvini). Results showed that application of 3200 mg NaCl Kg-1 soil, decreased transpiration rate and stomatal conductance by 69 and 16% respectively, whereas had no significant effect on photosynthesis rate. Also application of 5 mg Cu Kg-1 soil, caused maximum photosynthesis rate. Transpiration rate and stomatal conductance of Badami-e-Zarand was significantly higher than Ghazvini, but reverse trend was seen for photosynthesis rate. The highest salinity level (3200 mg NaCl Kg-1 soil), significantly increased SOD activity. Furthermore, all Cu levels increased SOD activity. As salinity increased, thickness of parenchyma layer and phloem rings, and number of resin channels of stem and root decreased and increased pulp thickness. Application of Cu in saline conditions, decreased thickness of xylem vessels and increased that of phloem rings and number of resin channels in stem.
Keywords: Salinity, Pistachio, Copper, Photosynthesis
