Soil science
Z. Barati; H.R. Owliaie; E. Adhami; M. Najafi-Ghiri
Abstract
IntroductionRecently, layered double hydroxides (LDHs) have attracted significant attention due to their variousapplications, particularly as slow release fertilizers for essential plant nutrients. Several studies have reported therelease of nitrate and phosphorus from LDHs. Additionally, micronutrients ...
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IntroductionRecently, layered double hydroxides (LDHs) have attracted significant attention due to their variousapplications, particularly as slow release fertilizers for essential plant nutrients. Several studies have reported therelease of nitrate and phosphorus from LDHs. Additionally, micronutrients such as zinc (Zn), copper (Cu), andmanganese (Mn) can be structurally incor porated into the metal hydroxide layers. Recent research indicates thatLDHs have considerable potential for releasing these micronutrients. However, further studies are needed toenhance our understanding of the mechanisms and reactions of LDHs under diff erent conditions. Currently, thereis a lack of information regarding the divalent (M 2+2+) to trivalent cation (M 3+3+) ratios in LDHs and the influence ofmalic acid on the release of Zn, Mn, and magnesium (Mg) from these compounds. This study aimed toinvesti gate the effects of malic acid and the ratio of M 2+2+/M 3+ on the kinetics release of Zn, Mn and Mg from MgZn Mn Al LDH intercalated with nitrate nitrate.Materials and MethodsAll chemicals used in this study including malic acid (C4H6O5), 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. The solutions were made with the 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 with varying the M+2(Zn+Mn+Mg)/M+3(Al) 3:1 and 4:1 in the precursor solution while being stirred vigorously in a nitrogen atmosphere. The pH was kept at 9.2-9.6 by adding volumes of 3 M NaOH. The crystals of LDH were ripened in the mixture for 2 h and after that, 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 h to dry. The chemical composition of the synthesized LDHs was determined by furnace atomic absorption spectrophotometry (SavantAA, GBC) after acid digestion. The physical, chemical, and morphological characteristics of the LDHs were determined using X-ray diffraction analysis (Panalytical x Pert ProX-ray diffractometer), Fe-SEM (Sigma VP), FT-IR (Nicolet iS10 spectrometer), and BET (BELSORP Mini II) techniques. A batch study was done to determine the effect of different ratios of M2+/M3+ in LDHs and the effect of malic acid on release of Zn, Mn,and Mg from LDH (3:1) and LDH (4:1). Briefly, 0.01 g of synthesized LDH were put in a centrifuge tube mixed with 10 ml background electrolyte (KCl 0.01 M) and 1.25 mM malic acid in initial pH=6-7 and constant temperature (25±0.5 °C). Blank samples (without ligand) were also considered. Suspensions were shaken at periods ranging from 5 to 720 min agitation (180 rpm). Then, the supernatant solution was separated using a centrifuge at a speed of 4000 rpm for 20 min. Zn, Mn, and Mg concentrations in supernatants solutions were determined by graphite furnace atomic absorption spectrophotometry. The effect of pH in the range of 5 to 10 on the release of Zn, Mn, and Mg from LDH was also studied. Two equations (pseudo-second-order and Elovich) were used to fit the kinetics data.Results and DiscussionThe results showed that the calculated molar ratio of divalent cation to trivalent cation was similar to their molar ratio in the solution prepared for the synthesis of LDH samples. The X-ray diffraction patterns of LDH (3:1) and LDH (4:1) samples showed the existence of strong and sharp peaks for 003 and 006 plates. Accordingly, the reflections of the 003 and 006 plates revealed the layered structure of the synthesized LDH materials. Two bands of FT-IR spectrums around 3480 and 1620 cm-1 for all synthesized LDH materials designated stretching vibrations of the O-H group of hydroxide layers and the interlayer water molecules. The sharp characteristic band around 1382 cm−1 in LDH (3:1) and band around 1354 cm-1 in LDH (4:1) was attributed to the antisymmetric stretching mode of nitrate anion in LDH. The specific surface area of LDH (3:1) and LDH (4:1) were 5.50 m2g-1 and 16.54 m2g-1 respectively. The average pore diameters in LDH (3:1) and LDH (4:1) were 1.92 nm and 2.55 nm, respectively. Time-dependent cumulative release of Zn, Mn, and Mg from LDH (3:1) and LDH (4:1) in the presence and absence of malic acid was investigated. Time-dependent Zn, Mn, and Mg release from LDH (3:1) and LDH (4:1) was accelerated in the presence of malic acid. The Zn, Mn, and Mg release from the LDHs was likely to be separated into two stages. In the initial stage from 0 to 60 min, the release rate of Zn, Mn, and Mg was rapid, then either remained constant or slightly enhanced during 60–720 min. In this research, among the non-linear models used to determine the release kinetics of Zn, Mn, and Mg, the result with the highest R2 values was chosen. The R2 values were 0.91–0.99, 0.93–0.99, 0.93–0.99, 0.89-0.99, and 0.55–0.86 for pseudo-first-order, pseudo-second-order, Elovich, power function, and parabolic diffusion, respectively. So, pseudo-second-order and Elovich models were used to analyze kinetic data. The amounts of release of Zn, Mn and Mg were higher from LDH (4:1) than from LDH (3:1) because of greater specific surface area, volume, and pore diameter in LDH (4:1). A comparison of metal release versus time profiles exhibited that dissolution was greatly dependent on the pH.ConclusionTheresults of this research indicated that the release of Zn, Mn, and Mg from layered double hydroxides(LDHs) was influenced by factors such as time, ligand, solution pH, and the type of LDH. According to thekinetics models fitted to the experimental data, the release rate of Zn, Mn, and Mg from LDH (4:1) was higherthan that from LDH (3:1). In both types of LDH s , the presence of malic acid significantly increased both the rateand amount of Zn, Mn, and Mg release compared to the absence of malic acid. While this study demonstratedthat varying the ratios of divalent to trivalent cations can influence the amount and rate of Zn and Mn release,further greenhouse studies are required to confirm the effectiveness of LDH as a slow release fertilizer incalcareous soils.
Elham Yazadni; Vahid Hosseini; Kyumars Mohammadi Samani
Abstract
Introduction: Fires are natural processes in many ecosystems, constituting a natural, even vital, component of forests. Fire can change the soil properties depending on its severity. In semi-arid regions, the effects of fire are more vigorous in comparison with other regions. In these regions, forests ...
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Introduction: Fires are natural processes in many ecosystems, constituting a natural, even vital, component of forests. Fire can change the soil properties depending on its severity. In semi-arid regions, the effects of fire are more vigorous in comparison with other regions. In these regions, forests restoration is much more difficult especially in the summer when temperatures reach maximum levels and cause fires that reduce soil nutrients by burning organic matters and vegetation. Since the frequency of fire events in Zagros oak forests have been increasing in recent years, therefore, in this study, the chemical properties of soil investigated immediately after fire. Most wildfires in these forests are surface fires with low-to-moderate severity due to low forest density, great distances between trees and few forest floor plants.
Materials and Methods: The study area is located in Kurdistan Province, western Iran, around Marivan that has been burned in July 2017. One transect was installed on the contour line with 250 m length on the burnt slope. Eight Persian oak trees were selected at 30 meters interval. Two soil samples were collected in each tree from depth of 0-5 cm. The two positions of soil samples including: the first one was 50 cm far from the base trunk and the second one was on the edge of tree crown border. In the control area, eight Persian oak were selected in the adjacent area of burned area with same topographic and plant conditions and soil samples were collected same as burned area. Finally, soil organic carbon (SOC), Total nitrogen (TN), available phosphorus, potassium, calcium, magnesium, pH, and EC were analyzed.
Results and Discussion: The results of this study showed that fire has a significant effect on soil properties, so that organic carbon reduced and amount of available phosphorus, calcium, magnesium and potassium of soil increased in burned soil. Organic carbon decreased significantly (P<0.01) in the burned soil in comparison to control treatment near tree trunk while it did not have any significant difference in the border of tree crown. The lowest Organic carbon was 6.19% in burned soil near tree trunk and the highest 9.15% in unburned soil in the border of tree crown. Total nitrogen did not show any significant difference between all treatments. Phosphorus increased significantly after the fire in the burned soil by comparison with control in the both positions. The increase of available P in soil after fire can be due to added ash as the fire partially and completely combusted plant debris in the soil. The highest phosphorus was 130.08 mg/kg in the burned soil near tree trunk and the lowest was 65.67 mg/kg in soil of control area in the border of tree crown. Cations including Ca, Mg and K were significantly higher near tree trunks in burned soil compared with control area, while only Ca and Mg of soil showed significant differences in the border crown position. The pH of burned soil was 7.62 and 7.05 near tree trunk and border of tree crown, respectively, and it was 7.15 and 6.89 near tree trunk and border of tree crown, respectively, in control area. The EC of burned soil was 1.70 mS/cm and 0.66 mS/cm near tree trunk and border of tree crown, respectively and it was 0.44 mS/cm and 0.54 mS/cm near tree trunk and border of tree crown, respectively in control area. One-way ANOVA showed that two positions of soil samples had significant effect on all soil parameters except nitrogen. In the Zagros oak forests, there are a lot of flammable materials inside stands, which can lead to low and medium intensity fire .According to the results of this study, the amount of organic carbon of burned soil near tree trunk was less than the crown border because of high accumulation of flammable materials and high fire intensity.
Conclusion: In general, it can be concluded that wildfire causes significant changes in chemical properties of forest soils. Changes in the chemical properties of soil between burned soil and control area differed with movement from tree trunk to border of tree crown, so that the amounts of phosphorus, potassium, magnesium, calcium, acidity and electrical conductivity were reduced and the amount of carbon increased. Hence, it seems that properties of soil burned has diffiered by moving from the tree trunk to the border of crown trees probabley because of the differences in the amount of accumulated litter, consequently has an effect on the characteristics of the soil in different postions.
M. Hojjati; M. Asadiyan
Abstract
The presence of livestock within forest stands in north of Iran, as one of the main hindrances for optimal forest managing influence the productivity of that individual forest ecosystem in a waste area. The present study was conducted to investigate the effects of the long lasting presence of cattle ...
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The presence of livestock within forest stands in north of Iran, as one of the main hindrances for optimal forest managing influence the productivity of that individual forest ecosystem in a waste area. The present study was conducted to investigate the effects of the long lasting presence of cattle on soil properties in Hyrcanian forests. The investigated area was a part of Parchinak district, Mazandaran -Sari (in 4 Livestock husbandry campus and adjacent forest stands). Soil samples were collected from soil depths of 0-10 cm, 10-20 cm using coring method (8 cm diameter) in each site randomly (n=5) for determining soil physical, chemical and biological characteristic. Results showed that some soil physical characteristics (bulk density and moisture content) and many soil chemical properties (carbon and organic matter, nitrogen, phosphorus, potassium and calcium) were higher in husbandry area than the adjacent forest stand. Also, Net N mineralization and net nitrification have been observed only in Livestock campus. Our findings indicated a significant impact of livestock presence (input of a huge amount of cattle dung and high soil compaction) on forest soil.
