Soil science
Z. Sokhanvar Mahani; N. Boroomand; M. Sarcheshmeh Pour
Abstract
IntroductionPhosphorus (P) is one of the most important elements necessary for plant growth and production of agricultural products. In calcareous soils, phosphorus deficiency is a general issue due to high pH, high soil calcium carbonate content, lack of organic matter and moisture. Phosphorus absorption ...
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IntroductionPhosphorus (P) is one of the most important elements necessary for plant growth and production of agricultural products. In calcareous soils, phosphorus deficiency is a general issue due to high pH, high soil calcium carbonate content, lack of organic matter and moisture. Phosphorus absorption capacity depends on different soil reactions such as: adsorption, sedimentation, stabilization and release. The speed and amount of plant available P depends on the soil reactions. Studying the kinetics of P release from soil is a good indicator to check the status of P uptake by plant. The kinetics of P release in soils is a subject of importance in soil and environmental sciences. The aim of this research was to investigate the kinetics of P release and derive the most suitable equation to describe the release of P from a calcareous soil when subjected to the acidification of rock phosphate and the addition of vermicompost. Materials and MethodsIn order to investigate the ability of acidified rock phosphate and vermicompost in P release, an experiment was conducted with 2 replications on a light-textured soil with low OC and Olsen-P (1.2 mg/kg). One hundred grams air dried calcareous soil was transferred into special containers and 5 treatments including: 1- control (soil), 2- rock phosphate, 3- acidified rock phosphate (20 CC nitric acid 0.1 N and 5 g rock phosphate), 4- vermicompost, and 5- acidified vermicompost (20 CC nitric acid 0.1 N and 5 g vermicompost) were applied. The treatments incubated two weeks in 20±2℃ temperature. The Kinetics of P release was studied by adding 20 mL of 0.5N NaHCO3 to, one gram of air dried treatments. Extraction times were considered to be 0.25 h to 256 h (in 11 times) based on the time of adding the NaHCO3 extractant until filtering. After adding the extractant, the samples were shaken and centrifuged. After filtering, the concentration of released P in samples were determined by spectrophotometer (Model: CE 292 Series2, ultraviolet). For higher accuracy in the measurements, acid-washed containers were adjusted based on the amount of soil moisture which was dried in the oven (105℃). Finally, the P release data were fitted to different kinetic equations. The effect of different fertilizer treatments on P release in specified times and then kinetics parameters were investigated and compared with the control. Results and DiscussionAddition of acidified and non acidified rock phosphate and vermicompost increased the amount and speed of P release in the calcareous soil. Six kinetic equations were fitted to describe the release of P in the period of 0.25 h to 256 h from the soil to evaluate the effect of the treatments. The highest release of P was in vermicompost and acidified rock phosphate treatment, which were an organic fertilizer and a source for preparing phosphate fertilizers. To describe the release rate, kinetic equations were used. The best equations were chosen by highest coefficient of determination (R2) and the least of standard error (SE). The zero, first, second order equations could not describe the release of P in the studied calcareous soil. The R2 value decreased from the zero to second order equation. The simplified Elovich equation described well the release of P from the soil with the average R2 of 0.79 and with the average SE of 0.4. Comparison of the average effect of the studied treatments with the control showed that the acidifed vermicompost and rock phosphate treatments increased the capacity and speed of P release compared to the control. On the other hand, acid addition has increased the capacity and speed of P release in the calcareous soil. ConclusionThe findings indicated an initial rapid release of P, which then decreased over time. Notably, the application of vermicompost and the acidification of the soil with rock phosphate resulted in a pronounced and accelerated release of P. Generally, organic fertilizer treatments exhibited a higher release of P compared to chemical fertilizer treatments. This observation is in accordnce with the findings of the data presented by Ghorbanzadeh et al. (2009), who explored the P release potential of bone meal. Their data demonstrated that the acidification of bone meal accelerated and enhanced P release. To further enhance the practical relevance of these results, it is recommended to conduct this research in the presence of plants.
N. Abdar; R. Ghasemi
Abstract
Introduction: Zinc (Zn) is an important nutrient element for plants growth, which plays an important role in the metabolism of plant. Zn uptake by plants requires release of Zn adsorbed onto the soil constituents and even Zn containing minerals. The release of Zn from soil surface to the soil solution ...
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Introduction: Zinc (Zn) is an important nutrient element for plants growth, which plays an important role in the metabolism of plant. Zn uptake by plants requires release of Zn adsorbed onto the soil constituents and even Zn containing minerals. The release of Zn from soil surface to the soil solution is an important factor that controls availability of Zn for growing plants. Kinetics of Zn release from soil could indicate ability of soil to Zn supply to plants. The purpose of present study was to investigate the effects of soil depth and canopy of three cultivars of palm including Shahani, Ghasab and Halavani on release kinetics of native Zn by AB-DTPA extractant.
Materials and Methods: In order to investigate the effects of depth and vegetation on the pattern of Zn release, 54 soil samples were collected from inside and outside canopy of different palm cultivars (Shahani, Halavani and Ghasab), three depths (0-20, 20-40 and 40-60 cm) with three replications. These samples were collected from village of Simakan, located in the city of Jahrom. Extraction was performed after eight shaking times (5, 15, 30, 60, 120, 240, 480, and 1440 min) with ammonium bicarbonate-diethylene triamine penta acetic acid (AB-DTPA). After each shaking time, samples were immediately centrifuged for 15 min, and then filtered through filter paper. The concentration of Zn in solutions were determined using an atomic absorption spectrophotometer (AA-67OG). Seven commonly used kinetics models in nutrient release studies were used to describe Zn release including zero-order, first-order, pseudo-first-order, pseudo-second-order, power function, parabolic diffusion, and simple elovich. Data analysis and drawing of charts were done by SAS software and Excel program, respectively. Relatively high value of coefficient of determination and low value of standard error of estimate were considered as criteria for the best fit.
Results and Discussion: The results of this study showed that the simplified Elovich, parabolic diffusion and power function equations well described the pattern of Zn release from soil as evidenced by higher coefficient of determination and lower values of the standard error of the estimate. The Zn release pattern in all soil samples consisted of a quick stage from the start of the experiment to 240 minutes and a slower stage at subsequent times. The correlation between the coefficients of the kinetic equations of the power function, simplified Elovich and parabolic diffusion showed that there was higher correlations between the coefficients of the equations obtained from the under canopy in comparison with those of out of canopy. Although soil is a major factor influencing vegetation growth and characteristics, plants could, in turn, also affect different soil properties. In addition, the palm root system and the rhizosphere exhibit a complex diversity, which could regulate the plant homeostasis. The interaction of root-microorganism in the rhizosphere can cause many of the physical, chemical and biological properties of the rhizosphere soil that are different from the bulk soil. Important changes in the soil properties of the rhizosphere environment include soil pH, soil oxidation-reduction reactions, soil moisture, and nutrient availability for microorganisms and plant. Root exudates also contribute to enhance of the availability of elements by reducing the pH of the rhizosphere and creating bioavailable Zn complex. Recent studies have shown that root exudates can act as an influential factor in extracting significant values of plant nutrients from calcareous soils. Our results showed that the amount of accumulated Zn released from the under canopy soils was more than the out of canopy soils, and the highest amount of accumulated Zn was released in the soils under canopy of Ghasab cultivar.
Conclusion: Results of present study showed that the values of Zn released from the under canopy soils was higher than interspaces soils, and the highest amount of accumulated Zn was released in the soils under canopy of Ghasab cultivar. Such observations clearly indicate that palm trees are able to supply Zn absorption capacity under their own canopy soils. Therefore, it appears that higher rates of Zn release from the under canopy soils in comparison with interspaces could be attributed to higher root exudates which impact soil properties, microorganism activities and lower pH which, in turn, increase the amounts of metals including of Zn release and bioavailability. Further researches on the effect of palm root system on physical and chemical properties of soil, including organic matter, soil pH, which could cause great impacts on the amount of Zn release are highly recommended.
sanaz ashrafi saeidlou; Mirhasan Rasouli-Sadaghiani; Abbas Samadi; mohsen barin; ebrahim sepehr
Abstract
Introduction: Potassium is one of essential nutrients for plants and its importance in agriculture is well known. Non-exchangeable potassium that is mainly placed with in layers of K-bearing minerals, such as K-feldspar and mica, is considered as an important source of potassium for plant growth in most ...
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Introduction: Potassium is one of essential nutrients for plants and its importance in agriculture is well known. Non-exchangeable potassium that is mainly placed with in layers of K-bearing minerals, such as K-feldspar and mica, is considered as an important source of potassium for plant growth in most soils. Regarding that low molecular weight acids (LMW) play an important role in improving the bioavailability of soil nutrients such as non-exchangeable K (NEK), and the release rate of NEK plays a significant role in supplying necessary K for plants, the purpose of this study was comparison of potassium release kinetic from K-bearing including feldspar, illite as well as phlogopite minerals and choose the best kinetic equation describing potassium release process, influenced by organic as well as mineral extractants.
Material and Methods: The experiment carried out in a completely randomized design with three replications. Experiment factors were including extractant type (0.01 mol l-1 oxalic acid, 0.01 mol l-1 calcium chloride, control (deionized water)), potassium mineral type (feldspar, illite and phlogopite) and incubation time (1, 2, 4, 8, 12, 16, 24, 32, 48, and 64 hours). Elemental composition of minerals identified by Fluorescence spectroscopy device (S4 Pioneer). Used minerals in the experiment including feldspar, phlogopite and illite were ground and filtered through a 230 mesh sieve. In order to remove exchangeable K, samples were saturated by calcium chloride solution (with a ratio of 2:1), after washing with HCl, samples were dried at 105 °C for 48 hours. 100 mg of washed minerals, was weighed carefully and transferred to centrifuge tubes. Then 20 ml of each of extractants (oxalic acid and calcium chloride 0.01M) was added to the tubes. After 15 minutes shaking, tubes containing a mixture of minerals-extractants was carried out in a controlled incubation chamber for periods of 1, 2, 4, 8, 12, 16, 24, 32, 48 and 64 hours at 25 °C. After each period, samples were centrifuged at 3000 rpm for 10 minutes and filtered using Whatman paper (No. 41). pH and potassium concentration of samples were measured by pH meter and flame photometer, respectively. Data related to potassium release was fitted by zero order, first order, second order, power function, parabolic diffusion and ellovich equations.
Results and Discussion: Results showed that the effect of extractant type was significant on kinetic of potassium release, so that potassium release amount in samples extracted with oxalic acid was 1.48 and 2.35 times higher than samples extracted with calcium chloride and control (deionized water), respectively. Also, different minerals released various amounts of potassium. K release from phlogopite was 1.99 and 2.95 times higher than feldspar and illite, respectively. The maximum potassium concentration (440 mg kg-1) was seen in phlogopite which was extracted with oxalic acid. So that, amount of potassium in this treatment was 3.15 times higher than control one. Furthermore, the effect of extraction time on K release was significant. So that, at the beginning of incubation period the release of potassium by different extractants was more, but its amount decreased over time and finally continued with a constant speed. Kinetic equation fitting showed that zero order, first order, power function, parabolic diffusion and ellovich equations are able to describe potassium release but second order model cannot justify it. Among these five equation, the power function and parabolic diffusion equations with the maximum coefficient of determination (R2) and the least standard error of estimate (SE), could reasonably describe the K release kinetics, so they are introduced as the best models for data fitting. The slope (b) and interception (a) of ellovich equation indicate interlayer and initial K release, respectively. Oxalic acid and phlogopite had the most amount of interception, it means that the impact of oxalic acid on initial and interlayer release rate of K in phlogopite, is more effective than calcium chloride.
Conclusions: It is concluded that different factors like mineral and extractant type influence kinetic of potassium release and organic extractant have more ability in extracting non-exchangeable potassium from minerals structure. Also, the adjustment of the results of this study with first order, parabolic diffusion and power function equations suggest that nonexchangeable potassium release from minerals can be affected by diffusion process from the surface of the study minerals, indicating that NEK release rate is controlled by K diffusion out of the mineral interlayer.
Hadis Hatami; Ali reza Karimi; A. Fotovat; H. Khademi
Abstract
Aluminosilicates such as K-feldspar and micaceous minerals are the main source of potassium in soils. The objectives of this study were to investigate the release of K from micaceous minerals (biotite, phlogopite, muscovite) and K-feldspars (Zanjan and Yazd) using sequential extraction by 0.05 M BaCl2 ...
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Aluminosilicates such as K-feldspar and micaceous minerals are the main source of potassium in soils. The objectives of this study were to investigate the release of K from micaceous minerals (biotite, phlogopite, muscovite) and K-feldspars (Zanjan and Yazd) using sequential extraction by 0.05 M BaCl2 and determine the effect of mineral grain size and application of kinetic models to describe K release. For this purpose, sequential extraction with BaCl2 was conducted on two sizes of 50-100 and less than 50 micron for the periods of 2-600 hours. The amount of K released into the solution was measured by flame photometer. The results indicated that after 13 times of extraction, in the both sizes, biotite and muscovite had the highest and lowest values of K release, respectively. Meanwhile, the released K increased by decreasing the mineral size. The kinetics of K release from minerals consisted of two phases, the first phase was relatively rapid and then continued with a slow rate to end of the experiment. Regarding the high determination coefficient (R2) and low standard error of the estimate (SE), parabulic diffusion and exponential function equations could reasonably describe the K release kinetics. Therefore, it may be concluded that the release of K is controlled by diffusion process from the surface of the study minerals.
