Malihe Talebi Atouei; Rasoul Rahnemaie; Esmaiel Goli Kalanpa; Mohammad Hossein davoodi
Abstract
Introduction: Natural environments, including soils and sediments, are open and complex systems in which physico-chemical reactions are in semi equilibrium state. In these systems, bioavailability of plant nutrients, like phosphate, is influenced by environmental conditions and concentrations of other ...
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Introduction: Natural environments, including soils and sediments, are open and complex systems in which physico-chemical reactions are in semi equilibrium state. In these systems, bioavailability of plant nutrients, like phosphate, is influenced by environmental conditions and concentrations of other ions such as calcium and magnesium. Magnesium is a dominant cation in irrigation water and in the soil solution of calcareous soils. Recent evidences show relative increase in the concentration of magnesium in irrigation water. Because of the importance of chemical kinetics in controlling concentrations of these ions in the soil solution and for understanding their effects of adsorption kinetics of magnesium and phosphate ions, in this research, adsorption kinetics of these two ions on goethite is investigated as function of time and pH in single ion and binary ion systems. The experimental data are described by using the adsorption kinetics equations. These data are of the great importance in better understanding adsorption interactions and ion adsorption mechanism.With respect to the importance of these interactions from both economical and environmental point of view, in this research, the kinetics and thermodynamics of phosphate and Mg2adsorption interactions were investigated as function of pH on soil model mineral goethite in both single and binary ion systems.
Materials and Methods: Kinetics experiments were performed in the presence of 0.2 mM magnesium and 0.4 mM phosphate in 0.1 M NaCl background solution and 3 g L-1 goethite concentration as function of pH and time (1, 5, 14, 24, 48. 72 and 168 h) in single ion and binary ion systems. After reaction time, the suspensions were centrifuged and a sample of supernatant was taken for measuring ions equilibrium concentrations.Phosphate concentration was measured calorimetrically with the ammonium molybdate blue method by spectrophotometer (Jenway-6505 UV/Vis). Magnesium concentration was determined by atomic absorption spectrophotometer (AA-670Shimadzu AA/FE). The amounts of adsorbed ions were calculated from the difference of the initial and the equilibrium concentrations. The experimental data were described by using the several widely-used kinetic models. Models performance was evaluated based on their ability to describe experimental data and obtained values for coefficient of determination (R2) and standard error of the estimate (SE).
Results and Discussion: The results demonstrate that phosphate and magnesium adsorption on goethite reached equilibrium within the 24 h equilibration time. The equilibration time is, however, pH-dependent. No systematic differences are observed among time-dependent adsorption isotherms for phosphate at pHpHPZC. It seems that the effect of pH on kinetics of phosphate and magnesium adsorption is related to the mineral surface charge, which influences electrostatic interactions between the ions and the surface charges.thus electrostatic attractive and repulsive forces dominantly control the reaction. The equilibration time for phosphate and magnesium adsorption on goethite was calculated to be ≤1 h when electrostatic forces are attractive and approximately 24 h when electrostatic forces are repulsive. In binary ion systems, phosphate and magnesium enhanced the amount and accelerated the adsorption rate of each other. Adsorption of phosphate could reverse electrostatic forces from repulsive to attractive for the adsorption of magnesium and vice versa. Also, because of the smaller ionic radius of magnesium (0.065 nm) in comparison with phosphate (0.22 nm), reduction in equilibration time of magnesium adsorption in the presence of phosphate could be partly diffusion-controlled. Fitting different kinetic models on experimental data showed that pseudo-second order model can successfully describe phosphate and magnesium adsorption data in both single and binary ion systems with highest determination coefficient (R2~0.99) and lowest standard error of the estimate (SE
M. Mohammadi; Mohammad Jafar Malakouti; K. Khavazi; F. Rejali; Mohammad Hossein Davoodi
Abstract
Introduction: Use of unbalanced chemical fertilizers especially P, having low absorption efficiency and low solubility compounds with soil components, has resulted in the production and use of bio-fertilizers (17, 23 and 29). Bio-fertilizer is a preservative material consisting of one or several specific ...
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Introduction: Use of unbalanced chemical fertilizers especially P, having low absorption efficiency and low solubility compounds with soil components, has resulted in the production and use of bio-fertilizers (17, 23 and 29). Bio-fertilizer is a preservative material consisting of one or several specific beneficial micro-organisms or their metabolic products used to supply plant nutrients and development of root systems (29). There are a lot of micro-organisms in soil capabling help to plant nutrition and uptake of nutrient elements in different ways that can be mentioned by the dual symbiotic relation between micro-organism and plant. Mycorrhizal fungus and plant growth promoting rhizobacteria (PGPR) such as Azotobacter and Pseudomonas are able to increase uptake of nutrient elements particularly when they are applied with others and hence they increase the yield of different crops (12, 14; 24 and 30). P solubilizing fungus and bacteria facilitate uptake of slowly diffusing nutrient ions such as P, Zn and Cu and increase their availabilities usually by increasing volume of soil exploited by plants, spreading external mycelium, secreting organic acids, production of dehydrogenase and phosphates enzymes and reducing rhizosphere acidity (9, 15, 19, 23 and 26). The main beneficial use of micro-organism is increasing of host plant growth. It can be done with increase of nutrient elements uptake. The main objective of this study was to evaluate the effect of P and Zn bio-fertilizers on yield, yield components and shoot nutrient elements in two cultivars of bean for the first time in the Chaharmahal-va- Bakhtiari province.
Material and Methods: This field experiment was carried out as a factorial in a randomized complete block design (RCBD) with three replications. The treatments of this research consisted of two cultivars of Chiti bean (Talash and Sadri), four levels of P (P0: Control, P1: Chemical fertilizer on the basis of soil test, P2: 50 percent of recommended P + bio-fertilizer (P), and P3: bio-fertilizer (P)), three levels of Zn (Zn0: Control, Zn1: 50 kg ha-1 Zinc sulphate, and Zn3: bio-fertilizer (Zn)). Bio-fertilizer (P) treatment consisted of mycorrhizal and five strains of Azotobacter chroococcum. Bio-fertilizer (Zn) treatment consisted of Pseudomonas aeruginosa strain MPFM and Pseudomonas fluorescent strain 187. Grain inoculation (5%) was done in shadow and after drying, inoculated grains were immediately cultivated. Two g of mycorrhizal fungus was applied at the base of the grain hole just prior to sowing. Chemical fertilizers were applied from TSP at a rate of 100 and 50 kg ha-1 in P1 and P2 respectively, 50 kg ha-1 ZnSO4.7H2O in Zn1 and 50 kg ha-1 urea as a starter before planting. The size of each plot was 3 × 4 meters. Statistical analysis was done with SAS) statistical software. Duncan’s multiple range test was used to separate means.
Results and Discussion: The results revealed that there were significant differences between the two cultivars on seed yield, number of seeds per pod, 100 seed weight and concentrations of nitrogen (N), potassium (K), and Zn, but there was no significant difference between the other parameters. P treatment showed a significant effect on the examined parameters except the number of seeds per pod. The highest content of yield (3446 kg ha-1) was observed in P2 treatment (18.5% seed yield increase). Zinc treatment also had a significant effect on the parameters being studied except the number of seed per pod and manganese (Mn) concentration. The maximum seed yield (3339 kg ha-1) was monitored in Zn1 and Zn2 treatments. The effect of interactions between P and Zn was significant on the number of pods per shrub, 100 seed weight and K concentration, but it was not significant on the other parameters. However the highest content of seed yield (3520 kg ha-1) was obtained from P2Zn1 (32.5% seed yield increase) treatment. Our results were similar to findings of other researchers (1, 3, 12, 15, 17, 26 and 30). They reported that dual inoculation increases plant productivity. In this study, phosphate and Zn bio-fertilizers caused an increase in yield, yield component and shoot nutrient by increasing nutrient uptake, photosynthesis, growth hormones and creating favorable growth conditions. Also results showed that the consume of P fertilizers were decreased (50 percent) with proper integration of chemical and bio-fertilizers. These results correspond with the results of other researchers (17, 22, 23, 24 and 27).
Conclusion: In this research proper integration of bio- and chemical fertilizers was shown to increase yield and yield components with increasing and improving P and other nutrients’ uptake in both bean cultivars. The result also indicated that combining bio and chemical phosphate fertilizers increased the efficiency of phosphate fertilizers by 50 percent. Sadri cultivar is a suitable cultivar for Chaharmahal-va- Bakhtiari province and regions with a similar climate.
Keywords: Phosphorus, Zinc, Mycorrhizal fungi, Bean (Phaseolus vulgaris L.), Insoluble phosphorus and zinc solubilizers
M.H. Davoodi; R. Rahnemaie; M.J. Malakouti
Abstract
Abstract
Phosphate is an essential element for plants, animals, and human. Mobility and availability of phosphate in the natural systems is controlled by the adsorption-desorption and dissolution-precipitation reactions. Iron (hydr)oxides including goethite play an important role in phosphate adsorption ...
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Abstract
Phosphate is an essential element for plants, animals, and human. Mobility and availability of phosphate in the natural systems is controlled by the adsorption-desorption and dissolution-precipitation reactions. Iron (hydr)oxides including goethite play an important role in phosphate adsorption reactions in soil. Surface area, crystallinity, and morphology of iron (hydr)oxides are the most important characteristics influencing phosphorus adsorption capacity. With respect to the importance of adsorption process in controlling equilibrium concentration of phosphate in soil and other natural systems, in this research phosphate adsorption reactions on goethite was investigated on three samples of goethite differed in surface area over a wide range of pH and initial phosphate concentration. The goethite charging behavior was calculated from acid-base titration in different levels of ionic strength. The experimental data were analyzed with the CD-MUSIC surface complexation model. Titration data revealed pHpzc= 9.1. Experimental data revealed that phosphate adsorption is strongly pH-dependent. Maximum phosphate adsorption was measured at low pH. It was gradually decreased with increasing pH. Adsorption data were successfully described using two inner-sphere surface complexes, i.e . and . The calculated CD values indicated that 0.28 and 0.46 vu charge is transferred to the goethite surface due to the adsorption of and , respectively. Mole fraction calculation showed that and are the dominant surface species at low and high pH, respectively. Furthermore, experimental data and model calculations revealed that surface area influence phosphate adsorption considerably; however the change in the surface area has no measurable effect on the goethite site density. Therefore, the entire experimental data were successfully predicted by using one set of adsorption parameters.
Keywords: Adsorption, Phosphate, Goethite, CD-MUSIC model, Charging behavior
