Abstract
This study was conducted in the laboratories of Soil and water resources Department, College of Agricultural Sciences Engineering, University of Baghdad for the purpose of disclosing the effect of ionic strength from different salt mixtures on the adsorption of Boron in a silty clay loam calcareous soil taken from the prior location of the college of Agriculture in Abu Ghraib, after a quite equilibrium of Boron solution prepared from Boric acid at( 0, 1, 5, 7.5, 10 and 20) μmole B.ml-1 at 298 Kalvin. Three solutions with different ionic strength were used( 0.1, 0.2, 0.3) mole.L-1 of four different salts CaCl2, MgCl2, NaCl and composed salt of the three salts at 3:1:1 ratios respectively. Langmuir single surface line equation was used for better description of the reactions of Boron adsorption in soil.Results showed a significant increase in Boron adsorbed quantity in soil with the increase of the applied Boron. The increase in ionic strength led to a significant increase in adsorbed Boron for all salts with different rates. These different salts showed significant differences in adsorbed quantity of Boron, where CaCl2 treatment was exceeded followed by MgCl2, mixture salt, then NaCl treatments as an averages of the three ionic strengths where it reached (68.95, 65.26, 58.38 and 44.37) μmole B.gm-1 soil respectively and at maximum adsorption capacity (Xm) at (58.26, 55.92, 47.90, 46.17) mg B. Kg-1 soil, while bonding energy to soil particles (K) was (0.279, 0.244, 0.244 and 0.125) ml μ B for the mentioned salts respectively. In general, soil is considered to have a high maximum adsorption capacity (42.88 mg B.Kg-1 soil) and low bonding energy (0.216 ml μ-1 B) .
Highlights
Boron is considered as one of the necessary nutrients for plant and it comes in the seventh order of the micro nutrients necessary for plant growth [18], plant uptakes this nutrients from soil solution as B4O7, BO3, HBO2, and H2BO3
Its availability depends on soil chemical and physical properties, where carbonate minerals, organic matter, soil reaction, soil salinity, and cycles of wetting and drying are affecting Boron adsorption in soil [3, 14, 19, 20]
Knowledge in Boron distribution in each liquid and solid phase of soil is important to know the range of availability and reactions that occur in soil, where the available concentrations of this nutrient in soil solution are related to adsorption and release of this nutrient on soil particles [24, 26]
Summary
Boron is considered as one of the necessary nutrients for plant and it comes in the seventh order of the micro nutrients necessary for plant growth [18], plant uptakes this nutrients from soil solution as B4O7, BO3, HBO2, and H2BO3. Its availability depends on soil chemical and physical properties, where carbonate minerals, organic matter, soil reaction, soil salinity, and cycles of wetting and drying are affecting Boron adsorption in soil [3, 14, 19, 20]. Using the adsorption isotherms curves shows the quantity of the adsorbed material on the sorbent part throughout equilibrium and fixed temperature, in a form that could be mathematically represented by Langmuir linear equation of one surface where the equation’s constants could be used to describe the adsorption characteristics of soils and determine fertilizers recommendations [8,18, 28]Keren and O’Conner [11] showed that Boron adsorption is being higher when Ca++ is available more than Na where Sodium ions lead to decrease the adsorption of Boron.
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