J.C. Joardar*
Soil, Water and Environment Discipline, Khulna University, Khulna-9208, Bangladesh
S. Sikder
Soil, Water and Environment Discipline, Khulna University, Khulna-9208, Bangladesh
S.B. Hasib
Soil, Water and Environment Discipline, Khulna University, Khulna-9208, Bangladesh
Calcareous soil, Phosphorus, Sorption
Agricultural field at Gutudia of Dumuria upazilla, Khulna
Crop-Soil-Water Management
Physico-Chemical
The experiment was conducted in the laboratory of Soil, Water and Environment discipline, Khulna University, Bangladesh.
General information about soil sampling sites Soil samples were collected from the agricultural field at Gutudia of Dumuriaupazilla, Khulna. Calcareous soil belongs to Dumuria soil series and noncalcareous soil belongs to Barisal soil series. The land type is medium high land for both soils. The lands are mainly used for rice cultivation.
Collection and preparation of soil samples Both soils were collected at a depth of 0-15 cm on the basis of the composite sampling method. Field identification method was used to identify calcareous and non-calcareous soils. The emergence of effervescence or fizzing after placing few drops of dilute hydrochloric acid (10% HCl) indicated the presence of free CaCO3 in soil. After that, the collected soil samples were air-dried and the larger aggregates were broken gently by crushing with a wooden hammer and passed through a 0.5-mm sieve and the samples were preserved in plastic bags for experiment and analysis.
Soil analysis Particle size analysis of the soils was done by the combination of sieving and hydrometer method as described by Gee and Bauder (1986). Textural classes were determined by Marshall’s triangular coordinate system by the respective percentage of soil separates (Brady and Weil, 2002). Soil pH, EC and total P were determined by following the procedure (Huq and Alam, 2005).
P sorption studies Equilibration procedure Both calcareous and non-calcareous soils were used for this experiment. Triplicate 1.0g soil sample was weighed into a series of 50-ml polyethylene centrifuge tubes. Twenty five (25) ml each of P solution, containing 0, 2.5, 5.0, 10.0, 20.0 and 50.0 μg P ml-1 , were added to the tubes. The pH of the soil suspensions was adjusted to 6.0 with 0.1M HCl or 0.1M NaOH. The amount of HCl or NaOH added for adjusting pH was taken into account in calculating the total volume of the equilibrating solution. The reason for choosing pH 6.0 in this experiment was that adsorption isotherms have been reported to be better defined at this pH than at other pH levels (Shuman, 1975). The tubes were shaken on a reciprocating shaker for two hours and were allowed to equilibrate at room temperature for 6, 12, 24 and 48 hours. Immediately following the equilibration period, the suspensions were centrifuged and filtered. The filtrates were analyzed for P by spectrophotometry.
Statistical analysis The results were expressed as the average of four replications. The data was subjected to ANOVA using computer built-in statistical software program Minitab– 16. Differences between means were statistically analyzed using the Fisher method (p=0.05). Graphs were prepared by using a computer built-in Microsoft Excel–2010 program.
SAARC J. Agric., 17(2): 117-126 (2019)
Journal