Zinc Sorption Behavior in Soils with Divergent Characteristics

Adsorption studies are important to determine the retention and release of applied plant nutrients and the efficiency of fertilization. The present study was conducted to delineate the zinc (Zn) adsorption behavior of soils with varying characteristics. In this study, adsorption behavior of Zn was studied at varying Zn concentrations and temperatures in three different soils collected from the Research Farm of Indian Agricultural Research Institute (IARI), New Delhi (Inceptisols, Typic Haplustepts), soil (Inceptisols, Typic Ustocrept) from a farmer's field in Shamgarh, Karnal, Harayana, and the Hayathnagar Research Farm of Central Research Institute For Dryland Agriculture (CRIDA), Hyderabad, (Haplustalf). The results of this study revealed that the adsorption of Zn as well as differential buffering capacity (DBC) was greater in Typic Haplustepts of IARI and Typic Ustocrept of Karnal than Haplustalf of CRIDA, Hyderabad. However, the supply power as well as percentage saturation (% sat.) was greater in Haplustalf of CRIDA, Hyderabad, than Typic Haplustepts of IARI and Typic Ustocrept of Karnal The results also revealed that irrespective of the soil types, Zn adsorption increased with an increase in Zn concentration and increase in temperature from 20 °C to 35 °C. When the adsorption data were fitted to isotherms, Langmuir and Freundlich isotherm fits were excellent, as evidenced by high r 2 (0.71 to 0.99) values. Thermodynamic parameters such as standard free energy (ΔG) were negative in both Typic Haplustepts and Typic Ustocrept soils, indicating spontaneous Zn adsorption reaction, but nonspontaneous reaction was observed in the case of Haplustalf soils.. Interestingly, both standard enthalpy (ΔH) and standard entropy (ΔS) were negative in all the three types of soils studies. The analogy and results of the present study would be useful in deciding the Zn fertilizer needs for a given soil type.