Adsorption – Desorption Behavior of Zinc in Soils Under Prominent Cropping Systems of Western Uttar Pradesh

Abstract

Zinc (Zn) among the nine essential micronutrients required for proper growth and development of plants. It plays important roles in carbohydrate metabolism, maintenance of cell turgidity, protein synthesis, auxin regulation and pollen formation. According to recent estimate, about 43% of Indian cultivated soils are deficient in Zn, which is playing an important role as limiting factor in crop productivity and quality of the produce. The availability of Zn depends upon various physico-chemical factors of the soil however, its recovery on its application is very low especially on the buffered soil respective to the cropping system when are cropped for the longer period. Therefore, the present study was conducted to assess the adsorption-desorption behaviour of Zn in the soils under western UP of prominent cropping system. To achieve the objectives of our study firstly, the soil were sampled from the farmers field at various locations of western UP at three different depths (0-15, 15-30 and 30-45 cm) who were practicing the specific cropping system from the last 10-12 years. The soils were analyzed for various physico-chemical properties, of which pH, organic carbon, available nitrogen, exchangeable potassium, clay content, available phosphorous, texture, cation exchange capacity and percentage calcium carbonate are the factors which affect the sorption phenomena. To understand the adsorption phenomena, four adsorption isotherms were studied (Freundlich, Langmuir, Temkin and Dubinin - Radushkevich Adsorption Isotherm). Freundlich and Langmuir both Isotherm revealed that Zn is adsorbed monolayered (sugarcane - ratoon – wheat) as well as multilayered (sugarcane - ratoon - wheat - rice). Monolayer formation of Zn depends upon the clay content while multilayered formation depends upon the silt content along with calcium carbonate and cation exchange capacity. It is evident from the Temkin Isotherm that the spontaneous bond formation takes place with the release of energy under all the soils of different cropping system however, the approach of Zn towards all the soils was physisorption instead of chemisorption.