Distribution variability of total and extractable zinc in cultivated acid soils of India and their relationship with some selected soil properties

Incidence of zinc (Zn) deficiency in soils and plants has been reported worldwide including India. The present study was conducted to assess the distribution pattern and variability of total and extractable Zn in cultivated acid soils of India. A total of 400 representative surface (0–15 cm) soil samples were collected from cultivated soils representing four (100 each) soil series namely Hariharapur, Debatoli, Rajpora and Neeleswaram situated in Orissa, Jharkhand, Himachal Pradesh and Kerala state of India respectively. The status of total and extractable Zn in soils and other soil properties like pH, electrical conductivity (EC), organic carbon (OC) content, neutral normal ammonium acetate extractable potassium (K), calcium (Ca) and magnesium (Mg) were assessed. Results revealed that concentrations of total as well as extractable Zn varied widely among the acids soils and the amount of Zn extracted by different extractants also differed. Zn deficiency was observed in 7 to 82% soil and 2 to 57% soils based on the diethylenetriaminepentaacaeticacid (DTPA) extractable Zn and 0.1 M hydrochloric acid (HCl) extractable Zn respectively. Correlation analysis revealed that the extracted Zn by DTPA, Mehlich 1, Mehlich 3, 0.1 N HCl and ammonium bicarbonate DTPA (ABDTPA) extractants was significantly correlated. The contribution of soil organic carbon (OC) content towards total and DTPA-Zn was higher as compared to soil pH. Geostatistical analysis revealed that total and DTPA-Zn concentrations in acid soils of India were influenced by different sets of environmental factors. Spatial distribution maps of total and DTPA-Zn in soil indicated their differential distribution pattern.

Research Highlights
► Concentration of total as well as extractable Zn varied widely among the acids soils and the amount of Zn extracted by different extractants also differed.
► Correlation analysis revealed that the trend of extraction of zinc by DTPA, Mehlich 1, Mehlich 3, 0.1 N HCl and ABDTPA extractants used for this investigation, was similar indicating their useful for the extractions of the Zn in acid soils.
► Soil pH as well as soil organic carbon content were positively correlated with the DTPA extractable Zn and total Zn content in soil; however contribution of soil organic carbon towards extractable Zn was higher as compared to soil pH.
► Total and DTPA-Zn in acid soils of India had wide variability in spatial distribution pattern and were differentially influenced by the environmental factors.