Distribution of Cationic Micronutrients in Some Acid Soils of West Bengal

The sporadic distribution of DTPA-extractable cationic micronutrients (Fe, Mn, Cu and Zn) in different soil layers under tarai situations of West Bengal was governed by the nature of the soil acidity. Eleven locations under three series of the order Entisols were surveyed to explore the availability of the cations under varying soil conditions and reflections thereof, if any, on the dominant forms of acidity in soils. The soils were acidic in reaction having wide variations in electrical conductivity (EC 0.01–0.21 dS m⁻¹), cation exchange capacity (CEC 1.7–7.9 cmol(p⁺)kg⁻¹), (Ca²⁺+Mg²⁺ 0.40–2.75 cmol(p⁺) kg⁻¹), organic carbon (4.32–17.52 g kg⁻¹), available phosphorus (0.89–59.4 mg kg⁻¹) and nitrogen (21.5–240 kg ha⁻¹). A gradual decrease in the extractable micronutrients with the soil depths was observed in general. Soil pH and the organic carbon made major contributions towards the variation in the extractable cations. The exchangeable Al and total acidity contributed to the variation in extractable Fe, Mn and Cu, while all forms of acidity, except non-exchangeable form, accounted for the availability of Zn. The different forms of acidity of the soils were quite comparable, although, the contribution of exchangeable acidity to the total potential acidity was low in all the soils. Hence, the availability of the cationic micronutrients varied with the soil depth and forms of acidity under the tarai situations.