Assessing Suitability of Different Extractants for Estimating Plant Available Boron in Lateritic Soils (Alfisols)

The depth-wise distribution of plant available boron (B) extracted by dilute HCl (HCl), tartaric acid (TA), hot calcium chloride (HCC), hot water (HW), ammonium acetate (AA), Ammonium Bicarbonate-Diethylene Triamine Penta Acetic acid (AB-DTPA) and mannitol calcium chloride (MCC) in some acidic lateritic soils (Alfisols) of Birbhum, West Bengal, India, was examined in relation to their physicochemical properties and grain yield, concentration and removal of B by rice grain to screen out the most suitable extractant for lateritic soils. The highest overall mean B concentration of surface soils (0.325 mg kg(-1)) was obtained by 0.05 M HCl, whereas its lowest content was obtained by MCC (0.145 mg kg(-1)) and with increasing depth its content was decreased for all the extractants used. The sequence of B extraction by various extractants was as follows: HCl > TA > HCC > HW > AA > AB-DTPA > MCC. Higher extractability of HCl is due to lower pH and attendant dissolution of soil minerals. Most often, decrease in organic carbon, clay, CEC, amorphous iron and aluminum oxides or increase in manganese oxide contributed to the observed drop in B along soil depth. The B extracted by different extractants showed significant positive correlations among themselves. The HCl extracted B showed the highest correlation with grain yield, concentration, and removal of B by rice grain. The HCl extractable B enhanced adjusted R2 value in multiple regression equation, boosting the predictability of the model. Thus, in acidic lateritic soils (Alfisols), the 0.05 M HCl is the best extract for estimating plant available B.