Soil properties influence distribution of extractable boron in soil profile

Depth distribution of boron (B) extractable by hot calcium chloride (HCC), potassium dihydrogen phosphate (PDP), and tartaric acid (TA) in some typical B-deficient Inceptisols, Entisols, and Alfisols in relation to soil properties was studied. The magnitude of B extraction followed the order HCC > PDP > TA for Inceptisols, TA > HCC > PDP for Entisols, and PDP > HCC > TA for Alfisols and showed a decrease along soil depth. The low pH of TA and effective desorption of B by phosphate of PDP are attributed to their higher efficiency in extracting B in Entisols and Alfisols, respectively. A decrease in organic carbon (C), clay, and amorphous iron oxide content was responsible for the observed decrease in extractable B along depth of soil profile. The HCC showed more efficiency than PDP and TA for extracting B in soils high in organic C. Multiple regression equations explained only 21, 57, and 59% of the variability in PDP-, HCC-, and TA-extractable B content in soils by the soil properties analyzed, of which organic C and clay were the most important. There were dynamic equilibria among the amount of B extracted by the extractants, indicating B extraction by them from more or less similar pools in the soils.