Soil and wheat plant samples were collected during 2009–10 from a long-term experiment that continued since 1971–72 on a Typic Haplustept at Indian Agricultural Research Institute, New Delhi, to study the distribution of native soil boron (B) in different fractions and their contributions towards B availability and uptake by wheat. Treatments included N alone, NP, NPK, 150% of recommended NPK, NPK+farmyard manure (FYM) and an unfertilized control. Five soil B fractions were determined along with hot CaCl2-extractable (available) B. Readily soluble, specifically adsorbed and organically bound B fractions were significantly greater under continuous use of NPK+FYM compared with other treatments, resulting in higher values of available B in NPK+FYM treatment. Soil organic C and cation exchange capacity were the important soil characteristics that governed the distribution of soil B in different fractions. Organically bound and specifically adsorbed B appeared pivotal regarding the availability of native B for plant uptake.
Soil B fractions, B uptake, wheat, long-term experiment, Inceptisol
