The aim of this work was to study the extraction of available boron using hot water and CaCl2 5 mmol L-1, and a microwave oven as the heating device. Boron was determined using azomethine-H. The influence of some soil characteristics on the performance of the extractants, was also studied. Corn plants were grown in a greenhouse, in a completely randomized block design, using 17 soil types and 6 B rates (0.0, 0.15, 0.30, 0.60, 0.90 and 1.5 mg dm-3) in a factorial with three replications. Plant dry weight and boron concentration in the aerial part of the plant were determined. There was a similar capacity of the extractants in determining B availability. The CaCl2 solution recovered 8% more B than the hot water. Increasing the contents of free iron, clay, organic matter and the values of humidity equivalent of the soil decreased the recovering rate of B, for both extractants. Plant dry weight decreased as the B contents of the soil were above 0.1 mg dm-3 (CaCl2 extraction) and as the contents of B in the plant were above 7.8 mg dm-3.
soil analysis; boron availability; extractants