Technical Abstract: In this study we evaluated the boron (B) release from soils containing elevated native B and examined the extent to which incubation time affected B release. Five soils varying in initial pH and clay content were selected for the study. The soils were spiked with five varying doses of B as H3BO3 (0-100 mg B/kg) and equilibrated for a total of five months at field capacity water content. The soils were incubated in a temperature controlled room at 25oC. At monthly intervals, the soils were thoroughly mixed and subsamples removed. The subsamples were extracted with DTPA-sorbitol, boiling hot water, and 0.1 M NaCl to provide various B extraction protocols. Boron desorption decreased as a function of time for at least some of the extractions and treatments for all five soils. This is consistent with literature that added B becomes less extractable with increased incubation time. Comparison between the three extractants revealed no statistically significant difference in amounts of adsorbed B for three of the soils. For the two others the order of desorbed B amount was: hot-water-soluble < 0.1 M NaCl extractable < DTPA-sorbitol extractable. The decrease in B release appears to be approaching zero for all five soils for most of the extractant solutions. This indicates that a five month incubation is adequate to obtain an accurate assessment of the amount of B available for release. Since the decrease in extractable B with time is not large (except for one soil), a very good indication of extractable soil B can be obtained from a one month incubation study.