A greenhouse procedure for determining the relative B content of soils is presented. Five sunflower plants are grown in one pound of soil which receives complete nutrient soln. minus B. The criterion of its B status is the age of the culture from the planting date until the initial stages of B-deficiency symptoms become apparent. This "age value" was found to be reproducible and capable of detecting an initial addition of 9 7 of B per pound of sand. To compensate for variations in greenhouse environments, a set of quartz sand cultures receiving definite increments of B was included in each expt. Age values for soils were interpreted in relation to this calibration series. Applicability of the procedure was studied by determining the age values of a large number of soils whose B status had been detd. by field experimentation. A deficiency of B could be expected to exist in a field of alfalfa if the age values for the 0- to 12-inch and 12- to 24-inch horizons averaged less than that of the 0.3 ppm. B quartz sand culture, which, under the conditions reported in this study, was around 36 days. An excellent correlation was obtained between age values of several orchard samples and B-deficiency records on apples from these orchards. Although the age value limits may vary depending upon a number of conditions, a significant feature is the parallelism between the B contents or degree of deficiency in the field, and the age values of the corresponding soils as detd. by this procedure.