Management of boron (B) in soils can be difficult since a narrow range exis
ts between plant deficiency and toxicity. A greenhouse study was conducted
to evaluate the effectiveness of four soil-applied B fertilizers varying in
solubility (Granubor, Hydroboracite, Ulexite, and Colemanite) in supplying
B to alfalfa (Medicago sativa L.). Boron was incorporated at rates of 0, 1
, or 2 mg B kg(-1) into Norfolk (fine-loamy, kaolinitic, thermic, Typic Kan
diudults) or a Cecil (fine, kaolinitic, thermic Typic Kanhapludults) soil a
nd planted with alfalfa. After establishment, shoots were harvested four ti
mes at approximately five-week intervals and analyzed for dry matter and B.
Following the last harvest, soil samples were taken and analyzed for Mehli
ch-1 extractable B. There was no effect of fertilizer material, application
rate, or their interaction on the dry weight of alfalfa. Boron concentrati
ons in alfalfa did not significantly decline with each successive cutting,
indicating that a sufficient amount was applied for the duration of the stu
dy. In the first cutting, plants grown with Granubor and Ulexite had higher
concentrations of B than those with Hydroboracite, which was in turn highe
r than Colemanite, reflecting differences in solubility. However, by the th
ird and fourth cuttings, there were no significant differences in tissue B
concentrations among the four fertilizer sources. This indicates that given
adequate time, even less-soluble fertilizer sources may provide sufficient
B to growing plants.