Pot culture experiment was conducted by using bulk soil samples collected from twenty different sites of Kumoun region of Uttarakhand (India). The critical limit of boron (B) for soil and Brassica napus plant was determined. Five treatments consisting of five different levels of B with two replicated pots in each type of soil were imposed with common recommended levels of N, P and K in respective sets of pots. Five soil test methods were evaluated for response of Brassica napus to boron application and the suitability of the extractant was in the order: Mehlich 3> Hot-water > 0.05 M HCl > 0.01 M CaCl2 + 0.05 M mannitol > 0.01 M CaCl2 on the basis of highest degree of correlation with Bray's per cent yield. Therefore, hot-water, 0.05 M HCl and Mehlich 3 extractants could be used as an index of available boron for B. napus grown on soils of Kumoun region. The critical level being 0.37, 0.79 and 7.73 mg kg-1 B in the soil on the basis of hot-water, 0.05 M HCl and Mehlich-3 extractants. The critical limit of boron in B. napus at 40 days was 23.19 mg B kg-1 dry plant tissue.