Comparison of conventional methods with Haney H3A version 4 for available phosphorus and potassium in southern Manitoba soils.

The H3A-4 extraction is a new method to determine plant available nutrients but has not been compared with standard soil tests or calibrated to crop response in Manitoba, Canada. Olsen P and ammonium acetate K were related to H3A-4 P and K for 961 soil samples. Significant relations were found between Olsen P and H3A-4 (R² = 0.74, P < 0.01) and ammonium acetate K and H3A-4 (R² = 0.83, P < 0.01). New thresholds were established for fertilizer recommendations with H3A-4 as 24 mg kg^–1 for P and 32 mg kg^–1 for K. [ABSTRACT FROM AUTHOR]