P in Missouri Subsoils

Soil samples to a 3-foot depth show that the subsoil is a greater reservoir of P than the topsoil over most of Missouri.

Current University of Missouri fertilizer recommendations have a target level of 45 lb P/acre (22 ppm P) measured with the Bray 1 test. Measurements of Bray 1 P in 180 deep soil samples across Missouri shows that the subsoil often contains more than three times this much P in eastern Missouri, with levels declining toward the west.