Soil tests to inventory the initially available levels and to assess the fates of added P and K as bases for improved fertilizer recommendations

Abstract

Preliminary studies indicate that “quicktest”; methodology can be used to measure the individual tendencies of soils to fix (or not to fix) added P and K into plant‐unavailable forms. It appears that the fraction of added P recovered after two hours in Bray 1 or of K in 1N NH₄OAc extracts can be used for adjusting fertilizer recommendations to maximize yields. It is suggested that the reciprocals of the recovery fractions be used as multiples of the differences between sufficiency and existing levels of available P and K to obtain amounts of fertilizer P and K to apply. This method offers promise for both improving fertilizer recommendations and identifying soils of unique fixation tendencies where choice of fertilizer materials or application methodology may be most suitable. The possibility of using the new extracting solution of Mehlich to assess‐ the fate of both applied P and K in one extractant looks promising.