Factors Affecting Change in Soil Test Phosphorus Following Manure and Fertilizer Application

In many states, Morgan (M) or Mehlich‐3 (M3) extractions are the basis for P fertility recommendations and P runoff risk assessment. The impact of timing of sampling, P source, and extractable Al on agronomic soil test P (STP) and P release to the environment are not well understood. Incubation studies were conducted to determine: (i) changes in M‐P, M3‐P, and 0.01 M CaCl 2 –P with time following Ca(H 2 PO 4 ) 2 addition; (ii) the efficiency of...