Fig. 3. The Mehlich-3 extractable soil P of a mixture of 5 g of 0- to 5-cm and 15 g of 5- to 20-cm depth samples (i.e., 1:3 ratio) as a function of the weighted mean of Mehlich-3 P of 0- to 5-cm and 15 g of 5- to 20-cm depth samples for the 18 Oklahoma and Pennsylvania profiles.