Mehlich 3 (M_3), Olsen, Bray 1, Bray 2, and Ammonium Acetate (AA) were compared to select an extractant both suitable for extracting P and K from acid and calcareous paddy soils in Guangdong.

• 用Mehlich 3(M_3)、Olsen、Bray 1、Bray 2和醋酸铵(AA)对广东主要水稻土的有效磷、钾进行测定比较。