INORGANIC LEAF PHOSPHORUS AND SOIL TESTS AS INDICATORS OF PHOSPHORUS-NUTRITION IN CEREALS

A plant extraction method, which measures the inorganic phosphorus (Pi) in leaves, and four different soil testing methods were studied as indicators of phosphorus availability. Analytical values were compared with the yield responses and P uptakes of pot-grown barley and oats. The inorganic leaf phosporus test was a sensitive indicator for P availability. This simple plant extraction method appeared to be at least as reliable as the best soil tests. of the four soil tests studied, the water extraction test (Pw) was the most accurate method for mineral soils, but the water method as well as its modification with CaCl2 addition (P-Cl) gave overly high relative values for acid organic soils. The acid ammonium acetate test (P-AAc) which is currently used in Finland, indicated excessively high P availabilities in strongly acid mineral soils, and gave erroneously low relative values in clay soils. The acid ammonium acetate EDTA method (P-EDTA), which is used for micronutrients and could possibly serve as a universal extraction method, was found to be inferior to the other tests studied. © 1990, Taylor & Francis Group, LLC. All rights reserved.