Pot experiments on the agronomic efficiency of rock phosphates. III. Determination of the readily available P content of the soil using the FeO technique and conventional methods

摘要

In a pot experiment using acid sandy soil from Nyirlugos and acid clay loam soil from Ragaly, Hungary, the conventional methods of soil P analysis were compared with the FeO technique (using impregnated strips with iron oxide) for their ability to estimate the P-supplying capacity of soils treated with five types of slow released rock phosphates from different sources or with hyperphosphate. The methods were also evaluated for pots treated with superphosphate or superphosphate + calcium carbonate. Correlations were investigated between the readily available P content of the soil, the solubility of the P content of the rock phosphates and the yield and P uptake of red clover. Results indicated that on soils treated only with rock phosphates, the P content measured using the FeO method exhibited a close correlation with that recorded using the AL, LE and H2O-P methods on acid sandy soil, while there was little correlation with the Olsen-P content. On the clay loam soil, however, the FeO-P content was most closely correlated with the Olsen P content, and exhibited the loosest correlation with H2O-P content. A joint evaluation of the soils from Ragaly and Nyirlugos for all the sources of P gave the following order for the closeness of the correlation between the readily available P content of the soil and the P uptake of red clover: FeO > LE=H2O > AL > Olsen > Bray 1. The experiments confirmed that the FeO method was less dependent on soil properties than conventional P methods, as the best correlations were observed for the FeO-P content of the soils..