Time-dependent phosphorus extractability from soils treated with different fertilizer phosphorus sources
2004
Indiati, R. | Neri, U.
Effect of application of different fertilizer phosphorus (P) sources (diammonium phosphate-DAP, single super phosphate-SSP, phosphate rock-PR, partially acidulated phosphate rock-PAPR, basic slag phosphate-BSP, and humo phosphate-HP), and time (up to three years of soil-fertilizer P equilibration) on soil extractable P was studied on two representative Italian soils, principally differing in pH values and the capacity to retain P. Phosphorus extractability was measured by seven chemical and two nonconventional soil P test methods based on the use of anion exchange resin membranes and iron oxide coated paper strips. The increases in the amount of extracted P following soil P fertilization were practically in the same order for both Ravenna and Paliano soils: DAP > SSP > HP > BSP > PAPR > PR; that order reflecting the corresponding scale of P water solubility. More P tended, however, to be dissolved from PR treatment in more acidic soil. On an average, the effectiveness of the different soil P test procedures in extracting P from two soils was in the order: Egner-P > Bray2-P > Olsen-P > Mehlich3-P > resin-P > iron oxide-strip-P > Bray1-P > water-P > CaCl2-P. The Egner soil P test method appeared to overestimate P bioavailability of all P treatments in the calcareous soil, while both the Egner and Bray2 soil tests overestimated the amount of extractable P of the PR treatment in the other soil. Data of P extracted by the Olsen and Mehlich3 procedures resulted the most closely correlated with the corresponding data obtained with the nonconventional soil P test procedures, currently considered with potential for use in widely ranging soils fertilized with water soluble as well as water insoluble P fertilizers.
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