Comparing soil phosphorus extractors for different sources of phosphorus and time of application

Abstract

An experiment was held from 1978 to 1983 to know how soil phosphorus extractors compare when samples are colected at different periods after application of triple superphosphate, Mg-thermophosphate or rock phosphate from Araxá. The fertilizers were broadcasted to the soil at rates of 0 - 145 - 290 - 435 and 580 kg/ha of total P(2)0(5) and then incorporated with a heavy horrow. Each 120 days, in a period of 48 months, a composite soil sample was collected from 15 sites of each plot and analyzed for P by extraction with 0,05 N H2SO4, Bray-l and Olsen extractors. The results showed that all extractors were efficient in recovering phosphorus applied either as triple superphosphate or Mg-termophosphate; when applied as phosphate from Araxá the best result was obtained with Bray-l method. Olsen method gave the most consistent results for samples collected at different times after application of triple superphosphate or Mg-thermophosphate ; when phosphate from Araxá was applied results were most consistent whith Bray-l and Olsen extractors. At the 32nd month after application of phosphate from Araxá and thereafter it was observed a tendency for the extraction methods to be similar in respect to phosphorus extraction.