Extractors evaluation to determination of available phosphorus in soils cultivated with Brachiaria brizantha

Conduziu-se um experimento com o objetivo de determinar a disponibilidade de P em solos cultivados com Brachiaria brizantha pelos extratores Mehlich-1, Mehlich-3 e Bray-1, e de correlacionar o P absorvido e acumulado pelas plantas com o P extraído. Utilizaram-se amostras superficiais, com diferentes teores de argila, às quais foram aplicadas doses de P definidas pelos valores do P remanescente. O experimento consistiu de um fatorial 6 solos e 6 doses de P, em blocos ao acaso, com 3 repetições. O extrator Bray-1 apresentou a maior recuperação do P aplicado, e o Mehlich-1, a menor. Os níveis críticos variaram de 15,03 a 138,52mg dm-3, no primeiro corte, e de 2,07 a 62,31mg dm-3, no segundo corte. Os extratores que melhor se correlacionaram com o P absorvido e acumulado pelas plantas foram o Mehlich-1 e o Mehlich-3.Phosphorus critical levels, estimated by Mehlich-1, Mehlich-3 e Bray-1 extractors, were studied on six soils, for the cultivation of Bracharia brizantha. This research was carried out under greenhouse conditions, using surface soil samples, with different clay contents. Applied phosphorus doses were defined by the remaining phosphorus values. The experiment was conducted on six soils and six phosphorus levels full factorial, under a complete blocks design, with three replicates. Phosphorus recovery ranked in the following way: Bray-1 > Mehlich-3 > Mehlich-1. Phosphorus critical levels varied according to the buffer capacity phosphorus and extractor used: Bray-1 > Mehlich-3 > Mehlich-1 for the first cut, with values ranging from 15.03 to 138.52mg dm-3, and Mehlich-3 > Bray-1 > Mehlich-1 for the second cut, with values ranging form 2,07 to 62.31mg dm-3. The best correlated extractors to absorbed P accumulated by plants were Mehlich-1 and Mehlich-3