Resumo

SUBERO, Neudis; RAMIREZ, Ricardo; SEQUERA, Omaira  e  PARRA, Julio C. Fractions of phosphorus in soils cultivated with rice for long periods: II. Organic-inorganic phosphorus relationship. Bioagro [online]. 2016, vol.28, n.2, pp.81-86. ISSN 1316-3361.

Rice production in the irrigation system of Guarico River in Venezuela dates back more than 50 years, during which phosphate fertilizer has been applied continuously. The residual fractions of organic phosphorus were studied in 43 soil samples, fertilized between 5 and 50 continuous years. A sequential P extraction procedure was carried out in each soil sample. Data of inorganic P were reported in a previous paper. Total organic P (PoT) was approximately 4.3 times lower than total inorganic P (PiT); however, between 50.6 and 84.7 % of P labile corresponded to organic P. On the contrary, moderately and slightly labile organic fractions (PoLL and PoML) were less abundant than the corresponding inorganic fractions (PiML and PiLL). The organic matter content of the soils showed a significant positive linear relationship with the PoML, but a lower relationship with PoLL and occluded Po.

Palavras-chave : Labile phosphorus; occluded phosphorus; organic matter.

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