Resumo

SILVA ROSSI, M. M.; ROLLAN, A. A.  e  BACHMEIER, O. A.. Phosphorus bioavailability in a soil of the south of Santa Fe (Argentina): Effects of two phosphate sources and their mixtures with urea. Agriscientia [online]. 2006, vol.23, n.2, pp.91-97. ISSN 1668-298X.

The aims of this work were: i) to determine to what extent the phosphorus sources and the mixtures with urea affect P bioavailability, ii) to test interaction of urea/phosphate- source effects, and iii) to test the effect of urea on the native P of the soil . The experiment was performed in a Santa Isabel Typic Hapludoll (soil organic matter: 29 g kg^-1; pH: 6.1; extractable P: 12.4 mg kg^-1; and total P: 446 mg kg^-1; CBM 35.8 L kg^-1). Fertilization assays of wheat with two phosphate sources were carried out: monoammonium phosphate and diammonium phosphate in rates of 0. 9 and 17 kg P/ha, in physical mixtures with urea in rates of 0. 19 and 37 kg N/ha. It was concluded that in the soil tested, the use of urea causes no effects on the native phosphorus in the application band. Besides, the availability of the applied phosphorus varies with the dose and phosphate source used: the application of monoammonium phosphate increases the bioavailability of the nutrient in this soil, in relation to the same rates of diammonium phosphate. When compared to pure phosphate applications, the use of mixtures of phosphate fertilizers with low doses of urea increases the bioavailability of the nutrient for wheat.

Palavras-chave : Fertilization; Wheat; Hapludoll; N/P interaction.

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