Resumo

DAZA, Martha Constanza; ALVAREZ, Javier Giovanni  e  ROJAS, Leyla Amparo. Effect of organic and inorganic materials on the phosphorus fractions of an oxisol of the Llanos Orientales (Colombia). Agron. colomb. [online]. 2006, vol.24, n.2, pp.326-333. ISSN 0120-9965.

One of the biggest problems for the fertility of the soils of the Llanos Orientales is the high fixation of phosphorus caused mainly by compounds presented in their clay fraction. The use of mixtures of organic materials and minerals can help to reduce this fixation, for that two organic materials (chicken manure and compost) and two inorganic materials (lime and super phosphate triple) were used. A total of thirteen treatments prepared at random blocks and composed by the different combinations among mineral and organic fertilizers were used. The measure of the fractions of P was made at the moment of the crop establishment and 10 weeks later, using the sequence proposed by Hedley. Response variables in the experiment were the available P, biologically available P, organic P easily mineralizable, inorganic P linked to oxides of Fe y Al, organic P linked to humic substances, inorganic P linked to calcium, and the non-available P. The highest values in all fractions of P corresponded to the treatments that combined an organic material and a mineral fertilizer improving the availability of P for the plants. The use of organic materials with mineral sources diminished the retention of P on the part of iron and aluminum oxides increasing the available P in soil and total phosphorus. It was not possible to modify the initial and final quantity of non-available P, neither found significant differences among treatments in this fraction.

Palavras-chave : oxisol; chicken manure; phosphorus; compost; Llanos Orientales.

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