03442naa a2200205 a 450000100080000000500110000800800410001910000250006024500780008526000090016330000110017252028360018365000120301965000240303165000190305565000210307470000220309570000210311777300980313815663022003-02-19       2002    bl uuuu     u00u1 u    #d1 aANDRADE, L. R. M. de  aCarbonatites as a natural nutrient source for Cerrado soil fertilization.  c2002  a10 p.   aIn the Cerrado region of Brazil, about 50 million-hectares are occupied with pastures. About 80% of these areas are under some degree of degradation, with less than 0.8 AU ha-1. This low productivity is due to low soil fertility and inadequate pasture management. Research results for this region indicate that liming and soil fertilization can increase pasture productivity and animal support capacity. With the objective of reducing the costs of pasture establishment, related with the use of chemical fertilizers, some trials have been conducted using ground rocks as alternative natural fertilizers. Carbonatite complexes found in Brazil, with hight levels of carbonates and certain levels of P and K, can be used as an alternative  natural source of fertilizer in pasture establishment. This work was carried out with the objective of evaluating the performance of carbonatite rock (CBT), as a source of P and K, for a Brachiaria ruziziensis pasture. Two experiments were established in December/1999. The soil was a clay-loam red yellow, Oxisol, with low nutrients availability. The total composition of the rock was 29.8% CaO; 10.3% MgO; 4.8% P2O5, and 1.5% K2O. The treatments consisted of Experiment 1 included seven treatments: 0; 44 and 88 kg P ha-1 as CBT and the same levels of P as TSP; 88 kg P ha-1 as CBT+13 kg P ha-1 as TSP anf finally 100 kg P ha-1 as TSP. Experiment 2 included four treatments: 0 and 50 K kg ha-1 as CBT and 50 K kg ha-1 as KCI; and an additional treatment: three applications of 16.7 kg K ha-1, as KCI - at planting, and after each cutting. Each treatment, in both experiments, was replicated four times in a randomized block design. The seeds of B. ruziziensis were sowed in December/1999. The plants were cut at the flowering stage in: April/2000, in February/2001, and May/2001. The concentration of major and miror nutrients in plant leaves and shoot dry matter were determined. Soil samples were collected and analyzed for chemical composition. Results obtained 560 days after the application of the treatments demonstrated that higher dry matter (DM) productions were achieved with 88 kg P ha-1 - TSP (24.7 t ha-1). There was no significant effect (P&lt0.05) of the CBT (88 kg P ha-1), as a P source, on DM production (8.7 t ha-1), in comparison with the treatment where there was no application of phosphate to be soil (8.7 t ha-1). However, when a small amount of soluble phosphate (13 kg P ha-1) was applied with CBT (88 kg P ha-1), there was a significant increase in the DM (14.7 t ha-1). The ccumulated P in the plant tissue in the treatments with CBT was significantly lower than in the treatments with soluble phosphate. Due to the initial K content in the soil, there were no significant differences among the tratments with or without K application, regardless of the K sources.  aCerrado  aFertilidade do Solo  aManejo do Solo  aQuímica do Solo1 aMARTINS, E. de S.1 aMENDES, I. de C.  tIn: WORLD CONGRESS OF SOIL SCIENCE, 17., 2002, Thailand. Abstracts. Thailand: [s.gn.], 2002.