Resumen

FERNANDEZ, Shirley M  y  MEZA, Carlos A. Residual effect of acidulated or burnt Riecito phosphoric rock on maize grown in soils with variable levels of calcium. Bioagro [online]. 2004, vol.16, n.2, pp.93-98. ISSN 1316-3361.

With the purpose of evaluating the residual effect of phosphoric rock from Riecito (Venezuela) treated with vinaza or high temperatures, three successive crops of corn, used as indicative plant, were grown in an acid soil (pH 3.7) whitewashed up to pH 5.7 and 6.8. The treatments consisted in the use of: a) rock of Riecito natural (RFN), b) rock burnt at 900 ºC for 7 hours (RFC), c) acidulated rock with vinaza in proportion 1/1 (RFV), d) amoniacal phosphate (FMA), and e) a control without phosphorus (Te). The dose of phosphorus applied was 300 mg·kg^-1. The plants were harvested 30 days after planting to determine their dry biomass. For the acid soil, in the first crop, the treatment RFV produced values of dry biomass comparable to the FMA, in the second crop the treatments RFV, RFC and RFN presented a similar behavior to the FMA; for the third crop the RFC was able to overcome the FMA. The control always showed the lowest values. In the soil with pH 5.7 the sources RFV, RFC and RFN showed an inferior residual effect to the one found in the soil pH with 3.7. In the soil pH with 6.8 the FMA overcame all the other sources. The results suggest that the acidification of the phosphoric rock with vinaza or burning at high temperatures increases its solubility, when the soil pH is less than 5.7.

Palabras clave : Water heater-phosphate; phosphorus; acid soil; biomass.