Organic and inorganic phosphorus fractions in calcareous soil from Villa Clara

Soil phosphorus (P) is an essential nutrient for plant growing, which very often appears as the main limiting element in many agricultural Systems For studying P transformations and identify the effects of soil type and land use on P distribution among the different soil P pools two soil from Villa Clara were selected: brown calcareous soil and Humus-rich calcareous soil, classified as Pardo Mullido Medianamente Lavado y Humico Calcimorfico Tipico Carbonatado, in the Cuban soil classification system (Hernandez et al., 2005) Three land uses were selected for this study: sugarcane, pasture, and woodland For P fractionation was used the methodology from Tiessen and Moir (1993), based on the bioavailability of P pools. The results showed that P distribution and its availability were influenced by management and soil properties. Plant residues and manure increased P levels in pasture and woodland areas. In general, the humus-rich calcareous soil presented higher P content than the brown one. However, in all ecosystems 60% P was retained in non-available forms. The organic P (Po) fraction represented only a 16% in the sugarcane areas, but it was 38% and 36% in the pasture and woodland areas, respectively. Even much lower than the inorganic fraction (Pi), Po constitute an important P source in both soils and it can determine the availability of this nutrient, considering that mist of Pi in non-available for plants.