An approach for predicting phosphorus requirement for coffee in soils of the Colombian coffee zone. Un enfoque para predecir el requerimiento de fósforo para el café en los suelos de la zona cafetera de Colombia

Coffee crop demands phosphorus (P) during the nursery stage and vegetative growth. These requirements are commonly satisfied by applying a high dose of soluble phosphatic fertilizers, which increases production costs and causes environmental concerns. The Colombian coffee zone has a great diversity of soils with variable mineral composition and organic matter (OM) content. These conditions exhibit a long-term stability, concomitantly govern soil P availability and, hence, a standard recommendation for P fertilization may cause nutritional imbalance in the soil solution. To accurately estimate soil P-availability in Colombian coffee soils, a P-fixation (PF)-based approach using sorption isotherms technique was evaluated in five Andisols and four Inceptisols. Changes in the soil solution P concentration were monitored over time. Results showed that PF value was overestimated (> 68 %) during 36 h of equilibration; after this period, the system stabilized, providing reliable PF values. The relation between PF and applied P was assessed at a concentration of 0.2 mg L-1 (P0.2), level considered adequate in the soil solution to support maximal crop yields in different cultivated plants, was achieved by applications between 104 and 773 mg kg-1 of P in Andisols, and between 0 and 349 mg kg-1 of P in Inceptisols. OM content (OM: 7.7%), presence of non-crystalline materials, texture, and mineralogy explained the PF across soils. These finding suggest that a PF-based approach could serve as a valuable tool for developing site-specific P fertilization strategies and useful for establishing future P coffee fertilization in Colombia.