Ramírez-Avila, John J.

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    Transporte de sedimentos y fósforo en escorrentía bajo simulación de lluvia
    (2005) Ramírez-Avila, John J.; Sotomayor-Ramírez, David; College of Agricultural Sciences; Martínez Rodríguez, Gustavo A.; Pérez Alegría, Luis R.; Department of Crops and Agro-Environmental Sciences; Segarra García, Rafael
    Phosphorus (P) in runoff from agricultural soils is an important contributor to surface water eutrophication. To quantify P losses from organic (poultry litter [PL]) and inorganic (triple superphosphate [TSP]) P amended soils, the relationship between runoff P and Olsen and Bray I soil test P (STP) in two geographic zones in Puerto Rico was evaluated, using simulated rainfall. The soils were an Ultisol-Oxisol complex with nativized pastures in Mayagüez and an Ultisol with grass cover (Brachiaria Decumbens) in Corozal. The dissolved P fraction (DP) corresponded to 80% of total P (TP) concentrations in runoff Mayagüez, while in Corozal DP represented between 32 and 35% of TP concentrations in runoff in TSP and PL amended soils, respectively. Topography and groundcover variability between two areas was an incidental factor on the DP/TP ratios observed. The TP and DP concentrations in runoff increased with STP following an exponential model. Organic residues in surface soil and plant material increased P losses and concentrations in PL amended soils. Runoff P fractions and concentrations were reduced with increases in runoff volume and antecedent soil moisture. Environmental critical STP levels under inorganic amended soils, calculated based on a 1 mg L-1 DP threshold were between 176 and 184 mg kg-1 Olsen P and 206 mg kg-1 for Bray I P, respectively. In organic amended soils it threshold values were 88 and 111 mg kg-1 Olsen and Bray I, respectively.