Eficiência agronômica de fertilizantes fosfatados fluidos e sólidos

The effectiveness of fluid (phosphoric acid and 10-30-00 colloidal suspension) and solid (monoammonium phosphate and triple superphosphate) fertilizers was evaluated in a greenhouse experiment at the Center for Nuclear Energy in Agriculture (CENA), University of Sao Paulo, Piracicaba, State of Sao Paulo, Brazil, from June to October, 1992. Corn plants were grown in pots (8 plants per pot; 3 replicates) containing 1 kg of two red-yellow latosols with different phosphorus retention capacities, for three successive cycles (30 days each). The fertilizers were applied prior to first sowing at rates of 0 (control), 70, 140 and 210 mg kg-1 of P2O5 (0, 30.6, 61.2 and 91.8 mg kg-1 of P). Plants were weighed for dry matter yield and analysed for phosphorus uptake. Indexes of agronomic efficiency and equivalent of triple superphosphate were calculated. Results showed no difference between the effects of fluid and solid phosphate fertilizers on dry matter yield and phosphorus uptake. However, the rates of phosphorus applied were significantly and positively related with dry matter yield and phosphorus uptake. In both soils, the agronomic effectiveness of fluid and solid phosphate fertilizers was equivalent.