Availability of phosphorus in soil and straw in successive tropical grasses crop fertilized with different phosphates

Objective: The aim of this study was to evaluate the availability of P in soil and straw during successive tropical grasses crop fertilized with different phosphates. The crops were grown in 18 dm-3 pots for 50 days. Methodology: The experimental design was completely randomized, using a 4x4 factorial design with four replication. The experimental trataments were Urochloa brizantha, Urochloa ruziziensis, Urochloa decumbent and Pennisetum glaucum and those grasses were fertilized with 0 (control) e 100 mg P kg-1 with triple superphosphate, Arad rock phosphate and Alvorada rock phosphate. Results: The pots were subjected to seven cycles of growing plants and the phosphate fertilizers were applied only in the first cycle. If the goal is fast response and high agronomic efficiency, the best alternative is to use triple superphosphate associated with pear millet. If the intention is to increase P labile of soil in the long term, the best option is the arad phosphate rock, which can be management with the U. brizantha , U. decumbens, U. ruziziensis or Pennisetum glaucum. Conclusion: The Alvorada rock phosphate does not have satisfactory performance but the agronomic efficiency of this source of P can be increased if it is associated with U. decumbens.