Resumo

CRISTIAN ANDRES, Britos Benítez1 et al. Phosphorus fertilization in no-till mechanized farming of eastern Paraguay. Investig. Agrar. [online]. 2012, vol.14, n.2, pp.87-92. ISSN 2305-0683.

No-till agriculture is increasing in Paraguay and it is necessary to adapt phosphorus fertilizer recommendations for this production system. The main objectives of this work were to determine the effect of P fertilization on wheat, corn and soybeans yields and to calibrate the soil test methodology for extracting P using the Mehlich-1 extractant. Four experiments were conducted in the Departments of Caaguazú and Amambay. The experimental design was a randomized block with split plots and three replications. Main plots were fertilized with 0, 50, 100, 200 and 400 kg P₂O₅ ha^-1 to create P levels and wheat was planted. In the summer cycle, the subplots were fertilized with 0, 40, 80 and 120 kg P₂O₅ ha^-1, and planted with soybeans and corn. Crops responded to P application and the degree of response was inversely related to P concentration in the soil at a depth of 0–10 cm. The critical soil P level was 16 mg kg^-1 in soils with 110 to 200 g clay kg^-1 and 10 mg kg^-1 in soils with 310 to 600 g clay kg^-1. On average, the dose for maximum production was 69 kg P₂O₅ ha^-1. By grouping the data of this study with those of other recent research, the critical concentration for phosphorus was set at 11.4 mg dm^-3. Our results contributed to improve P fertilizer recommendation in the Eastern Region of Paraguay.

Palavras-chave : Calibration,; fertilization,; phosphorus; no-tillage..

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