Resumen

RILLO, SERGIO; ALVAREZ, CRISTIAN; DIAZ-ZORITA, MARTIN  y  NOELLEMEYER, ELKE J. Aplicación de fósforo en secuencias agrícolas en siembra directa en hapludoles énticos. Cienc. suelo [online]. 2016, vol.34, n.2, pp.245-251. ISSN 1850-2067.

The levels of soil extractable phosphorus (P) from most of the soils in the pampas region decreased due to the extraction in intensified crops and pastures systems. Sites with limited P levels are frequent thus P fertilization is required for the enhancement of agricultural yields. Fertilization recommendations practices vary depending on the location of the applied nutrient. Our objective was to quantify the grain yield response of wheat (Triticum aestivum L), soybean [Glycine max (L) Merrill] and corn (Zea mays L) in rotation depending on the location of the fertilizer. The study was performed during 3 crop rotational cycles in 9 sites from the center part of the subhumid Pampas region with Entic Hapludolls. The treatments were: control without P fertilization and fertilized crops with 22 kg ha^-1 of P broadcasted (P_broadcasted) and in the planting furrow (P_furrow). Crop yield components, P use efficiency (PUE) and soil extractable (Bray Kurtz I) levels were yearly measured. The application of P increased 43% the wheat grain yields, 26% the corn production, 49% first crop soybean yields and 26% second crop soybean grain production. Similar crop responses to P fertilization between the 2 location treatments (P_broadcasted and P_furrow) were observed. The mean PUE was greater when the fertilizer was Pfurrow applied, mainly for corn crops. In the treatments without P fertilization, the soil extractable P levels decreased at rate of 0.4 mg kg^-1 year^-1. At the end of the study, the soil extractable contents were greater in the P fertilized treatments than in the control without fertilization. The difference varied from 2.0 mg kg^{-1 in the Pfurrow to 4.0 mg kg-1 in the P}_broadcasted. The decision about where to locate the P fertilizer requires, not only taking into account soil extractable levels but also defining the target crop and the purpose of the practices maximizing the efficacy to produce grains or to enhance the soil P contents.

Palabras clave : Dryland agriculture; Corn; Wheat; Soybean.

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