Abstract

MARINO, M. A  and  ECHEVERRIA, H. E. Diagnosis of phosphorus requirement for alfalfa (Medicago sativa L.) in argiudols. Agriscientia [online]. 2018, vol.35, n.1, pp.11-24. ISSN 1668-298X.

The aim of this work was to determine the soil Bray P critical level (CL) and to develop phosphate fertilization guidelines for alfalfa in Argiudolls soils. Results from four years' dry matter production (DM) and P response were re-analyzed. The relationship between DM relative yield (RY) and Bray P was evaluated with logarithmic, quadratic, linear-plateau, quadratic-plateau and arcsine-logarithm models (modified ALCC). The modified ALCC model fulfilled the assumption of homogeneity of variance and explained the greater percentage of variation between RY and P Bray (R²= 0.87). The CL (18.1 mg kg^-1, confidence interval between 15.8 and 20.1 mg kg^-1) coincides with those determined in other environments. Seven Bray P categories were calibrated and guidelines were designed for fertilization and refertilization according to the sufficiency, reconstruction and maintenance criteria. For 5 mg kg^-1 Bray P, the recommended superphosphate rate was 118 kg ha^-1 according to the sufficiency criterion. According to the reconstruction and maintenance criteria, the recommended P rate ranged from 160 to 248 kg ha^-1, for target production of 8 to 15 Mg MS ha^-1, respectively. This information will allow a more rational use of phosphate fertilizers in alfalfa pastures.

Keywords : Forage legume; Phosphate nutrition; Soil analysis calibration; Fertilization recommendation.

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