Phosphorous availability in Argisols and sufficiency range in sugarcane in the Northeast of Brazil

Resumo

Phosphorous is a limiting nutrient in sugarcane cultivated in Argisols in the Northeast of Brazil, and understanding its availability in the soil, as well as determining sufficiency ranges in the plants is essential when recommending levels of phosphorus fertiliser. The aim of this study was to: (i) Define classes for interpreting P availability in Argisols of the Northeast using the Mehlich-1 and Anion Exchange Resin (AER) extractors; (ii) Evaluate P extraction by the same extractors; and (iii) Correlate the P content of the soil with the P content of the plants, and establish sufficiency ranges in the plants. Three field trials were carried out in a sandy (PVAd₁), medium (PAdx) and clayey (PVAd₂) Argisol, applying the following amounts of P: 0, 40, 80, 120, 160 and 200 kg ha^-1 P₂O₅. The AER extracted more P than did Mehlich-1 from each of the soils. The P content of the classes for interpreting P availability determined by the AER were higher than those determined by Mehlich-1. AER was the best extractor to represent P availability in the Argisol with the clayey texture (PVAd₂), and Mehlich-1 in the Argisol with the sandy texture (PVAd₁). The ranges of P sufficiency in the leaves of the sugarcane varied between soils, with values of 0.66-0.73 g kg^-1 in PVAd₁, 0.59-0.69 g kg^-1 in PVAd₂ and 0.34-0.47 g kg^-1 in PAdx. As such, the texture of Argisols cultivated with sugarcane in the Northeast of Brazil should be a criterion for choosing the P extractor used in assessing its availability.