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vol.33 issue3Phosphorus in representative soils of the state of paraíba: I- adsorption isotherms and indicators of the phosphorus capacity factorAvailability of copper and zinc in soils from southern Brazil author indexsubject indexarticles search
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Revista Brasileira de Ciência do Solo

On-line version ISSN 1806-9657


FARIAS, Daise Ribeiro de et al. Phosphorus in representative soils of the state of paraíba: II- phosphorus availability for corn plants. Rev. Bras. Ciênc. Solo [online]. 2009, vol.33, n.3, pp.633-646. ISSN 1806-9657.

The soil fertility laboratories of the State of Paraíba use only Mehlich-1 as extractant to evaluate soil available P, independently of the soil weathering degree. Since most soils of the state are less weathered than elsewhere in Brazil, the efficiency of Mehlich-1 and of other extractors to evaluate the plant P availability must be tested. The objective of this study was to evaluate the efficiency of Mehlich-1 (M-1), Mehlich-3 (M-3), Bray-1 (B-1) and mixed ion exchange resin (RTI) as extractants for the quantification of available P for corn plants in soils of the state of Paraíba. Samples of 12 representative soils of the state were collected in the 0- 30 cm layer (six with higher and six with lower weathering degree), with a wide variation of physical and chemical properties. Rates of 0; 43.75; 87.5; 175 and 350 mg dm-3 P were applied to the soils PA, PVe, LA, RL, TX, SX and RY. To the soils PAC and RR rates of 0; 37.5; 75; 150 and 300 mg dm-3 P were applied. For the soils PVA, PVd and VX the P rates were 0; 51.25; 102.5; 205 and 410 mg dm-3. The experiment was carried out in a greenhouse and the applied P rates were homogenized in 100 % of the soil volume of each pot (3 dm3). Corn plants were cultivated for 30 days and the critical P levels in the soil were determined by the extractors as well as the critical P level in the plant. Regardless of the applied P dose, M-3 extracted the most P from the soils while B-1 extracted the least. At low P doses, M-1 and RTI extracted similar P quantities, but at higher doses RTI extracted more P than M-1. Opposite to what was verified for the plant and for RTI, for the extractants M-1, M-3 and B-1 the P recovery rate was correlated with FCP. On the other hand, the critical P levels in the soil by the extractants M-1, M-3 and B-1 and the critical P levels in the plant were not correlated with soil properties that determine FCP. An opposite pattern was observed for the critical P levels in the soil by RTI. Since there was a good correlation between P extracted by the several extractants and plant P uptake, any of the evaluated extractants may be used to determine the plant P availability in representative soils Paraíba State.

Keywords : extractants; soil analysis; phosphorus capacity factor.

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