Resumen

PEREZ, M.J.. Efficiency of some leguminous crops to use P from phosphate rock. Rev. Fac. Agron. [online]. 2007, vol.24, n.1, pp.113-132. ISSN 0378-7818.

Nodule leguminous plants receive most of their N from N₂ fixation. Therefore, excess of cations could occur with a consequent rizosphere acidification and the phosphate rocks dissolution (PRs). The objective of this study was to compare the accumulation cations pattern among six leguminous crops types: cowpea (Vigna ungiculata cv. Tuy), pigeon pea (Cajanus cajan cv. Arorita), Soybean (Glycine max cv. Cristalina), Stylosanthes (Stylosanthes guianensis), Crotalaria (Crotalaria juncea), and Indigo (Indigosfera lespedeciode), and its relationship with the legumes efficiency to use P from Riecito phosphate rock (RPR). A green house experiment was carried out by using an acid Ultisol (pH 5.0), deficient in P (5.0 mg.kg^-1) and Ca (0.26 cmol.kg^-1). An experimental design of divided plot was used, in where the legume type represented the main plot and P treatments the subplot. Treatments consisted of applying 0, 25, 50 and 75 mg.kg^-1 of soluble P in neutral ammonium citrate, from Riecito phosphate rock (RFR). In plant, aerial dry material, nodule fresh weight, total N, cations sum (Ca²⁺, Mg²⁺, K⁺ and Na⁺) and anions (H₂PO₄^- and SO₄^2-) in aerial biomass, were determined. In soil, pH, exchangeable Ca and P availability, were determined. Crop's efficiency to use P from RPR had the following decreasing order: Indigo ³ Cow pea > Stylosanthes > Soybean ³ Crotalaria ³ Pigeon pea. Higher efficiency of Indigo, Cowpea and Stylosanthes to use P from RFR was associated with a high accumulation of Ca, total N and a cations excess in these legumes compared to Soybean, Crotalaria and Pigeon pea. Relative values of Ca and cations excess accumulated in plant, could serve as indicators to select crops by their efficiency to use P from phosphate rocks of medium-high reactivity such as RPR.

Palabras clave : legumes; P use efficiency; available P; phosphate rocks; N2 fixation.