Maize for acid soils. Third scientific report - 2003 : INCO2 contract No ICA4-CT-2000-30017

The objectives for the third year of the Work Package 10 were the validation of the model for Al-H-P interactions in acid soils, while putting the emphasis on the interactions between H, Al, P and organic anions released by roots. The development of the model has been purchased in the direction of interactions between phosphate and organic anions adsorbed. The model was validated at the laboratory in relation to the associates (7.8) who have provides the numerical parameters acquired in the experiments with the field and necessary to this validation, i.e. biomass and mineral mass, growth of the roots. The final objective was a substantial contribution to the comprehension of the functioning of the rhizosphere in the acid soils and the interactions between Al-H-P. The model highlighted the particular characteristics of the soils in relation with the rate of Al dissolution, the fixation and the dissolution of P and its interaction with an organic acid excreted by the roots of maize, the citrate. The influence of the excretion of citrate on the dynamics of P is shown. However, the simulated citrate concentrations remain weak. So the incidence of the increase in the solubility of P on the mineral nutrition of this element by maize remains to be quantified. In prospect, it is necessary to note the need for studying the dynamics of slow fixing of P on the soil as well as the influence of the conditions of medium on the excretion of citrate and other organic acids. The study of citrate fixed on the soil during the cultivation must also be the object of a methodological investment related on the extraction and the analysis of the fixed element. (Résumé d'auteur