The soil management modifies their humic acids and the availability of heavy metals

Abstract

The agronomic management not efficient and with not very sustainable conditions induces unfavorable effects in the agro ecosystem, constituting source of entrance of pollutants and modifications of soil properties. In Cuba this information is not modernized, representing a danger for the agricultural production and the alimentary security. The objective of this work was to evaluate the effect of the management practices on properties of the acids humic and the availability of heavy metals two different management of a Nitisol soil of Mayabeque province, one with low antropic activity (natural grasses) and another of high antropic activity, dedicated to several cultivations. In the extracted humic acids they were evaluated optic coefficient E4/E6, threshold of clotting, the carboxylic, fenolic acidity and total acidity. It was also evaluated the pseudototal content of cations of metals heavy availability. The results demonstrated the effect of the management system, evidencing differences in the evaluated properties. The hydrophobicity, the level of structural condensation, the quantity of carboxylic groups and the total acidity of the humic acids diminished as consequence of the intensive cultivation, what could imply that they are affected the functions that the humic acids should exercise in the soil plant system. In that management they also registered affectations in the remaining evaluated properties, registering the biggest values for Cu²⁺, Ni²⁺, Pb²⁺ and Zn²⁺, as well as that was a superior content to the one referred as permissible maximum in several countries in the case of the Cd²⁺ and for the Nitisol soils of Cuba.