EXTRACCIÓN SECUENCIAL Y CARACTERIZACIÓN FISICOQUÍMICA DE ÁCIDOS HÚMICOS DE DIFERENTES COMPOSTS Y SU EFECTO SOBRE EL CULTIVO DEL TRIGO

Sequential extraction and physicochemical characterization of humic acids of different composts and their effect on wheat Humic substances (HS) in a compost, as well as their physicochemical characteristics, are responsible for their quality and the response of crops to their applications. The SH extraction by a single turmoil leaves a considerable amount of these compounds in the substrate, so the sequential extractions with different reagents can separate residual SH, resulting in a more realistic estimate of the quality of the compost. The objectives of this study were to assess the extraction capacity of HS in a sequential manner in four different composts, determine the functional groups and physico-chemical parameters of humic acids (HA), and evaluate their agronomic effects on wheat growth. Composts of maize stubble (MS), wheat straw (WS), fruit residues (FR) and cattle manure (CM), with six months of humification, were used. Sequential extraction was performed with 0.5 M NaOH, 0.1 M Na4P2O7, and 0.1 M NaF, and assessed the physicochemical properties of the obtained HA. Extraction yields were 21.7 % for MS, 15.3 % for WS, 16.9 % for FR, and 19.6 % for CM. The SH of the studied composts, showed significant differences (P≤0,05) in their properties, indicating different chemical constitution. Total dry biomass of wheat was not affected by the different doses of HA applied to the soil (P>0.05) which could be attributed to the short time that the crop was under the effect those substances.