EXTRACCIÓN SECUENCIAL Y CARACTERIZACIÓN FISICOQUÍMICA DE ÁCIDOS HÚMICOS EN DIFERENTES COMPOST Y EL EFECTO SOBRE TRIGO* SEQUENTIAL EXTRACTION AND PHYSICOCHEMICAL CHARACTERIZATION OF HUMIC ACIDS IN DIFFERENT COMPOST AND THE EFFECT ON WHEAT

The physiochemical characteristics of the humic substances contained in compost are accountable for the soil properties and the response of crops to their application. The extraction of humic substances with a single turmoil leaves considerable amounts of compounds in the substrate, and therefore sequential extractions with different reagents separate the residual humic substances, resulting in a real estimation of the quality of the compost in agricultural management. The aims of this work were: a) to sequentially remove the humic substances of four composts using three solutions; b) to determine the functional carboxylic, phenolic and oxidrylic groups of humic acids contained in the compost; c) to determine the physiochemical parameters C/N, CIC, pH, ΔpH and E4/E6; and d) to evaluate the agronomic effects of humid substances on wheat growth. Compost with six months of humification was used, made from maize stubble, wheat hay, fruit waste and bovine manure; the sequential extraction was carried out with NaOH 0.5M, Na4P2O7 0.1M and NaF 0.1M, and its physical and chemical properties were evaluated. The yields obtained were 21.73% for maize stubble, 15.3% for wheat hay, 19.62% for bovine manure and 16.89% for fruit waste. The humic substances studied of the compost displayed significant differences in their properties, which indicate different molecules. The yields