Accumulation of humic substances in an Oxisol fertilized with pig slurry for 15 years

ABSTRACT The growth of swine production in Brazil has increased the amount and use pig slurry (PS) as soil fertilizer. This product provides nutrients to plants, a continuous application this residue usually increases total organic carbon (SOC) content. objective study was determine SOC content its distribution into humic substance fractions (humic acids, fulvic humin) an Oxisol annually fertilized with PS for 15 years. experiment implemented 2001 maize oat crop rotation under no-tillage system Campos Novos, SC, Brazil. treatments used were: at rates 0 (Control), 25, 50, 100, 200 m3 ha-1 year-1, mineral fertilizer, combined applied on surface once year. 0-2.5, 2.5-5, 5-10, 10-20, 20-40, 40-60 cm layers were evaluated acid, humin, E4/E6 ratio substances. Increases up 100 5-10 layer; however, decreased proportion acid fractions, favoring accumulation humin fraction. higher when using fertilizer than that found PS.