CARBON, NITROGEN AND HUMIC SUBSTANCES IN BIOGENIC AND PHYSICOGENIC AGGREGATES OF A SOIL WITH A 10-YEAR HISTORY OF SUCCESSIVE APPLICATIONS OF SWINE WASTE

Abstract

Applications of swine waste on the soil promote changes in soil aggregation pathways and, consequently, in the chemical attributes of these aggregates. This study aimed to evaluated the effects of different sources and amounts of swine waste on the levels of total organic carbon (TOC), total nitrogen (TN), and C and N levels of humic substances (HSs) of the biogenic and physicogenic aggregates in an Ultisol with a history of applications of swine waste for 10 years. Undisturbed soil samples were collected at the depths of 0-5 cm and 5-10 cm, in the treatments without application of waste (CONTROL), with the application of pig slurry (PS) and deep litter (DL) at doses equivalent to one and two times the nitrogen recommendation for maize and oats (PS1X, PS2X, DL1X and DL2X, respectively). The aggregates were separated according to the biogenic and physicogenic formation pathways. Subsequently, TOC, TN, as well as C and N of HSs were quantified: humin (C-HUM/N-HUM), humic acids (C-HAF/N-HAF) and fulvic acids (C-FAF/N-FAF). The application of DL increased the total C and N levels of the aggregates and of the HSs. The continuous application of swine waste have increased TOC, TN, C-HUM, C-HAF, and N-HUM in the biogenic aggregates when compared to physicogenic ones.