The concern about soil quality has increased considerably due to environmental problems related to land degradation and demand on agricultural sustainable intensification. The current challenge in agriculture in Brazil is to maintain and advance the productive capacity of soils by using green technologies that are capable of promoting the sustainable expansion of agricultural production. Soil organic matter (SOM) plays an important role in environmental sustainability, due to contribution to biological, chemical and physical soil properties. Their main constituents are humic substances (HS) and their fractions (e.g., Humic Acids – HA, Humin). Among the different analytical techniques that could be used to characterize the humification index and chemical stability of organic materials we employed Nuclear Magnetic Resonance (NMR) and Laser Induced Fluorescence Spectroscopy (LIFS). In this work we examined SOM and HA from soils under Integrated Crop-Livestock-Forest Systems (ICLF) to establish a humification index. For this, samples of a dystrophic Red-Yellow Latosol (Oxisol) were collected from the experimental site of a research station called Embrapa Pecuária Sudeste (located in the Southeast of Brazil), five years after the implantation of the ICLF systems. Soil samples were extracted for HA following the protocol of the International Society of Humic Substances (IHSS). Also, whole soils, without any chemical treatment, were prepared for analysis by LIFS with excitation at 405 nm and emission scan from 465 nm to 800 nm. For <sup>13</sup>C NMR a multi-CP/MAS approach was employed with a 400 mHz Bruker Avance II. Results showed that the humification index, determined by LIFS in the whole soils, are directly related to <sup>13</sup>C NMR aromaticity of HA with a Pearson correlation of R =0.65 and this aromaticity was higher in ICLF area than native vegetation area. So, in these integrated systems we observed an increase in organic matter stability, a promising result in line with agricultural sustainable intensification concepts; and that the LIFS technique provides an excellent alternative for structure determination of the SOM, without the need to perform chemical fractionation of soils.

Structural evaluation of humic acids and soil organic matter from integrated crop-livestock-forest systems

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.