TOTAL AND PARTICULATE CONTENTS AND VERTICAL STRATIFICATION OF ORGANIC CARBON IN AGROFORESTRY SYSTEM IN CAATINGA

Bruna De Freitas Iwata,Regis Dos Santos Braz,Luiz Fernando Carvalho Leite,Mirian Cristina Gomes Costa,Maria Letícia Stefany Monteiro Brandão

doi:10.1590/1983-21252021v34n220rc

Abstract

ABSTRACT The objective of this work was to evaluate the variation in total and particulate organic carbon contents, carbon vertical stratification, and sensitivity index of organic matter fractions in soils with organic residues arranged in alleys in an agroforestry system, with and without use of fire, in the Caatinga biome, in Brazil. The experiment was conducted in a split-plot arrangement with four replications, with the factor fire in the plots, and the factor organic residues in the subplots. The organic residues used consisted of Gliricidia sepium plants; G. sepium plants and carnauba processing residue; G. sepium plants and bio-compost; and G. sepium plants, carnauba processing residue, and bio-compost, which were evaluated in three soil layers. The alleys with carnauba processing residue, G. sepium plants, and bio-compost presented a better maintenance of particulate, and mineral-associated organic carbon contents. Thus, the agroforestry management in alleys using these three residues was efficient for the maintenance of labile and recalcitrant organic matter compartments. Particulate organic carbon was more sensitive to changes in soil management than total organic matter content, in all alleys, presenting higher sensitivity indexes.

Highlights

IntroductionStudies have shown that total soil organic matter (SOM) contents are not a sensitive indicator to evaluate agroecosystems, since small changes in total carbon are difficult to detect in a short time, partly because the soil natural variability is high
Soil managing results in important changes in organic matter contents; soil carbon stocks are quality indicators for agricultural practices, because of its correlation with soil physical, chemical, and biological attributes (NANZER et al, 2019; ARAÚJO, 2019).Studies have shown that total soil organic matter (SOM) contents are not a sensitive indicator to evaluate agroecosystems, since small changes in total carbon are difficult to detect in a short time, partly because the soil natural variability is high
The objective of this work was to evaluate the variation in total and particulate organic carbon contents, carbon vertical stratification, and sensitivity index of organic matter fractions in soils with organic residues arranged in alleys in an agroforestry system, with and without use of fire, in the Caatinga biome, in Brazil

Summary

Introduction

Studies have shown that total soil organic matter (SOM) contents are not a sensitive indicator to evaluate agroecosystems, since small changes in total carbon are difficult to detect in a short time, partly because the soil natural variability is high. Increases or decreases in carbon contents in the SOM fractions enable a better measurement of changes caused by management systems. The evaluation of different carbon compartments, mainly labile fractions, assists in understanding the dynamics of managed areas and possible paths of increasing and decreasing carbon processes (MOURA-BUENO, DALMOLIN, DIEGO, 2017). Short-time changes are detected through evaluations of the particulate fraction, which is the more labile part of the SOM, and the main cementing agent of organic matter in the soil aggregation process, mainly for macroaggregates (FERREIRA et al, 2019; MENEZES et al, 2017)

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