Labile and stable fractions of soil organic matter under management systems and native cerrado

Abstract

SUMMARYSoil organic matter can be analyzed on the basis of the different fractions. Changes in the levels of organic matter, caused by land use, can be better understood by alterations in the different compartments. The aim of this study was to evaluate the effect of different management systems on the labile and stable organic matter of a dystrophic Red Latosol (Oxisol). The following properties were determined: total organic C and total N (TOC and TN), particulate organic C and particulate N (POC and PN), organic C and N mineral-associated (MOC and NM) and particulate organic C associated with aggregate classes (POCA). Eight treatments were used: seven with soil management systems and one with native Cerrado as a reference. The experiment was designed to study the dynamics of systems of tillage and crop rotation, alternating in time and space. The experimental design was a randomized block design with three replications. The soil samples were collected from five depths: 0-5, 5-10, 10-20, 20-30 and 30-40 cm. Changes in organic C by land use occurred mainly in the fraction of particulate organic matter (> 53 mm). Proper management of grazing promoted increased levels of particulate organic matter by association with larger aggregates (2-8 mm), demonstrating the importance of the formation of this aggregate class for C protection in pasture.Index terms: fractioning, particulate organic carbon, aggregates, no-tillage, pasture.(1) Part of the doctoral thesis of the first author, developed at the Escola de Agronomia e Engenharia de Alimentos da Universi- 0-5, 5-10, 10-20, 20-30

Soil organic matter pools under management systems in Quilombola Territory in Brazilian Cerrado

“…This behavior was also observed by Figueiredo et al (2010), who reveal that, possibly, the low LC content in native areas is due to the predominance of compounds of higher chemical stability and high molecular weight, such as lignin, under natural vegetation. These compounds are not quantified when potassium permanganate is used as the oxidation agent (Blair et al, 1995).…”

“…These compounds are not quantified when potassium permanganate is used as the oxidation agent (Blair et al, 1995). In addition, the lower proportion of C in the labile form probably explains the higher contents of TOC in areas under natural vegetation in the Cerrado biome obtained in other studies (Figueiredo et al, 2010;Leite et al, 2013).…”

“…In this context, many authors (Figueiredo et al, 2010;Fontana et al, 2011;Costa et al, 2013) have demonstrated the benefits of conservation systems such as no-tillage, croplivestock integration and organic agriculture in the reduction of losses of SOM fractions and improvement of soil quality.…”

Soil Organic Matter Fractions in Preserved and Disturbed Wetlands of the Cerrado Biome

“…In many studies, POC contents are more sensitive to changes in soil use than TOC, and agricultural areas are generally more degraded than those under native vegetation (Figueiredo et al, 2010;Salton et al, 2011). Pastures form large amounts of POC, mostly because of the extensive root system and aerial biomass of foraging plants (Franzluebbers and Stuedemann, 2002;Salton et al, 2011;Loss et al, 2012).…”

“…Although the determination of total organic carbon (TOC) content alone cannot express the changes resulting from soil use in certain situations, it is often used to quantify SOM levels and changes (Figueiredo et al, 2010). In these cases, the great diversity of SOM fractions or the relative distribution of C and N among them is not considered.…”