Physicogenic and biogenic aggregates under different management systems in the Cerrado region, Brazil

Pinto, Luiz Alberto da Silva Rodrigues; Torres, José Luiz Rodrigues; Morais, Igor de Sousa; Ferreira, Robert; Silva Júnior, Wanderson Farias da; Lima, Sandra de Santana; Beutler, Sidinei Júlio; Pereira, Marcos Gervasio

doi:10.36783/18069657rbcs20200114

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Division – Soil Use and Management, Commission – Soil and Water Management and Conservation • Rev. Bras. Ciênc. Solo 45 • 2021 • https://doi.org/10.36783/18069657rbcs20200114 copy

Physicogenic and biogenic aggregates under different management systems in the Cerrado region, Brazil

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

An important strategy for the sustainable management of Cerrado soils is no-till (NT) systems, which may improve soil properties, particularly aggregation. Soil aggregates can be categorized according to their formation pathways into physicogenic (Phy) and biogenic (Bio). This study aimed (i) to quantify the relative proportion of physicogenic and biogenic aggregates and (ii) evaluate the levels of total organic carbon and their respective humic and physical fractions in the aggregates’ formation pathways. The following managed and unmanaged sites were evaluated: a 6-year no-till site (6NT), an 18-year no-till site (18NT), a conventional tillage site (CT), and a reference Cerrado site (RS). Retained aggregates were analyzed morphologically, separated into Phy and Bio, and quantified. Subsequently, aggregates were subjected to total organic carbon (TOC) determination, fulvic acid carbon, humic acid carbon, humin carbon, particulate organic carbon (POC), mineral-associated organic carbon, and free light fraction carbon (FLFC). The proportion of Bio aggregates increased with decreasing management intensity. When TOC and humic acid carbon levels were compared between sites, it was found that Bio aggregates from 18NT and 6NT contained higher carbon content than Bio aggregates from CT. Particulate organic carbon and FLFC differed between aggregate types, with higher POC values observed in Bio aggregates from CT and 18NT and higher FLFC values in Bio aggregates from CT, 6NT, and 18NT. The practices adopted in the conservation management system favored biogenic aggregation in the Cerrado region, which can be proven through the study of the fractions of soil organic matter contained in these aggregates. The biogenic aggregation changed the SOM dynamics. Principal component analysis showed a clear distinction between conventional and conservationist management systems.

aggregate formation pathways; no-till system; carbon sequestration

Site	FAC		HAC		HUMC

	Phy	Bio	Phy	Bio	Phy	Bio
	-------- g kg⁻¹ --------
0.00-0.05 m soil layer
CT	1.23 ^{NS ns}	1.43 ^{NS ns}	1.90 ^{NS ns}	1.63 ^{B ns}	3.53 ^{NS ns}	4.33 ^{NS ns}
6NT	1.49 ^{NS ns}	1.51 ^{NS ns}	2.13 ^{NS ns}	2.43 ^{A ns}	3.57 ^{NS b}	4.57 ^{NS a}
18NT	1.60 ^{NS ns}	1.71 ^{NS ns}	2.48 ^{NS ns}	2.49 ^{A ns}	4.02 ^{NS b}	5.36 ^{NS a}
CV₁ (%)	18.8		16.5		17.0
CV₂ (%)	23.9		20.5		16.2
RS	4.28	4.59	2.71	3.81	9.94	10.66
0.05-0.10 m soil layer
CT	1.37 ^{NS ns}	1.30 ^{NS ns}	1.27 ^{NS ns}	1.47 ^{NS ns}	3.22 ^{NS ns}	3.80 ^{NS ns}
6NT	1.60 ^{NS ns}	1.61 ^{NS ns}	2.05 ^{NS ns}	2.04 ^{NS ns}	3.10 ^{NS ns}	3.80 ^{NS ns}
18NT	1.70 ^{NS ns}	1.43 ^{NS ns}	1.95 ^{NS ns}	2.16 ^{NS ns}	3.33 ^{NS b}	4.44 ^{NS a}
CV₁ (%)	16.3		18.4		15.2
CV₂ (%)	23.7		28.8		25.7
RS	3.39	3.73	1.97	2.97	6.94	7.65

Site	POC		MAOC		FLFC

	Phy	Bio	Phy	Bio	Phy	Bio
	-------- g kg⁻¹ --------
0.00-0.05 m soil layer
CT	1.40 ^{B b}	2.59 ^{NS a}	7.09 ^{NS a}	4.50 ^{B b}	0.52 ^{NS b}	1.86 ^{A a}
6NT	2.13 ^{A ns}	2.62 ^{NS ns}	6.58 ^{NS ns}	7.11 ^{A ns}	0.45 ^{NS b}	0.71 ^{B a}
18NT	1.93 ^{AB b}	2.98 ^{NS a}	7.89 ^{NS ns}	8.19 ^{A ns}	0.45 ^{NS b}	0.79 ^{B a}
CV₁ (%)	17.3		11.2		32.0
CV₂ (%)	21.3		14.8		29.8
RS	3.44	6.58	17.51	17.96	1.05	1.46
0.05-0.10 m soil layer
CT	1.38 ^{NS b}	2.50 ^{NS a}	6.06 ^{NS a}	4.18 ^{C b}	0.51 ^{NS b}	0.77 ^{NS a}
6NT	1.85 ^{NS ns}	2.14 ^{NS ns}	6.64 ^{NS ns}	6.72 ^{A ns}	0.41 ^{NS b}	0.65 ^{NS a}
18NT	1.71 ^{NS b}	2.58 ^{NS a}	6.28 ^{NS ns}	5.69 ^{B ns}	0.44 ^{NS b}	0.68 ^{NS a}
CV₁ (%)	19.8		6.6		17.8
CV₂ (%)	21.6		12.8		30.6
RS	1.57	2.55	13.93	14.43	0.76	0.81

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[1] * Corresponding author: E-mail: mgervasiopereira01@gmail.com