Microstructural changes in Oxisols under long-term different management systems

Ngolo, Aristides Osvaldo; Oliveira, Fábio Soares de; Oliveira, Maurílio Fernandes de; Fernandes, Raphael Bragança Alves

doi:10.36783/18069657rbcs20230051

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Division – Soil in Space and Time, Commission – Soil Genesis and Morphology • Rev. Bras. Ciênc. Solo 47 • 2023 • https://doi.org/10.36783/18069657rbcs20230051 copy

Microstructural changes in Oxisols under long-term different management systems

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

There has long been a discussion about the effects of soil management on its structure. Since changes can occur due to management and time of use, more accurate assessments can be achieved if carried out in long-term experiments. This study investigated the long-term effects of soil management on the physical quality of a Cerrado Oxisol (Latossolo Vermelho), focusing on microstructural changes. Micromorphology and computed tomography techniques were used to assess the soil's microstructure. The study compared areas under long-term and different soil management practices, including disc plowing, no-tillage, and disc harrow+subsoiler. A native Cerrado area was considered as the reference. Micromorphology revealed some changes in the pedological features of soil aggregates, but the granular structure showed good resistance even after two decades of use and management. It also indicated a decrease in larger pores and an increase in the surface soil layer micropores for the disc plowing and no-tillage treatments. These results were consistent with traditional laboratory evaluations of soil porosity. Computed tomography was limited due to increased soil bulk density in the cultivated treatments, but it showed potential for assessing soil porosity and pore connectivity. We concluded that micromorphology effectively identifies microstructural changes in Oxisols with small and strong granular structures, and the granular soil aggregates displayed resilience even after long-term management. The micromorphometric evaluation corroborates with traditional methods and suggests loss of pores associated with the disc harrow+subsoiler treatment.

Keywords
soil microstructure; pores morphometry; X-ray microtomography; soil micromorphology

Dates	Soil mangement
Dates	Disc plowing (DP)	No-tillage (NT)	Disc harrow+subsoiler (DHS)
<1995	Pasture	Pasture	Pasture
1995-2005	Corn and soybean annual succession	Corn and soybean annual succession	Corn and soybean annual succession
2006-2016	Corn cultivation	Corn and soybean rotation	Corn cultivation

Property	Hor. A	Hor. Bw	Property	Hor. A	Hor. Bw
Bd (kg dm^-3)	0.98	1.03	Ca²⁺ (cmol_c dm^-3)	1.93	0.30
Pd (kg dm^-3)	2.34	2.45	Mg²⁺ (cmol_c dm^-3)	0.16	0.04
Microporosity (m³ m^-3)	0.43	0.44	Al³⁺ (cmol_c dm^-3)	0.94	1.50
Macroporosity (m³ m^-3)	0.15	0.16	H+Al (cmol_c dm^-3)	8.80	7.90
Total porosity (m³ m^-3)	0.58	0.60	SB (cmol_c dm^-3)	2.13	0.36
Clay (g kg^-1)	810	788	t (cmol_c dm^-3)	3.07	1.86
Silt (g kg^-1)	50	75	T (cmol_c dm^-3)	10.93	8.26
Sand (g kg^-1)	140	137	V (%)	19.5	4.4
pH (H₂O)	4.90	4.84	m (%)	30.6	80.6
P (mg dm^-3)	0.8	0.2	OM (dag kg^-1)	4.94	3.93
K (mg dm^-3)	16.0	11.0	P-Rem (mg L^-1)	15.3	9.9

Type of management	Depth	Microstructure	Groundmass			Organic compounds	Soil features
Type of management	Depth	Microstructure	Coarse Material	Micromass	c/f_2µm relative distribution	Organic compounds	Soil features
NC	Surface	Well to moderately separated granular. Moderately separated subangular blocks, formed by coalesced granules. Compound packing voids.	Subangular quartz grains, fine sand, and opaque minerals	Dark brown to reddish-brown, undifferentiated to granostriated b-fabric	Enaulic	Roots, root traces, humified organic matter, coal and nodules	Typical ferruginous nodules and loose continuous inffilings
	0.10 m	Well separated granular. Moderately separated subangular blocks, formed by coalesced granules. Complex packing voids.	Subangular quartz grains, fine sand, and opaque minerals	Reddish-brown, undifferentiated to granostriated b-fabric	Enaulic	Roots, root traces, humified organic matter, coal and nodules	Typical ferruginous nodules and loose continuous inffilings
	0.50 m	Rounded well separated granular. Complex packing voids.	Subangular quartz grains, fine sand, and opaque minerals	Reddish-brown to reddish-yellow, undifferentiated to granostriated b-fabric	Enaulic	Root traces, humified organic matter, coal and nodules	Typical ferruginous nodules and loose continuous inffilings
NT	Surface	Vughy with little or not at all connected voids, without noticeable aggregates. Rounded to subrounded voids, with circular orientation. There are also root channels	Subrounded to rounded quartz grains, fine to medium sand, and opaque minerals	Reddish-brown with some yellowish-red portions, undifferentiated b-fabric	Porphyric	Roots, organic punctuations in micromass and charcoal	Typical ferruginous nodules
	0.10 m	Moderately separated subangular blocks, with planar voids. Also occur vughs with poorly connected voids.	Subrounded to rounded quartz grains, fine to médium sand, and opaque minerals	Brown to reddish-brown, undifferentiated b-fabric	Porphyric	Roots, traces of roots, organic punctuations in micromass and charcoal	Typical ferruginous nodules
	0.50 m	Well to moderately separated granular. Compound packing voids.	Subrounded quartz grains, fine to médium sand, and opaque minerals	Dark brown to reddish-brown, undifferentiated to granostriated b-fabric	Enaulic	Organic punctuations, coal and nodules	Typical and concentric ferruginous nodules
GHS	Surface	Moderately separated granular. Moderately separated subangular blocks. Compound packing voids and vughs.	Subrounded quartz grains, fine to médium sand, and opaque minerals	Dark brown, undifferentiated to granostriated b-fabric	Enaulic-porphyric	Traces of roots, organic punctuations in the micromass, nodules and charcoal	Typical ferruginous nodules
	0.10 m	Poorly separated subangular blocks. Vughy with poorly connected pores. The vughs are rounded to subrounded, and, in some cases, oriented.	Subrounded quartz grains, fine to medium sand, and opaque minerals	Redissh to reddish-brown, undifferentiated b-fabric	Porphyric	Traces of roots, organic punctuations in the micromass, nodules and charcoal	Typical ferruginous nodules
	0.50 m	Vughy with poorly connected pores. The vughs are rounded to subrounded, and shown circular orientation. Poorly separated subangular blocks, with planar voids.	Subrounded quartz grains, fine to medium sand, and opaque minerals	Redissh to reddish-brown, undifferentiated b-fabric	Porphyric	Organic material soaking the micromass and charcoal	Typical ferruginous nodules
DP	Surface	Poorly separated planar microstruscture, with voids of major axis parallel to the surface. Subordinately, angular blocks, poorly separeted, with planar voids.	Subrounded quartz grains, fine to medium sand, and opaque minerals	Reddish-brown, undifferentiated to monostriated b-fabric	Porphyric	Traces of roots, organic punctuations in the micromass, and charcoal	-
	0.10 m	Poorly separated planar microstruscture, with voids of a major axis parallel to the surface. Poorly separated angular blocks, with planar voids.	Subrounded quartz grains, fine to medium sand, and opaque minerals	Reddish-brown, undifferentiated to monostriated b-fabric	Porphyric	Traces of roots, organic punctuations in the micromass, and charcoal	Typical ferruginous nodules
	0.50 m	Moderately separated granular. Complex packing voids	Subrounded quartz grains, fine to medium sand, and opaque minerals	Dark brown, undifferentiated to granostriated b-fabric	Enaulic	Organic material soaking the micromass and charcoal	Typical ferruginous nodules

Treatments	Bd	Pd	Mi	Ma	TP
	————— kg dm^-3 —————		————— m m^-3 —————
	0.10 m
NC	0.98	2.34	0.43	0.15	0.58
NT	1.37 ^* *()** different from NC by Dunnett’s test (p<0.1); different letters on the line differ from each other by the Tukey test (p<0.1). ab	2.54	0.46 ^* *()** different from NC by Dunnett’s test (p<0.1); different letters on the line differ from each other by the Tukey test (p<0.1).	0.01 ^* *()** different from NC by Dunnett’s test (p<0.1); different letters on the line differ from each other by the Tukey test (p<0.1).	0.47 ^* *()** different from NC by Dunnett’s test (p<0.1); different letters on the line differ from each other by the Tukey test (p<0.1).
DHS	1.28 ^* *()** different from NC by Dunnett’s test (p<0.1); different letters on the line differ from each other by the Tukey test (p<0.1). b	2.43	0.47 ^* *()** different from NC by Dunnett’s test (p<0.1); different letters on the line differ from each other by the Tukey test (p<0.1).	0.00 ^* *()** different from NC by Dunnett’s test (p<0.1); different letters on the line differ from each other by the Tukey test (p<0.1).	0.47 ^* *()** different from NC by Dunnett’s test (p<0.1); different letters on the line differ from each other by the Tukey test (p<0.1).
DP	1.30 ^* *()** different from NC by Dunnett’s test (p<0.1); different letters on the line differ from each other by the Tukey test (p<0.1). a	2.50	0.48 ^* *()** different from NC by Dunnett’s test (p<0.1); different letters on the line differ from each other by the Tukey test (p<0.1).	0.01 ^* *()** different from NC by Dunnett’s test (p<0.1); different letters on the line differ from each other by the Tukey test (p<0.1).	0.49 ^* *()** different from NC by Dunnett’s test (p<0.1); different letters on the line differ from each other by the Tukey test (p<0.1).
CV (%)	2.80	4.10	2.40	44.80	3.90
	0.50 m
NC	1.03	2.45	0.44	0.16	0.60
NT	1.26 ^* *()** different from NC by Dunnett’s test (p<0.1); different letters on the line differ from each other by the Tukey test (p<0.1). a	2.58	0.44	0.07	0.51 ^* *()** different from NC by Dunnett’s test (p<0.1); different letters on the line differ from each other by the Tukey test (p<0.1).
DHS	1.15 b	2.55	0.42	0.13	0.55
DP	1.03	2.45	0.44	0.16	0.60
CV (%)	4.50	2.80	4.00	37.40	4.70

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[1] *Corresponding author:E-mail: raphael@ufv.br