Prediction of soil shear strength in agricultural and natural
               environments of the Brazilian Cerrado

The objective of this work was to develop uni- and multivariate models to predict maximum soil shear strength (τ_max) under different normal stresses (σ_n), water contents (U), and soil managements. The study was carried out in a Rhodic Haplustox under Cerrado (control area) and under no-tillage and conventional tillage systems. Undisturbed soil samples were taken in the 0.00-0.05 m layer and subjected to increasing U and σ_n, in shear strength tests. The uni- and multivariate models - respectively τ_max=10^(a+bU) and τ_max=10^(a+bU+cσ_n) - were significant in all three soil management systems evaluated and they satisfactorily explain the relationship between U, σ_n, and τ_max. The soil under Cerrado has the highest shear strength (τ) estimated with the univariate model, regardless of the soil water content, whereas the soil under conventional tillage shows the highest values with the multivariate model, which were associated to the lowest water contents at the soil consistency limits in this management system.

cohesion limits; machine-ground interaction; mechanical resistance; precompression stress; soil compaction; soil physical quality.

Authorship

Reginaldo Barboza da Silva

Universidade Estadual Paulista, Campus Experimental de Registro, Avenida Nelson Brihi Badur, no 430, Vila Tupy, CEP 11900-000 Registro, SP, Brazil. E-mail: rbsilva@registro.unesp.br, pieroiori@registro.unesp.br, alcivania@registro.unesp.br Universidade Estadual PaulistaBrazilRegistro, SP, BrazilUniversidade Estadual Paulista, Campus Experimental de Registro, Avenida Nelson Brihi Badur, no 430, Vila Tupy, CEP 11900-000 Registro, SP, Brazil. E-mail: rbsilva@registro.unesp.br, pieroiori@registro.unesp.br, alcivania@registro.unesp.br

Moacir de Souza Dias Junior

Universidade Federal de Lavras, Departamento de Ciência do Solo, Caixa Postal 3037, CEP 37200-000 Lavras, MG, Brazil. E-mail: msouzadj@dcs.ufla.br Universidade Federal de LavrasBrazilLavras, MG, BrazilUniversidade Federal de Lavras, Departamento de Ciência do Solo, Caixa Postal 3037, CEP 37200-000 Lavras, MG, Brazil. E-mail: msouzadj@dcs.ufla.br

Piero Iori

Francisca Alcivânia de Melo Silva

Sergio Mauro Folle

Embrapa Cerrados, Rodovia BR-020, Km 18, Caixa Postal 08223, CEP 73310-970 Planaltina, DF, Brazil. E-mail: sergio.folle@embrapa.br, claudio.franz@embrapa.br Embrapa CerradosBrazilPlanaltina, DF, BrazilEmbrapa Cerrados, Rodovia BR-020, Km 18, Caixa Postal 08223, CEP 73310-970 Planaltina, DF, Brazil. E-mail: sergio.folle@embrapa.br, claudio.franz@embrapa.br

Claudio Alberto Bento Franz

Zigomar Menezes de Souza

Universidade Estadual de Campinas, Departamento de Água e Solo, Avenida Cândido Rondon, no 501, Cidade Universitária Zeferino Vaz, Barão Geraldo, CEP 13083-875 Campinas, SP, Brazil. E-mail: zigomarms@feagri.unicamp.br Universidade Estadual de CampinasBrazilCampinas, SP, BrazilUniversidade Estadual de Campinas, Departamento de Água e Solo, Avenida Cândido Rondon, no 501, Cidade Universitária Zeferino Vaz, Barão Geraldo, CEP 13083-875 Campinas, SP, Brazil. E-mail: zigomarms@feagri.unicamp.br

SCIMAGO INSTITUTIONS RANKINGS

Figures | Tables

Figures (4)
Tables (4)

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Figure 1:
Maximum shear stress (τ_max) of a Latossolo Vermelho distrófico (Rhodic Haplustox) under no-tillage, conventional tillage, and Cerrado, at 0.00-0.05 m depth, for each evaluated level of normal stress (s_n), according to soil water contents (U). **Significant at 1% probability.

Thumbnail

Figure 2.
Maximum shear stress (τ_max) of a Latossolo Vermelho distrófico (Rhodic Haplustox) under no-tillage (NT), conventional tillage (CT), and Cerrado (CE), at 0.00-0.05 m depth, subjected to different soil water contents (U) and normal stresses (σ_n). **Significant at 1% probability.

Thumbnail

Figure 3:
Maximum shear stress (τ_max) of a Latossolo Vermelho distrófico (Rhodic Haplustox) under no-tillage, conventional tillage, and Cerrado, at 0.00-0.05 m depth, according to soil water contents (U) and normal stresses (σ_n). * and **Significant at 5 and 1% probability, respectively.

Thumbnail

Figure 4:
Maximum shear stress (τ_max) of a Latossolo Vermelho distrófico (Rhodic Haplustox) estimated by the multivariate model τ_max=10^(a+bU+cσ_n), according to soil consistency limits - SL, shrinkage limit; PL, plastic limit; and LL, liquid limit - and to the precompression stress, considered as normal stress, under no-tillage, conventional tillage, and Cerrado, at 0.00-0.05 m depth.

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Table 1:
Characterization of hydrophysical and mechanical attributes of a Latossolo Vermelho distrófico (Rhodic Haplustox) under Cerrado and no-tillage and conventional tillage systems.

Thumbnail

Table 2:
Tunning parameters of the equations obtained from samples of Latossolo Vermelho distrófico (Rhodic Haplustox) under different uses and soil management systems, and soil water content based on the Mohr-Coulomb envelope (τ=c+σ_n tgΦ).

Thumbnail

Table 3:
Comparison between equations from the univariate model τ_max=10^(a+bU), after linearization of normal stresses (σ) in the soil management systems, using the procedure proposed by Snedecor & Cochran (1989)SNEDECOR, G.W.; COCHRAN, W.G. Statistical methods. Ames: Iowa State University Press, 1989. 503p..

Thumbnail

Table 4:
Comparison between equations from the univariate model τ_max=10^(a+bU), after linearization of the effects of soil management systems according to the evaluated normal stresses (σ_n), using the procedure proposed by Snedecor & Cochran (1989)SNEDECOR, G.W.; COCHRAN, W.G. Statistical methods. Ames: Iowa State University Press, 1989. 503p..

Figure 1: Maximum shear stress (τ_max) of a Latossolo Vermelho distrófico (Rhodic Haplustox) under no-tillage, conventional tillage, and Cerrado, at 0.00-0.05 m depth, for each evaluated level of normal stress (s_n), according to soil water contents (U). **Significant at 1% probability.

Figure 2. Maximum shear stress (τ_max) of a Latossolo Vermelho distrófico (Rhodic Haplustox) under no-tillage (NT), conventional tillage (CT), and Cerrado (CE), at 0.00-0.05 m depth, subjected to different soil water contents (U) and normal stresses (σ_n). **Significant at 1% probability.

Figure 3: Maximum shear stress (τ_max) of a Latossolo Vermelho distrófico (Rhodic Haplustox) under no-tillage, conventional tillage, and Cerrado, at 0.00-0.05 m depth, according to soil water contents (U) and normal stresses (σ_n). * and **Significant at 5 and 1% probability, respectively.

Figure 4: Maximum shear stress (τ_max) of a Latossolo Vermelho distrófico (Rhodic Haplustox) estimated by the multivariate model τ_max=10^(a+bU+cσ_n), according to soil consistency limits - SL, shrinkage limit; PL, plastic limit; and LL, liquid limit - and to the precompression stress, considered as normal stress, under no-tillage, conventional tillage, and Cerrado, at 0.00-0.05 m depth.

Table 1: Characterization of hydrophysical and mechanical attributes of a Latossolo Vermelho distrófico (Rhodic Haplustox) under Cerrado and no-tillage and conventional tillage systems.

Table 2: Tunning parameters of the equations obtained from samples of Latossolo Vermelho distrófico (Rhodic Haplustox) under different uses and soil management systems, and soil water content based on the Mohr-Coulomb envelope (τ=c+σ_n tgΦ).

⁽¹⁾
c, apparent cohesion intercept; σ_n, normal stress (kPa); and Φ, tan^-1 b.
^{* and **}
Significant at 5 and 1% probability, respectively.

Table 3: Comparison between equations from the univariate model τ_max=10^(a+bU), after linearization of normal stresses (σ) in the soil management systems, using the procedure proposed by Snedecor & Cochran (1989)SNEDECOR, G.W.; COCHRAN, W.G. Statistical methods. Ames: Iowa State University Press, 1989. 503p..

^ns
Nonsignificant.
^{* and **}
Significant at 5 and 1% probability, respectively.

Table 4: Comparison between equations from the univariate model τ_max=10^(a+bU), after linearization of the effects of soil management systems according to the evaluated normal stresses (σ_n), using the procedure proposed by Snedecor & Cochran (1989)SNEDECOR, G.W.; COCHRAN, W.G. Statistical methods. Ames: Iowa State University Press, 1989. 503p..

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Prediction of soil shear strength in agricultural and natural environments of the Brazilian Cerrado

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[TFN01t02] ⁽¹⁾
c, apparent cohesion intercept; σ_n, normal stress (kPa); and Φ, tan^-1 b.

[TFN02t02] ^{* and **}
Significant at 5 and 1% probability, respectively.