Improvement of a testing apparatus for dynamometry: procedures for penetrometry and influence of strain rate to quantify the tensile strength of soil aggregates

Abstract

SUMMARYSoil penetration resistance (PR) and the tensile strength of aggregates (TS) are commonly used to characterize the physical and structural conditions of agricultural soils. This study aimed to assess the functionality of a dynamometry apparatus by linear speed and position control automation of its mobile base to measure PR and TS. The proposed equipment was used for PR measurement in undisturbed samples of a clayey "Nitossolo Vermelho eutroférrico" (Kandiudalfic Eutrudox) under rubber trees sampled in two positions (within and between rows). These samples were also used to measure the volumetric soil water content and bulk density, and determine the soil resistance to penetration curve (SRPC). The TS was measured in a sandy loam "Latossolo Vermelho distrófico" (LVd) -Typic Haplustox -and in a very clayey "Nitossolo Vermelho distroférrico" (NVdf) -Typic Paleudalf -under different uses: LVd under "annual crops" and "native forest", NVdf under "annual crops" and "eucalyptus plantation" (> 30 years old). To measure TS, different strain rates were applied using two dynamometry testing devices: a reference machine (0.03 mm s -1 ), which has been widely used in other studies, and the proposed equipment

Penetration resistance according to penetration rate, cone base size and different soil conditions

“…The variation in the results according to the rate can be explained by complex interactions between the rate and strength of penetration, in which a small increase in the penetration rate of the cone can have a positive, negative or no influence on measurements of soil penetration resistance (Figueiredo et al, 2011). This is due, for example, to the rate of energy dissipation, and also to dilatancy properties of soil in particular (Bradford, 1986).…”

“…The range of penetration rates used for penetrometer analysis is wide (Figueiredo et al, 2011), but when assessing Brazilian studies with optimal water range, it is observed that the predominant rate used for the analysis of resistance under laboratory conditions is 0.166 mm s -1 (Bergamin et al, 2010;Beutler et al, 2007), but with a wide variation in methodology among studies and in relation to the original methodology, not taking into account variations caused by penetration rate and cone size.…”

Critical soil bulk density for soybean growth in Oxisols

“…After reaching the equilibrium at each potential, the samples were weighed and the soil penetration resistance (PR) was determined using an electronic penetrometer similar to that described by Figueiredo et al (2011) with a 30º cone and base area of 0.1256 cm 2 . The device was settled to register a reading every one second.…”

Changes in the Structure of a Nigerian Soil under Different Land Management Practices

“…In order to describe the effect of land use or land-related management on soil and its functions, soil parameters such as bulk density and air capacity (Reynolds et al, 2007), aggregate size analysis (Ogunwole, 2008;Lawal et al, 2009), and soil penetration resistance (Ogunwole, 2005;Figueiredo et al, 2011) have been used in many studies. In contrast, Pires et al (2008a) and Dexter and Richard (2009) used the Pore Size Distribution (PSD) approach to study soil structure, and this approach is relevant to fluid transport in soils.…”