Tensile strength values for the degrees of soil consistency using human perception and TS-Soil device

Abstract

Tensile strength of aggregates, defined as the force per unit of area required to cause rupture of aggregates, is useful to quantify the effects of both use and management on soil quality. The present study considered the hypothesis that the evaluator’s perception, combined with the force applied to break the aggregate, measured by the TS-Soil device, can be used to define ranges of tensile strength for the degrees of dry soil consistency. The objective in this study was to define ranges of tensile strength for the degrees of dry soil consistency. For this purpose, aggregates (mean diameter of 22 mm after preparation) were collected in five horizons: A and Bi of a Cambissolo Háplico (Cambisol), Bt with a cohesive character of an Argissolo Vermelho Amarelo (Lixisol), Bt of a Luvissolo Crômico (Luvisol) and Bw of a Latossolo Vermelho-Amarelo (Ferralsol). One hundred aggregates of each horizon were evaluated for tensile strength, measured in the TS-Soil device, and, concomitantly, when pressed, were analyzed by an evaluator to assign the following scores to their consistency: 1- loose, 2- soft, 3- slightly hard, 4- hard, 5- very hard, and 6- extremely hard. Data were initially analyzed by descriptive statistics. Then, evaluator’s scores and tensile strength measured by the TS-Soil device were considered to define the ranges of values for the degrees of dry soil consistency. The following tensile strength (kPa) ranges were obtained: >0 to <21 for soft consistency, ≥21 to <38 for slightly hard, ≥38 to <65 for hard, ≥65 to <110 for very hard and ≥110 for extremely hard. It was concluded that the TS-Soil device makes it possible to combine the evaluator’s perception with the force applied to break the aggregate, enabling the definition of ranges of values for the degrees of dry soil consistency, and that the qualitative perception (evaluator) associated with tensile strength values (TS-soil device) gives better quality to the process of evaluating dry soil consistency.