Abstract
Soil penetration resistance is an important property that affects root growth and elongation and water movement in the soil. Since no-till systems tend to increase organic matter in the soil, the purpose of this study was to evaluate the efficiency with which soil penetration resistance is estimated using a proposed model based on moisture content, density and organic matter content in an Oxisol containing 665, 221 and 114 g kg-1 of clay, silt and sand respectively under annual no-till cropping, located in Londrina, Paraná State, Brazil. Penetration resistance was evaluated at random locations continually from May 2008 to February 2011, using an impact penetrometer to obtain a total of 960 replications. For the measurements, soil was sampled at depths of 0 to 20 cm to determine gravimetric moisture (G), bulk density (D) and organic matter content (M). The penetration resistance curve (PR) was adjusted using two non-linear models (PR = a Db Gc and PR' = a Db Gc Md), where a, b, c and d are coefficients of the adjusted model. It was found that the model that included M was the most efficient for estimating PR, explaining 91 % of PR variability, compared to 82 % of the other model.
Highlights
Soil mechanical resistance is an important property that affects root growth and elongation and water movement in the soil
Soil moisture content and bulk density are considered the most significant of these properties (Silva & Kay, 1997; Imhoff et al, 2000), and the model most commonly used to estimate penetration resistance (PR) is that proposed by Busscher (1990), in which PR is obtained as a function of bulk density and moisture content (θ), and regression parameters “a”, ‘b” and “c” are obtained by non-linear adjustments that vary from one soil to another
The results showed that, when the soil is drier, the most influential properties for PR estimates are density and organic matter content
Summary
Soil mechanical resistance is an important property that affects root growth and elongation and water movement in the soil. Most commonly, this property is evaluated using an impact penetrometer which works on the principle of soil penetration resistance (PR) with a vertical impact representing a force (F) on a rigid rod that drives a cone of specific size into the soil (Vaz & Hopmans, 2001). Soil moisture content and bulk density are considered the most significant of these properties (Silva & Kay, 1997; Imhoff et al, 2000), and the model most commonly used to estimate PR is that proposed by Busscher (1990), in which PR is obtained as a function of bulk density and moisture content (θ), and regression parameters “a”, ‘b” and “c” are obtained by non-linear adjustments that vary from one soil to another. To validate the data obtained with a penetrometer, provided it is used correctly, the soil must have been characterized (Oliveira et al, 2007), which is not always the case
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