Correction of resistance to penetration by pedofunctions and a reference soil water content

Moacir Tuzzin De Moraes,Henrique Debiasi,Julio Cezar Franchini,Vanderlei Rodrigues Da Silva

doi:10.1590/s0100-06832012000600004

Abstract

The soil penetration resistance is an important indicator of soil compaction and is strongly influenced by soil water content. The objective of this study was to develop mathematical models to normalize soil penetration resistance (SPR), using a reference value of gravimetric soil water content (U). For this purpose, SPR was determined with an impact penetrometer, in an experiment on a Dystroferric Red Latossol (Rhodic Eutrudox), at six levels of soil compaction, induced by mechanical chiseling and additional compaction by the traffic of a harvester (four, eight, 10, and 20 passes); in addition to a control treatment under no-tillage, without chiseling or additional compaction. To broaden the range of U values, SPR was evaluated in different periods. Undisturbed soil cores were sampled to quantify the soil bulk density (BD). Pedotransfer functions were generated correlating the values of U and BD to the SPR values. By these functions, the SPR was adequately corrected for all U and BD data ranges. The method requires only SPR and U as input variables in the models. However, different pedofunctions are needed according to the soil layer evaluated. After adjusting the pedotransfer functions, the differences in the soil compaction levels among the treatments, previously masked by variations of U, became detectable.

Highlights

The soil compaction level can be assessed based on soil penetration resistance (SPR), which is determined by penetrometry
In the 5.5-10.5 cm layer, bulk density (BD) varied from 1.10 Mg m-3 (NTCh) to 1.50 Mg m-3 (NTH20), which is near the maximum BD estimated by the Normal Proctor Test for this Oxisol, corresponding to 1.53 Mg m-3 (Torres & Saraiva, 1999)
The BD variation range was large in both soil layers, which is a basic requirement for adequate pedofunction adjustments to correct SPR to a reference U value

Summary

Introduction

The soil compaction level can be assessed based on soil penetration resistance (SPR), which is determined by penetrometry. Despite the advantages of using penetrometers, SPR varies directly in function of soil bulk density (BD) and inversely in function of soil water content (U) (Busscher, 1990; Bengough et al, 2001; Vaz et al, 2011) This fact limits comparisons of soils of the same type with different water contents, once a small reduction or increase in U results in a large increment or reduction of SPR (Vaz et al, 2011), leading to an under- or overestimation of the soil compaction level. Vaz et al (2002) indicated that the ideal procedure would be to measure U together with SPR, and apply some type of correction or normalization for a reference value of soil water content afterwards This procedure may reduce interpretation problems of results obtained under different field conditions and soil management systems (Busscher et al, 1997)

Objectives

Methods

Results

Conclusion