Penetration resistance in a latosol under different moisture and penetration speeds

Walter Francisco Molina Jr,Sônia Maria Stefano Piedade,Juarez Rennó Amaral

doi:10.1590/s0034-737x2013000500016

Abstract

The soil penetration resistance has been used to represent the compaction situation and several authors have attempted to relate the cone index (CI) with the bulk density. The importance of using the CI as source of information for decisions in agricultural activities, livestock and forestry manner, has become increasingly larger, which requires more knowledge about the penetrometers and penetrographs behavior. This study aimed to verify, in controlled laboratory conditions, the influence of soil water content and cone penetration rate to obtain the cone index, when density variation occurs. The soil was compacted by compression through a universal press cylinder which was specially designed to produce the test specimens. Bulk densities were determined from samples taken from the test specimens and their moisture content. The CI values obtained were between 0.258 and 4.776 MPa, measured in 4 moistures and 7 soil densities with 3 penetration speeds. It was concluded that the determination of IC is strongly influenced by the soil moisture but the penetration speed variation, used in this study, was not sufficient to influence the IC determination. However, the decrease in soil water content may increase the sensitiveness to detect a variation in bulk density by the use of cone index.

Highlights

The cone index achievement, resulting from resistance measurement offered to the soil by the penetration of a metal cone in the profile, is one expedite method to characterize its physical state
Regardless the cone penetration speed (Table 2), it was observed that as the soil moisture decreases, the cone index values increase with increasing of bulk density, which agrees with the results of Lima et al (2007)
As the bulk density values decrease, there is a difficulty in correlating its variation with the corresponding value obtained for the cone index, which is evident in the case of higher moisture levels (U1, U2)

Summary

Introduction

The cone index achievement, resulting from resistance measurement offered to the soil by the penetration of a metal cone in the profile, is one expedite method to characterize its physical state. The interest in cone index measurement was considerably increased with the acreage developing under no tillage system, where there is the compaction increase of the soil surface layers and its consequential interference in the agricultural productivity. The information about the negative effects of soil compaction in crop productivity, under field conditions, are scarce, as a result of the difficulty in isolating the factor soil compaction (Secco et al 2004). These authors concluded that densities up to 1.51g cm-3 and penetration resistance of 2.6 MPa did not affect soybean yield. Working in different soil conditions, variety and moisture, Beutler & Centurion (2004) found productivity decrease ( for soybean) from penetration resistance with superior values than 0.85 MPa. Freddi et al (2009) affirm that both increases, the bulk density and the penetration resistance, influenced negatively in corn yield, even as top values of root growth were at intermediate levels between the highest and lowest penetration resistance values obtained in the study

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