Estimating Sample Size of Soil Cone Index Profiles by Bootstrapping

Carlos Agustín Alesso,María Josefina Masola,María Eugenia Carrizo,Silvia Del Carmen Imhoff

doi:10.1590/18069657rbcs20160464

Abstract

ABSTRACT Measurements of the soil cone index are widely used to assess soil resistance to root penetration (SR) and to monitor the soil compaction status of agricultural fields. However, soil sampling for SR estimation is a rather challenging task in view of the high spatial and temporal variability of the soil. This study proposed a bootstrapping method to determine the minimum sample size required to estimate the vertical profile of mean soil cone index (CI) values at different levels of [...]

Highlights

Soil mechanical resistance to root penetration (SR) is a key soil physical property that controls root expansion, and modulates the crop oxygen and water uptake (Letey, 1985)
Soil water contents at both sampling times were near field capacity and had low variation in the explored depth range; no correction was applied to cone index (CI) values (Table 1)
The sample CI profiles were more concentrated around the vertical profile of mean CI values before than after tillage

Summary

Introduction

Soil mechanical resistance to root penetration (SR) is a key soil physical property that controls root expansion, and modulates the crop oxygen and water uptake (Letey, 1985). Periodic monitoring of the soil compaction status of agricultural fields through CI is an effective way to assess the effects of different management systems and cultural practices on soil structure and root growth and development (Tavares Filho and Ribon, 2008). Soil sampling for the estimation of SR can be challenging, because of the high spatial and temporal intrinsic variability of this soil property, which often increases the required sampling effort (Castrignanò et al, 2002; Han et al, 2016). The question about how many observations are required for a reliable estimation of the vertical profile of mean CI values, i.e., the mean CI values per layer, is a key aspect of the sampling design for soil compaction monitoring

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Conclusion