Soil compaction is a physical attribute widely studied mainly because it causes decreases on crop yield due to mechanical limitations to root growth among other factors. For the diagnosis of soil compaction the most commonly used method is the Cone Index (CI), which despite being indirect has become a very practical and quick way of evaluating the compaction in large areas. The CI represents the resistance exerted by the soil in reaction to the penetration of a tapered tip; an equipment called penetrometer is used in this practice. Currently there are different models of penetrometers and different principles of operation, but they must have tapered tip standardized and maintain the standard penetration speed. There is also need to estimate the optimal number of replications for each point sampled in an attempt to reduce the coefficient of variation (CV) of a population sample because literature has reported high values of CV on CI. So this study aims to compare the performance and evaluate the behavior of some most common types of penetrometer through field-testing, aiming to characterize and compared the results among these sensors for the purpose of comparability and validation. The analysis of variability among readings sample is also object of this study aiming to determine a minimum number of replications that could serve as a recommendation.
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