Dissertations and Theses

Magnetic susceptibility for the estimation of soil attributes and mapping of areas under sugarcane cultivation.

Author: Diego Silva Siqueira

Keywords: pedometry; multivariate analysis; step semivariogram

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Summary

The objective of this study was to evaluate the potential of magnetic susceptibility to estimate soil attributes and to map specific management areas for the sugarcane crop. Two experiments were carried out. In the first one, 50 points were randomly sampled in an area of ​​2 ha, at a depth of 0.00 - 0.20 m. A calibration curve was constructed to convert the readings of soil samples made on the scale into magnetic susceptibility measurements. The magnetic susceptibility measured by an analytical balance had a correlation of 0.58 with the clay content, -0.75 with the organic matter content, 0.41 with the base saturation and 0.82 with the hematite content of the soil depth 0,00 - 0,20 m. The multivariate statistical analysis of the main components showed that the magnetic susceptibility explains 10.69% of the variance of the set of soil attributes studied. In the second experiment, 110 samples were randomly collected (irregular grid) in an area of ​​770 ha in two depths, 0.00-0.20 m and 0.20 - 0.40 m, for the evaluation of granulometric, chemical and susceptibility attributes magnetic properties of the soil. The attributes of sugarcane in 32 subareas were evaluated. The spatial dependence of the attributes was estimated by semivariogram, scaled semivariogram and spatial distribution maps. The results show that the magnetic susceptibility presented a 33 to 50% lower error than the other physical and chemical attributes of the soil in the delimitation of the limits for specific management areas for sugarcane. In addition, the magnetic susceptibility had a significant spatial correlation with the physical and chemical attributes of the soil and the attributes of the sugarcane, and could be used to help map the areas of specific management for the sugar cane crop.