SPATIALIZATION OF ELECTRICAL CONDUCTIVITY AND PHYSICAL HYDRAULIC PARAMETERS OF SOILS UNDER DIFFERENT USES IN AN ALLUVIAL VALLEY

Iug Lopes,Abelardo Antônio De Assunção Montenegro

doi:10.1590/1983-21252019v32n122rc

Abstract

ABSTRACT Evaluating spatial variability of hydraulic properties and salinity of soils is important for an adequate agricultural management of alluvial soils, and protection of riparian vegetation. Thus, the objective of this work was to evaluate the accuracy of geophysical techniques for indirect measurements of apparent electrical conductivity (ECa), using an electromagnetic induction equipment (EM38®), and soil physical hydraulic parameters and their spatial interrelations. The study was carried out at the Advanced Research Unit of the UFRPE, in the Brígida River Basin, in Panamirim, state of Pernambuco, Brazil, in the second half of 2016. This river had a 100 m wide riparian forest strip transversely to the river bank on both sides of the river. A regular 20×10 m grid with 80 points was used to evaluate the soil hydraulic conductivity and ECa. The geostatistics showed the spatial dependence and the dependence of the soil attributes, their spatialization, and precise mapping through indirect readings. Most of the variability (86%) in soil electrical conductivity was explained by indirect readings using the EM38®. Ranges of 80 m, 380 m, and 134 m were found for soil moisture, ECa, and hydraulic conductivity, respectively, presenting strong spatial dependence. The results showed the importance of riparian forests to the maintenance of soil moisture and porosity to the improvement of soil water infiltration capacity even under severe water deficit conditions and soil subsurface layers.

Highlights

Soil spatial information has been increasingly required for decision-making regarding the environment, and land use managements (BORRELLI et al, 2014)
The objective of this work was to evaluate the accuracy of geophysical techniques for indirect measurements of apparent electrical conductivity (ECa) using an electromagnetic induction equipment (EM38®), characterize the spatial variability of soil moisture and salinity, and evaluate soil variables of a riparian zone of the Brígida River Basin, and physical hydraulic parameters of soils with different uses under severe water deficit in its alluvial valley
The electromagnetic induction equipment (EM38®) used was efficient to verify the presence of salts in the alluvial soil of the Brígida River valley, in Panamirim, state of Pernambuco, Brazil

Summary

Introduction

Soil spatial information has been increasingly required for decision-making regarding the environment, and land use managements (BORRELLI et al, 2014). The spatial variability of soil attributes, which can be evaluated by geostatistics techniques, is important for the management of agricultural areas (LABORCZI et al, 2015). Alluvial valleys have strategic importance for the Brazilian semiarid region; they determine water flow and soil water storage capacity in both saturated and unsaturated zones (MONTENEGRO; MONTENEGRO, 2006). From the ecohydrological point of view, these valleys favor the development of riparian vegetation, which intercepts precipitation, favoring water infiltration into the soil. Vidon (2013) described the connection between riparian vegetation and the potentiometric dynamics of the alluvial water table, and spatial and temporal variabilities of nutrients (phosphorus and nitrogen). The main soil properties of agricultural importance that influence the ECa are salinity, water content, texture, and chemical attributes (RHOADES et al, 1989; MOLIN; FAULIN, 2013)

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Conclusion