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

Lopes, Iug; Montenegro, Abelardo Antônio de Assunção

doi:10.1590/1983-21252019v32n122rc

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Engenharia Agrícola • Rev. Caatinga 32 (01) • Jan-Mar 2019 • https://doi.org/10.1590/1983-21252019v32n122rc copy

SPATIALIZATION OF ELECTRICAL CONDUCTIVITY AND PHYSICAL HYDRAULIC PARAMETERS OF SOILS UNDER DIFFERENT USES IN AN ALLUVIAL VALLEY¹ 1 Paper extracted from the doctoral thesis of the first author.

ESPACIALIZAÇÃO DA CONDUTIVIDADE ELÉTRICA E PARÂMETROS FÍSICO-HÍDRICOS SOB DIFERENTES USOS EM REGIÃO ALUVIAL

Authorship SCIMAGO INSTITUTIONS RANKINGS

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.

Keywords:
EM38; Ecosystem services; Soil use; Beerkan; Geostatistics

Soil layer (m)	Equation for electrical conductivity - Rhoades e Corwin (1981RHOADES, J. D.; CORWIN, D. L. Determining soil electrical conductivity - depth relations using inductive electromagnetic soil conductivity meter. Soil Science Society America Journal, v. 45, n. 2, p. 54-60, 1981.)			Equation
0-0.3	-0.1285EM₀+0.1446EM₁+5.3878EM₂-17.4476EM₃+15.0549EM₄-0.1309			(1a)
0.3-0.6	-1.3259EM₁+4.8938EM₂+55.8250EM₃-94.0405EM₄+47.4196EM₄-0.9169			(1b)
0.6-0.9	9.1705EM₀-8.4116EM₁-18.3090EM₂+50.6298EM₃-42.5033EM₄-0.1224			(1c)
0.9-1.2	1.1090EM₀+0.2352EM₁-23.3536EM₂+221.0100EM₃-266.8789EM₄-3.5012			(1d)
Soil layer (m)	Equation for electrical conductivity - Rhoades et al. (1989RHOADES, J. D. et al. New calibrations for determining soil electrical conductivity-depth relations from electromagnetic measurements. Soil Science Society America Journal , v. 53, n. 1, p. 74-79, 1989.)	N	R²	Equation
	EM_H ≤ EM_V
0-0.3	ECr0.25 = 2.539EM_H0.25 - 1.413EM_V0.25 - 0.068	759	0.810	(2a)
0.3-0.6	ECr0.25 = 2.092EM_H0.25 - 0.81EM_V0.25 - 0.179	761	0.895	(2b)
0.6-0.9	ECr0.25 = 1.894EM_H0.25 - 0.407EM_V0.25 - 0.292	758	0.840	(2c)
	Para EM_H> EM_V
0-0.3	ECr0.25 = 1.164EM_H0.25 - 0.078EM_V0.25	165	0.922	(2d)
0.3-0.6	ECr0.25 = 0.640EM_H0.25 + 0.568EM_V0.25 - 0.114	163	0.969	(2e)
0.6-0.9	ECr0.25 = 1.367EM_V0.25 - 0.209	162	0.919	(2f)
Soil layer (m)	Equation for electrical conductivity - Rhoades, Chanduvi and Lesch (1999RHOADES, J. D.; CHANDUVI, F.; LESCH, S. Soil salinity assessment methods and interpretation of electrical conductivity measurements. 57. ed. Rome: FAO, 1999. 155 p.)			Equation
0-0.3; 0.3-0.6 and 0.6-0.9	ln(EM_H)-ln(EM_V) 0.04334+0.03058 ln(EM_H)+0.00836(EM_H)²			-3
	Equation for electrical conductivity - Beerkan			Equation
	Ks=b1/{0.67[(2.92/(rα))+1]}			-4

Variable	Mean	Median	Variance	Coef. of variation (%)	Coef. of asymmetry	Coef. of kurtosis	Largest error	KS 5%
EC 0-0.3 m	37.350	32.966	27.859	446.881	11.966	15.541	0.1331	0.1870
EC 0.3-0.6 m	47.989	41.824	65.144	531.861	10.358	0.3761	0.1582	0.1870
EC 0.6-0.9 m	24.650	20.252	25.532	648.234	0.8006	-0.0656	0.1404	0.1870
EC 0-0.3 m	0.0521	0.0521	0.0000	114.909	10.128	0.3474	0.1454	0.1870
EC 0.3-0.6 m	0.0768	0.0763	0.0001	136.365	0.4660	0.0241	0.0496	0.1870
EC 0.6-0.9 m	0.0878	0.0880	0.0004	213.106	-0.1004	-0.3762	0.0494	0.1870
Ks	0.0603	0.0551	0.0006	404.810	0.1744	-0.5949	0.1159	0.1870

						Cross validation
	Model	C ₀	C+C₀	C	A	MR*	SDR*	R²	SD*
Moisture 0-0.3 m	Spherical	0.004	0.318	0.314	86.0	0.001	1.237	0.834	0.012
Moisture 0.3-0.6 m	Spherical	0.008	0.876	0.868	72.3	0.093	0.749	0.745	0.009
Moisture 0.6-0.9 m	Spherical	0.1	3.215	3.115	72.1	0.026	0.998	0.809	0.031
ECa 0-0.3 m	Spherical	1.173	3.992	2.819	410.9	0.016	1.163	0.847	0.291
ECa0.3-0.6 m	Spherical	1.4	9.809	8.409	377.9	0.007	1.151	0.898	0.142
ECa0.6-0.9 m	Spherical	0.46	3.93	3.47	359.9	0.005	0.812	0.95	0.117
Ks	Gaussian	0.0002	0.00057	0.00037	134	0.016	0.996	0.972	0.351
Moisture x EC 0-0.3 m	Gaussian	-0.001	-2.003	-2.002	711.7	---	---	0.895	0.001
Moisture x EC 0.3-0.6 m	Gaussian	-0.001	-2.011	-2.01	293.9	---	---	0.96	0.001
Moisture x EC 0.6-0.9 m	Gaussian	-0.001	-1.922	-1.922	184.3	---	---	0.962	0.001

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E-mail: caatinga@ufersa.edu.br

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[1] * Corresponding author: abelardo.montenegro@ufrpe.br

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SPATIALIZATION OF ELECTRICAL CONDUCTIVITY AND PHYSICAL HYDRAULIC PARAMETERS OF SOILS UNDER DIFFERENT USES IN AN ALLUVIAL VALLEY1 1 Paper extracted from the doctoral thesis of the first author.

ESPACIALIZAÇÃO DA CONDUTIVIDADE ELÉTRICA E PARÂMETROS FÍSICO-HÍDRICOS SOB DIFERENTES USOS EM REGIÃO ALUVIAL

ABSTRACT

SPATIALIZATION OF ELECTRICAL CONDUCTIVITY AND PHYSICAL HYDRAULIC PARAMETERS OF SOILS UNDER DIFFERENT USES IN AN ALLUVIAL VALLEY¹ 1 Paper extracted from the doctoral thesis of the first author.