Avaliação da salinidade de neossolo usando-se dispositivo de indução eletromagnética

Abstract

RESUMOA concentração de sais nos solos e nas águas disponíveis em áreas irrigadas no semiárido pode comprometer a produção agrícola. Neste trabalho, desenvolvido em um vale aluvial, a salinidade do solo foi estimada a partir de leituras com o aparelho de indução eletromagnética EM38, considerando-se a condutividade elétrica aparente do solo (EM). Além de disposto na superfície do solo, o equipamento foi posicionado a diferentes alturas acima da superfície, de modo a incluir distintas escalas verticais na estimativa da condutividade elétrica real do solo (CE r ). Modelos de regressão linear múlti-pla foram desenvolvidos para as condições locais e os resultados analisados através da estatística clássica e de metodologia geoestatística. As estimativas de CE r se ajustaram a uma distribuição log-Normal e apresentaram dependência espacial em escala de lote, nas camadas 0-30; 30-60 e 60-90 cm.Verificou-se que o EM38 é uma ferramenta adequada para estimativa da salinidade do solo quando submetido a calibrações locais, em escala de lote, e de vale, mesmo em áreas com heterogeneidades verticais relevantes. Obtiveram-se coeficientes de determinação superiores a 90% para os modelos de regressão linear múltipla. Palavras-chave: condutividade elétrica, vales aluviais, EM38Fluvisol salinity evaluation using electrical magnetic device ABSTRACT Salt concentration in soil and in the available waters in irrigated areas in the semi-arid regions is not always suitable, and it may interfere with the agricultural yield. In this work, soil salinity has been estimated from readings of an electrical magnetic device EM38 in an alluvial valley, considering the apparent soil salinity (EM). The equipment has been placed not only at the soil surface, but also at different heights above the soil level, as a way to encompass distinct vertical scales on the actual soil electrical conductivity estimation (EC r ). Multiple regression models have been developed for the local conditions. The results have been analysed both by descriptive statistics and by the geostatistical methodology. The EC r estimates fitted to a logNormal distribution and presented a spatial dependence at a plot scale in the 0-30, 30-60 and 60-90 cm layers. It has been verified that the EM38 is a suitable tool for soil salinity mapping, when local calibrations are considered, at plot scale, and in the valley scale, even in areas with relevant vertical heterogeneities. Determination coefficients higher than 90% has been verified for the multiple linear regression models.

Spatialization of Electrical Conductivity and Physical Hydraulic Parameters of Soils Under Different Uses in an Alluvial Valley

“…Areas of alluvial valleys present heterogeneous soils, thus, the regressions for the EM38 ® values provided important and accurate information that shows qualitative and quantitative variations of physical and chemical attributes of the soil profiles, mainly for soil management, as also pointed out by Montenegro et al (2010). Lesch et al (1992) evaluated the same models used in the present study and found satisfactory results, thus, these models can be used for areas with different sizes and high salinity amplitude.…”

“…The electromagnetic induction was used in vertical and horizontal modes with an electromagnetic induction equipment (EM38 ® ) positioned at different heights in relation to the ground level (0, 0.3, 0.6, 0.9, 1.2, and 1.5 m), as recommended by Rhoades and Corwin (1981) and Montenegro et al (2010).…”

“…Corwin and Lesch (2003); Corwin (2005) reported the efficiency of geophysical techniques based on electromagnetic readings with an electromagnetic induction equipment (EM38 ® ) in precision agriculture. However, their quality is dependent on accurately calibration of this tool, especially in areas with high spatial heterogeneities, such as alluvial valleys and riparian zones (THIESSON et al, 2014;MONTENEGRO et al, 2010). Schlosser et al (2013) applied geophysical techniques of electrical resistivity in an alluvial valley, following transects transverse to the main water course, to evaluate the dynamics of unsaturated flows during rainfall events.…”

Variabilidade espacial de atributos físicos em solos de vale aluvial no semiárido de Pernambuco

“…Alcances da ordem de 320 m foram obtidos para a taxa de infiltração e de 333 m para classes de solo predominantes, mediante uma malha de amostragem composta de pontos aleatórios e conjuntos de transectos, tendo-se identificado regiões de maior susceptibilidade à salinização. Adicionalmente, Montenegro et al (2010) abordaram a variabilidade espacial da condutividade elétrica de Neossolo em escala de lote e obtiveram alcances da ordem de dezenas de metros, constatando o melhor desempenho do modelo gaussiano para representar tal dependência espacial.…”

Temporal dependence of potentiometric levels and groundwater salinity in alluvial aquifer upon rainfall and evapotranspiration

“…Mimoso alluvial valley in the Northeast semiarid has been intensively instrumented (MONTENEGRO, 1997), monitored and studied for groundwater recharging mechanisms (ALBUQUERQUE et al, 2015), groundwater spatial distribution (FONTES JÚNIOR et al, 2012;MONTENEGRO;, soil salinity spatial variation (MONTENEGRO et al, 2010), for agricultural support evaluation (SOUZA et al, 2011).…”