Salinity Effects on Soil Moisture Measurement Made with a Capacitance Sensor
- R. B. Thompson *a,
- M. Gallardoa,
- M. D. Fernándezb,
- L. C. Valdezc and
- C. Martínez-Gaitána
- a Dpto. Producción Vegetal, Univ. de Almería, La Cañada, 04120 Almería, Spain
b Research Station of the Cajamar Foundation, Autovía del Mediterráneo, km. 416.7, 04710 El Ejido, Almería, Spain
c Dpto. Ciencias del Agua y Medio Ambiente, Instituto Tecnológico de Sonora, 5 de Febrero 818 Sur, Cd. Obregón, Sonora, México
Three field experiments examined the effects of soil salinity on volumetric soil water content (SWC) measured with a capacitance sensor (CS). They were conducted in field-grown vegetable crops fertigated with complete nutrient solutions. Experiment 1 compared nutrient solutions with electrical conductivities (ECns) of 6.5 dS m−1 (+SAL) and 2.4 dS m−1 (control), applied in equal volumes, following fertigation with ECns of 2.4 dS m−1 Once +SAL commenced, SWC (0–20-cm depth) increased rapidly and then remained approximately 30% higher than in the control. Soil matric potential (SMP, 10-cm depth) was consistently very similar in both treatments. In Exp. 2, increasing ECns from 2.1 to 5.5 dS m−1 in irrigation treatments receiving 100% of crop evaporation (ETc) and 25% of ETc caused SWC (0–20 cm) to respectively increase appreciably and maintain relatively constant values. Experiment 3 examined the effect of increased salinity and whether normalizing sensors with higher ECns alleviated this effect. Treatments were equal volumes of: (i) ECns of 5 dS m−1 with sensor normalization at EC of 5.2 dS m−1 (SAL-N5.2); (ii) ECns of 5 dS m−1 with normalization at EC of 1.9 dS m−1 (SAL-N1.9); and (iii) ECns of 1.9 dS m−1 with normalization at 1.9 dS m−1 (control). Previously, the three treatments were fertigated with ECns of 1.9 dS m−1 The SWC (5–15 cm) increased by approximately 10% in both SAL-N5.2 and SAL-N1.9, and maintained relatively constant values in the control. The SMP (10 cm) was consistently very similar in the three treatments. Normalizing the CS at 5.2 or 1.9 dS m−1 had no effect on the response to salinity. In the three experiments, changes in SWC generally paralleled changes in EC of soil water (ECsw); relative increases were 4 to 7.5% in SWC for each 1 dS m−1 increase in ECswPlease view the pdf by using the Full Text (PDF) link under 'View' to the left.
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