Saline water irrigation in semiarid region: I – effects on soil chemical properties

Abstract

The use of saline water for crop irrigation is a commonly adopted practice among the farmers in the semiarid regions around the world, but the magnitude of soil salinization resulting from the use of these waters is currently insufficiently understood. This work aims to evaluate the chemical attribute changes of two Fluvisols cultivated with onion and subjected to irrigation with increasing levels of salinity, expressed by electrical conductivity (EC) and sodium adsorption ratio (SAR). Sandy loam and silty clay loam soils were irrigated with three different levels of saline waters with electrical conductivity (EC - 200, 700 and 2,000 μS cm-1) and six levels of sodium adsorption ratio (SAR - 0, 5, 10, 15, 20 and 25 (mmolc L-1)0.5). Thus, the experiment consisted of a complete factorial arrangement 2 x 3 x 6 (two soils, three EC levels and six SAR levels), in four replicates. The soils were cultivated with onion and pH levels of the soil were measured at 90 days after transplanting, as were the contents of exchangeable and soluble cations. ESP and SAR values were then calculated. This study revealed that the use of water with salinity at or above 700 μS cm-1 is capable of promoting changes in the chemical properties of soils and the continuous use of irrigation water with high EC and high SAR values may promote salinization and sodification of Fluvisols in a semiarid environment. These changes were found to be more severe in silty clay loam soils than in sandy loam soils.

The Effect of Sodic Water Type on the Chemical Properties of Calcareous Soil in Semi-Arid Irrigated Land

“…With the sodic water application, the water-soluble Na + content increased together with the EC e of soil, and subsequently, Na + leached downwards, especially when NaCl water was used (Figure 4). Researchers from different countries have reported a highly positive relationship between soil EC e and water-soluble Na + [48,[57][58][59][60]. In a study conducted for two years, the Na + concentration increased up to 21.6% for three different salt levels in irrigation water, and Na + concentration was consistent with soil EC e [61].…”

“…Tavakkoli et al [65] reported that treating sandy soils with NaCl waters decreased the exchangeable Mg 2+ concentration in the semi-arid region of South Australia. Moreover, Pessoa et al [48] and Saygın et al [53] established that using irrigation waters with different EC and SAR values decreased the exchangeable Mg 2+ concentration similar to the Na + -Ca 2+ shift in soil exchange complexes. The saline irrigation water did not significantly affect the change of water-soluble K + values at the soil surface and the subsurface layers (Supplementary Figure S2).…”

“…Several studies from dry regions also have shown that the salinity of irrigation water and the intervals between them do not affect soil pH [51][52][53]. On the other hand, Pessoa et al [48] found that in salt-affected sandy and silty loamy soils, irrigation water with varying types of salt containing Cl − increased the rate of the soluble Cl − over CO 3 2− and HCO 3 − concentration in the soil; thus, pH in the soil extract decreased. In the current study, the increases in the pH values after the 3rd and 4th periods in the SAR 40 level of the NaHCO 3 water were significant compared to the other periods.…”

“…However, in the 3rd watering period, a considerable downward movement of various ions depended on their solubility and chemical properties. Many studies from arid and semi-arid regions found that the salt content of the clay soil increases during the irrigation season and decreases in the rainy season due to leaching [46][47][48]. While the ions in the soil profile are transported downwards with irrigation or rain, they move upwards by capillary forces during evaporation, particularly in clayey soils and when water with high sodium is used.…”

Supplemental irrigation using brackish water on maize in tropical semi-arid regions of Brazil: yield and economic analysis

“…The occurrence of brackish water sources is common in the Brazilian semi-arid region, predominantly with electrical conductivity between 1.5 and 6.0 dS m -1 , low sulfate concentrations and high concentrations of chloride and sodium (Silva Júnior et al, 1999). Continuous use of brackish waters in irrigation causes accumulation of salts in the soil (Beltrán, 1999;Pessoa et al, 2019), resulting in the inhibition of physiological processes and reduction in maize yield (Barbosa et al, 2012;Muuns and Tester, 2008). However, studies conducted on certain annual crops have shown that irrigation with saline water for short periods does not cause significant damage to yield and the negative impacts on soil are minimal (Barbosa et al, 2012;Kang et al, 2010;Murtaza et al, 2006;Neves et al, 2015;Terceiro Neto et al, 2013).…”