Effect of sodium adsorption ratio and electric conductivity of the applied water on infiltration in a sandy-loam soil

Headnote

ABSTRACT

Infiltration measurements using a double-ring infiltrometer were conducted on a sandy-loam soil located in Saudi Arabia. The measurements were performed for an undisturbed soil. The effect of sodium adsorption ratio (SAR) and electric conductivity (EC) of the applied water on infiltration rate was examined. The infiltration rate at the initial time was high, in the order 305 > 240 > 137 > 104 > 65 mm/h for SAR of 3.34, 3.52, 4.14, 4.18, and 7.60, respectively. The results showed that 180 min after the initial time of measurement in the sandy-loam soil, the final infiltration rates were in the range of 21.1-44.0 mm/h for the different qualities of water considered in this study, with an average value of 33.8 mm/h. Hence, the infiltration rate is sensitive to the SAR of the applied water. The final infiltration rate (IR_f) and the final cumulative infiltration depth (Z_f) after 180 min could be predicted using the following equations:

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Keywords: Infiltration, Kostiakov, electric conductivity, sodium adsorption ratio

(ProQuest: ... denotes formulae omitted.)

INTRODUCTION

Infiltration rate is defined as the rate at which soil is able to absorb rainfall or irrigation water (Ahaneku, 2011). It is a fundamental variable in irrigation processes, as its influence on the movement of water over the soil is considerable (Aljoumani, 2012). Moreover, it is employed in planning water-conservation techniques (Mbagwu, 1993). The infiltration rate varies with the applied water quality (Warrence et al., 2002). The two most common waterquality factors influencing infiltration rate are the salinity of the water and its sodium content relative to calcium and magnesium content. The concentration of sodium relative to calcium and magnesium is the sodium adsorption ratio (SAR). It is a measure of the suitability of water for use in agricultural irrigation. In general, the higher the SAR, the less suitable the water is for irrigation. The infiltration rate generally decreases with either a decrease in salinity or increase in sodium content relative to calcium and magnesium. High sodium levels in irrigation water will lead to a decrease in the infiltration rate because of soil dispersion and structure breakdown (Shainberg and Letey, 1984). El-Morsy et al. (1991) found that the SAR of irrigation water significantly affects the water-transmission properties of the...