The higher relative concentration of K ⁺ to Na ⁺ in saline water improves soil hydraulic conductivity, salt-leaching efficiency and structural stability

Abstract. Soil salinity and sodicity caused by saline water irrigation are widely observed globally. Clay dispersion and swelling are influenced by sodium (Na+) concentration and electrical conductivity (EC) of soil solution. Specifically, soil potassium (K+) also significantly affects soil structural stability, but for which concern was rarely addressed in previous studies or irrigation practices. A soil column experiment was carried out to examine the effects of saline water with different relative concentrations of K+ to Na+ (K+ / Na+), including K+ / Na+ of 0:1 (K0Na1), 1:1 (K1Na1) and 1:0 (K1Na0) at a constant EC (4 dS m−1), and deionized water as the control (CK), on soil physicochemical properties. The results indicated that at the constant EC of 4 dS m−1, the infiltration rate and water content were significantly (P<0.05) affected by K+ / Na+ values, and K0Na1, K1Na1 and K1Na0 significantly (P<0.05) reduced saturated hydraulic conductivity by 43.62 %, 29.04 % and 18.06 %, respectively, compared with CK. The volumetric water content was significantly (P<0.05) higher in K0Na1 than CK at both 15 and 30 cm soil depths. K1Na1 and K1Na0 significantly (P<0.05) reduced the desalination time and required leaching volume. K0Na1 and K1Na1 reached the desalination standard after the fifth and second infiltration, respectively, as K1Na0 did not exceed the bulk electrical conductivity required for the desalination prerequisite throughout the whole infiltration cycle at 15 cm soil layer. Furthermore, due to the transformation of macropores into micropores spurred by clay dispersion, soil total porosity in K0Na1 dramatically decreased compared with CK, and K1Na0 even increased the proportion of soil macropores. The higher relative concentration of K+ to Na+ in saline water was more conducive to soil aggregate stability, alleviating the risk of macropores reduction caused by sodicity.