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 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+, including K+/Na+ of 0:1 (K0Na1), 1:1 (K1Na1), 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, 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 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 applied water was more conducive to soil aggregate stability, alleviating the risk of macropores reduction caused by sodicity.
Sihui Yan et al.
Status: open (until 20 Apr 2023)
RC1: 'Comment on egusphere-2022-1390', Manfred Sager, 18 Mar 2023
- AC1: 'Reply on RC1', Sihui Yan, 22 Mar 2023 reply
- RC2: 'Reply on RC1', Manfred Sager, 22 Mar 2023 reply
Sihui Yan et al.
Sihui Yan et al.
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In 1999, I performed a column study of almost equal design on 3 chernozem soils pH 6,8-8,6), together with a master student. Our question was to simulate the vertical transport of a single addition of NPK fertilizer solution by rainwater, containing sulfate and phosphate as anions, beneath anionic trace elements. Addition of K+ led to the release of all other soluble cations, like Na, Li, Mg, Ca, Sr, Ba and H+ (acidification!). In this work, the goal is the substitution of sea water intrusion by KCl fertilizer, which is not so clear from the abstract.
It is well known that clay minerals exert stronger affinity to K+ and NH4+ than to Na+ and others.
From the experimental part, it is not quite clear that obviously the NaCl and KCl solutions (of equal conductivity) had not been added to columns run in parallel, but subsequently to the same columns (I took this from figures 3 and 5). 6 liters of approximate pore volume is realistic. But how much salt solution was added, and was there a wash-down with water inbetween? What had been measured to obtain the amount of released salt? Only Na and K, but also Ca, Mg, Sr, Ba, sulfate, carbonate? These data are completely missing!
Line 212) The abbreviation Ksat is misleading, because this is not saturated potassium, but saturated hydraulic conductivity!
Fig. 2) The given saturated hydraulic conductivity obviously starts from differently pretreated soils, if the test solutions had been added to the same column subsequently.
My main discipline is analytical chemistry, and not soil physics - no comments upon hydraulic parameters