The effect of mineral-ion interactions on soil hydraulic conductivity

The reuse of winery wastewater (WW) could provide an alternative water source for vineyard irrigation.The shift of many wineries and other food processing industries to K+-based cleaners requires studies onthe effects of K+on soil hydraulic conductivity (HC). Depending on clay content and mineral composition,K+additions can affect the HC either positively or negatively. Soil mineralogy was anticipated to exhibita strong influence on HC responses and, therefore, soils of contrasting mineralogy were evaluated forchanges in soil HC resulting from applications of solutions elevated in Na+and K+. To examine the impactof mineral-ion relationships on HC, soils dominant in montmorillonite, vermiculite, or kaolinite from theNapa and Lodi wine regions of California, were packed into soil columns to observe changes in leachatechemistry and HC. Irrigation with Na+- and K+-rich WW was simulated by applying solutions at sodiumabsorption ratio (SAR) values of 3, 6, and 9 and potassium absorption ratio (PAR) values of 1, 2, 4, and 9.While HC was reduced in the 2:1 clay soils (montmorillonite and vermiculite) for all SAR treatments, thevermiculite and the kaolinite rich soils exhibited equal or greater reductions in HC for PAR treatments, ascompared with the SAR treatments. Findings from this evaluation of the interaction of Na+and K+withthree different mineral soils suggest that the reuse of WW with increasing PAR are least problematic formontmorillonite dominated soils and most detrimental to the HC of the vermiculite dominated soil. Thepresence of minerals with a high affinity for K+(e.g., vermiculite, mica) in this soil suggest that the inter-layer binding of K+could lead to greater reductions in HC. Full analysis of soil and WW is recommendedprior to all land applications