This soil has poor soil physical structure with limited soil aggregates, and soil colloid surfaces are overloaded by Na+ [48]. Wang et al. (2011) reported that the addition of the soil conditioner HPMA induced flocculation of soil selleck kinase inhibitor colloids with looser structure and larger aggregates [26]. The findings on AFM, SEM images, and soil particle size indicate that the function of the fungus extract is like that of the soil conditioner (e.g., HPMA [26]), and a chemical reaction instead of physical adhesion may occur between the fungus extract and soil colloids. The mechanism of saline-alkali soil improvement by HPMA conditioner is to activate inorganic calcium in the soil via a chemical reaction between calcium carbonate and HPMA, as well as the exchange of Ca2+ and excessive Na+ on the surface of soil colloids [26].

A similar chemical reaction is possibly activated after the addition of the fungus extract to soil colloids from saline-alkali soils, owing to the fact that organic acids were present in the fungus extract solution. It is worth mentioning that carbonate functional groups appear obviously reduced by 25%, perhaps because saline-alkali soil is basically an alkaline soil with a pH of 9-10 and includes more carbonate (CaCO3) in calcite, while the fungus extract is generally acidic; therefore, combining them may cause some chemical reaction and lead to calcium carbonate being dispersed. Dissolution of calcium carbonate could lead to more Ca2+ being adsorbed on the surface of soil colloids, which would tend to increase soil colloid dispersion and form a more loose soil colloid apparent structure [26], as shown in Figure 2.

Measuring differences in mineral composition on the surface of soil colloids and in mineral crystallinity may help explain the changes in particle diameter and surface structure as shown in Figures Figures11�C3. The Drug_discovery techniques of XRD, IR, and XPS are commonly used for mineral crystallinity observation [42, 43], functional group identification in soils [44], and elemental composition changes [50]. These methods could be used to examine mineral crystallinity changes, variable functional group changes, and the elemental composition of soil colloids, together with surface and particle size changes after the addition of the fungus extract.XRD data proved that fungus extract treatment could change the relative crystallinity and grain size of variable soil minerals and showed differences between dark brown forest soil and saline-alkali soil (Figure 4). In the case of dark brown forest soil, addition of fungus extracts 30%~400% increased crystallinity of kaolinite, hydromica, and quartz, while 17%~58% decreases were found in saline-alkali soil (except for a 15% increase for quartz) (Figure 4).