This study investigated the effects of soil crust development on the underlying soil properties. The field sampling work was conducted in June 2016 in the Hobq Desert in Inner Mongolia, North China. Soil crust samples and 0–6, 6–12, 12–18, 18–24, and 24–30 cm deep underlying soil samples were taken from five representative areas of different soil crust development stages. All samples were analyzed for physicochemical properties, including water content, bulk density, aggregate content, organic matter content, enzyme activities, and microbial biomass carbon and nitrogen. The results showed that the thickness, water content, macro-aggregate (>250 μm) content, organic matter content, microbial biomass, and enzyme activities of the soil crusts gradually increased along the soil crust development gradient, while the bulk density of the soil crusts decreased. Meanwhile, the physicochemical and biological properties of the soils below the algal and moss crusts were significantly ameliorated when compared with the physical crust. Moreover, the amelioration effects were significant in the upper horizons (approx. 0–12 cm deep) and diminished quickly in the deeper soil layers.

Coal fly ash (FA) and polyacrylamide (PAM) are two common amendments for improving hydraulic properties of sandy soil. However, their interaction effect on infiltration-runoff processes in sandy soil has been scarcely reported. In this study, FA and anionic PAM granules were mixed thoroughly with a 0–0.2 m sandy soil layer at FA rates of 0%, 10%, and 15% (w/w soil), and PAM rates of 0%, 0.01%, and 0.02% (w/w soil) along with each FA rate. A simulated rainfall laboratory experiment (slope gradient of 10°, rainfall intensity of 1.5 mm/min) was conducted. During the rainfall, the cumulative runoff yield increased while the average infiltration rate decreased with increasing FA and PAM rates. A higher FA rate of 15% and varying PAM rates resulted in a prominent increase in cumulative sediment yield. After the rainfall, the two-dimensional distribution of water content retained in the soil profile reflected that both FA and PAM increased the water retention capacity of sandy soil, and the effect became more obvious at higher FA and PAM rates. The possible mechanism for the effect of FA and PAM on inhibiting water infiltration during the rainfall and retaining water in the soil layer after the rainfall is attributed to the filling of pores of the coarse soil particles by fine-sized FA particles and flocculation function and binding action of PAM.

Selenium (Se) is an essential trace element for human health, and humans mainly consume Se through diet. China is recognized as a Se-deficient country, and the study of Se migration and accumulation relationships between crops and soils is essential for Se-deficient areas. In this experiment, the greenhouse pot experiment of Chinese cabbage (Brassica rapa L. ssp. pekinensis), wheat (Triticum aestivum L.) and pepper (Capsicum annuum L.) were carried out with the Guanzhong region of Shaanxi Province and common farmland soils from Beijing Province. The relationship between the Se content in soil and crops organs (e.g., roots, stems, leaves, grain and fruit) and the differences in the Se-enriching capacity of the organs were analyzed. The following results were obtained: (1) all three field crops could absorb Se from soil, including Se-rich and -regulated soil and reach the standard of Se-enriched vegetables; (2) different organs of Chinese cabbage had different Se-enriching capacity, which can be arranged as leaf > stem > root, while the Se enrichment capacity of wheat was root > leaf > stem > grain, and for pepper it was root > leaf > fruit > stem; (3) when the soil Se regulation content reached 1.0–1.5 mg/kg, the utilization rate of Se in Chinese cabbage and pepper were higher, but when the soil Se regulation reached 4.0–5.0 mg/kg, the utilization rate of Se in wheat was higher.