To improve the potassium availability of feldspar at ordinary temperatures, the mechanical grinding and addition of sodium hydroxide/salts were employed to study the effects of mechanical activation and strong alkali addition on particle characteristics, water-soluble potassium, and the available potassium of feldspar. A laser particle size analyzer was utilized for the direct determination of particle size distribution (PSD) using ground samples. The Brunauer–Emmett–Teller (BET) method was employed for specific surface areas. X-ray diffraction (XRD) was employed for structural characterization, scanning electron microscopy (SEM) for morphology exploration, and energy dispersive spectroscopy (EDS) to determine the chemical composition of potassium feldspar powder. The results revealed that the mechanical activation of potassium feldspar could reduce the particle size and produce agglomerated nanoparticles in the later period. The addition of NaOH and sodium salt did not cause agglomeration, and NaOH dissolved the nanoparticles. The water-soluble potassium content of feldspar in each treatment increased during mechanical grinding, from 21.64 mg kg⁻¹ to 1495.81 mg·kg⁻¹, by adding NaOH 5% weight of potassium feldspar powder and to 3044.08 mg·kg⁻¹ by adding NaOH 10% weight with effects different from those of mechanical shaking. By comparison, only 162.93 mg·kg⁻¹ water-soluble potassium was obtained by adding NaOH 5% weight. The dissolved potassium in the former case was significantly higher than in the latter, and the addition of NaOH and sodium salts significantly enhanced the water-soluble potassium contents due to ion exchange. Furthermore, the addition of sodium hydroxide improved the water-soluble potassium due to its mechanochemical action on potassium feldspar. The mechanical energy changed the crystal structure of potassium feldspar, explaining the increase in available potassium. The addition of sodium salts did not promote change in the feldspar’s structure, thereby did not raise the available potassium content. The reason for this was related to the mechanochemical action on sodium hydroxide and feldspar, which could promote the dissolution of fine particles, thereby incrementing the available potassium.

Humic acid is a macromolecular organic compound with active groups that, when applied to the soil, can regulate the storage and release of nutrient elements. The effects of a humic acid application at two application rates (F-1: 15 t·hm⁻² and F-2: 30 t·hm⁻²) on soil physicochemical properties and plant growth and yield were compared in field experiments to explore the impact of the humic acid dosage on the soil fertility of aeolian sandy soils. The CEC, EC, pH, organic matter, and available nutrient content were measured in the 0~20 cm and 20~40 cm soil before and after the humic acid application. The results showed that the soil organic matter and available nutrient content increased significantly with an increased humic acid application rate. In the 0~20 cm soil layer, the contents of soil alkaline-hydrolyzable nitrogen, available potassium, and organic matter were the highest in the F-2 treatment, at 24.97, 207.66 mg·kg⁻¹, and 8.99 g·kg⁻¹, respectively, which increased by 76%, 66%, and 54% compared with the control treatment. On the other hand, the content of available phosphorus was the highest in the F-1 treatment, at 13.23 mg·kg⁻¹, which was 38% higher than the control. In the 20~40 cm soil layer, the contents of soil alkaline-hydrolyzable nitrogen, available phosphorus, and available potassium were the highest after the F-2 treatment, at 16.33, 8.51, and 17.14 mg·kg⁻¹, respectively, which increased by 19%, 113%, and 58% compared with the control. The organic matter content was the highest in the F-1 treatment, at 7.61 g·kg⁻¹. After the humic acid application, the CEC and EC increased significantly, and the pH decreased. In addition, the growth status (leaf length, tillering number, and chlorophyll content) and yield of the Cyperus plants significantly increased with an increase in the humic acid dosage. In short, adding humic acid can effectively improve the physical and chemical properties of aeolian soils, regulate the nutrient circulation in the soil, and increase the yield and income from Cyperus cultivation.