1 26 rate of over 95%. The plants reached an average height of approximately 7 cm around half a month after sowing and entered maturity by day 30. A notable observation was the change in leaf color from dark green to a shiny, black-green hue. For comparison, spinach was sown concurrently in a nearby plot using the same cultivation practices but in the native soil. While the growth of the soil-grown spinach was comparable to that in the substrate, the final harvest results of spinach grown in the soil–in terms of both plant height and leaf coloration–were superior than those in the prepared substrate. The product has undergone heavy metal testing by Tangshan Academy of Agricultural Sciences, and the test results meet the limit requirements for food contaminants in national standards. 30 days after sowing in substrate 39 days after sowing in ordinary field 4. RESEARCH FOR IMPROVEMENT OF LOW-PRODUCTIVITY LAND The research results were used as conditioners for the improvement of severe salinealkali land in Minqin, Gansu, desert land in Ordos, Inner Mongolia, and loess land in Shouyang, Shanxi. By adjusting the mixing ratio of conditioners and low-quality soils, the improvement needs of different low-quality soils can be met. In the improvement of salinealkali land and sandy land, numerous potted planting experiments and small-scale field experiments have shown that the improvement needs can be achieved when 10%-50% of conditioners are added, and the improvement effect is best when 40% of conditioners are applied. The salt precipitation rate of saline-alkali land after the optimal ratio improvement increased by 35%, and the soil pH value decreased by 0.5-1.2 units. For sandy land with the optimal ratio improvement, the underground water from coal mine was fully utilized, and the stability of soil aggregates and soil water retention and moisture conservation performance were significantly enhanced under the action of microorganisms. In the improvement of loess land in Shouyang, the local land consolidation and ecological backfill treatment of coal mining subsidence areas were fully utilized to study the improvement effect of large-dose conditioners. The low-quality soils applied with 80% conditioners can not only meet the improvement of loess, but also process coal gangue on a large scale. Malabar spinach, Phaseolus vulgaris L., and cucumber were planted in the improved saline-alkali land, sandy land, and loess land, respectively. Figure 6 reveals a superior growth trend compared to that in the original soil, indicating that organic microbial fertilizer can accelerate microbial metabolism, promote organic matter mineralization, and rapidly improve soil nutrient cycling and soil fertility; a certain ratio of coal gangue can improve the aggregate structure of low-
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