Increasingly, poor soils are used for plant cultivation involving chemical fertilizer (CF) usage which in turn lowers soil quality. To improve the quality of poor soils, promote plant growth, and reduce CF use, bio-organic-mineral fertilizer (BF) was introduced to poor soil to examine its effects on both soil and plants. Organic fertilizer (OF), CF, and mineral powder (MP) were applied as controls. When cotreating water spinach with fertilizer, the soil quality was improved with the increased doses of BF, OF, and MP. The BF treatment produced the most pronounced improvement. Applying CF reduced the soil quality. Under the CF treatment the largest plant-growth-promoting effect was observed within 30 d, whereas plants treated with BF showed the most favorable growth after 50 d. Moreover, for BF, plants’ nutritional quality was also higher, particularly in the long term. When poor soil was treated with fertilizer without plants, the soil quality changed as in the previous treatment; however, the change in this treatment was more pronounced and the remaining available elements in soil were higher, particularly in the case of CF treatment. These results indicate that BF treatment without CF can be applied to improve the quality of poor soil, and meanwhile promote plant growth and quality.