Objectives To address issues such as reduced fertilizer utilization efficiency and decreased yield and quality caused by unreasonable fertilization in facility cucumber production, this study investigates the scientific ratios of basal to top-dressing fertilizers and the frequencies of top-dressing applications, aiming to provide technical support for high-quality and high-yield cucumber cultivation management.

Methods Using 'Jinxiu No. 8' cucumber as the test material, under the premise of consistent total chemical fertilizer application (N 750 kg/hm², P₂O₅ 300 kg/hm², K₂O 1050 kg/hm²), four basal to top-dressing ratio treatments for fertilizer were set up, as 1∶9 (T1), 2∶8 (T2), 3∶7 (T3), and 4∶6 (T4). During the full fruiting period, rhizosphere soil samples were collected to analyze nutrient content and microbial abundance, while plant and fruit samples were gathered to measure root vigor, growth, yield, and quality, and the optimal basal to top-dressing fertilizer ratio was screened. Subsequently, under the optimal ratio, four top-dressing frequency treatments were established, with applications every 3 days (D3), 6 days (D6), 9 days (D9), and 12 days (D12). During the peak fruiting period of cucumber, rhizosphere soil and plant samples were collected for analysis of similar indicators.

Results As the proportion of top-dressing fertilizer increased, the contents of available N, available P, and available K in soil at harvest gradually increased, while the plant height, leaf area, and yield of cucumbers showed a trend of first increasing and then decreasing, with the highest yield observed under the 2∶8 basal to top-dressing ratio (T2). Under consistent irrigation and fertilization amounts, the differences in available N, available P, and available K contents between D6 and D9 treatment were not significant, but both were significantly higher than those of D3 and D12 treatment. The organic matter content was highest in D12. In the spring crop, compared to D3, the D9 treatment significantly enhanced soil microbial abundance, enzyme activity, root vigor, and photosynthetic rate (Pn), achieving the highest total yield and fertilizer utilization efficiency. It increased yield by 8.64% and improved nitrogen, phosphorus, and potassium fertilizer utilization efficiencies by 22.69%, 22.38%, and 40.71%, respectively, compared to D3, with no significant difference from D6. In the autumn crop, the D6 treatment yielded the best overall growth and production of cucumbers.

Conclusion Appropriately increasing the proportion of top-dressing fertilizer can significantly improve microbial community structure, enhance soil organic matter, available nitrogen, and available phosphorus contents, boost soil enzyme activity and root vigor, thereby promoting plant growth and increasing cucumber yield, with the best results observed at a basal to top-dressing ratio of 2∶8. On this basis, for spring cucumbers, top-dressing every 6 to 9 days results in the best soil porosity, microbial abundance, soil fertility, fertilizer utilization efficiency, chlorophyll content, net photosynthetic rate, carbon-nitrogen metabolism capacity, and yield, along with the best overall quality. For autumn cucumbers, top-dressing every 6 days yields the best comprehensive results.