Objectives Excessive fertilizer application and imbalanced nutrient ratios are prevalent in greenhouse cucumber production in China, leading to low fertilizer use efficiency and constrained yield improvement. This study investigated optimized fertilization for greenhouse cucumber using the Nutrient Expert (NE) system and tested the effects.

Methods Field experiments were conducted in 2023 and 2024 in major greenhouse cucumber production regions, including Beijing, Tianjin, Hebei, and Jiangsu. Each experiment included five treatments: conventional farmer practice (FP), Nutrient Expert-recommended fertilization (NE), and NE-based treatments excluding nitrogen (NE-N), phosphorus (NE-P), or potassium (NE-K). Cucumber yield, nutrient uptake, and fertilizer use efficiency were measured.

Results Compared with FP, the NE treatment significantly reduced N, P₂O, and K₂O input amount by 330.3, 342.8, and 462.0 kg/hm², respectively, while maintaining similar cucumber yield, and increased the net profit by 6000 yuan/hm². The NE treatment improved N, P₂O, and K₂O uptake by 28.3, 4.9, and 43.3 kg/hm², respectively, while reduced the apparent nutrient surpluses by 359.9, 347.2, and 504.3 kg/hm², representing reductions of 63.4%, 87.7%, and 97.7%, respectively. The fertilizer nutrient recovery efficiencies were thereby increased by 8.5, 3.6, and 6.5 percentage points for N, P, and K, respectively, the partial factor productivity of fertilizers rose by 89.8, 390.0, and 108.5 kg/kg, and the agronomic efficiency improved by 11.5, 44.5, and 12.4 kg/kg.

Conclusions The Nutrient Expert system optimized fertilization for greenhouse cucumber by effectively reducing fertilizer input, significantly increasing nutrient uptake and fertilizer use efficiency, and lowering nutrient surplus without compromising yield. It is recommended as a viable approach for fertilizer recommendation in greenhouse cucumber production.