Fertilization status-quo in greenhouse vegetable production in Tianjin and the potential and countermeasures of fertilizer reduction

Objectives Low fertilizer utilization efficiency and environmental pollution, caused by excessive fertilization, are common in greenhouse vegetable production. We investigated the current fertilizer application rates in greenhouse vegetable fields in Tianjin, to provide some scientific and reasonable proposals for the efficient and environmental friendly fertilization.

Methods We investigated the fertilizer application information in 193 greenhouse vegetable fields in Tianjin, and summarized the main nutrient sources, input rates and ways, and at last predicted the reducing potential of both total and chemical nutrient input in greenhouse vegetable fields.

Results The average amounts of N, P₂O₅ and K₂O input were 775.6 kg/hm², 715.5 kg/hm² and 524.9 kg/hm² in solar greenhouses, respectively, which were significantly higher than those in plastic greenhouse (670.9 kg/hm², 584.5 kg/hm² and 425.3 kg/hm²). Of the total N, P₂O₅ and K₂O input, more than half were from organic manures in both solar and plastic greenhouses. Chemical fertilizers contributed 44.2% of total P₂O₅ input in solar greenhouses and 48.8% in plastic greenhouse, respectively. Basal application was the main fertilization method in greenhouse vegetables, which accounted for 79.4% of total N, 80.2% of total P₂O₅ and 73.5% of total K₂O input in solar greenhouses, and 70.2% of total N, 78.2% of total P₂O₅ and 67.4% of total K₂O input in plastic greenhouses, respectively. The average ratios of N, P₂O₅ and K₂O were 1∶0. 92∶0.69 in solar greenhouses and 1∶0.87∶0.63 in plastic greenhouses, respectively. Comparing with the recommended nutrient rate in vegetables, both current N and P₂O₅ inputs were excessive for most vegetables, but K₂O input was insufficient in pakchoi and cabbages. The relative potential reduction was 31.5%–65.0% for the total nutrients input (N + P₂O₅ + K₂O), and is 22.4%–66.6% for the total chemical nutrients input in greenhouse vegetable fields in Tianjin.

Conclusions Basal application is the main nutrient fertilization method in Tianjin. The total nutrient input are excessive in most greenhouse vegetable fields, especially those of N and P₂O₅ in Tianjin, comparing with the recommended nutrient rate. The most concerned vegetables with excessive N and P₂O₅ inputs are eggplants, tomatoes and celery. Therefore, the fertilizer reduction in greenhouse vegetable fields should focus on eggplants, tomatoes and celery in Tianjin.