Greenhouse vegetable cultivation plays a vital role in ensuring high yields and stable supply of fresh produce. As living standards rise and urbanization accelerates, the demand for diverse, high-quality, and off-season vegetables has increased significantly. This has led to the emergence of the "Vegetable Blue Project," which has become a key focus in municipal planning. With the development of greenhouse farming, seasonal limitations have been overcome, creating a new independent agricultural system. Not only does this bring substantial economic returns to farmers, but it also provides social benefits by addressing food shortages during winter in northern regions. For example, the Shouguang Vegetable Base in Shandong has greatly improved the vegetable supply in Beijing and Tianjin. Similarly, Haicheng City in Liaoning has not only met the needs of major cities in Northeast China but even exported vegetables to Russia. Many rural areas have transformed from poverty to prosperity due to the growth of greenhouse agriculture.
Greenhouse vegetables are known for their high yield and short growth cycle, allowing multiple harvests throughout the year. This requires consistent and adequate fertilizer input. On average, 1500–2250 kg of compound fertilizer per hectare is applied. Traditionally, ammonium sulfate was widely used as a nitrogen source, while ammonium bicarbonate and urea were less common due to the risk of ammonia toxicity in enclosed environments. High nitrogen concentration can lead to leaf burn and stunted growth in leafy vegetables, prompting farmers to avoid these fertilizers for safety reasons. However, long-term use of ammonium sulfate can cause soil compaction, degrade soil structure, and pollute groundwater.
To address these issues, farmers began using ammonium bicarbonate and urea instead, applying them more frequently—about 5–6 times per season—to reduce ammonia volatilization. Although this approach helps prevent damage, it leads to inefficiencies in labor and resource use. The introduction of slow-release ammonium carbonate and urea has provided a better solution. When combined into long-acting compound fertilizers, they offer a more balanced and sustainable option for greenhouse vegetable production. Field trials in Dalian demonstrated impressive results: when applying 1800–1950 kg/ha of long-acting compound fertilizer during transplanting, cucumber yields reached 9150 kg/ha, and tomato production increased by 11,250 kg/ha, significantly boosting economic returns. This advancement has brought real benefits to farmers, improving both productivity and sustainability in greenhouse agriculture.
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