Fertilization Methods for Lettuce
1. Base Fertilizer: Sufficient base fertilizer is essential for growing lettuce. Only with adequate base fertilizer can the germination rate be effectively improved, preventing seed and sprout rot. Base fertilizer is usually applied during land preparation. Typically, 10 kg of well-rotted organic fertilizer, 0.5 kg of superphosphate, and 0.2 kg of potassium sulfate are applied per 10 square meters, mixed thoroughly.
2. Topdressing
(1) Germination Period: The germination period refers to the time from seed germination to cotyledon unfolding. It is recommended to apply some water-soluble fertilizer when the seed has germinated and the fourth true leaf has emerged. Water-soluble organic fertilizer containing humic acid is preferred, as it promotes root growth and seedling development.
(2) Seedling Stage: Lettuce seedlings have a high demand for nitrogen fertilizer, followed by phosphorus fertilizer, and a relatively low demand for potassium fertilizer. Generally, watering can be done 1 to 3 times as needed, and foliar fertilization with a 0.1% potassium dihydrogen phosphate and 0.3% urea solution can be applied 1 to 2 times for significant yield increase. (3) Rosette Stage: The rosette stage, also known as the vegetative growth stage, occurs when all the leaves have fully unfolded from the initial cluster to the second leaf ring. At this stage, lettuce requires more nitrogen and potassium fertilizer. Generally, 6-8 kg of urea and 5-6 kg of potassium sulfate per acre are needed. Alternatively, a high-nitrogen, high-potassium fertilizer like Moore's Quick-Acting Water-Soluble Fertilizer can be used, with 5 kg per acre diluted in water for irrigation.
(4) Heading Stage: Lettuce requires more potassium fertilizer and less nitrogen fertilizer during the heading stage. Generally, 11-14 kg of urea and 8-9 kg of potassium sulfate or 20-25 kg of 45% high-nitrogen, high-potassium compound fertilizer per acre are applied. For foliar fertilization, a 0.2% potassium dihydrogen phosphate solution can be sprayed on the leaves 2-3 times during the heading stage.
In general, fertilization is essential for high lettuce yields, but more fertilizer is not necessarily better. It is crucial to avoid this misconception and apply fertilizer rationally based on the growth of the lettuce at each stage.
