Fertilizer requirement characteristics and fertilization skills of heading lettuce

The characteristics of fertilizer requirement of heading lettuce is a herbaceous plant of Asteraceae lettuce, which is suitable for slightly acidic clay soil or soil with rich organic matter and strong ability of water and fertilizer conservation. The growth cycle of heading lettuce can be divided into germination stage, seedling stage, rosette stage and heading stage. It is generally believed that every 1000 kg lettuce needs to absorb 3.7kg N, 1.45kg P and 3.28kg K. Heading lettuce grows rapidly, likes nitrogen fertilizer, and absorbs less fertilizer at the initial growth stage. When it enters the heading stage 70-80 days after sowing, the nutrient uptake increases sharply. In one month of the heading period, the nitrogen absorption can account for more than 80% of the whole growth period. The absorption of phosphorus and potassium is similar to that of nitrogen, especially the absorption of potassium is not only large. And it lasts until the harvest. Phosphorus deficiency at seedling stage had the greatest effect on growth, and phosphorus deficiency at heading stage would affect lettuce heading. The lack of potassium during the heading period seriously affected the leaf weight. Fertilization techniques the amount of fertilizer applied per mu of heading lettuce during the whole growth period is 25003000kg of farm manure (or 35000kg of commercial organic fertilizer), 14017kg of nitrogen (N), 68kg of phosphate (P205) and 1113kg of potassium (K20). Organic fertilizer is used as base fertilizer, nitrogen and potassium fertilizer is divided into base fertilizer and topdressing, and phosphate fertilizer is all used as base fertilizer. Mixed application of chemical fertilizer and farm manure (or commercial organic fertilizer). The basic fertilizer applied 25003000kg / mu of farm manure (or 350kg / mu of commercial organic fertilizer), 4kg of urea, 13kg of diammonium phosphate, 7kg of potassium sulfate, and 20kg of calcium nitrate per mu of calcium-deficient soil. Topdressing at rosette stage: urea 6kg / mu, potassium sulfate 5kg / mu. Topdressing at the initial stage of heading: 912kg of urea and 6kg of potassium sulfate per mu. Topdressing in the middle stage of heading: 6kg of urea and 5kg of potassium sulfate per mu. Extra-root topdressing can be foliar sprayed with 0.2% potassium dihydrogen phosphate solution for 2 or 3 times during the heading period. In the case of soil calcium deficiency, 1% calcium nitrate solution can be sprayed on the leaves of the rosette stage for 3 consecutive times, once every 7 days, and stop spraying at the end of the rosette stage. Protected cultivation can increase the application of carbon dioxide gas fertilizer.