To increase the yield and economic benefits per unit area, it is more important to promote the formation and improvement of tobacco leaf quality, which is the ultimate goal of fertilization of flue-cured tobacco and the final expression of the quality of flue-cured tobacco products. The quality of tobacco leaves is the result of a combination of soil, climate and human factors (variety, fertilization, etc.). In this system, fertilization is the biggest variable factor. Fertilization first affects the soil environment, which in turn affects the quality of tobacco leaves. There is an inevitable connection between the three. Moreover, soil and fertilization issues are important factors in determining the sustainable and stable development of tobacco production.
First, the determination of the amount of flue-cured tobacco
　　 1. Determination of the amount of nitrogen fertilizer
Nitrogen fertilizer has a great role in the formation of tobacco leaf yield and output value. In the production, there is often too much nitrogen fertilizer application, and the application of nitrogen fertilizer is too much. Although the yield of tobacco leaves increases, when the nitrogen application rate exceeds a certain limit , the fertilizer benefit, that is, the yield per mu minus the cost is significantly reduced, and the quality of tobacco leaves is deteriorated. After years of multi-point test, under intensive conditions, the cultivation of tobacco on k326 medium soil fertility, clouds 85, v2, clouds need a large amount of fertilizer and other 87 varieties, appropriate amount of nitrogen typically 7-9 　 k/ mu; red big, g28 and other varieties requiring less fertilizer are 4 ~ 6 　 k/ mu, of which red is 4 to 5 　 k / acre, g28 is 5-6 　 k/ mu.
　　 2 , the determination of the amount of phosphate fertilizer
The ratio of nitrogen to phosphorus ( n : p2o5 ) can generally be reduced from the previous 1 : 2 to 1 : 0.5 to 1.0 . Under normal circumstances, such as the application of 12-12-24 , 10-10-25 , 15-15-15 tobacco compound fertilizer, it is not necessary to apply calcium or calcium magnesium phosphate fertilizer; such as the application of tobacco compound fertilizer is Potassium nitrate, applying calcium or calcium magnesium phosphate per acre 20 to 30 　 k , can meet the needs of flue-cured tobacco production . The phosphate fertilizer can be applied in a targeted manner based on the results of the soil analysis and the compound fertilizer used.
　　 3 , the determination of the amount of potassium fertilizer
From the level of potassium application, when the amount of potassium applied ( k2o ) reaches 20 　 Above k/ mu, the potassium content of tobacco leaves does not increase with the increase of potassium application. In addition, the ratio of nitrogen fertilizer and potassium fertilizer is also closely related to the amount of nitrogen fertilizer. The ratio of potassium fertilizer at low nitrogen application level is higher than that at high nitrogen application level, such as planting safflower Dajinyuan, g28, etc. Variety, nitrogen application 4 ~ 6 　 k / mu, nitrogen to potassium ratio ( n : k2o ) should be 1 : 2.5 ~ 3.0 : such as planting k326 , Yunyan 85 , Yunyan 87 , v2 and other varieties, nitrogen application 7 ~ 9 　 k / mu, the ratio of nitrogen to potassium can be 1 : 2.5 ~ 3 . In short, the amount of potassium applied per mu can be controlled within the range of 15 to 20 kg.
Second, flue-cured tobacco fertilization method
Mastering proper fertilization methods can improve the quality of flue-cured tobacco and fertilizer utilization.
　　 1. Application of nitrogen, phosphorus and potassium fertilizers
( 1 ) Compound fertilizer and potassium sulfate should be determined according to the groundwater level and fertility level, and it is recommended to apply less or no pond fertilizer (low soil fertility is less, soil fertility is not applied), heavy or topdressing (water table) Low is heavy , such as smoke and mountain smoke; when the groundwater level is high, it is heavy, such as Tianyan. 1/3 of the available tobacco and potassium fertilizer as banding, pond fertilizer for 1/3 1/3 15 to 20 days after transplanting as a top dressing. Tianyan uses 1/3 of compound fertilizer and potassium sulfate as pond fertilizer, and 2/3 as top dressing.
( 2 ) Pu-calcium or calcium-magnesium-phosphorus fertilizer is suitable for strip application, that is, evenly applied to the bottom of the soot before the treatment, can improve the fertilizer efficiency. In addition, calcium magnesium phosphate fertilizer is an alkaline fertilizer, and should not be mixed with acidic fertilizers such as compound fertilizer or potassium sulfate to avoid chemical reaction and reduce fertilizer efficiency, and the application effect on acidic soil is better.
( 3 ) To prevent direct contact between fertilizer and tobacco plants, ring fertilization can be used to keep fertilizers and tobacco plants 10 to 15 　 The distance of m to avoid burning seedlings. Particularly disposable fertilizing mulch smoke, but also to pay attention to this problem.
　　 2 , the application of medium and micro nutrients
The application rate of micronutrients in flue-cured tobacco is generally low, but it has a physiological role that cannot be ignored in the growth and quality formation of flue-cured tobacco. The application of medium and micronutrients should be based on the principle of “lack of what, what to supplementâ€. Cloud opium planting tobacco soil and widespread magnesium deficiency, boron deficiency, lack of local molybdenum, zinc, these types of control methods deficiency symptoms are as follows:
Magnesium deficiency: 2-3 sprays with 0.2 to 0.5% magnesium sulfate solution or 10-15 magnesium sulfate per acre 　 k
Boron deficiency : : Foliar application with 0.1 to 0.25% borax solution or 0.5 kg of borax per acre combined with other fertilizers
Molybdenum deficiency: Spray with 2 to 3 times with 0.05 to 0.1% ammonium molybdate .
Zinc deficiency: Spray with 0.1 to 0.2% zinc sulphate solution 2 to 3 times.
　　 3 , the application of cake fertilizer
The fertilizer content of cake fertilizer (mainly rapeseed cake) is generally 4 to 5% , and the suitable application amount per mu is 20 to 30. 　 k . Excessive application of cake fertilizer tends to make the middle and upper leaves more mature and the nicotine content is further increased.
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