From the perspective of agricultural production, flue-cured tobacco is an important part of agricultural production of double cypress, and the purpose of fertilization is to improve the benefit of fertilization per unit area; From the perspective of cigarette industrial production, tobacco production should meet the needs of cigarette formula, which is conducive to the stable improvement of cigarette quality, which is the ultimate goal of tobacco production and the ultimate embodiment of tobacco product quality. Therefore, the fertilization of flue-cured tobacco should obey the needs of cigarette formula, not blindly pursue high yield, but aim at high quality and suitable production, so as to ensure the sustainable development of "two cigarettes"

(1) Fertilization principle of flue-cured tobacco

Correct fertilization of flue-cured tobacco depends on the types of flue-cured tobacco, characteristics of varieties, soil fertility conditions, fertilizer properties, temperature and rainfall during the growth period of flue-cured tobacco, and on obtaining the appropriate yield of tobacco leaves, so as to determine the appropriate amount of nitrogen, the proportion of nitrogen, phosphorus and potassium, the types of fertilizers, the amount of base fertilizer and the application method.

① the principle of nutrient balance

the normal growth and development of flue-cured tobacco and the formation of yield and quality need a variety of nutrients necessary for tobacco plants. Moreover, there is a balanced proportional relationship between these elements. For example, with the increase of fertilizer application, the middle and upper leaves of tobacco plants often turn green and white during the ripening process, which is caused by the imbalance of magnesium in tobacco plants. Nutrient balance is the basic principle of balanced fertilization. If we ignore this principle and blindly increase the dosage of a certain nutrient element, the yield and quality of tobacco leaves will be affected.

② fertilization principle according to soil

The main tobacco-growing soils of Shuangbai are yellow soil, paddy soil and purple soil. According to its moisture conditions, it can be divided into two categories: one is mountainous soil, such as purple soil, which has low groundwater level, less fertilizer loss and high fertilizer utilization rate; The other is paddy soil and yellow soil with high groundwater level, which have large fertilizer loss and low utilization rate. Therefore, the application amount of field tobacco is generally higher than that of ground tobacco.

③ Fertilization principle of varieties

Different flue-cured tobacco varieties are determined by their genetic characteristics, and their absorption and utilization of soil and fertilizer nutrients are quite different. The utilization rate of nitrogen, phosphorus and potassium fertilizer in Honghuadajinyuan (referred to as Hongda) is higher, while the utilization rate of fertilizer in K326 is lower. Therefore, under certain conditions, the difference in fertilizer demand of tobacco varieties is the main basis for determining the amount of fertilizer applied. Different varieties use different ratios of nitrogen, phosphorus and potassium. Among the suitable fertilizer ratios for varieties with weak fertilizer tolerance, such as Hongda and G28, the appropriate ratio of N and P2O5 is 8% ~ 12%, and K2O is 2% ~ 25%, that is, N ∶ P2O5 ∶ K2O = 1 ∶ 1 ∶ 2.5 ~ 3. K326, Yunyan 85 and other varieties with strong fertilizer tolerance have the following advantages: N content is 12% ~ 18%, P2O5 content is 5% ~ 8%, and K2O content is 22% ~ 28%, that is, N ∶ P2O5 ∶ K2O = 1 ∶ .5 ∶ 2 ~ 2.5.

④ Because of the principle of climate fertilization

Climate conditions mainly refer to the amount of rain and the temperature in tobacco field in that year. In rainy years, the loss of fertilizer is large, the temperature decreases correspondingly, the utilization rate of fertilizer decreases, and the fertilizer consumption of tobacco, especially nitrogen fertilizer, should be increased appropriately. On the contrary, the amount of fertilization should be reduced appropriately.

(2) Fertilization methods and periods

Under different climatic conditions, tobacco fields with different soil properties have different release, loss and absorption of nutrients, so different fertilization methods must be adopted to give full play to the benefits of fertilizers and regulate the nutrient supply of tobacco plants.

most of the double cypress flue-cured tobacco fertilizers are combined with base fertilizer and topdressing. In order to promote the growth of tobacco plants in the early and middle stages, most of them use heavy base fertilizer, with 2/3 or more of the total amount of fertilizer applied as base fertilizer and the rest as topdressing. The function of topdressing is not only to ensure the nitrogen supply in the middle and late growth period, but also to prevent premature fertilization and premature aging in the mature period. At the same time, the original amount of topdressing can be increased or decreased according to the appearance, soil and climate of tobacco plants in the field, so as to correct the original planned fertilizer consumption. If all fertilizers are used as base fertilizer, it will be difficult to recover the adverse effects on quality when the designed amount of fertilizer is too much. Therefore, topdressing is also a remedial measure to adjust nitrogen. Moreover, it is an effective means to achieve consistent growth in the field by applying partial fertilizer to weak seedlings and small seedlings to promote them to catch up with strong seedlings. For those tobacco fields with poor water and fertility conservation, less potential nitrogen and weak nitrogen supply capacity in the later stage, as well as areas with excessive rain and water in the early and middle stages and serious soil and nutrient loss, topdressing is an effective means to ensure nitrogen nutrient supply in the middle and late stages of tobacco plants and stabilize yield and quality.

the p>15N tracer test showed that the nitrogen utilization rate was lower in the whole strip application treatment, the middle in the 2/3 basal dressing treatment and the higher in the 1/3 basal dressing treatment. However, when the proportion of topdressing reached 5%, the nicotine content in the middle and upper leaves increased significantly, which was not good for improving the quality and retrieval of tobacco leaves. Therefore, the proportion of topdressing should be controlled at 3 ~ 4%.

Mastering proper fertilization methods and periods can improve tobacco yield, quality and fertilizer utilization rate. In actual production, we should pay attention to the following issues:

① Compound fertilizer and potassium sulfate should be determined according to the groundwater level and fertility level, and it is recommended to apply less pond fertilizer (if the soil fertility is low, less pond fertilizer will be applied; if the soil fertility is high, no pond fertilizer will be applied), and the cyclic fertilization or topdressing will be repositioned (if the groundwater level is low, the cyclic fertilization will be repositioned, such as ground tobacco and mountain tobacco; If the groundwater level is high, it will be topdressing.

(2) calcium superphosphate or calcium magnesium phosphate fertilizer is suitable for strip application, that is, it can be evenly spread at the bottom of tobacco moisture before soil moisture management, which can improve fertilizer efficiency. In addition, calcium magnesium phosphate fertilizer is an alkaline fertilizer, so it is not suitable to be mixed with acid fertilizers such as compound fertilizer or potassium sulfate to avoid chemical reaction and reduce fertilizer efficiency, and the application effect is good in acid soil.

③ To prevent direct contact between the fertilizer and the roots of tobacco plants, ring fertilization method should be adopted to keep the distance between the fertilizer and tobacco plants at 1 ~ 15cm to avoid burning seedlings.