Analysis on Management of Water and Fertilizer in Tobacco Field

Compared with most other crops, the particularity of tobacco is that it harvests leaves. Tobacco leaves are gradually grown by tobacco roots absorbing nutrients and water from the soil. Therefore, in order to cultivate high-quality tobacco leaves, water and fertilizer management in tobacco field is very important. Scientific fertilization ensures yield and quality soil provides nutrients and water for tobacco plants, and the structure and nutritional composition of different types of soil are also different. In order to meet the growth needs of tobacco plants, it is necessary to change the soil nutrient structure by fertilization. Tobacco is a crop which is very sensitive to fertilizer. the type, amount, ratio, period and methods of fertilization will have a great impact on the yield and quality of tobacco. Too little fertilizer application, insufficient nutrient supply, can not achieve the desired production goal; excessive fertilizer application will greatly reduce the quality of tobacco leaves, not only increase the production cost, but also reduce the quality of tobacco leaves. Therefore, scientific and rational fertilization is the key to the production of high-quality tobacco leaves. In the process of fertilization, it is necessary to master the following key points. First of all, a reasonable amount of fertilizer application should be determined according to ecological factors such as soil types, water conservancy resources, climatic conditions and so on. When the soil is too loose or the rainfall is too much, the nutrients are easy to be lost, so the amount of fertilizer should be increased appropriately; when the soil is sticky or Rain Water is too little, the amount of fertilizer should be reduced appropriately to avoid the late ripening of tobacco leaves caused by slow release of fertilizer effect. Secondly, the reasonable fertilization method should be determined according to the growth characteristics of tobacco leaves. After transplanting, tobacco seedlings absorbed little nitrogen, phosphorus, potassium and other nutrients in the early stage. With the passage of time, the nutrient absorption rate of tobacco plants gradually accelerated, began to increase sharply one month after transplanting, and reached the maximum about 55 days after transplanting, and then decreased rapidly, in which the absorption of nitrogen decreased the fastest, followed by potassium, and the absorption of phosphorus changed relatively steadily in the whole growing period. Therefore, fertilizer supply should be "rich when young and poor when old" in order to meet the growth needs of tobacco leaves. Fertilization in tobacco field is usually based on the combination of base fertilizer and topdressing, and heavy application of base fertilizer, less or early application of topdressing. In the application of base fertilizer, double-strip fertilizer application method is often used. Before transplanting and ridging, 2 + 3 of the total amount of fertilizer was applied on both sides 15 cm away from the tobacco line, with a depth of about 20 cm, to ensure the growth needs of tobacco plants in the early and middle stages after transplanting. Topdressing can not only ensure the nitrogen supply in the middle and later stages of tobacco seedling growth and prevent early senescence during tobacco maturity, but also increase or decrease the original amount of topdressing according to the appearance, soil and climate of tobacco plants in the field. to correct the planned amount of fertilizer. If all fertilizers are used as base fertilizer, too much fertilizer will have a bad effect on the quality of tobacco leaves. Therefore, topdressing is also a remedial measure to adjust nitrogen. When topdressing, we should apply partial application to weak seedlings and small seedlings to promote them to catch up with strong seedlings, which is an effective means to improve the uniformity of tobacco seedlings in tobacco field. For those tobacco fields with poor water and fertility conservation, less potential nitrogen, weak nitrogen supply capacity in the later stage, and plots with too much Rain Water and serious nutrient loss in the early and middle stages, topdressing is an effective means to ensure the supply of nitrogen nutrients and stabilize the yield and quality of tobacco leaves in the middle and later stage. Topdressing can be done by irrigating roots and fertilizing outside roots. In general, the roots were irrigated with potassium nitrate aqueous solution (ternary compound fertilizer or diammonium phosphate aqueous solution) within 25 days after transplanting, and topdressing was divided into 2 to 3 times according to rainfall and tobacco seedling growth. In the middle and later stages of tobacco seedling growth, potassium deficiency sometimes occurs in tobacco leaves. According to tobacco leaf growth and soil fertility, extra-root topdressing method is adopted. The positive and negative sides of the leaves are sprayed with 0.2% green Fenwei solution or 0.5% potassium dihydrogen phosphate solution. It should be sprayed in the rosette stage, the prosperous period and the later stage of tobacco growth. Because the nutrient absorption rate of tobacco seedlings at night is 3-10 times higher than that during the day, it is better to spray at night or in the evening. Choose windless weather for spraying in order to facilitate the absorption of tobacco seedlings. Reasonable irrigation and drainage according to the growth characteristics of flue-cured tobacco is the basis for the growth and development of flue-cured tobacco and ensuring the quality of flue-cured tobacco. According to the characteristics of water demand of tobacco leaves at different growth stages, reasonable irrigation and drainage methods are adopted to maintain suitable moisture in tobacco field is a necessary condition to ensure high quality and stable yield of tobacco leaves. In the period of returning tobacco seedlings, the nutrient body of tobacco plant is small, the evaporation is less, and the water consumption of tobacco field is not large. However, due to the damage to the root system during transplanting, the absorption capacity decreased, and the transpiration of the aboveground part was still going on, the water balance in the tobacco plant was easy to lose balance, which led to tobacco wilting. Therefore, in the seedling stage, there should be sufficient water supply, increase the soil moisture, promote the rooting and return of tobacco seedlings, and improve the survival rate of transplanted tobacco seedlings. During this period, the soil water content should reach 70% to 80% of the maximum field capacity. In the root extension stage of tobacco seedlings, with the rapid growth of roots, stems and leaves also grew gradually, transpiration changed from surface evaporation to leaf transpiration, and the water consumption increased gradually. If the soil moisture is insufficient, the growth of tobacco will be hindered, but if the water supply is too much, it will affect the root growth of tobacco, so it is appropriate to keep the soil water content at about 60% of the maximum field capacity. The vigorous period of tobacco leaves is the period when tobacco leaves grow most vigorously and accumulate the most dry matter. The stems of tobacco plants grow taller and thicker rapidly, the leaves increase rapidly, and the roots grow further. The physiological activity of tobacco plant is exuberant, transpiration increases sharply, and the main form of water consumption is foliar transpiration. If the water supply is insufficient during this period, it will have an irreparable impact on the yield and quality of tobacco, so irrigation must be strengthened to keep soil moisture up to more than 80% of the maximum field capacity to meet the needs of tobacco growth. In the mature stage of tobacco leaves, after budding, tobacco leaves mature one after another from bottom to top, and the physiological activities of tobacco plants are mainly the synthesis, accumulation and transformation of dry matter. With the increase of harvest times, the field leaf area coefficient decreased gradually, the transpiration intensity decreased accordingly, the form of water consumption in tobacco field gradually changed from foliar transpiration to surface evaporation, and the water consumption decreased. In order to make the tobacco leaves yellow and mature normally, the soil moisture should be kept at about 70% of the maximum field capacity during this period. Tobacco is a very sensitive crop to flooding, and too much water is harmful to the growth of tobacco. Excessive soil moisture will cause lack of soil air, affect root system development and tobacco growth, and seriously cause tobacco plant death; flooding during maturity will cause bottom drying, dry matter can not be fully accumulated, leaves are thin, no aroma, sugar and alkali content decreases, seriously affecting the quality of tobacco leaves. Therefore, we should actively do a good job of tobacco field drainage in the rainy season. In short, it must be irrigated and discharged reasonably according to tobacco production period and environmental conditions to ensure the demand of tobacco growth, so as to effectively improve the yield and quality of tobacco.