Influence Of Reducing Fertilizer Nitrogen On Yield And Quality Of Flue-Cured Tobacco And Their Evaluation Of Technological Economic

Flue cured tobacco is an important economic crop in our country,and also a relatively large input of economic crops,in which fertilizer input accounts for a large proportion.Excessive application of chemical fertilizer will threaten the quality of tobacco leaves and the safety of ecological environment,and influence the sustainable development of flue-cured tobacco production.In order to reduce the amount of chemical fertilizer and improve the utilization efficiency of chemical fertilizer,the technology of reducing nitrogen application and increasing efficiency of flue-cured tobacco was studied in the rice growing and tobacco area respectively in Southern Hunan and the mountain area in Northwest Hunan,to provide reference for flue-cured tobacco fertilizing in the tobacco area of hunan.The main research conclusions are as follows:(1)The amount of nitrogen fertilizer could be reduced by increasing the density of rice stubble flue-cured tobacco.The effects of planting density and nitrogen application on flue-cured tobacco were studied during the two-factor field experiment with planting density(13890 plants/hm~2?16680 plants/hm~2?18195 plants/hm~2)and application amount of nitrogen fertilizer(120 kg/hm~2?142.5 kg/hm~2?165 kg/hm~2)in the rice growing and tobacco area of Southern Hunan.The results showed that:(1)With the increase of nitrogen application,the agronomic characters,SPAD value,leaf area index and photosynthetic characteristics of flue-cured tobacco increased;With the increase of planting density,the plant height,stem circumference and leaf area decreased,the chlorophyll and net photosynthetic rate increased first and then decreased;The interaction of nitrogen and density had a significant impact on agronomic and photosynthetic characteristics.(2)Based on the combination of planting density 18195 plants/hm~2 and nitrogen application quantity 142.5 kg/hm~2,planting density13890 plants/hm~2 and nitrogen application quantity 120 kg/hm~2,the physical characteristics of upper and middle tobacco leaves were more outstanding.By the combination of the planting density of 18195 plants/hm~2 and the application quantity of nitrogen 120 kg/hm~2,the planting density of 16680 plants/hm~2 and the application quantity of nitrogen 120 kg/hm~2,the chemical composition of tobacco leaves in the upper and middle part was better.The economic properties of tobacco leaves were better in the treatment group by planting density18195 plants/hm~2 and applying nitrogen quantity 142.5 kg/hm~2.(3)The physical characteristics of tobacco leaf were mainly affected by the planting density(contribution rate34.46%)and the amount of nitrogen applied(contribution rate 36.18%),the chemical composition of tobacco leaf was mainly affected by the amount of nitrogen applied(contribution rate 48.71%),and the economic properties of tobacco leaf were mainly affected by the amount of planting density(contribution rate 41.28%).The yield and quality of 18,195plants/hm~2 and 142.5kg/hm~2 were better in the rice growing and tobacco area in Southern Hunan.(2)The replacement of organic fertilizer for flue-cured tobacco in rice stubble could reduce the application of nitrogen fertilizer by 50%?75%.In the rice and tobacco growing area of South Hunan,five treatments were designed to replace 0%,25%,50%,75%and100%of chemical fertilizer nitrogen.The effects of reducing chemical fertilizer nitrogen were studied,by replacing organic fertilizer nitrogen on the agronomic characteristics,photosynthetic characteristics,dry matter accumulation and distribution,nutrient accumulation and distribution,fertilizer utilization efficiency,economic characteristics and tobacco quality of flue-cured tobacco.The results showed that:(1)The agronomic characters of flue-cured tobacco treated with 50%organic nitrogen and 75%organic nitrogen were better.(2)The application of organic nitrogen could increase the chlorophyll content and photosynthetic characteristics of flue-cured tobacco in the growth and development period,increased the total dry weight of tobacco plant,promoted the accumulation of nitrogen,phosphorus and potassium,and improved the fertilizer utilization rate of flue-cured tobacco.(3)The chemical composition,coordination and smoking quality of the organic nitrogen treatment were higher than the 100%nitrogen treatment.(4)In addition to the physical and economic characteristics of the application of 100%organic fertilizer nitrogen was lower than that of 100%chemical fertilizer nitrogen,the application ratio of organic fertilizer nitrogen and chemical fertilizer nitrogen could improve the chemical,yield and output value of tobacco,the economic benefit of 50%organic fertilizer was the best,followed by 75%organic fertilizer.(3)The application of fertilizer nitrogen could be reduced by 9?18 kg/hm~2 by turning green manure into flue-cured tobacco.In the mountainous area of Western Hunan,planting Vicia sativa and ryegrass green manure,four levels of nitrogen reduction were designed,i.e.0 kg/hm~2,9 kg/hm~2,18 kg/hm~2 and 27 kg/hm~2.The effects of nitrogen reduction on the agronomic characteristics,chlorophyll dynamic changes,canopy indexes,photosynthetic characteristics,economic effects and tobacco quality of flue-cured tobacco were studied.The results showed that:(1)The effect of nitrogen application on flue-cured tobacco was significant after turning Vicia sativa and ryegrass as green manure.(2)There was no significant difference in agronomic characters,canopy index,photosynthetic characteristics and physical characteristics between 9?18 kg/hm~2 of nitrogen reduction and no nitrogen reduction treatment,but the chemical composition,sugar alkali ratio,sugar nitrogen ratio,potassium chloride ratio,fine tobacco ratio,yield,output value and economic benefit of tobacco leaves were significantly better than those of the control group and no nitrogen reduction treatment.(3)There was no significant difference in agronomic characters,tobacco canopy index,photosynthetic characteristics and physical characteristics of upper tobacco leaves,and yield between the treatment with 9 kg/hm~2 nitrogen reduction after turning over ryegrass and the treatment with no nitrogen reduction,but the ratio of sugar to alkali,ratio of sugar to nitrogen,proportion of premium tobacco and output value of the middle tobacco leaves were significantly better than the control group and the treatment with no nitrogen reduction.(4)The amount of nitrogen reduced after turning over the green manure was too large(27 kg/hm~2).The physical properties and economic properties of flue-cured tobacco were lower than those of the control group and other treatments of turning over the green manure.Excessive nitrogen reduction resulted in nutritional imbalance of flue-cured tobacco,which affected the growth of flue-cured tobacco leaves and reduced the output and output value of flue-cured tobacco.(5)Turn over the pressure of green manure to return to the field should be based on the type of green manure and soil fertility conditions to reduce the amount of nitrogen flue-cured tobacco application;In Western Hunan,9?18 kg/hm~2 of nitrogen is suitable to be reduced for Vicia sativa and 9 kg/hm~2 for ryegrass.(4)The evaluation of technological and economic was established for nitrogen reduction of flue-cured tobacco.The evaluation indexes were established by the combination of literature research and expert consultation,the index weight was determined based on the multiple correlation method of expert group opinion,the effect measurement model and membership function were used to standardize the evaluation indexes,and the comprehensive scores were calculated by the index and method to build the evaluation model of agricultural technology and economy,and the technology and economy evaluation of the representative nitrogen reduction measures of chemical fertilizer in Hunan tobacco area were carried out.