Effects Of Chemical Fertilizer Reduction And Humic Acid On The Growth And Yield Quality Of Flue-cured Tobacco

In view of the practical problems such as waste of resources,ecological environment pollution,and decline in the yield and quality of flue-cured tobacco caused by excessive application of chemical fertilizers in the process of flue-cured tobacco planting in Yunnan Province.Starting from the substitution of humic acid for part of the chemical fertilizer and the reduction of the chemical fertilizers application to increase efficiency.It is important to conduct research on the effects of chemical fertilizer reduction and humic acid application on the growth and development,economic benefits and internal and external quality of flue-cured tobacco is of great significance to promoting the sustainable development of green and high-quality tobacco leaves in Yunnan Province.In order to clarify the actual effect of humic acid partially replacing chemical fertilizers,under the condition of controlling the amount of chemical fertilizer application,two trial plots were selected in Chuxiong Tobacco Area of Yunnan Province in 2021 to carry out field experiments with the flue-cured tobacco variety"K236"as the research material.The experiment set up five fertilizer dosage gradients:conventional fertilizer application(G0),15%reduction of conventional fertilizer application(G1),30%reduction of conventional fertilizer application(G2),45%reduction of conventional fertilizer application(G3),and without chemical fertilizer application(G4).Two humic acid application gradients:without application of humic acid(H0)and conventional application of humic acid(H1),for a total of ten treatments,the main research results are as follows:(1)Effect of chemical fertilizer reduction and application of humic acid on the growth of flue-cured tobacco.Under the conditions of this test,compared with conventional fertilizer treatment(H0G0),when the dosage of chemical fertilizer was reduced by less than 30%,it will not affect the agronomic traits of flue-cured tobacco and the dry and fresh weights of tobacco leaves during the topping period.When the chemical fertilizer application was reduced to more than 45%,the agronomic traits of the tobacco plant began to decrease significantly.Tobacco plant growth was slowed down in the early stage,and the cluster,bud and flowering stages were delayed by one to four days,and the fresh and dry weight of the tobacco leaves at the topping stage were significantly reduced.The maximum leaf length,maximum leaf area,stem circumference,plant height,number of onset leaves and effective leaf number of flue-cured tobacco were significantly improved by humic acid application,which could promote the later stage of tobacco better maturation of tobacco leaves and shorten the growth period of flue-cured tobacco,which range from zero to five days.The application of humic acid at the same fertilizer dosage,increased the fresh weight of upper flue-cured tobacco and middle tobacco leaves is increased by 2.70%to 9.10%,the dry weight is increased by 2.60%to 12.5%,and the dry matter accumulation of upper and middle leaves is promoted.The amount of chemical fertilizer applied had a significant effect(P<0.05)on all agronomic traits indices throughout the roductive period of flue-cured tobacco,which was the main determinant of all indicators.The interaction between humic acid and chemical fertilizer reduction has a significant impact on flue-cured tobacco cluster planting stage.(2)The effect of chemical fertilizer reduction and application of humic acid on the economic benefits of flue-cured tobacco.Without the application of humic acid,compared with the conventional fertilization treatment(H0G0),when the chemical fertilizer application amount was reduced by less than 30%,the net benefit of the H0G1 treatment increased by3.23%～11.6%,and the rest of the economic benefits were not significantly different.Under the same amount of chemical fertilizer application,the application of humic acid has improved the yield production value and economic benefits of flue-cured tobacco.H1G1 treatment had the best comprehensive economic benefit.Compared with the conventional fertilization treatment(H0G0),the H1G1 treatment increased yield by 5.12%to 6.16%,the output value by 7.35%to 11.6%,and the net profit by13.0%to 20.3%.The effects of humic acid and fertilizer application on the yield of flue-cured tobacco have reached highly significant levels(P<0.01).(3)The effect of chemical fertilizer reduction and application of humic acid on the quality of flue-cured tobacco.In this trial,flue-cured tobacco with a 15%fertilizer reduction combined with humic acid treatment(H1G1)had the highest overall appearance quality score,and the conventional chemical composition and coordination were also improved.Compared with the conventional fertilization treatment(H0G0),the comprehensive score of appearance quality of the upper leaf in the H1G1 treatment increased by0.45～0.69(ten-point system),the middle leaf increased by 0.61～0.71,the lower leaf increased by 0.1～0.28,the total sugars of the upper,middle and lower leaves decreased by 6.07%～13.8%,the reduced sugars decreased by 6.25%～23.6%,and the glyco-alkali ratio decreased by 8.66%～34.9%.In the case of no humic acid application,the comprehensive score of the appearance quality of flue-cured tobacco treated with 15%reduction of chemical fertilizer(H0G1)is the highest,and the conventional chemical composition and coordination indexes are more similar to the suitable range of high-quality tobacco leaves.When chemical fertilizer application was reduced by 30%or more,the appearance quality indexes and comprehensive scores of tobacco leaves showed a downward trend with the decrease of chemical fertilizer application,and the conventional chemical composition and coordination indexes gradually deviated from the suitable range of high-quality tobacco leaves.In the case of the same amount of chemical fertilizer application,the combined application of humic acid mainly improves the appearance quality of the upper and middle tobacco leaves of flue-cured tobacco by improving the maturity of the tobacco leaves,increasing the oil content and making the tobacco leaves more loose.It also promoted the reducing sugars,total sugars,sugar-alkali ratio and potassium-chloride ratio of tobacco leaves to be closer to the suitable range of conventional chemical composition and coordination of high-quality tobacco leaves,so that the internal chemical composition of tobacco leaves in each leaf position were more coordinated,but the effect was weakened with the increase of fertilizer application.Both chemical fertilizer application amount and humic acid can affect the conventional chemical composition and coordination index of tobacco leaves.The interaction between the two has a significant effect on reducing sugar in upper leaves(P<0.05).The effect on reducing sugars and total sugars in middle leaves reached a significant level(P<0.05),and there was no significant effect on the lower leaves.In summary,the results of the study on the growth and development,economic benefits and yield quality of flue-cured tobacco in the two test sites of this experiment show that:under the existing cultivation conditions in Chuxiong Tobacco Area,the most suitable chemical fertilizer application range is 15%～30%of conventional chemical fertilizer(fertilization application amount:15.40～18.70 kg/666.7m~2tobacco-specific compound fertilizer with 27.72～33.66 kg/666.7m~2tobacco-specific topdressing).In summary,H1G1 treatment(18.70 kg/666.7m~2tobacco-specific compound fertilizer and 33.66 kg/666.7m~2tobacco-specific topdressing with 4.18kg/666.7m~2humic acid water-soluble fertilizer)can be used as a fertilization reference program for K326 variety in Chuxiong Tobacco Area,which can promote the growth and development of flue-cured tobacco and improve the yield quality of flue-cured tobacco while reducing the amount of chemical fertilizer application.