Effect Of Charcoal-based Organic Fertilizer On Carbon Distribution In Soil Aggregates And Quality Of Roasted Tobacco Production

The quality of roasted tobacco production has been declining due to soil acidification,carbon deficiency and microbial imbalance.In recent years,the charcoal-based organic fertilizer made by compounding biochar with organic fertilizer has a prominent role in maintaining the balance of soil ecosystem,fixing carbon and fertilizer,regulating carbon and nitrogen,improving soil organic carbon index,improving soil structure and promoting crop growth and development due to its unique physicochemical properties.In this study,a typical red soil planted with tobacco in Sichuan was selected as the research object,and five treatments were set up through field trials: control(CK),single application of biochar(T2),single application of organic fertilizer(T3),50 % rotted cow manure compounded with biochar 50 % charcoal-based organic fertilizer treatment(T4),and 70 % rotted cow manure compounded with biochar 30 % charcoal-based organic fertilizer treatment(T5).To investigate the effects of charcoal-based organic fertilizer on soil chemical characteristics,composition and stability of soil aggregates,distribution of organic carbon in soil aggregates,as well as the growth and chemical quality of roasted tobacco leaves,and determine the results of the application of charcoal-based organic fertilizer in the improvement and fertilization of tobacco plant soil and roasted tobacco production.The main research results are as follows:(1)Charcoal-based organic fertilizer can regulate the nutrient balance of roasted tobacco throughout the reproductive period and provide better nutrient support for the growth and development of roasted tobacco.0-20 cm soil layer,the p H value of charcoalbased organic fertilizer(T4 and T5)treatment at maturity increased by 1.78 % to3.38 %,organic matter content increased by 28.84 % to 33.21 %,and fast-acting phosphorus increased by 52.84 % to 62.19 % compared with T2(biochar)and T3(rotted cow manure)treatments.The fast-acting phosphorus increased by 52.84 % to 62.19 %.In comparison between the charcoal-based organic fertilizer treatments,the T5 treatment increased alkaline nitrogen more significantly(p<0.05),while the T4 treatment increased fast-acting potassium content more significantly(p<0.05).(2)With the passage of the roasted tobacco reproductive period,the stability of the soil agglomerates of tobacco first increased and then decreased,and the agglomerates of <0.053 mm particle size transformed to 0.25-2 mm and 0.053-0.25 mm particle size,and the 0.25-2mm particle size was dominant.The charcoal-based organic fertilizer could influence the distribution of agglomerates’ particle size and improve the soil structure.In the 0-20 cm soil layer at maturity,the charcoal-based organic fertilizer treatments(T4 and T5)had 1.99 % to4.19 % higher agglomerate content at the 0.25-2 mm grain level,4.41 % to 19.67 % higher mean weight diameter of agglomerates(MWD),and 4.67 % to 17.57 % higher agglomerate content larger than 0.25 mm(R0.25)than the treatments with biochar(T2)and organic fertilizer(T3)alone.The redundancy analysis showed that the soil organic matter contet was significantly and positively correlated with the particle size distribution of 0.25-2 mm and0.053-0.25 mm agglomerates in the regrowth,vigorous and maturity stages,explaining66.50 %,69.80 % and 80.90 % of the variation in the particle size distribution of agglomerates,which was the main influencing factor on the particle size distribution of tobacco-planted soil agglomerates.(3)Total organic carbon(TOC),easily oxidizable organic carbon(ROC)and dissolved organic carbon(DOC)of soil with tobacco planting were concentrated in 0.25-2 mm(30.20 %～46.53 %)and 0.053-0.25 mm(20.94 %～30.90 %)granular aggregates at maturity,while the carbon pool management index of 0.25-2 mm granular aggregates was the highest.0-20 cm soil layer,the organic fertilizer(T4 and T5)treatments increased the TOC content of 0.25-2 mm aggregates by 20.20 % to 40.43 %,ROC by 13.33 % to35.29 %,DOC by 40.96 % to 51.96 %,and carbon pool management index by 10.37 % to33.20 % compared with the biochar(T2)and organic fertilizer(T3)treatments alone.Redundancy analysis showed that the organic matter content of the soil was the main factor affecting the distribution of organic carbon fractions in different size aggregates,and it was the most correlated with the organic carbon of each fraction in 0.053-0.25 mm size aggregates.(4)Charcoal-based organic fertilizer is beneficial to promote the growth of roasted tobacco and improve the quality of tobacco production.Compared with the single-applied biochar(T2)and organic fertilizer(T3)treatments,the charcoal-based organic fertilizer(T4and T5)treatment increased plant height by 4.13 % to 16.67 %,increased stem circumference by 5.45 % to 15.79 %,increased tobacco yield by 5.06 % to 7.40 %,and the reducing sugar content of tobacco leaves(16 % to 18 %)at maturity period.The percentage of superior tobacco in the first baking tobacco increased by 1.15 %～2.22 %.In terms of different charcoal-based fertilizer proportions,the economic efficiency of roasted tobacco with 50 %rotted cow manure and 50 % biochar(T4)was slightly higher than that with 70 % rotted cow manure and 30 % biochar(T5).In conclusion,charcoal-based organic fertilizer can improve the particle size composition of aggregates,promote the formation of large aggregates,enhance the stability of aggregates,improve the carbon pool management index,improve the soil structure,balance the nutrient demand of roasted tobacco throughout the reproductive period,and improve the economic benefits of roasted tobacco.