Effects Of Biochar Aging On Growth Of Flue-cured Tobacco

As a new type of environment-friendly carbon-rich material,biochar has been more and more applied in improving soil physicochemical properties and promoting crop growth.Biochar is extremely stable and can last for thousands of years in the natural environment.However,it will be aging in soil under the influence of the environment.This aging phenomenon will affect the surface structure and physical and chemical properties of biochar,and then affect the application of biochar in production and the improvement of soil.In this three experiments,carbonized rice husk(A1)pyrolysis at 450～500℃,carbonized rice husk(A2)pyrolysis at 600～650℃and bamboo charcoal(A3)pyrolysis at 600～650℃ were used as three source biochar.Experiment 1: The above biochar was aged in the same aging mode to explore the changes of physical and chemical properties of different biochar after the same aging.Experiment 2: A1 was used as the source material,and phosphoric acid was used as the extraction agent to modify the aging biochar,and the changes of its physical and chemical properties were studied.The extraction residue was used to replace the grass carbon in the matrix in different proportions to study the change of physicochemical properties of the substituted matrix and the effect of the substituted matrix on the growth of flue-cured tobacco seedlings.Experiment 3: A1 biochar and its aging biochar were collected to explore the effects of aging biochar on the growth and rhizosphere soil of flue-cured tobacco by pot experiment.The main research results are as follows :(1)The trend of physical and chemical properties of different kinds of biochar after aging is the same.The p H value decreases,the specific surface area increases,the porosity decreases,the carbon content decreases,and the oxygen-containing functional groups increase.The surface of the washed aged biochar will be smoother,the surface of the oxidized aged biochar has traces of destruction,and the surface of the aged biochar has produced more micro-pore structures.Fourier infrared analysis showed that the vibration frequency of aged biochar in the oxygen-containing functional group band increased,and the functional groups such as carboxyl,hydroxyl and carbonyl groups increased.The increase of these functional groups provided more binding sites for biochar,which enhanced the adsorption capacity of aged biochar.(2)The physicochemical properties of acid-extracted aged biochar residues will change further after aging.The p H value is closer to neutral,and the specific surface area of acid leaching aged biochar residue is larger than that of unleached aged biochar.The substitution ratio of acid leaching biochar residue instead of peat matrix can meet the industry standard of matrix.Tobacco seedlings grew best when the substitution ratio was 50 %.When the substitution ratio is greater than 50 %,the agronomic traits and other indicators of tobacco seedlings grown on the substrate replaced by acid leaching and washing aged biochar residues can still reach the level of control tobacco seedlings.(3)After biochar aging,soil nutrients were still improved,but the results were significantly lower than those of fresh biochar.The effect of biochar aging on soil bulk density reduction will be weakened;the effect of improving soil p H was reduced,and the content of organic matter and available nitrogen in soil was lower than that of fresh biochar.The content of available phosphorus and available potassium increased first and then decreased with the increase of aging degree,and the microbial diversity of aged biochar soil decreased.After biochar aging,due to the weakening of the effect of reducing soil bulk density,the soil permeability also decreased,the space for flue-cured tobacco root growth was blocked,and the root volume was significantly smaller than that of fresh biochar.However,due to the enhanced adsorption capacity of biochar after aging,the roots of flue-cured tobacco can absorb more nutrients,which will increase the root activity of flue-cured tobacco and the absorption of soil nutrients nitrogen,phosphorus and potassium.In summary,the aging phenomenon of biochar will change the physical and chemical properties of biochar;the modification of different aged biochar will affect the application effect of biochar in production.The aging of biochar in soil will affect the growth of plant roots and the absorption of nutrients.