| China is a big tobacco producing country,and the total amount of tobacco straw(hereinafter referred to as tobacco straw)produced each year exceeds 4.5 million tons.The tobacco stalk is rich in lignin and cellulose,is not easy to be decomposed and is easy to carry pests and germs,so it is not suitable to return to the field or compost to return to the field.At present,tobacco stalks are generally burned or discarded,which not only pollutes the environment,but also causes a loss of a large number of beneficial elements,and the disposal of tobacco stalks is in urgent need of new methods.Biomass pyrolysis refers to the technology of converting biomass into biochar under anoxic conditions.By converting the tobacco rod into tobacco rod biochar and returning to the farmland,it not only overcomes the direct decay of the tobacco rod but also is not easy to rot.Disadvantages of the spread of pests and diseases.At the same time,the soil has been improved,and the water-soluble organic carbon in the biochar has a good effect of promoting plant root growth and promoting plant photosynthesis.In this study,four kinds of pyrolysis temperatures(300℃ 350 ℃,400℃,450℃)were used to produce tobacco stalk biochar.By analyzing its physical and chemical properties,450℃ biochar was determined as a follow-up research material,with phosphoric acid.The extracts were prepared by leaching with water and potassium hydroxide,and diluted 25 times,50 times,100 times for cucumber seedling cultivation and cucumber growth application.The effects of different treatments on cucumber seedling growth,cucumber growth and quality were studied and analyzed.(1)Effect of carbonization temperature and extraction method on biochar and its extract;Different physical and chemical properties of biomass carbon are different at different carbonization temperatures.With the increase of carbonization temperature,biochar ash,P,K content and trace elements increased gradually,N,volatile matter and CEC decreased correspondingly;while Cd and Pb increased before 400℃ and decreased after 400℃.Both the carbonization temperature and the leaching method will affect the composition of the leaching solution.With the increase of carbonization temperature,the contents of N,Mn,Cu and Cd in biocharic acid,water and potassium hydroxide extracts showed a downward trend,while the contents of P,K,Fe and Zn increased gradually.The content of Cd and Pb in the three extracts is extremely low,which is in line with the current national agricultural foliar fertilizer related application standards.(2)The effect of extraction method and dilution ratio on the growth of cucumber seedlings;During the seedling raising process of cucumber,the biochar acid extract was sprayed,and the plant height,stem diameter,chlorophyll and leaf area of seedlings increased significantly compared with the control group,but the effect decreased with the increase of dilution factor.However,different treatments can not affect different indicators such as cucumber stems,leaves and leaf area.Under the treatment of potassium hydroxide extract diluted 25 times,the plant height and leaf area of cucumber increased significantly compared with the control.The tobacco stalk biochar phosphate extract significantly increased the dry weight of the above ground and lower parts of the seedlings,but the difference was not significant under different dilution factors.The treatment had no effect on the root-shoot ratio,but the dilution of 25 times increased the yield by 69.3%,66.4%and 27.6%compared with the control N,P and K,respectively.The dilution of the aqueous extract was 25 times and 100 times,significantly increased by 30.8%,38.5%.Diluting 25 times and 100 times of potassium hydroxide extract can promote the distribution of seedling material and increase the ratio of root to shoot.Each treatment promoted the accumulation of seedling N,and the effect was reduced as the dilution gradient increased.Under each treatment,the cucumber seedling index was significantly improved.Under the action of biochar phosphate extract,the total root length,surface area,number of branches,number of root tips and total volume of cucumber seedlings increased significantly compared with CK.Compared with CK treatment,the total root length and total surface area of the roots of the seedlings were significantly improved.At the same time,except for the dilution of 100 times,the average diameter,number of branches,total volume and number of root tips of seedlings increased significantly compared with CK treatment;the treatment of potassium hydroxide extract significantly promoted the total root length of roots.However,it does not have a significant effect on the average diameter of the root system.According to the comprehensive evaluation index,each extract treatment can promote the growth of cucumber seedlings.Among them,the most significant effect was the biochar phosphate leach solution,and the effect between water and potassium hydroxide extract was basically the same.(3)Effects of different extraction methods and dilution ratios on soil nutrients,cucumber growth and quality;The soil pH was higher than CK treatment under different extracts.Phosphorus extract can not improve the total nitrogen content of soil,but it has a significant effect on soil available phosphorus and available potassium.Under the treatment of water extract,the total nitrogen,available phosphorus and available potassium of CK increased by 9.2%,16.3%and 4.7%,respectively.The dilution of potassium hydroxide extract by 25 times had no obvious effect on soil total nitrogen,but it could significantly increase soil organic matter,available phosphorus and available potassium,which increased by 16.1%,17.6%and 4.7%,respectively.The 50-fold dilution of the tobacco stalk biochar phosphate extract has the most prominent effect on the quality of cucumber.Under the action of biochar extract,the soluble protein and sugar content of cucumber increased significantly.Not only that,the nitrate content was significantly reduced compared with CK treatment.Under the action of potassium hydroxide extract,the content of soluble protein and organic acid in cucumber increased significantly compared with CK,and the effect of dilution 50 times was the most significant,with the increase of 29.1%and 24.6%,respectively.The effect of phosphate extract on the growth,nutrient accumulation and biomass of cucumber plants showed that the effect decreased with the increase of dilution factor.A 25-fold dilution can significantly promote plant growth,nutrient accumulation,and biomass increase.The dilution of the aqueous extract by 50 times can significantly increase plant height,stem diameter,stem and leaf and root dry weight,which are 4.7%,11.1%,5.7%,and 25%,respectively.Under the action of potassium hydroxide extract,it had a positive effect on the growth of cucumber plants,which can promote the increase of biomass at the same time,and the treatment with dilution of 50 times was the most obvious.According to the test data,the dilution of the biomass carbonic acid and potassium hydroxide extracts by 50 times can significantly improve the quality of the cucumber.Under the action of water extract,the 25-fold dilution treatment has the most obvious effect on cucumber quality improvement. |
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