Effect Of Biochar On Soil Physicochemical Properties, Tobacco Growth And Tobacco Black Shank

A large amount of chemical fertilizer resulted in a series of problems, mainly including: increased soil acidification, soil structure destruction and serious disease. Biochar refers to a carbon rich solid material produced by biomass pyrolysis. Bioahcar is rich in nutrients and has a good structure. It can improve the physical and chemical properties of the soil, and it is an important way to realize the sustainable development of cultivated land. However, viewpoints about the effect of biochar application are differs, which is closely related to the soil type. Therefore, This paper studies effects of different proportions of biochar on soil physical and chemical properties of two different types of soil(paddy soil and brown soil) and flue-cured tobacco growth and development, and explores the effect of biochar on Phytophthora parasitica var. Nicotianae and its mechanism. The specific results are as follows:1. Flue-cured tobacco straw was made of biochar. Adding0%,1%,2%,4%,10%,20%of biochar to paddy soil and brown soil respectively, we studied the influence of biochar on soil physical and chemical properties.(1)Applying biochar could increase the field capacity and soil porosity, and reduce soil bulk density. These effects were proportional to the amount of biochar. With the increase of the proportion of biochar, the field capacity of paddy soil and brown soil were increased by 1.75%~6.88% and 1.54%~8.89% respectively, and they were significantly higher than that of the control treatment. The soil bulk density of paddy soil and brown soil of biochar treatment were reduced by 5.59%~11.19% and 0.68% ~13.70%. The soil bulk density 20% of biochar treatment were 1.27 g/cm3 and 1.26g/cm3. This was suitable for crop root growth. Total porosity and capillary porosity of two soils increased with increasing proportion of biochar and high proportion of biochar had significant difference.(2)Applying biochar could effectively increase the soil p H and reduce the soil exchangeable acid. Soil p H increased with the increase of the proportion of biochar in two different types of soil. The p H of paddy soil increased by 1.08~3.41 units and that of brown soil increased by 0.66~2.89 units at the end of culture. With the passage of culture time, p H changed slightly, indicating that the change of soil p H was lasting. Soil exchangeable acid significantly decreased with the increase of the proportion of biochar. The exchangeable acid was not detected, when the ratio of biochar was more than 10%. With culture changed over time, soil exchangeable hydrogen and exchangeable aluminum of biochar treatment showed a decreasing trend. In the late culture period, the exchangeable aluminum of two soils of 4%of biochar were not detected, and significantly decreased the aluminum toxicity to crop.(3)Applying biochar could improve the exchange capacity of the soil. With culture changed over time, the paddy soil exchangeable potassium, sodium, calcium, magnesium and the total amount of exchangeable base showed decreased first and then increased trend, and exchangeable sodium was less affected. While effect of biochar on brown soil exchangeable potassium was larger and exchangeable sodium, calcium, magnesium and the total amount of exchangeable base were less affected in the late culture period. For both soils, the largest increase was exchangeable potassium, which was related to the higher content of the biochar.(4)Applying biochar significantly increased the content of soil organic matter, available P and K in two types of soil, and increased with the increase of the proportion of biochar. The largest increase was the available potassium content. At the end of incubation, in paddy soil and brown soil, the content of available K of 20% of biochar treatment were 2436mg/kg 2484mg/kg, respectively 27.93 times and 24.24 times of the control treatment, the effect of increasing significantly.2. Adding0%,1%,2%,4%,10%,20%of biochar of flue-cured tobacco straw to paddy soil and brown soil respectively, we studied effect of biochar on the growth of flue cured tobacco. Applying biochar could affect the growth and development of flue-cured tobacco in two types of soil. During the growth period, the dry matter accumulation and nitrogen, phosphorus and potassium accumulation in flue-cured tobacco increased first and then decreased with the increase of the proportion of biochar. The effect of 2% and 4% of biochar was better, significantly higher than the control treatment. High biochar treatment(10%) decreased, even lower than the control treatment. 25 days after transplanting, compared with the control treatment, flue-cured tobacco root, stem and leaf dry matter accumulation of two soils of 10% of biochar were decreased by 47.87%, 78.83%, 51.97% and 57.4%, 79.19%, 63.95%, respectively and reducing effects were significant.3. We studied the effect of the flue-cured tobacco straw biochar and the rice straw biochar on Phytophthora parasitica var. nicotianae. Both tobacco straw biochar and rice biochar could inhibit the growth of the mycelium of Phytophthora parasitica, and the inhibition effect was more obvious with the increase of the proportion of biochar. The inhibition rates of different proportions of two types of biochar on the mycelium growth respectively were 15.06%~28.62% and 11.34%~25.09%, and the inhibition effects were significant. The mechanisms of this inhibition effect were mainly the p H and the absorption and toxins of biochar. The control efficiencies of different proportions of biochar were 4.35%~46.55% to black shank 9 days after application, and the treatment difference was significant. The result indicated that the biochar could effectively control tobacco black shank, and reduce the extent of the occurrence of this disease.