Study On The Mechanism Of Tobacco Planting Soil Quality Improvement By Tillage Management And Returning Granulated Straw

The plow layer,aggregate structure as well as low organic matter content of tobacco-growing soil is becoming more and more deterioration due to the continuous rotary tillage and excessive application of chemical fertilizer.The granulation of the maize straw(MS),a kind of abundant agricultural resource,was more efficiency in improving tobacco-growing soil fertility compared to the raw MS for its higher rates of MS decay which sequently led to higher rate of nutrients release.Hence,a field experiment was carried out in the typical tobacco planting areas of Zhucheng city Shandong province from 2016 to 2018,which was conducted to study the combined effect of tillage management and MS granulation application on the soil physic-chemical and biological properties as well as the yield and quality of flue-cured tobacco.Spilt pot experiments contained the primary factor of tillage management of deep ploughing(GT)and rotary tilliage(GR)and the secondary factor of 2 250 kg/ha,4 500 kg/ha and 6 750 kg/ha MS application,were employed.The main findings were as follows:1.The combined application of MS granulation and tillage management significantly improved the soil physical properties.The decrease of soil bulk density and the increase of field water capacity and soil porosity in 0 ~ 20 cm and 20 ~ 40 cm soil layers increased with the increase of straw particles.However,compared with MS granulation,tillage management was the main factor to cause the differentiation of soil physical properties,according to regulate soil aggregate particle size composition and furthermore changes soil physical properties.y.The combined application of GR and MS granulation was more beneficial to enhance the aggregate stability of 0 ~ 20 cm and 20 ~ 40 cm soil layer.In addition,the 0.5 ~ 1 mm and 0.106 ~ 0.25 mm aggregates were the dominant factor determined the soil physical properties of 0 ~ 20 cm and 20 ~ 40 cm soil layer,respectively,which explained more than 66% and 48% of 0 ~ 20 cm and 20 ~ 40 cm soil physical properties variation.2.The MS granulation was favored to the improvement of soil available nutrients and organic carbon content in the all tobacco growing stages.Increasing the amount of straw particles which has a positive effect on improving the available N,K nutrientss and organic carbon content in different soil layers.The combined application of MS granulation and GR was beneficial to the ammonium nitrogen accumulation of 0 ~ 20 cm and 20 ~ 40 cm soil over time.In contrast,the GT combined with MS granulation led to the accumulation of nitrate nitrogen and available potassium in both soil layers.The soil organic carbon(SOC)and dissolved organic carbon(DOC)content increased with the increasing quantity of MS under different tillage management.The best way to improve the content SOC is 6 750 kg/ha MS application treatment.During three years,the SOC of 0 ~ 20 cm and 20~ 40 cm soil layer were both significantly increased by 5.04% ~ 23.46% and 20.77% ~3 9.26% respectively.The DOC were both significantly increased by 5.26% ~ 53.96% and 10.99% ~ 72.00% respectively.The tillage management,MS quantity and their interaction were all significantly changed the content of SOC and DOC.3.The tillage management and MS granulation quantity regulate the diversity and structure of bacterial community.The dominant bacteria phylums each treatment were all Actinobacteria,Proteobacteria,Thaumarchaeota,Chloroflexi,Acidobacteria and Gemmatimonadeteswhichaccounted for 87.9%-93.9%.The MS granulation quantity significantly altered the OTU number and diversity of 16 S bacteria(P < 0.05).In contrast,the given tillage management significantly affected the 16 S bacterial community structure(P < 0.01).Under the condition of GT,the amount of MS granulation affected the overall structure of bacterial community by causing the available potassium and organic carbon;Under the condition of GR,the amount of MS granulation affects the overall structure of bacterial community by causing soil aggregate and nitrate nitrogen.4.The yield and quality of flue-cured tobacco was significantly improved by the combined application of MS granulation and GT through regulating the stems,roots and leaves growth in each growing stage.The combined application of tillage management and MS granulation significantlyaffect the development of tobacco stemin the earlyFlue-cured tobacco growing stage,the effect of GT was remarkable.The combined application of tillage management and MS granulation affect the development of tobaccoroots and leaves in the middle and late stage.The potassium content of tobacco leaves was significantly improved by the MS granulation application and GT,and the economic benefits were also significantly increased by GT,the combined 6 750 kg/ha MS application and GT treatment still had a certain effective in the second year.Overall,the appropriate tillage way combined with suitable quantity of MS granulation was beneficial to improve the soil physic-chemical and biological properties as well as the yield and quality of flue-cured tobacco,the best treatment way is the combined 6 750 kg/ha MS application and GT.