Effects Of Straw Biochar Application On Tobacco Soil Carbon And Nitrogen Forms And Related Enzyme Activities

Due to the tobacco planting years,long-term utilization of chemical fertilizer,the soil structure was deteriorated,soil microbial activitywas declined,and soil-borne diseases were aggravated.These restricted the improvement of yield and quality of tobacco.Straw-biochar has received extensive attention in agricultural applications,but it’s using on the tobacco planting soil fertility improving and flue-cured tobacco growth promoting werelack of attention.In this paper,the field experiment was conducted,the two different types of straw biochar（corn and rapeseed straw）were used,and three different application methods（band,band and hole,hole）were implemented.In the flue-cured tobacco rosette stage,vigorous growing stage,squaring stage and mature period,the top soil（0-15 cm）and subsoil（15-30 cm）sampleswere collected.The effects of different straw biochar types,different application methods on soil carbon and nitrogen content,soil enzyme activity,and their relantionship were studied.This research has importmant improvement in tobacco planting soil fertility,and providing scientific basis for rational utilization of tobacco planting soil.The main results are as follows:（1）The application of straw biochar significantly increased the content of soil organic carbon and labile organic carbon（Dissolved organic carbon,Readily oxidation organiccarbon,Particulate organic carbon,Microbial biomass carbon）（P<0.05）.Compared to conventional fertilization（CG）,using rape straw charcoal increased the most carbon content,which increasedorganic carbon content and its active components 39.70%and 51.24%respectively;rape straw carbon and corn straw carbon were no significant differences in enhance particulate organic carbon content.From different application methods,the increase in content and component of upper（0-15cm）TOC represented as hole>banding and hole>banding,and there was no significant difference betweenhole and ’banding and hole";the increase in content and component of lower（15-30cm）TOCrepresented as banding>banding and hole>hole,and there was significantdifference between banding and "banding and hole" in enhanceeasily oxidation organic carbon and microbial biomass carbon content.（2）The application of straw biocharsignificantly influenced the content of soil total nitrogen,microbial biomass nitrogen（P<0.05）.With the growth of flue-cured tobacco,soil total nitrogen（TN）,nitrate nitrogen（NO₃^--N）,ammonium nitrogen（NH4--N）content of the upper layers（0-15cm）decreased,while thesoil total nitrogen（TN）,nitrate nitrogen（NO₃^--N）,microbial biomass nitrogen（MBN）content of deeper layers（15-30cm）increased maximum and then decreased.Comparedwithconventional fertilization（CG）,using straw biochar significantly reduced the content of NO₃^--N and NH₄⁺-N.From the view of different types of biological carbon,compared with conventional fertilization（CG）,soil NO₃^--N and NH₄⁺-N content ofthe upper layers（0-15cm）decreased fasterwhen applied rape straw carbon thanapplied corn straw carbon,whereas soil TN content of deeper layers（15-30cm）increased fasterwhile appliedthe corn straw carbon than applied straw carbon,but the difference was not significant.From different application methods,holeincreased the most soil TN and MBNof the upper layers（0-15cm）,and "banding and hole"increased the most soil TN and MBN of thedeeper layers（15-30cm）.（3）The application of straw biochar had significantlyeffect on soil enzyme activity,but the effect has noobvious regularitywith growth stagechange over time.Compared with conventional fertilization（CG）,using straw biochar significantly increased the soil invertase activity;the effect of straw biocharon beta glucosidase activity was not obvious,and straw biocharonly had significant influence during the rosette stage（0-15cm）and mature period（15-30cm）of tobacco;straw biochar had appreciable impacton urease during the budding stage（0-15cm）and mature stage（15-30cm）;straw biochar had appreciable impactonprotease activity during the vigorous growing period,budding stage and mature stagerespectively.From the view of different types of biochar,the application of corn straw increased more soil invertase activity and beta glucosidase activityduring vigorous growing stage at 0-15cm soil depth,while the effect on urease,protease activity was not significant;the application of corn straw increased moreinvertase activity during squaring stage at 15-30cmsoil depth and vigorous glucosidase activity duringvigorous growing stage,whereas the application ofrape strawincreased moreurease activity and protease activity.From different application methods,soil invertase and protease were appropriate with hole,β-glucosidasewas appropriate with"banding and hole" at 0-15cm soil depth;soil invertase,urease and protease activity increased most withbandingat 15-30cm soil depth.（4）Correlation analysis of soil carbon,soil nitrogen forms and soil enzyme activitiesshowed thatsoil layers of 0-15cm and soil invertasesignificantly related with carbon species,of which the total soil organic carbon（TOC）and microbial biomass carbon（MBC）had the highestcorrelationcoefficents.However,TN and MBN were significantly related with the form of nitrogen;beta glucosidasehad no significant correlation with soil organic carbon forms,whilesignificantly related with NH₄⁺-N;ureasesignificantly related withsoilMBC,but had no significant correlation with NH4’-N;protease had the highestsignificant correlation withMBC,and significantly related to soil TN and MBN.At soil depth of 15-30cm,except MBC,soil invertase activity had significantlypositiveeffect on soil carbon and nitrogen forms,of which correlation coefficents with soil TOC and MBN were highest;beta glucosidasewas significantly correlated withTOC and MBC,and had significantly positive effect onthe change of nitrogen forms;soil ureasehad significantly positive effect onsoil carbon and nitrogen forms,of whichcorrelation coefficent with soil soluble organic carbon（DOC）was the highest;soilproteasewas significantly correlated withreadilyoxidation carbon（ROC）and MBC,while had no significant correlation with NO₃^--N and NH₄⁺-N.In general,the straw biochar（corn,rapeseed traw）application,compared with conventional fertilization（CG）,promoted soil sucrase,protease activity,significantly increased soil organic carbon content and total nitrogen,microbial biomass nitrogen.The biochar application may have obvious effect on the activation and soil nutrient supply,improve soil structure and land productivity.Compared with the conventional fertilization（CG）,the application of biochar significantly reduced the content of NO₃^--N,NH₄⁺-N,which is conducive to the conversion of nitrogen in soil,to prevent nitrogen leaching.The promoting effect of rape straw biochar was better than that of corn straw carbon.The hole application method has the effect on the soil fertility on the 0-15cm soil layer,which was better in banding application on the 15-30cm soil layer.