Study On The Degradation Of Wheat Straw By Nano-carrier Bacteria

A large number of straw were produced every year in china.If handled and utilization not properly,it will cause a series of environmental problems and resource waste.At present,straw returning to field is the direct way and method of straw utilization.However,there are some problems of straw direct returning to the field under the current conditions,such as the sowing quality affected by slow degradationof straw,the increase of nitrogen fertilizer to stabilize the yield,and aggravation of diseases and insect pests.In this study,a nano-carrier bacteria(NCB)was constructed from attapulgite and straw degradation bacteria(SDB).Nylon mesh bag method was used to study the degradation law treated by straw returing agent,and the scanning electron microscope,fourier transform infrared spectrometer,X-ray diffraction and thermogravimetric were also used for the study of degradation mechanism.In addition,the effects on the crop growth,greenhouse gas emission and crop yield by straw returning agent were also studied.The main research results are as follows:(1)we construct a straw returning agent from attapulgite and three compound bacteria,then the situ degradation characteristics studied by nylon mesh bag method.The results showed that the straw returning agent played an important role in improving the degradation efficiency of straw.At the same time,it could accelerate the release rate of nutrients in straw and increase the content of nutrients in soil.Compared with the treatment of compound bacteria,the straw returning agent can increase the degradation efficiency of straw by 19.21%.At the same time,the in situ degradation experiment of straw showed that the nutrient has a rapid release in the initial degradation stage;In the whole process of straw degradation,the release effect straw returning agent on the nitrogen,phosphorus and potassium in straw was more significant.At 80 days,the release efficiency of nitrogen was 25.64%higher than that of bacteria compound,and potassium release efficiency increased by 24.84%at 100 days.(2)Straw returning can improve soil fertility level and soil microbial structure,thus affecting the growth and development of crops.In this study,the effects on soil fertility and soil microorganisms were studied by spraying the straw returning agent with plot experiment.The results showed that it could effectively increase the content of nitrogen,phosphorus,potassium and other nutrients in soil treated by straw returning agent.In different growth stages,NPK can be increased by 1.20%-27.14%?9.45%-75.37%?2.20%-17.42%,respectively.In addition,it plays a important role in promoting the improvement of cellulose biodegradable microorganisms in soil.Compared with conventional straw treatments,compound bacteria and straw return agent can increase proteobacterium(36.8%,42.6%)?bacteroidetes(5.39%,3.23%),respectively,which provides a basis for the rapid degradation of straw after returning to the field.(3)Straw returning can increase greenhouse gas emissions in farmland.In this study,straw returning agent was sprayed on the wheat straw after returned to the field,and its emission effect on greenhouse gas of farmland was determined by FTIR measurement system.The results showed that compared with conwentional straw returning and compound bacteria,straw returning agent had a more significant effect on reducing greenhouse gases.CO2 concentration can be reduced by 5.11%-10.75%,CH4 concentration by 1.47%-2.97%,N2O concentration by 1.90%-3.56%,respectively.This provides a reference for reducing greenhouse gas emissions from farmland in the future.(4)The full amount of straw returning to the field has a negative effect on the emergence and frowth of later crops.Therefore,how to solve these problems is the foundation of straw returning work.In this study,the agronomic characters were investigated and analyzed of maize with wheat straw treated by straw returning agent.The results showed that the promoting effect on increasing seedling emergence rate,plant height,stem diameter,chlorophyll content was significant treated by straw returning agent.Compared with compound bacteria,the seedling emergence rate increased by 5.47%,plant height by 23.08%,stem diameter by 12.95%,and chlorophyll content by 2.10%-3.83%.However,it has no obvious effect on the enhancement of photosynthetic efficiency.Meanwhile,field experiments showed that it still played an important role in the improvement of the above agronomic traits,especially increased the maize yield by 11.93%..(5)The mechanism of straw degradation treated by straw returning agent was studied by scanning electron microscope,fourier transform infrared spectrometer,X-ray diffraction and thermal gravimetric analyzer.The results of scanning electron microscopy showed that the straw returning agent had a better adsorption effect on straw,and propagated rapidly in straw parenchyma cells,thus accelerating the degradation of vascular bundles and other tissues.The analysis of infrared spectrum and X-ray diffraction showed that the characteristic peak of cellulose in the straw treated by straw returning agent was weakened,and also had a decreased diffraction peak.These results indicated that the treatment of straw returning agent caused the degradation of cellulose and other substances in the straw.The degradation results showed that the rate of cellulose could be increased by 23.18%compared with compound bacteria.