Production And Characterization Of Giant Reed （Arundo Donax Linn.） Biochars For Inhibiting N₂O Emission From Soil

In order to improve crop yield in traditional farming, people often utilize mineral ororganic fertilizer into agricultural soil, which not only increace agricultural cost, butalso have adverse effects on the environment. N₂O is an important greenhouse gas,and is currently the dominant ozone depleting substance in the stratosphere.Agricultural soil is an impartant source of N₂O, and heavy dressing fertilizer willcause much N₂O emission form soil. In recent years, the research and application ofbiochar into agricultural soil has attracted the attention of many scientists fromvarious countries. Application of biochar into soil can not only sequester atmosphericCO2into soil on a large scale, but also increace the production of crops and reduce theutilization of fertilizers. Recent research has shown evidences of biochar inhibitingN₂O emission from agricultural soils. But some other evidences indicate biochar hasno effect on N₂O emission, in some particular situation biochar can even increace soilN₂O emission. Also, The associated mechanisms of biochar on soil N₂O emission arenot clear.The purpose of research is to product and characterize giant reed （a kind of wetlandplant） biochar, then add biochar to agricultural soil to investigate the influence on soilN₂O emission and associated mechanisms. The main results were as follows:（1） As the pyrolysis temperature was raised, the yield of biochar reduced, yet pHvalue and ash content increased. The results of elementary analysis indicatedthe percentage of H and O in giant reed biochar reduced as temperature wasraised, while C element increased.（2） After potassium nitrate solution was added to the soil, the N₂O emission wasincreased over time. When soil was cultivated for8to36h, the N₂O emissionreached the maximum, then went to zero after48h. The cumulate amount ofN₂O emission in the soils amended with L200, L300, L350, L400, L500andL600were0.90±0.48,5.06±1.68,6.63±3.40,11.10±0.51,3.35±1.36and1.68±0.73mg N·m^-2, decreased by97.30%,84.80%,80.09%,66.67%,89.94%and94.95%compared to the control, respectively. The results indicated thatgiant reed biochar has inhibited effect on soil N₂O emission, especially biocharpyrolysed at low temperature （L200） and high temperature （L500, L600）.（3） Applicatipn of biochar into soil will raise the soil pH value. But the extent ofpH rising has no relativity with N₂O emission. It means that the increase of thesoil pH is not the mechanism of biochar inhibiting soil N₂O emission.（4） Low temperature biochar （L200） has large amounts of phenols（e.g. hydroquinone）, which incorporated into soil may do harm to microorganismand, hence to inhibit soil N₂O emission.