Research On N₂O Emissions Characteristics And Related Factors From Dryland Of Agro-ecosystem In Hilly Area Of The Loess Plateau

N2O is an important greenhouse gas coming from the agricultural source. Although the content is very low in the atmosphere compared with CO2,N2O has a significant potential to global warming. An important source of global N2O emissions is the dry farmland ecological system.Therefore,to conduct the research on dryland farmland ecosystem N2O emissions has an important theoretical and practical significance on drawing up greenhouse gas emissions inventory and developing emission reduction countermeasures.Relying on semiarid agroecological ecosystem research station attached to Lanzhou University(36°02N,104°25E, an average elevation of2400m),Soil N2O emissions in the field of dry farmland ecosystem were observed from April to September2012.This experiment studied the N2O emissions characteristics and related factors under different management styles and nitrogen fertilization levels in hilly area of the Loess Plateau, and estimated the amount of N2O emission flux under different treatments and total emissins of soil N2O contributed by corns in different growth stage,discussed the mechanism of N2O emission reduction of farmland ecosystem.The major conclusion can be described as follows:(1)During maize growth stage,seasonal soil water content was consistent with soil temperature. Soil water content was positively correlated with rainfall.Treatments with plastic mulching had higher soil temperature and water content than non-mulching treatments.(2) In the different treatments,amounts of N2O emission from soil with time lag in maize growth period,as a whole,showed a bimodal change rule. In the early stage of maize growth,the N2O flux in the treatments of double ridges and furrows mulched with plastic film and fertilization with mulching were higher than other treatments. With the passage of growth period,the N2O flux in all treatments show a trend of fluctuating downward,and achieved peak at the harvest time of maize in all treatments, and then it declined rapidly and the bare land declined at the soonest.(3) For the fertilization conditions,three treatments the N2O concentration with fertilizer were higher than two no fertilizer treatments and bare land,N2O flux showed significant seasonal variation. Under non fertilizer treatment,the N2O flux of mulched treatment is lower than the N2O flux of non mulched treatment.In the treatment with fertilizer,the N2O flux of mulched treatment significantly higher than the mulched non fertilizer treatment.(4)By comparing the N2O emission flux characteristics in the three diurnal fluctuations change,we found that the amounts of N2O emission could be affected by weather conditions significantly.N2O flux have more regular emissions peak in sunny weather conditions,once appear at about12:00at noon, another appeared at about3:00. In time right,the first N2O emission peak appeared in two sunny weather conditions is the N2O emissions low in the rainy weather conditions.(5) Nitrogen fertilizer application,the change of soil water content and temperature conditions under mulched treatment,the content of soil nitrate nitrogen and ammonium nitrogen and crop itself are the main factors causing the N2O emissions in farmland system.To decrease the soil N2O emissions of dry farmland ecological system,reduce the amount of nitrogen fertilizer,vigorously promote long-term application of nitrogen fertilizer and controlled release fertilizer,improve the utilization of nitrogen fertilizer,and improve water management measures,etc are very important.