| In recent100years, the global climate was undergoing a significant change of warming, The5thassessment report of IPCC (2013) concluded it was very likely that global warming was human-induced.Methane and nitrous oxide were the second and third most important greenhouse gas(GHGs), ruducingemissions of them was an urgent tast according to the Kyoto Protocol. Rice(Oryza sative L) was themain grain crop in the world, and the paddy ecosystem was one of the most important sources ofmethane emission, and it was also a non-negligible source of nitrous oxide emission. The contribution toglobal warming of GHGs from paddy field was immense, which could not be underestimated. Thus theissue of methane and nitrous oxide emission from paddy ecosystem had been concerned within thescope of climate change research over years. Fertilization especially nitrogen was a majormanagement measure during rice growing season, which influenced the yield and emission directly. Itwas well known that controlled release fertilizer, nitrification inhibitor, microbial inoculants werenew typical kinds of nitrogen fertilizer at present. The effect of new nitrogen fertilizersabove-mentioned on GHGs emission and rice yield in a double rice field was investigated to evaluatetheir potential of GHGs reduction and yield promotion, this study is also very important for thedevelopment of low-carbon agriculture and the mitigation research of global warming.Taking the double rice in Jianghan Plain, Hubei province, Central China as the object, acontinuous observation of GHGs emission from five different nitrogen fertilizer treatments (CK:conventional urea, CRU: polymer-coated controlled release urea, CU: urea containing nitrapyrin,DMPP: nitrification inhibitor3,4-dimethylpyrazole phosphate, EM: effective microorganisms) wasconducted by using the automatic static chamber-GC (gas chromatography) method, the rice yield,soil and plant properties were also monitored simultaneously. Variation and characterization of GHGs(CH4and N2O) emission, greenhouse effect (CO2-e) and greenhouse gas intensity (GHGI) of eachtreatment were analyzed comprehensively. Then, we also tried to explain the mechanism of GHGsreduction and yield improvement preliminarily. The results showed as follow:(1) CH4and N2O emission flux in different fertilizer treatments had an obvious daily andseasonal variation law in double rice ecosystem. CH4emission was mainly concentrated in thetillering stage and earing stage. The first emission peak in late rice appeared quickly afte ricetransplanting, and almost a week in advance compared with early rice. There was no CH4emissioneven negative flux as paddy field drainage during mature stage in late rice while there exitedintermittent small emission flux in early rice. N2O emission was mainly concentrated in the period ofmiddle season field drying and late season wet-dry rotation, other small emission peak appeared in theperiod of transplanting and harvest. In addition, the N2O emission flux in late rice was far more thanearly rice.(2) In2012CK caused the highest CH4emission and CRU caused the lowest emission duringthe whole double rice season. In2013CK still kept the highest emission and NU presented the lowestemission. All treatments except DMPP reached significant difference with CK (p<0.05), and CRU dominated the fashion with the highest CH4reduction potential of56%in average compared to CK,followed by NU with41%, EM also got a considerable reduction percentage of32%. CRU, NU andEM were recommendable fertilization for CH4reduction. In addition, it showed a better reduction inlate rice than early rice.(3) CK caused the highest N2O emission and DMPP caused the lowest emission during thewhole double rice season in2012and2013. All treatments except EM reached significant differencewith CK (p<0.05), and DMPP dominated the fashion with the highest N2O reduction potential of63%in average compared to CK, followed by NU with51%, CRU also got a considerable reductionpercentage of40%. DMPP, NU and CRU were recommendable fertilization for N2O reduction. Inaddition, the annual difference of N2O emission was observed obviously, an increasing emissionexisted with the rice season changing.(4) In the view of global greenhouse effect (CO2-e，on100a horizon), CK had the highestgreenhouse effect in all rice seasons, CRU had the lowest in2012and so did NU in2013. All othernitrogen fertilizer treatments had a very significant difference compared with CK (p<0.01). Therefore,significant greenhouse effect reduction potential was also employed, CRU got the highest reduction(45%) in average during two years, followed by NU (44%), EM (34%) and DMPP (33%).(5) Controlled release urea, nitrification inhibitor and effective microorganisms contributed toincreasing rice plant height, chlorophyll concentration, tiller number, spike number, grain number and1000-grain weight, reducing empty-unfilled grain rate, ultimately improved straw and grain yieldeffectively. Among all treatments CRU achieved the highest yield increase by18%in average, and itshowed a better yield promotion in late rice than early rice. Furthermore, CRU, NU, DMPP and EMraised nitrogen recovery efficiency significantly compared to CK, of which CRU reached the highestrate by53%in average.(6) The soil ammonium nitrogen contents of CRU, NU, DMPP and EM were lower than CK inthe nutritive grow stage of rice, and higher than CK in the reproductive stage. What is difference, thesoil nitrate nitrogen contents of CK were the highest in all rice grow stage. There was a significantpositive correlation between ammonium nitrogen content and CH4emission, a significant highpositive correlation between nitrate nitrogen content and N2O emission.(7) Greenhouse gas intensity (GHGI) of CK was statistically higher than the other applications,and reached a very significant difference (p<0.01). Synthetically consideration of their economicearnings and environmental effects, the application of controlled release urea benefitted the most tothe rice production, followed by nitrification inhibitor and effective microorganisms under thecurrent field management conditions..The research about effect of controlled release fertilizer, inhibitor and inoculant on GHGsemission and yield promotion from rice field required years of various experiments under differentconditions to ensure the validity of conclusion. The explicit mechanism of GHGs reduction was stillwaiting for strong evidence to give explanation, which required a large number of exploration and research... |
PDF Full Text Request