Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Different Carbon Addition Effects on Greenhouse Gas Emissions and the Underlying Mechanisms in Semi-arid Northwest China

Auteur : Stephen Yeboah；

Grade : Doctoral Dissertation 2017

Université : Gansu Agricultural University

Résumé
Agroecosystems has become very important for its role in achieving food security and also in the mitigation of greenhouse gas emissions.Different conservation tillage techniques,carbon sources（biochar and straw）,and N fertilizers have been shown to boost soil and crop productivity.However,an improved understanding of the effects on greenhouse gas emission and the underlying mechanisms associated with the production of greenhouse gases is required to enhance agriculture sustainability in semi-arid areas.A study was carried out to investigate the effect of carbon addition sources and patterns on nitrous oxide（N2O）,methane（CH4）and carbon dioxide（CO2）emissions,soil properties and crop productivity in rainfed spring wheat cropping.The study was conducted at the Rainfed Agricultural Experimental Station（35°28′N,104°44′E,elevation 197-m above-sea-level）of Gansu Agricultural University,Dingxi,Gansu Province in Northwestern China.Experimental work of the carbon addition sources included the application of straw,biochar and N fertilizer（no carbon）.The straw and biochar were applied alone or combined with N fertilizer(50 and 100 kg N ha-1),whilst the N fertilizer was applied at 0,50and 100 kg N ha-1.The carbon addition pattern studied included ;conventional tillage with straw removed（T）,no till with straw removed（NT）,no till with straw retention（NTS）and conventional tillage with straw incorporated into the soil（TS）.The experiments were arranged in a randomized complete block design with three replications.Main findings are summarized as follows:All the treatments served as sources of atmospheric N2O,and a sink of atmospheric CH4throughout the sampling period.The pattern of seasonal N2O,CH4 and CO2 fluxes showed,the higher emissions occurred mostly when soil temperature and soil moisture were high.Overall,CO2 emissions reduced with increasing N fertilization rates under all treatments ;and the greatest N2O emissions and CH4 sink were recorded under the highest rate of N fertilization(100 kg N ha-1).Biochar treated soils produced the lowest N2O and CO2 emissions,and the greatest CH4sink.The mean cumulative N2O emission of biochar and straw treated soils were averaged at1.83 kg ha-1 and 2.03 kg ha-1,representing a decreased of 32.44%and 19.57%compared to no carbon soils,respectively.The cumulative CO2 emission was lower in biochar treated plots(2538 kg ha-1),followed by no carbon soils(2805 kg ha-1)and the greatest by straw treated plots(2928 kg ha-1).Application of biochar in combination with 100 kg N ha-1 had the greatest CH4sink than zero N treatment on soils without carbon treatment(-3.06 kg ha-1 versus-2.14 kg ha-1).No tillage treatments resulted in significant decrease in cumulative N2O and CO2 emissions,and a significant increase in CH4 sink compared to conventional tilled plots ;but the greatest effect occurred on straw treated plots.The mean cumulative N2O and CO2 fluxes were lower under no tillage with straw retained(2.01 kg ha-1)and(2696 kg ha-1)compared to conventional tillage with straw removed(2.64 kg ha-1)and(3257 kg ha-1)soils,respectively.No till with straw retention increased cumulative CH4 sink by 25.71%compared to conventional tillage with straw removed.The study indicated that biochar amended soils with 100 kg N ha-1 and no tilled soils with straw retention had lower global warming potential.Higher soil organic C,saturated hydraulic conductivity and lower bulk density and temperature occurred with the application of 100 kg N ha-1 under all carbon sources.Both biochar and straw treated soils produced the lowest bulk density（0-5 cm）at 1.15 g cm-3,and no carbon soils the highest at 1.20 g cm-3.Soil organic C and total N were lower with no carbon soils,followed by straw treated soils and the greatest in biochar treated soils.At a depth of 0-10cm,it was found that biochar amended soils contained higher soil C(13.01 g kg-1),representing an increase of 26.87%(10.25 g kg-1)and 17.14%(11.10 g kg-1)compared to soils without carbon amendment and straw treated soils,respectively.

Mots clés : Biochar； Greenhouse gases； Straw； Tillage； Soil organic C；

Présentation (CNKI)