| With the development of agriculture,fertilizer demand is also increasing in order to improve the quality and yield of crops,but large amount of chemical fertilizer application will cause loss of nitrogen,soil N2O emissions and other environmental problems.The impact of N2O emissions on the global climate change has been more and more concerned by scientists.In recent years,as a new kind of material,biochars enter into the sight of people because of its roles in reducing emissions of global warming gases due to its special physical and chemical properties.It is of great significance to study the effects of the biochar input into farmland soil on improving soil nitrogen utilization or promoting the sustainable development of agriculture.This research focuses on the effects of pyrolysis temperature on the properties of pig manure-derived biochars and the effects of pig manure-derived biochars,soil moisture content and nitrogen sources on soil N2O emissions and its related microorganisms.Various treatments were designed through combinations of three application levels of biochars(0%,1%and 3%w/w),two levels of soil moisture content(60%and 130%of field water holding capacity,60%FC and 130%FC)and two types of nitrogen sources(urea and sodium nitrate).The effects of the treatments on soil N2O emissions and the related microbial abundances of functional genes(AOB amoA?AOA amoA?nirK?nirS?nosZ)were investigated.Labile C in biochar derived from low pyrolysis temperature(300?)was extracted and its roles as an effective component on soil nitrogen cycling were studied.The main results were as follows:(1)The properties of pig manure-derived biochars at different temperatures(300? and 700?)were significantly different.With the increase of pyrolysis temperature from 300? to 700?,the pH value was increased from 7.08 to 10.07,the ash content was almost doubled,and the aromaticity and the stability were also increased.On the other hand,the percentages of the contents of carbon,hydrogen,oxygen and nitrogen and the content of labile C were decreased,and the surface polarity was also decreased.Addition of the 700? biochar increased the soil pH value by 1.96 units,and it was therefore considered that the biochar might be a good substrate as an acid soil improver due to its strong alkaline and high ash content.(2)With different amounts(0%,1%and 3%w/w)and types of pig manure-derived biochars(300? biochar and 700? biochar),the effects of biochar input into different soil environments of moisture content(60%FC and 130%FC)and nitrogen sources(urea and sodium nitrate)on soil properties and N2O emissions were investigated under incubation with constant temperature.The results showed that different biochars had different effects on the soil physical and chemical properties in different soil environments,and the effect on N2P emissions was also different.Soil pH value could be significantly enhanced by addition of pig manure-derived biochars.Input of 300? biochar could significantly enhance the soil dissolved organic carbon(DOC)content,while input of 700? biochar had no significant effect on soil DOC.Addition of 3%300 ? biochar increased soil DOC by 20-30 times.In this study,the addition of pig manure-derived biochars increased the total amount of soil N20 emissions,which was especially true in the denitrification reaction soil environment(130%FC with addition of sodium nitrate)where the total amount of soil N2O emissions reached 58.14 kg hm-1.Nitrification was the major reaction in low moisture content(60%FC)soil.Nitrification and denitrification occurred simultaneously in high moisture content(130%FC)soil with addition of urea,while denitrification was the major reaction in high moisture content(130%FC)soil with addition of sodium nitrate.Therefore,total amount of soil N2O emissions was the highest in the 130%FC soil added with sodium nitrate.(3)With different amounts(0%,1%and 3%w/w)and types of pig manure-derived biochars(300? biochar and 700? biochar),the effects of biochar input into different soil environments of moisture content(60%FC and 130%FC)and nitrogen sources(urea and sodium nitrate)on soil N2O emissions related microorganisms abundances were investigated under incubation with constant temperature.It was found that input of biochar increased abundances of ammonium oxidizing bacteria(AOB)and denitrification microorganisms,but inhibited abundances of ammonium oxidizing archaea(AOA)to some extent and the inhibition effect decreased with incubation time.(4)The contribution of labile C to biochar properties and the effect of labile C on soil properties after its addition were explored.It was found that soil DOC content was significantly increased with addition of labile C which was one of the factors promoting soil N2O emissions.The abundance of denitrification microorganisms could be enhanced by labile C in the biochars,which was probably related to the growth dependence of denitrification microorganisms on available carbon sources. |
PDF Full Text Request