Characteristics Of Organic Carbon Stability In Soda Saline-alkaline Paddy Soil Under Different Cultivation Time

In this thesis,Soda Saline-alkaline paddy soil as the research object,to study the characteristics of soil organic carbon stability with different cultivative time.Mainly divided into three aspects to analysis: physical,chemical and biological,and then clarify the change of soil organic carbon stability in saline-alkali paddy soil under different cultivative time,in order to reduce greenhouse gas emissions,increase the mount of organic carbon pools,and provide a basis for the improvement of soda saline-alkaline soil.The results showed that the soil pH could be significantly reduced by improve soda salinealkaline soil with planting rice.And the contents of total nitrogen nitrate nitrogen and available nitrogen in soil were significantly increased with the cultivation time.The content of organic carbon in soda saline-alkaline paddy soil increased significantly with the increase of planting period.The textures of soda saline-alkali soil were loose,and water-stable aggregates are mainly distributed on the grain size of 0.25 0.106 mm.However,with the increase of cultivation time,the number of > 0.25 mm aggregates increased from 33% to 51%,indicating that planting rice could significantly improve the colloidal dispersion of saline-alkali soil.The organic carbon mainly distributed on the aggregates of > 0.25 mm,which accounts for 73.31%-92.10% in the aggregated organic carbon.The content of organic carbon is significantly higher than the abandoned grassland,but there is no certain rule changes in each other.> 0.25 mm aggregate organic carbon have significantly positive correlation with cultivation time and soil physicalchemical properties.The result shows that the active ingredient in the soil above the refractory components,and the active ingredient ? > ?.The contents of active substances and refractory components increased significantly cultivation time.Soluble group HCl hydrolysis of total soluble fractions obtained with H₂SO₄ hydrolysis is basically the same.The content of acid-hydrolyzed organic carbon in soil was significantly correlated with soil physical-chemical properties.The carbon content of soil microbial biomass increased with the cultivation time.The content of water extractable organic carbon first increased then decreased,reaching the highest level at 3 years.The accumulation of mineralizable carbon first increased then turn to balacing with the culture time,and the mineralization rate of paddy soil was less than that of abandoned grassland.The composition and structure of water extractable organic carbon were changed with the cultivation time.The content of humic acid-like substance and fulvic acid-like substancewereincreased with the planting period,the degree of soil humification increased,and the aromaticity and molecular weight of organic matter increased.The rhizosphere bacterial community structure changed,and the microbial diversity increased with the cultivation years;The dominant bacterial were Proteobacteria,Acidobacteria,Firmicutes and Bacteroidetes in the rhizosphere community.With the increase in years under cultivation,Acidobacteria were increased,but the Proteobacteria were decreased.Moreover,the soil properties?pH,soil organic carbon,moisture content and available phosphorus?had a significant impact on bacterial community.