Soil Organic Carbon And Soil Microbial Properties Of Organic And Conventional Farming

There is an urgent need for developing sustainable agriculture taken into account harmonious development of both economy and ecological environment, according to the background of global climate change and national conditions of our country at present. There are more potential and greater advantages of carbon sequestration and emission reduction in organic agriculture in comparison with conventional agriculture. Comparative study on dynamic changes and relationships between soil organic carbon and microbial properties in this paper was based on the organic farm located study and laboratory stimulant cultivation experiment. This paper also emphasized on the relationship between soil organic carbon accumulation and dynamic changes of soil microbial properties under different fertilized condition during the organic planting process.The result of organic farm located study showed that, compared to the beginning of this located study, soil bulk density significantly decreased and soil organic carbon content and soil microbial activity also significantly increased for organic management; while these soil properties was showed a downward trend in conventional farming systems. Organic carbon density of topsoil in both two different organic systems and conventional systems were41.92t·hm-2,49.46t·hm-2and31.87t·hm-2respectively, with significant difference in2011. There were also more soil microbial biomass and higher activity of soil urease, acid phosphatase and catalase in the system under organic management for many years in comparison with conventional system, with significant difference. Correlation coefficient between soil organic carbon and some biological factors was significant at the0.05level in organic systems, which was more positive than that in conventional system.Effects on microbial community structure varied with different management. Soil fugal and actinomycetes colonies were significantly greater in organic system than in conventional system. More soil bacterial PLFA contents were detected in organic systems than in conventional systems, with significant difference. Multiple factors of soil organic properties in different systems were integrated by principle component analysis (PCA). Results of PCA showed that the factors of soil bacterial biomass and soil enzyme activity made the greatest contribution on the process of Eigenvalues extraction, and PCA scores on soil microbial properties in organic systems were higher than conventional system.This paper also emphasized on analysis of the effects of different fertilized condition on soil organic carbon accumulation and dynamic changes of microbial properties under organic management. Three different use levels organic fertilizer group (with low, medium and high organic fertilizer dosage) and photosynthetic bacteria combined with organic fertilizer group and bio-fertilizer combined with organic fertilizer group were designed in the cultivation experiment, according to the actual fertilization conditions of the organic farm. The control groups were also designed in accordance with the experiment requirement.The results showed that low and medium level of organic fertilizer application in soil were beneficial to increase soil organic carbon content, inhibit soil carbon mineralization process and promote soil carbon sequestration, while effect of high level organic fertilizer was not significant. Organic fertilizer application in soil increased soil microbial biomass carbon and nitrogen, and this effect became more and more significant as the increase of organic fertilizer dosage. Organic fertilizer application in soil significantly increased soil bacterial colonies; while it increased soil actinomycetes colonies and decreased soil fugal colonies, with no significant difference. The amount of Soil bacterial, fungal and actinomycetes colonies were increased as organic fertilizer dosage increased in soil. Photosynthetic bacteria and bio-fertilizer combined with organic fertilizer in soil increased soil organic microbial biomass carbon and soil organic carbon consumption. These two method increased soil bacterial and actinomycetes colonies. Bio-fertilizer application in soil can promote the growth of soil fungi. However, the effect of photosynthetic bacteria was opposite.