Effects Of Biochar On Soil Organic Carbon Pools In Phaeozem

Phaeozem is the main soil type in Heilongjiang Province which is rich in organic matter,it has loose texture,strong fertility,strong water retention,and good tillage.However,overexploitation and unreasonable utilization of phaeozem over the years have led to rapid decline in soil organic matter content,consequently,decreased soil fertility and soil degradation became serious.In order to restore the degraded phaeozem and increase its organic carbon pool,an outdoor cultivation was carried out where corn straw biochar were added to the soil at 0.5%?1.5%?2.5% mass ratio.Analysis was done to evaluate the effect of biochar application on the soil organic carbon pools and the correlation between their components.The difference between the two kinds of soil organic carbon storage in phaeozem of high and low organic matter was studied,so as to provide scientific basis for the improvement of degraded phaeozem.The result showed that,biochar application had significant effect on soil organic carbon composition of phaeozem with different level of organic matter concentrations.Similarly,biochar application increased total organic carbon content of the soil compared to the control,nonetheless the highest significant value was recorded in soil where biochar was applied at 2.5%.In addition,total organic carbon content was 52.81% and 51.84% higher than the control while that of high organic matter soil was 27.74% and 26.99% higher than the control at 150 and 515 days,respectively.Furthermore,amended soil had higher values of active organic carbon,microbial biomass carbon,particulate organic carbon,light fraction organic carbon compared to the control,however the water-soluble organic carbon content was low relative to the control and this reduced with increase in application rate of biochar.At the end of the experiment,biochar applied at 2.5% reduced the water-soluble organic carbon in low organic matter soil by 12.94%,respectively.While in higher organic matter soil biochar applied at 2.5% reduced the water-soluble organic carbon content by 9.91%,relative to the control,respectively.At the end of the experiment,the content of total organic carbon decreased,while the content of active organic carbon,microbial biomass carbon and water-soluble organic carbon increased,comparing with the control at 15 days.A positive correlation existed between soil organic carbon pools except in water-soluble organic carbon which was negatively correlated with active organic carbon.Additionally,the contents of stable organic carbon such as heavy fraction organic carbon,mineral-bound organic carbon,and recombinant organic carbon were all higher compared to the control,and increased with increase in biochar application rate.The effect of biochar on the mineral-bound organic carbon in low organic carbon soil was higher than that of high organic soil.The total organic carbon in the soil was positively correlated with the mineral-bound organic carbon,heavy fraction organic carbon,and recombinant organic carbon.The active organic carbon and the microbial biomass of treated soil increased at the early stage of the experiment.At the end of the experiment,biochar applied at 1.5 % increased the active organic carbon and microbial biomass carbon in low organic matter soil by 6.93 % and 5 %,respectively.While in higher organic matter soil biochar applied at 1.5 % increase the active organic carbon content and the microbial biomass by 20.23 % and 4.19 % relative to the control,respectively.In summary,1.5% biochar treatment has the highest effect on the active organic carbon and microbial biomass carbon content in low organic matter soil.2.5% biochar treatment has the highest effect on the increase of total organic carbon,particulate organic carbon,light fraction organic carbon,heavy fraction organic carbon,mineral-bound organic carbon,and recombinant organic carbon in low organic matter soil.High biochar application rate can inhibit microbial activity thus affect the soil active organic carbon.Hence,application of biochar at moderate quantity based on soil test recommendation to a low organic carbon black soil can improve the organic carbon content of degraded phaeozem and thus improve its productivity.