| Aiming to explore the effects of different Eucalyptus branches biochar application on soil nitrogen composition and microbiological characteristics of Eucalyptus plantation in Northern Guangxi,find the best biochar application amount and provide scientific theoretical guidance for the efficient utilization of forest residue and soil improvement.The soil of four-year Eucalyptus plantation at Huangmian forest farm in Northern Guangxi was selected as the research object,and six treatments including 0?CK?,0.5%?T1?,1.0%?T2?,2%?T3?,4%?T4?and 6%?T5?were set through the branches of eucalyptus plantation waste preparation biochar?500?,anaerobic?,applying a year later for Eucalyptus plantation soil physical and chemical properties under different processing components,nitrogen,soil microbiological characteristics?soil microbial population,microbial commu-nity structure,microbial biomass nitrogen and soil enzyme activity?were determined.Compared with 0-30 soil layer of the control treatment,the main results are as follows:?1?Biochar application improved soil physical and chemical properties.After one year,with the increase of biochar addition,soil bulk density decreased,and soil natural water content,capillary porosity,and total capillary porosity increased by 3.88%33.55%,8.96%33.19%,and 9.28%35.89%.There were significant differences between different soil layers.The contents of soil exchangeable acid,exchangeable aluminum,exchangeable hydrogen and exchangeable sodium in soil were reduced,the decreasing rates were8.28%70.03%,5.55%70.34%,5.10%21.78%,and 12.81%49.27%.Biochar applic-ations significantly increased mean the cation exchange capacity,electrical conductivity,exchangeable magnesium and exchangeable calcium by 27.08%160.39%,117.00%546.64%,17.10%66.14%,and 17.38%71.38%,respectively.Soil pH was increased significantly after biochar addition by 0.17-1.29.The contents of soil organic carbon,total phosphorus,total potassium,available phosphorus,available potassium and available nitrogen in soil were increased,the increasing rates were 10.94%51.37%,14.29%59.45%,6.48%59.57%,6.28%29.41%,4.79%19.81%and 7.72%75.87%.There was positive correlation among the main physical factors,chemical factors and each other.?2?Application of biochar increased the content of organic nitrogen in soil.The total nitrogen,total organic nitrogen,total nitrogen of acidolysis,ammonium nitrogen of acidolysis and amino acid nitrogen of acidolysis in soil showed a trend of gradual increase,with the increased by 34.59%112.82%,22.69%119.65%,28.26%129.73%,10.91%155.23%,20.80%120.20%.The amino glycosylated nitrogen showed a trend of decreasing first and then increasing.The change rule of unknown nitrogen and non-acid nitrogen is not obvious.Nitrate nitrogen,dissolved organic nitrogen and soil microbial biomass nitrogen showed a trend of increasing first and then decreasing,and the content of ammonium nitrogen tended to decrease.The contents of different components of soil organic nitrogen fractions in all treatments showed an order of ANA>AAN>HUN>NUN>ASN.There was positive correlation among the main physicochemical factors and soil nitrogen fractions each other.Application of biochar could improve nitrogen supplying capabilities in soils of Eucalyptus plantation,which had a positive effect on on the increasing of soil nitrogen storages.?3?Application of biochar increased the number of soil microorganisms and improved the soil microbial community structure.The number of soil bacteria,nitrogen-fixing bacteria and ammonia-oxidizing bacteria increased significantly with the increase of biochar application.The number of actinomycetes and fungi increased first and then decreased slightly,which was significantly higher than that of the control group.The content of actinomycetes was the highest in T4 treatment,and that the amount of fungi was the highest in T3 treatment.It showed significant promoting effects upon the different phospholipid fatty acids,the number of soil bacterial phospholipid fatty acid content were the most,while the arbuscular mycorrhizal fungi phospholipid fatty acid were the most lowest.The application of biochar increased the amount of total phospholipid fatty acids,bacteria phospholipid fatty acids,actinomyces phospholipid fatty acids,gram-positive bacteria phospholipid fatty acids,gram-negative bacteria phospholipid fatty acids and arbulocorrhizal fungi phospholipid fatty acids,which decreased in T5.The number of fungi phospholipid fatty acid was the highest in T3 treatment.The soil layers had obvious vertical distribution characteristics significantly.In different treatments,the proportion of bacterial phospholipid fatty acid in the total phospholipid fatty acid content of soil phospholipid fatty acids were higher.Abundance of gram-positive bacteria phospholipid fatty acids and gram-negative bacteria phospholipid fatty acids were the most,which was the dominant bacteria group.?4?Application of biochar promoted soil enzyme activity.The contents of urease,catalase,dehydrogenase and?-glucosidase in soil showed an increasing trend with the increase of biochar dosage,particularly for dehydrogenase,?-glucosidase.The contents of sucrase and fibrinolysidase were the highest in T4 treatment,and the contents of acid phosphatase and leucine aminopeptidase were the highest in T3 treatment,and there were significant differences between different soil layers under the same treatment.?5?There was positive correlation among the soil physicochemical factors,soil microbial population,soil enzyme activity and nitrogen components.Addition of biochar increased the content of organic nitrogen and soil enzyme activity,which enhanced the mineralization of organic nitrogen,and the content of nitrogen were accumulated in soil.Soil physicochemical properties,soil microbial quantity,soil enzyme activity and soil microbial biomass nitrogen were important factor that affected the content of nitrogen component in soil.In conclusion,addition of Eucalyptus branches biochar payed an importent role in increasing the pH of the soil,improving soil physicochemical properties,increasing soil microbial quantity,improving the soil microbial community structure,promoting the soil enzyme activity and soil nitrogen composition content.Application of biochar could improve nitrogen supplying capabilities in soils of Eucalyptus plantation,which had a positive effect on on the increasing of soil nitrogen storages.The 4%-6%(4060 t·hm-2)of rape Eucalyptus branches biochar addition was the best,which would be of great practical significance for soil improvement,might influence the sustainable increase in soil quality of Eucalyptus plantation. |
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