Effects Of Different Fertilization Regimes On Soil Organic Carbon Components Of Degraded Artificial Grassland In Northeast Yunnan

The greenhouse gases and the maintenance of soil fertility are affected by soil organic carbon.The steady growth of plants and alleviate the greenhouse effect can be promoted by the stability of soil organic carbon.Improving the conversion of soil particles to aggregates is one of the effective ways to increase soil organic carbon.Grassland soil has a huge carbon sequestration potential,but it was destroyed by overgrazing and so on.The research on the response and attribute changes of the soil organic carbon in southern China grassland is still unclear.Fertilization management is one of the key measures to improve soil productivity and nutrient return.Based on field fertilization experiments of degraded artificial grasslands in Northeast,Yunnan.This study applied two different types of fertilizers（i.e.bio-organic fertilizer and nitrogen-phosphorus compound fertilizer）with multiple fertilization gradients(bio-organic fertilizer 30,60 and 120 g·m^-2·yr^-1.The nitrogen and phosphorus fertilizer treatments were（1）N:2 g·m^-2·yr^-1,P:0.7 g·m^-2·yr^-1;（2）N:4 g·m^-2·yr^-1,P:1.4 g·m^-2·yr^-1;（3）N:8g·m^-2·yr^-1,P:2.8 g·m^-2·yr^-1and control 0 g·m^-2·yr^-1,collect the soil in 0-10 cm and 10-20 cm.Exploring the effects of different fertilization patterns on soil organic carbon in degraded grasslands,which will be of great significance to reveal the stability mechanism of soil organic carbon.The main findings and conclusions are as follows:（1）The results of plant biomass show that,compared with the addition of chemical fertilizers,the addition of bio-organic fertilizers can increase the biomass of plants.In January 2021,the aboveground biomass was significantly higher than the control group by 70.17%and 67.53%in the medium and high concentration bio-organic fertilizer groups.produce significant changes.In addition,the results of soil enzyme activity determination showed that the highest enzyme activities related to carbon cycle appeared in the high-concentration fertilization treatment group.Among them,in 10-20 cm,the enzyme activity ofα-glucosidase of high-concentration bio-organic fertilizer was significantly higher than that of low-and high-concentration chemical fertilizers by 19.59%and 17.50%.（2）The results of soil organic carbon and related components showed that there was no significant difference between chemical fertilizers and bio-organic fertilizers on total organic carbon and dissolved organic carbon.Fertilization increased total organic carbon,but the response was not significant.The content of water-soluble organic carbon and potassium sulfate leaching organic carbon gradually decreased in different soil layers with time,and the performance was 2021.01>2021.04>2021.07.As for microbial biomass carbon,its content increased significantly with the increase of the fertilizer concentration.In 0-10 cm,the highest content in each season appeared in the medium-concentration organic fertilizer treatment group,and the content in January and April was significantly higher 103.27%and 68.11%in the control treatment group.（3）In January 2021,compared with chemical fertilizers,the proportion of agglomerates with a particle size of>2 mm in bio-organic fertilizers increased significantly.In January 2021,soil aggregate traits（mean weight diameter,geometric mean diameter,and fractal dimension）did not differ significantly between treatments.In July 2021,the fractal dimension,in 0-10 cm,the value of medium-concentration bio-organic fertilizer was significantly lower than that of the control group by 3.93%;in10-20 cm,the value of medium-concentration bio-organic fertilizer was significantly.It is 4.29%lower than the value of low-concentration bio-organic fertilizer.In addition,chemical fertilizers and bio-organic fertilizers had similar effects on soil aggregate organic carbon,and its content did not change significantly,but fertilization treatment would increase its content.In conclusion,compared with the fertilizer,bio-organic fertilizer has better effect on the restoration of degraded artificial grassland in northeastern Yunnan.High-concentration bio-organic fertilizer(120 g·m^-2·yr^-1)has the best effect on improving plant biomass and enzyme activity,while low-and medium-concentration bio-organic fertilizer(60 g·m^-2·yr^-1)has a certain promotion effect on the formation of large aggregates and the stability of aggregates in soil aggregates.