Effects Of Plant Material Addition On Organic Carbon Components Content And Enzyme Activities In Saline Soil

Soil salinization is the most extensive land degradation problem,which affects soil properties and restricts agricultural production.In order to face the food security problem,it is urgent to restore the productivity of saline soil.It is a way to improve saline soil by adding organic materials.Plant materials,cheap and easily available,have been gradually used in improve saline soil.In this paper,the effects of different plant material addition on saline soil in a short time were studied,and the responses of respiration rate,organic carbon content and enzyme activities to the addition of plant materials in saline soil were explored.Plant materials including the litter and fresh samples of alfalfa and sweet sorghum were added to the soil with low,medium and high salt content.The soil respiration rate changes with time was measured during 80 days of incubation under constant conditions.Changes of Soil dissolved organic carbon（DOC）,microbial biomass carbon（MBC）,particulate organic carbon（POC）,and mineral-associated organic carbon（MAOC）;β-glucosidase,urease,alkaline phosphatase and dehydrogenase activities at different stages of incubation were also texted.The main findings of the study are as follows:（1）The addition of plant material significantly increased the respiration rate of saline soil,and the effect of plant litter on soil respiration rate was higher than that of fresh plant sample.In 0-30 days of the incubation,the addition of plant materials significantly increased the respiration rate of saline soil,and gradually decreased with time.From 30 to 80 days were gradually stabilized.The cumulative CO₂ emission from soil increased gradually during the incubation period.（2）For the cumulative CO₂ release during the whole incubation period,taking the low-salt soil as an example,compared with the control,the cumulative CO₂ release after adding alfalfa and sweet sorghum litter and fresh samples were increased by 7.68,6.44,5.22 and 4.12times,respectively.Soil respiration rate was negatively correlated with soil salt content.In alfalfa and sweet sorghum litter,fresh alfalfa and sweet sorghum,the cumulative CO₂release in high-salt soil were 46.31%,30.43%,27.55%and 34.44%lower than that in low-salt soil,respectively.（3）The addition of plant materials increased the content of soil active organic carbon components.The contents of dissolved organic carbon,microbial biomass carbon and particulate organic carbon in the soil treated with plant litter were higher than those treated with fresh plant samples.However,the content of soil active organic carbon decreased with the increase of incubation time.In addition,the content of dissolved organic carbon,microbial biomass carbon and particulate organic carbon decreased with the increase of salt content.As a stable organic carbon pool,soil mineral-associated organic carbon didn’t change significantly in a short time.（4）The addition of plant litter significantly increased soil enzyme activities,while the addition of fresh plant sample had little effect on enzyme activities.However,the enzyme activity tended to decrease with the increase of incubation time.Correlation analysis showed that the activities ofβ-glucosidase,urease and alkaline phosphatase were positively correlated with the content of soil cumulative respiration,dissolved organic carbon and microbial biomass carbon（P<0.05）.In particular,β-glucosidase was significantly correlated with the active organic carbon component in soil.With the increase of soil salt content,the enzyme activity was inhibited.In conclusion,adding plant materials,especially plant litter,to saline soil can provide an energy substrate for microbial activities and alleviate the inhibition of salt on microorganisms in soil.The soil carbon mineralization rate and the content of soil active organic carbon components were increased,and the soil enzyme activities related to soil nutrient cycling were increased,thus improved saline soil property and plant growth.