Effect Of Different Molecular Weights Organic Carbon On The Formation Of Soil Aggregates

Nowdays,the soil environment is gradually deteriorating,and a shortage of soil carbon pool is likely to aggravated at any moment in China.It's a feasible option to mitigate soil degradation that using exogenous organic carbon increase soil organic carbon content as a soil conditioner.The studay prepared four kinds of exogenous organic carbons with different molecular weights and they were from kitchen waste.We completed the operation including both indoor and outdoor experiments.The exogenous organic carbon was added to the soil and we studied the effect on organic carbon content,soil aggregates and soil physical and chemical properties.Finally,we explored the mechanism of the effect of exogenous organic carbon on soil carbon storage.The main results are as follows:?1?The water-soluble organic carbon in the small-molecule exogenous organic carbon treatment group with a concentration of?1 kDa was increased by 0.383 g/kg compared with the blank treatment group,and the cumulative release of CO₂ reached?6.595±0.259?mg/kg?C?,microbial activity increased,the formation and mass ratio of>5 mm water-stable macroaggregates increased by 25.06%relative to the blank treatment group,and increased soil ammonia and nitrogen content.The results showed that the organic carbon of small molecules enhanced the activity of soil microorganisms.Microorganisms promoted the formation of water-stable macroaggregates through the mycorrhizal network entanglement,thereby increasing the mass fraction of larger aggregates and enhancing the stability of soil aggregates.?2?The content of organic carbon in 1 kDa<molecular weight<5 kDa was significantly correlated with the content of easily oxidized organic carbon,>0.25 mm aggregate mass fraction,and geometric average diameter of aggregates in exogenous organic carbon?P<0.01?.This shows that the organic carbon in this molecular weight range can bind soil particles and small aggregates,promote the development of water stable macroaggregates,and increase the stability of aggregates.?3?Traditional compost such as kitchen waste is mainly composed of macromolecular organic carbon of?5 kDa.Organic carbon in macromolecules of exogenous organic carbon can increase the content of organic carbon in the soil,which is 5.65 times that of the blank treatment group,0.5¹ mm water stable macroaggregates increased by 10.84%,and the organic carbon contribution rate increased by 14.79%,indicating that macromolecular organic carbon increased soil organic carbon by increasing the organic carbon content of soil particles and the organic carbon content in the soil particles.Contribution rate.The results shows that different molecular level exogenous organic carbon in different ways to improve soil aggregate structure,and further promote the soil organic carbon fixation.The proportion of organic carbon in organic fertilizer is reasonable,which can obviously improve soil organic carbon level and increase the stability of soil aggregates.