Effects Of Autumn Plastic Film Mulching On Soil Organic Carbon And Its Influence Mechanism In Dryland Of Northern China

Plastic film mulching is an important technical measure in dryland in northern China.Autumn mulching,as a plastic film mulching pattern constructed by prelonging the time of filming on the basis of spring mulching,it has the effect of suppressing the water consumption during the non-growing period and alleviating the drought in the spring.However,the mechanisms of effects of autumn plastic film mulching on soil organic carbon stock and farmland ecosystem carbon balance has not been revealed.The study of soil organic carbon and carbon balance mechanism under different film mulching modes is of great significance for the construction of low carbon film mulching mode.Above all,the current study based on a four-year observational experiment in Fuxin,Liaoning Province to study soil hydrothermal changes,soil organic carbon and its labile carbon fractions,soil aggregates and soil carbon of aggregates,and the functional diversity of soil microbial carbon source utilization under three treatments: Non-mulching(NM),spring plastic film mulching(SM),and autumn plastic film muching(AM).Eventually,the study calculated the carbon balance in the three modes.The main results as follows:(1)Compared with NM and SM treatments,AM treatment reduced the soil moisture loss during non-growth period,and significantly increased the surface soil average moisture content before sowing and corn growth period.The AM treatment can clearly increased the soil temperature of the soil surface during the growth period of maize than NM treatment,but there is no noticeable difference between SM and AM treatment.(2)There was no significant difference in soil organic carbon(SOC)content between different mulching treatments after 4 years.Compared to NM treatment,SM and AM treatments have an increasing trend of soil organic carbon,dissolved organic carbon and soil microbial biomass carbon in 0-30 cm soil layer,especially in 0-10 cm soil layer.The most important is that AM treatment clearly increased the dissolve organic carbon and microbial biomass carbon in the 0-10 cm soil layer by 27.2% and 31.2%,repectively.(3)AM and SM treatment can increased the mean weight diameter of soil aggregates in 0-15 cm,and increased the content and proportion of aggregates > 2mm,and increased the organic carbon content of water-stable large aggregates.In addition,the AM increased the contribution rate of the 0.25-2mm in soil total organic carbon,followed by >2 mm,and the microaggregate has the lowest contribution rate to soil total organic carbon.(4)The study indicated that the utilization of carbon sunstrate had clearly differences among different treatments.Carbohydrates and carboxylic acid carbon sources are the main carbon sources for soil microbes,followed by amino acid carbon sources and polymers under different treatment.Compared with the NM and SM treatment,the AM treatment significantly increased the microbial activity of the soil surface,and changed the capacity of carbon source utilization of the soil microorganisms,and Carbohydrates and amino acids are the perfered carbon substrate.In addition,the results also illustrated that MBC was strongly correlated with the utilization of the C substrate.(5)There were no significant differences of soil organic carbon stocks in the 0-100 cm among NM,SM and AM treatments after four years of observation,the results indicated that SM and AM will not cause the loss of soil organic carbon pool in the short term period.Compared with NM treatment,SM and AM noticeable increased the the annual carbon input of farmland ecosystems,with an increase of 18% and 37%,respectively,because they have a relatively high yield of grain,straw and roots.Due to the relatively high soil respiration and agricultural carbon dioxide emissions,the annual carbon output of the AM treatment was the highest,followed by the spring mulching,while the NM treatment was the lowest.Among them,the annual carbon output of AM was 35% higher than that of NM and 15% higher than that of SM.Based on the system analysis,the AM increased the carbon input and carbon output of the farmland ecosystem and reduced the net carbon emissions per unit of grain yield.Compared to SM treatment,AM treatment can improve the primary productivity and carbon input of farmland ecosystems,promoting the soil labile carbon fractions,increasing the stability of soil aggregates and the functional diversity of microbial communities,reducing the carbon emissions of per unit area and unit output.