Responses Of Soil Carbon And Nitrogen To Straw Mulching And Plastic Film Mulching In Dry Farmland

Soil organic carbon(SOC)and soil nitrogen had a close correlation,which directly restricted the cycle of soil organic matter.Their dynamic changes affected crop yield and soil quality directly or indirectly.In recent years,straw mulching and plastic mulching had been widely used in arid and semi-arid areas of Loess Plateau in China due to the preservation of soil moisture,temperature and temperature stability.Based on the field experiment and the indoor analysis,the contents of soil organic carbon,total nitrogen(TN)and its components in the loess plateau upland area were studied by using the soils of winter wheat and spring maize in the Loess Plateau,and the correlation among the components.Five treatments in a winter wheat field were included as control without mulching treatment(CK),plastic mulching during winter wheat growing season(PM),straw mulching at a rate of 9000 kg/hm2(SM)during fallow summer,straw mulching at a rate of 9000 kg/hm2(M1),straw mulching at rate of 4500 kg/hm2(M2)during winter wheat growing season.The contents of total organic carbon,nitrogen,potential mineralized carbon/nitrogen(PMC,PMN),microbial biomass carbon/nitrogen(MBC,MBN),particulate organic carbon/nitrogen(POC,PON),and its components were measured and analyzed.The main results were as follows:(1)The contents of soil organic carbon,total nitrogen and its components were significantly increased at the depth of 0?10 cm and 10?20cm(P<0.05),but not significantly increased at the depth of 20?40 cm.Which M1 treatment effect is most significant,SM and PM treatment are relatively weak.(2)The relative contents of soil microbial biomass carbon,potential mineralized carbon and organic carbon were 1.96%?3.31%,2.83%?3.78%and 18.13%?37.25%respectively.The relative contents of soil microbial biomass nitrogen,potential mineralized nitrogen and particulate organic nitrogen were 3.06%?4.91%?1.07%?1.75%and 7.94%?20.75%respectively.(3)There was a significant positive correlation between soil organic carbon,total nitrogen and its components in winter wheat field under different cover methods(P<0.01),except for particulate organic nitrogen with other components.The correlation coefficients of particulate organic carbon,microbial biomass carbon and potential mineralized carbon with soil organic carbon were 0.847,0.700 and 0.614.It could be seen that the relationship between soil carbon and nitrogen was very close.Microbial biomass carbon and particulate organic carbon could indicate soil fertility more sensitively.(4)The content of soil organic carbon and total nitrogen and their components decreased with the deepening of soil layer.And the deeper the soil layer was,the more slowly the change was.Three treatments in a spring corn field were included as control without mulching treatment(CK),plastic mulching during spring corn growing season and straw mulching at a rate of 9000 kg/hm2(S1).The main results were as follows:(1)Straw mulching and plastic film mulching were beneficial to increase the contents of soil total nitrogen,microbial biomass nitrogen and potential mineralized nitrogen at the depth of 0?10 cm and 10?20 cm.In addition,the two kinds of covering methods were beneficial to increase the contents of organic carbon and microbial biomass carbon at the depth of 0?10 cm and 10?20 cm,but not beneficial to increase the the content of potential mineralized carbon.Straw mulching and plastic film mulching had negative effects on particulate organic carbon/nitrogen,especially for the depth of 0?10 cm.(2)The relative contents of soil microbial biomass carbon,potential mineralized carbon and particulate organic carbon were 2.78%?3.95%,2.46%?3.58%and 8.82%?32.81%respectively.The relative contents of soil microbial biomass nitrogen,potential mineralized nitrogen and particulate organic nitrogen were 6.16%?7.64%,2.66%?3.26%and 12.41%?28.51%respectively.(3)The relationship between total organic carbon and total nitrogen was very close.Particulate mineralized carbon and soil microbial biomass carbon were more sensitive to responses to soil carbon pools.The contents of particulate organic nitrogen,potential mineralized nitrogen and microbial biomass nitrogen responded to dynamic changes of total nitrogen more quickly.There was a significant correlation between microbial biomass nitrogen and potential mineralized nitrogen(P<0.01),but there was no significant correlation between microbial biomass carbon and potential mineralized carbon.(4)The contents of nitrogen in maize field was lower than wheat land.(5)The contents of soil carbon and nitrogen decreased with the soil declining in spring corn land,which the changing trend was consistent with the trend in wheat land.