Effect Of Organic Fertilizer And Chemical Fertilizer Application On Soil Organic Carbon Fractions And Land Productivity In Maize-Soybean Intercropping System

Carbon cycling in agricultural ecosystems has great influences on global climate change.Fixing carbon in the soil is an important measure to relieve carbon emissions and green house effect,as well as improve soil fertility.Multiply planting patterns such as intercropping can increase crop biomass per unit area and have potential for carbon sequestration.At the same time,the addition of organic fertilizer made from agricultural waste is an important measure to increase soil organic matter content and reduce environmental pollution.This study took field trial as research platform.Three cropping patterns included maize and soybean intercropping（M/S）,maize monoculture（MM）,soybean monoculture（SS）,and four fertilization modes included no fertilization（CK）,application of chemical N、P and K fertilizer（NPK）,1/3 of chemical P fertilizer were replaced by organic manure(NP_2/3K+OM_1/3),1/2 of chemical P fertilizer were replaced by organic manure(NP_1/2K+OM_1/2),were carried out to explore the changes of crop aboveground biomass and soil organic carbon fractions under different cropping patterns and soil fertilization modes,so as to provide a theoretical basis for the sustainable development of agricultural ecology.The main results of the study were as follows:（1）In the same cropping pattern,fertilization significantly increased the crop aboveground biomass and grain yield;The land equivalence ratios（LER）were greater than1 under all fertilization modes,which showed that the intercropping pattern has obvious advantages over the monocropping pattern.In intercropping system,the yield of maize stalks was highest in treatment of NP_2/3K+OM_1/3,whereas maize grain yield was highest in NPK,followed by treatments of NP_2/3K+OM_1/3 and NP_1/2K+OM_1/2;For soybean,the straw yield in the three treatments with fertilizer(NPK,NP_2/3K+OM_1/3,and NP_1/2K+OM_1/2),were significantly higher than that of CK,whereas the grain yield in treatments of NPK and NP_2/3K+OM_1/3 were significantly increased compared with CK.（2）The soils in plough layer（0-20cm）were strongly affected by human management,such as fertilization,tillage,etc.,so the soil total organic carbon（TOC）content had large variation between different treatments.The TOC contents in 0-20cm soil layer in intercropping patterns were significantly higher than that in monocropping patterns.Whereas the soil TOC contents in sub-plough layer（20-40cm）were less affected by cropping patterns and fertilization treatments.（3）Under all fertilization modes,the content of soil EOC in the plough layer soil in intercropping pattern were significantly higher than that of monocropping pattern.Under the monocropping patterns,both of the soil EOC content of maize and soybean were the highest with NP_1/2K+OM_1/2,which were 18.9%and 8.8%higher than that of CK treatment,respectively.Under the intercropping pattern,the content of soil EOC in the plough layer of maize belt in treatment of NP_2/3K+OM_1/3 was significantly higher than that of NPK and CK treatments,which increased by 10.7%and 23.2%,respectively.The content of soil EOC of soybean belt plough layer in treatments of NP_1/2K+OM_1/2 and NPK were significantly higher than that of CK,with 5.5%and 10.6%increase,respectively.（4）Generally,the MBC contents in the plough layer soil were higher than that of sub-plough soil,and the soil MBC contents in treatments with fertilizer were higher than that in treatments without fertilizer.The contents of MBC in the plough layer soil in intercropping pattern were higher than monocropping pattern.Under the monocropping pattern,both of the plough layer soil MBC contents for maize and soybean were the highest in treatment of NP_1/2K+OM_1/2,which increased by 10.6%and 13.9%,8.7%and5.8%,39.3%and 20%than that of NP_2/3K+OM_1/3,NPK,and CK,respectively.Under the intercropping pattern,the plough layer soil MBC content in maize belt in the treatment of NP_1/2K+OM_1/2was highest,which was 16.3%,10.3%and 14.2%higher than treatments of NP_2/3K+OM_1/3,NPK,and CK,respectively.（5）Fertilization significantly increased the content of soil DOC in the plough layer,and the soil DOC increased continuously with the increase of the amount of organic fertilizer application.Because of the rain leaching effect,the change trend of soil DOC in sub-plough layers was consistent with the plough layers.In summary,the replacement of a small amount of chemical fertilizers with organic fertilizers can ensure that crop yield without reduce,as well as improve the content of soil organic carbon,so as to maintain high land productivity,and to reuse the agricultural waste.