Decomposition Characteristics Of Organic Materials And Driving Factors In Typical Cropland Soils

The application of crop straw and livestock manure is an effective practice to improve soil organic carbon(SOC)and soil fertility of cropland.So far,it is still not satisfactorily found out what is the dominant factor controlling the decomposition of organic materials in cropland soils in different climatic zones.Meanwhile,little information is reported about the dynamics of microbial characteristics in soils developed from different parent materials after amendment with different organic materials under field conditions.In this study,the in situ and ex situ filed experiments were carried out in three different climatic zone of China,including Qiyang,Zhengzhou and Gongzhuling.Maize straw(MS),wheat straw(WS),maize root(MR),wheat root(WR),cattle manure(CM),and pig manure(PM)were applied to three cropland soils(Ferralic Cambisol,Calcaric Cambisol and Luvic Phaeozems)at three different climatic zone of China.Their decomposition over four years by the litterbags method and the change of soil microbial functional diversity by Biolog method were studied.The humification coefficient,stable C,decomposition rate constant,microbial biomass carbon(MBC),microbial biomass nitrogen(MBN),the average well color development(AWCD)and the microbial functional diversity indices(Shannon,Simpson and McIntosh)were calculated.Effects of climate,soil type and organic material quality on the decomposition of organic materials in typical cropland soils were clarified,and the relationship between microbial functional diversity and the decomposition process of organic materials was explored.The main results and conclusions were as follows:1.A two-component kinetic equation of soil accumulated temperature and decomposition of organic materials was established,and the decomposition of organic materials in different regions of China was predicted.The range of C remaining of straws and manures after one year decomposition between different climate zones were 23-73%and 38-86%,respectively,and the corresponding value were 19-35%and 33-61%after four years decomposition.The application of manures is more conducive to improve soil carbon sequestration in cropland.2.Soil,climate,organic material and their interactions all significantly affected the humification coefficient,stable carbon composition and decomposition rate constant of organic materials.Organic materials was the predominant factor,and explained 77.32%,71.75%,37.20%of the variance in the humification coefficient,stable carbon composition and decomposition rate constant,respectively.3.Organic material is the main controlling factor of soil microbial biomass carbon(MBC)and microbial biomass nitrogen(MBN).Organic material quality explained 29.5-50.9%of the variance in MBC and MBN when compared with the minor role of soil type(1.4-9.3%)at the end of the 1st and 12th months,and C/N ratio and total N of organic material were the main parameters.4.Soil is the main controlling factor of soil microbial function diversity.Soil properties,e.g.,organic C and clay content were the predominant influence on microbial functional diversity in particular at the end of the 12th month,and explained 61.8-82.8%of the variance in AWCD and the microbial functional diversity indices(Shannon,Simpson and McIntosh indices).