Evolution Characteristics and Influence Factors of Substitution Rate of Organic Nitrogen in Rice-wheat Rotation System in Taihu Lake Region
Substitution of chemical fertilizer with organic fertilizer is the key strategy for chemical fertilizer reduction.The main aims are to clarify themain limiting factors of substitution rate of chemical nitrogen with organic nitrogen(SR)in rice-wheat rotation system in Taihu Lake region,and to provide theoretical basis for SR promoting.This study based on the 40 years long-term field experiment,and three treatments were chosen,including no fertilization treatment(CK),chemical fertilization treatment(NPK)and organic fertilization treatment(OM).Urea,superphosphate and potassium chloride were applied in NPK treatment,and the annual average amounts of pure N,P2O5 and K2O were 225-300,119.4 and 179.1 kg/hm2,respectively.Pig manure or oil cake was used in OM treatment,which equaled to 103.1,82.7 and 70.1 kg/hm2.The soil organic carbon(SOC),soil total nitrogen(TN)and SR and soil C/N ratio were calculated as well.The results showed that long-term fertilization promoted SOC level,and the SOC contents of the above three treatments could be fitted by Michaelis-Menten equation.The SOC content in the first decade accumulated rapidly and tended to equilibrate in the last 30 years.The average SOC content was 16.8 g/kg for OM,15.8 g/kg for NPK and 15.1 g/kg for CK treatment.TN contents of OM,NPK and CK linearly increased with years,and the average TN contents were 1.71,1.64 and 1.47 g/kg.The dynamics of the SR could be fitted by a piecewise linear model,where the SR decreased slightly at early times but increased at late times,with the threshold years being the 11th and 15.5th years of the rice and wheat seasons,respectively.Linear regulation analysis showed no relationship between SR and SOC,but SR was significantly correlated with TN and C/N ratio.In rice-wheat rotation system in Taihu Lake region,long-term organic fertilization can effectively promote soil carbon and nitrogen pools,and a high level of SOC(＞17.0 g/kg)is the premise of improving SR.When the SOC approaches saturation,soil TN and C/N ratio are the main factors limiting the improvement of SR.
long-term fertilizationrice-wheat rotationsubstitution rate of chemical nitrogen with organic nitrogensoil organic carbonsoil total nitrogen
万方数据
维普
