Stimulation Effects Of Corn Stover And Biochar On Active And Inert Soil Carbon Pools

Agricultural residues are traditionally regarded as soil amendment for maintaining soil fertility and sustainability.However,soil organic carbon may be primed by the newly added organic matter,and thus resulted in a greater carbon loss.The stable carbon pool is the main component of soil organic carbon,and its content is much higher than that of active carbon pool.However,due to the limitation of methods,it is remains debatable about the response of soil organic carbon pools with different stability to the priming effect(PE),especially under warming.In this study,three soils(C₃)of old-field,bare-fallow,and bare-fallow+incubation(assumed as active,relatively stable,and stable soil carbon pools,respectively)were incubated by adding two agricultural residues(C₄),i.e.,maize and biochar,for a 180 d-incubation at 22 and 32?.Soil or plant derived-carbon was distinguished by a two-component mixed model using isotopic tracing method.The main results of as follows:(1)At 22?,the PE of the three soils are all positive;at 32?,the PE of the three soils induced by maize are all positive,while the PE in bare-fallow+incubation soil induced by biochar is positive,and the PE in old-field and bare-fallow soils induced by biochar is negative.This result shows that the maize can stimulate more stable soil to release carbon,while the biochar can reduce the carbon release of active soil at 32?.(2)The PE induced by maize was higher than biochar in the three soils at both temperatures.(3)The bare-fallow and bare-fallow+incubation soils have higher PE than old-field,indicating that stable soil was more sensitive.(4)According to the net carbon balance,it is known that the addition of maize or biochar increases soil carbon sequestration.(5)The temperature response of soil organic carbon decomposition after adding maize or biochar decreased,but it was still sensitive(Q₁₀>1).(6)Warming did not affect the relative PE induced by maize in the three soils,but significantly decreased the relative PE induced by biochar,especially in old-field soil(Q₁₀<0),indicate that warming will likely partly abate priming C induced by the addition of maize and biochar.Taking together,our study demonstrated that PE varies with different soil organic carbon pools and plant types.Compared to active soil,stable soil has a stronger PE,and this PE is insensitive to temperature rise.Future research should clarify the relevant mechanisms of PE in different soil carbon pools,and incorporating the PE and temperature sensitivity of different soil carbon pools into the carbon model to accuracy prediction the global carbon cycle.