Effect of long-term differentiated fertilisation regimes on greenhouse gas emissions from a subtropical rice-wheat cropping system

A field campaign was conducted using six treatments under the summer rice-winter wheat cultivation system to evaluate the response of soil greenhouse gas (GHG) emissions to long-term differentiated fertilisation regimes. The treatments included control, phosphorus plus potassium, nitrogen only, nitrogen plus phosphorus (NP), nitrogen plus potassium, and NP plus potassium (NPK). Compared to the control, mineral fertilisation increased CH4 emissions during the rice season by 69% to 175%. Phosphorus amendment also enhanced seasonal CO2 emissions by 21% to 34% when compared with the treatments without receiving P, while combined use of P and potassium suppressed seasonal N2O emission to the same level of control. Net CO2 and N2O emissions from the dried fallow and wheat seasons and CH4 emissions from the flooding rice season dominated annual budgets of individual GI (Gs. All of the soils under different treatments were net sources of global warming and the overall net global warming potential ranged from 9 799 to 14 178 kg CO2 eq/ha/year with CO2 emission contributing 52% to 76%, CH4 contributing 20% to 40% and N2O occupying the rest. The annual maximum grain yields and minimum GHG intensity was observed at the NPK treatment, suggesting it to be the environmental-friendly optimum fertilisation regime.