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

Abstract

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 CH<sub>4</sub> emissions during the rice season by 69% to 175%. Phosphorus amendment also enhanced seasonal CO<sub>2</sub> emissions by 21% to 34% when compared with the treatments without receiving P, while combined use of P and potassium suppressed seasonal N<sub>2</sub>O emission to the same level of control. Net CO<sub>2</sub> and N<sub>2</sub>O emissions from the dried fallow and wheat seasons and CH<sub>4</sub> emissions from the flooding rice season dominated annual budgets of individual GHGs. 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 CO<sub>2</sub> eq/ha/year with CO<sub>2</sub> emission contributing 52% to 76%, CH<sub>4</sub> contributing 20% to 40% and N<sub>2</sub>O 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.