Straw return amplifies the stimulated impact of night-warming on N2O emissions from wheat fields in a rice-wheat rotation system

Context

The rise in winter and spring nighttime temperatures is a hallmark of global climate change, and warming has been proven to stimulate N₂O emissions from wheat fields. However, it remains elusive whether this increasing effect is influenced by straw return, a practice considered globally as a future climate-smart agricultural strategy.

Objectives or methods

A 3-year field experiment (2020−2023) was conducted with two straw treatments (S0: straw removal; S1: straw return) and two warming treatments (W0: no-warming; W1: night-warming) to quantify the effects of straw return and night-warming on N₂O emissions from wheat fields in a rice-wheat rotation system.

Results

Straw return (S1) boosted post-jointing N₂O production, whereas night-warming (W1) stimulated N₂O emissions before the booting stage. Notably, the interaction between straw return and night-warming significantly affected seasonal cumulative N₂O emissions, with W1 causing an 11.1 % increase under S0 and a more substantial 18.1 % increase observed under S1. Moreover, both S1 and W1 increased N₂O warming potential, yield-scaled, and biomass-scaled N₂O emissions. Compared to S0W0, soil dissolved organic C and inorganic N content increased in S1W1, while pH declined. Both S1 and W1 enhanced soil nitrification enzyme activity, nitrate reductase activity, and nitrite reductase activity in comparison to their respective controls. Additionally, S1W1 increased N₂O production and inhibited N₂O reduction by upregulating AOB-amoA and nirS gene abundances and downregulating nosZ gene expression, as evidenced by the elevated (nirS+nirK)/nosZ ratio. Random forest analysis identified that denitrification enzyme activity was the most important factor influencing N₂O emissions.

Conclusions or implications

Our findings suggest that rice straw return may amplify the increasing effect of night-warming on N₂O emissions from wheat fields. From an environmental protection perspective, straw return under the context of future warming will lead to an increased risk of N₂O emissions, which may further exacerbate climate warming.