Eco-friendly yield-scaled global warming potential assists to determine the right rate of nitrogen in rice system: A systematic literature review

Abstract

Rice paddies are one of the largest greenhouse gases (GHGs) facilitators that are predominantly regulated by nitrogen (N) fertilization. Optimization of N uses based on the yield has been tried a long since, however, the improvement of the state-of-the-art technologies and the stiffness of global warming need to readjust N rate. Albeit, few individual studies started to, herein attempted as a systematic review to generalize the optimal N rate that minimizes global warming potential (GWP) concurrently provides sufficient yield in the rice system. To satisfy mounted food demand with inadequate land & less environmental impact, GHGs emissions are increasingly evaluated as yield-scaled basis. This systematic review (20 published studies consisting of 21 study sites and 190 observations) aimed to test the hypothesis that the lowest yield-scaled GWP would provide the minimum GWP of CH₄ and N₂O emissions from rice system at near optimal yields. Results revealed that there was a strong polynomial quadratic relationship between CH₄ emissions and N rate and strong positive correlation between N₂O emissions and N rate. Compared to control the low N dose emitted less (23%) CH₄ whereas high N dose emitted higher (63%) CH₄ emission. The highest N₂O emission observed at moderated N level. In total GWP, about 96% and 4%, GHG was emitted as CH₄ and N₂O, respectively. The mean GWP of CH₄ and N₂O emissions from rice was 5758 kg CO₂ eq ha^-1. The least yield-scaled GWP (0.7565 (kg CO₂ eq. ha^-1)) was recorded at 190 kg N ha^-1 that provided the near utmost yield. This dose could be a suitable dose in midseason drainage managed rice systems especially in tropical and subtropical climatic conditions. This yield-scaled GWP supports the concept of win-win for food security and environmental aspects through balancing between viable rice productivity and maintaining convincing greenhouse gases.

Keywords: GHGs; GWP; Methane; Nitrous oxide; Rice; Systematic review; Yield-scaled GWP.