Alternate wetting and drying maintains rice yield and reduces global warming potential: A global meta-analysis

Context

Rice production systems are significant sources of anthropogenic emissions of the greenhouse gases (GHGs) i.e., methane (CH₄) and nitrous oxide (N₂O). Practicing alternate wetting and drying (AWD) in rice substantially affects rice yield as well as CH₄ and N₂O emissions from rice fields. However, it is difficult to determine global impacts from individual experiments as these studies differ in practice, experimental design, locations, nature of soil, and agro-ecological regions.

Objective

The objectives of this article include (i) to conduct a global and comprehensive analysis to clarify the effects of AWD on rice yield, GHGs emissions, global warming potential (GWP), and greenhouse gas emission intensity (GHGI) in the context of a variety of climatic conditions and initial soil properties, and (ii) to explore the effects of different agronomic measures on rice yield and emissions of GHGs under AWD.

Method

In this study, we analyzed 72 peer-reviewed studies worldwide that provide insights into the effects of climate, initial soil conditions, and agricultural management practices on rice yields, GHGs, GWP, and GHGI under AWD conditions.

Results

The results found that AWD led to 1.52 % increase in rice yield with a 42.59 % increase in N₂O emissions, however, CH₄, GWP, and GHGI were reduced by 43.23 %, 36.84 %, and 38.57 %, respectively. Moreover, regional climatic factors and soil properties substantially affects the rice yield and GWP e.g., low mean annual temperature (≤ 15℃) and precipitation (≤ 1000 mm) are conducive for emission reduction potential of CH₄ and GWP. In addition, AWD reduced GWP highest in soils having pH ≤ 6.5, organic carbon content ≤ 12 g kg⁻¹, total nitrogen ≥ 2 g kg⁻¹, and high available N, P and K contents. Overall, rice yield improvements with decreased GHGs, GWP and GHGI were observed at 100–150 kg hm⁻² N fertilizer application rate, and the use of enhanced-efficiency fertilizers, deep fertilization, and biochar application. Furthermore, AWD increased economic benefits and energy use efficiency through the reduction of costs and energy losses associated with irrigation.

Conclusions

Thus, appropriate agronomic measures should be taken according to the local conditions for sustainable rice production with minimum emissions of GHGs.