Exploiting Co-Benefits of Increased Rice Production and Reduced Greenhouse Gas Emission through Optimized Crop and Soil Management

Abstract

Meeting the future food security challenge without further sacrificing environmental integrity requires transformative changes in managing the key biophysical determinants of increasing agronomic productivity and reducing the environmental footprint. Here, we focus on Chinese rice production and quantitatively address this concern by conducting 403 on-farm trials across diverse rice farming systems. Inherent soil productivity, management practices and rice farming type resulted in confounded and interactive effects on yield, yield gaps and greenhouse gas (GHG) emissions (N2O, CH4 and CO2-equivalent) with both trade-offs and compensating effects. Advances in nitrogen, water and crop management (Best Management Practices-BMPs) helped closing existing yield gaps and resulted in a substantial reduction in CO2-equivalent emission of rice farming despite a tradeoff of increase N2O emission. However, inherent soil properties limited rice yields to a larger extent than previously known. Cultivating inherently better soil also led to lower GHG intensity (GHG emissions per unit yield). Neither adopting BMPs only nor improving soils with low or moderate productivity alone can adequately address the challenge of substantially increasing rice production while reducing the environmental footprint. A combination of both represents the most efficient strategy to harness the combined-benefits of enhanced production and mitigating climate change. Extrapolating from our farm data, this strategy could increase rice production in China by 18%, which would meet the demand for direct human consumption of rice by 2030. It would also reduce fertilizer nitrogen consumption by 22% and decrease CO2-equivalent emissions during the rice growing period by 7% compared with current farming practice continues. Benefits vary by rice-based cropping systems. Single rice systems have the largest food provision benefits due to its wider yield gap and total cultivated area, whereas double-rice system (especially late rice) contributes primarily to reducing GHG emissions. The study therefore provides farm-based evidence for feasible, practical approaches towards achieving realistic food security and environmental quality targets at a national scale.

Fig 1. Relationships among management practices, soil inherent productivity and yield.

Note: soil inherent productivity was estimated as yields in zero-N plots (Yield-N0). Black points represent farming practice (FPs); red points represent best management practice (BMPs). a, early rice (n = 98); b, late rice (n = 148); c, single rice (n = 157).

Fig 2. Yield of farming practices (Y_f), attainable yield (Y_a), yield gap and the percentage of Y_f as Ya (Y_f /Y_a) for three rice faming systems.

Note: yield gaps were estimated as differences between yields in farming practice on soils with various productivity levels and ‘attainable yields’, determined as mean yields of the 20% highest-yielding locations under BMPs. E-R, early rice, L-R, late rice, S-R, single rice. Solid and dashed lines indicate median and mean yields, respectively. The box boundaries indicate upper and lower quartiles, the whisker caps indicate 90th and 10th percentiles, and the circles indicate the 95th and 5th percentiles.

Fig 3. Relationships among management practices, soil inherent productivity and yield gap.

Note: soil inherent productivity was estimated as yield in zero-N plots (Yield-N0). Yield gaps were estimated as differences between yields in farming practice on soils with various productivity levels and ‘attainable yields’, determined as mean yields of the 20% highest-yielding locations under BMPs. (a), early rice (n = 98); (b), late rice (n = 148); (c), single rice (n = 157).

Fig 4. Relationships among management practices, soil inherent productivity and N₂O emissions (a), CH₄ emissions (b), global warming potential (GWP, c), and greenhouse gas emission intensity (GHGI, d).

Note: soil inherent productivity was estimated as yield in zero-N plots (Yield-N0). The GWP and GHGI is the sum of emissions of CO₂-eq of N₂O and CH₄ at area and yield scale during the rice growing season, respectively. Black points represent farming practice (FPs); red points represent best management practice (BMPs). For b, c and d, L-R, E-R and S-R represent late rice (n = 148), early rice (n = 98) and single rice (n = 157).