How can China achieve GHG reduction and economic sustainability from sugar crops?

China is the fourth largest sugarcane and sugar producer in the world, with a sugarcane harvesting area of 1.29 Mha and an output of 103 Mt in 2022. The harvesting area of sugar beet was 0.16 Mha, and the yield was 8.93 Mt. However, there is no comprehensive research on greenhouse gas (GHG) emissions and economic benefits of sugar crop production in China. Using statistical yearbook data from 1980 to 2018, this study examined historical trends in crop yield, agricultural input, carbon footprint, and economic benefits in seven major sugarcane and sugar beet growing provinces in China. Using the historical data of these parameters, the relationship between them was analyzed by structural equation model, and the greenhouse gas emission reduction potential and economic benefit of China's sugar crops were analyzed by scenario analysis method.

The results showed that the yield of sugarcane and sugar beet increased from 47.6 to 76.9 t·ha^-1 and 14.2 to 52.2 t·ha^-1, respectively, with an average annual growth rate of 0.65 and 1.09 t·ha^-1, respectively. The carbon footprint per unit area of sugarcane increased almost linearly from 1980 to 2016 at an average rate of 136 kg·ha^-1·yr^-1 CO₂-eq, and showed a downward trend after reaching a peak in 2016. Carbon footprint per unit area of sugar beet also increased at an average rate of 94.5 kg·ha^-1·yr^-1 CO₂-eq. Structural equation analysis showed that fertilizer, especially nitrogen fertilizer, was a key driver of the carbon footprint of both crops. Labor inputs is another key driver of the carbon footprint, with reductions in labor inputs leading to increases in agricultural inputs (such as diesel, pesticides, fertilizers, and electricity), leading to increases in the carbon footprint. Over the past 40 years, sugarcane and sugar beet income have grown at an average rate of 925 and 725 CNY·yr^-1, respectively, but net income has not increased significantly. On the contrary, the ratio of income to cost showed a significant downward trend.  By transitioning the current cropping system to an improved model with optimized labor, N input and machinery use (called optimized crop; OC), the GHG emission and total annual cost of sugarcane and sugar beet production can be reduced by 32% and 24%, respectively, by 2030, compared to business-as-usual (BAU) scenario.

To achieve these goals, we need concerted action on the technical, economic and policy fronts. First, by consolidating small farms to create larger farms. Develop and implement appropriate policy and economic incentives to integrate farms and reduce farm lease costs. Second, maximize agricultural mechanization. Invest and promote research and development of agricultural mechanization. Third, improving soil health and soil fertility. This will require considerable research for region-specific optimization of fertilizer use, soil amendments and use of other agri-chemicals, and cropping system. Fourth, developing and providing high-quality and high-yield varieties suitable for various producing areas. Finally, actively adopting best management practices and recommendations for crop production. 

This study has been published in Frontiers of Agricultural Science and Engineering in 2024, Volume 11, Issue 3. DOI: 10.15302/J-FASE-2023529.