Comprehensive Environmental Assessment of Potato as Staple Food Policy in China

Abstract

The Chinese government projected 30% of total consumed potatoes as a staple food (PSF) by 2020. We comprehensively assessed the potential impacts of PSF on rice and flour consumption, rice and wheat planting, energy and nutrient supply, irrigation-water, chemical nitrogen (N), phosphorus pentoxide (P₂O₅) and potassium oxide (K₂O) fertilizer inputs and total greenhouse gases (GHG) emission for potatoes, rice and wheat, by assuming different proportions of potato substitutes for rice and flour. The results showed that per capita, 2.9 ± 0.3 and 4.7 ± 0.5 kg more potatoes per year would enter the Chinese staple-food diet, under the government's target. PSF consumed are expected to reach 5.2 ± 0.7 Tg yr^-1, equivalent to substituting potatoes for 4.2 ± 0.8-8.5 ± 0.8 Tg yr^-1 wheat and 5.1 ± 0.9-10.1 ± 1.8 Tg yr^-1 rice under different scenarios. While this substitution can increase the nutrient supply index by 63% towards nutrient reference values, it may induce no significant effect on staple-food energy supply with lower chemical fertilizer (except for K₂O) and irrigation-water inputs and GHG emissions in different substitution scenarios than the business as usual scenario. The reduction in rice and wheat demands lead to wheat in the North China Plain and early rice decrease by 6.1-11.4% and 12.1-24.1%, respectively. The total GHG reduction is equal to 1.1-9.0% of CO₂ equivalent associated with CH₄ and N₂O emitted from the Chinese agroecosystem in 2005. The saved irrigation water for three crops compared to 2012 reaches the total water use of 17.9 ± 4.9-21.8 ± 5.9 million people in 2015. More N fertilizer, irrigation-water, and GHG can be reduced, if the PSF ratio is increased to 50% together with potato yield improves to the optimal level. Our results implied that the PSF policy is worth doing not only because of the healthier diets, but also to mitigate resource inputs and GHG emissions and it also supports agricultural structure adjustments in the areas of irrigated wheat on the North China Plain and early rice across China, designed to increase the adaptability to climate change.

Keywords: chemical fertilizer inputs; irrigation-water use; nutrient reference values; substitution ratio; total GHG emission.

Figure 1

Staple-food consumption per capita and proportions in Chinese urban and rural households during 1980–2012, and projected future trends to 2020.

Figure 2

National rice-, flour- and potato consumptions; rice and wheat production demands (Tg yr⁻¹; left); potatoes as staple foods substituted for rice and flour, and rice and wheat production (Tg yr⁻¹); reduced early rice and wheat planting (million ha) under the different substitution scenarios in 2020, in comparison with 2012 (right).

Figure 3

Total GHG emission from different CO₂-eq emissions in conventionally grown (Potato-Con), and optimally grown (Potato-Opt) potatoes, winter wheat in the North China Plain (NCP; wheat A), winter wheat across China except for NCP (wheat B) and early, medium and late rice in China (left) and the yields and GHGI of Potato-Con, Potato-Opt, wheat A and early rice (right).

Figure 4

Chemical N-, P₂O₅- and K₂O-feitilizer inputs, irrigation-water consumptions and total GHG for rice, wheat, conventionally grown potatoes (Potato-Con), and optimally grown potatoes (Potato-Opt) under different scenarios, compared with 2012.