Sustaining food self-sufficiency of a nation: The case of Sri Lankan rice production and related water and fertilizer demands

Abstract

Rising human demand and climatic variability have created greater uncertainty regarding global food trade and its effects on the food security of nations. To reduce reliance on imported food, many countries have focused on increasing their domestic food production in recent years. With clear goals for the complete self-sufficiency of rice production, Sri Lanka provides an ideal case study for examining the projected growth in domestic rice supply, how this compares to future national demand, and what the associated impacts from water and fertilizer demands may be. Using national rice statistics and estimates of intensification, this study finds that improvements in rice production can feed 25.3 million Sri Lankans (compared to a projected population of 23.8 million people) by 2050. However, to achieve this growth, consumptive water use and nitrogen fertilizer application may need to increase by as much as 69 and 23 %, respectively. This assessment demonstrates that targets for maintaining self-sufficiency should better incorporate avenues for improving resource use efficiency.

Keywords: Agricultural intensification; Food security; Nitrogen runoff; Self-sufficiency; Water footprint; Water resources.

Fig. 1

Wet and dry zones of Sri Lanka

Fig. 2

Rice yields during the Maha (major) and Yala (minor) cultivation seasons in the two zones. In 2013, 68 % of rice produced in the WZ and 61 % rice produced in the DZ came from the Maha (major) season (DCS 2014). Rice yields have steadily increased in Sri Lanka at both the national and sub-national levels. Maha-WZ (a), Maha-DZ (b), Yala-WZ (c), and Yala-DZ (d) yields are best fit with an increasing linear function. For the Yala-DZ yield, an exponential fit had a lower rmse, but rmse was not significantly different from a linear fit. See Table S1 for more details on these statistics. Maha-DZ rice yield data for 1986 were not available

Fig. 3

Water use and human demand for rice production. Per ton (a) and national (b) water footprints of rice production are shown for different yield gap closures (YGCs). We include all three footprints together (green, blue and gray), but it is important to note that only blue and green water represent consumptive uses of water. c Current and projected populations (orange) are estimations from the UN (2012). These estimates of demand are compared to the number of people able to be fed under three rice supply scenarios—‘Yield,’ ‘Harvest,’ and Efficiency’—described in detail in “Materials and methods” section. The ‘Efficiency’ scenario utilized the water use efficiency value at 50 % YGC. Values are presented in Table S3