Southeast Asia must narrow down the yield gap to continue to be a major rice bowl

Southeast Asia's rice production has significantly increased over the past 50 years, primarily due to higher cropping intensity and yield improvements. This success has made the region a crucial global rice supplier, accounting for a substantial portion of global production and exports. However, several challenges threaten the region's ability to maintain this position. Firstly, despite earlier predictions, per capita rice demand remains relatively stable, meaning population growth alone will increase demand by approximately 18% by 2050. Secondly, Indonesia and the Philippines, two of the region's most populous nations, currently rely on rice imports. Thirdly, yield stagnation has been observed in several major rice-producing countries. Finally, expansion of irrigated rice areas is limited by factors such as investment constraints, water scarcity, and environmental concerns. The scope for further increasing cropping intensity is also limited, making yield gap closure a critical factor in ensuring future rice security. This study investigates the extent of yield gaps in major Southeast Asian rice-producing countries to determine whether production potential can be significantly increased on existing cropland and thereby maintain the region's role as a major global rice supplier.

The paper references several studies on rice production, consumption, and trade in Southeast Asia. It cites works forecasting global rice consumption, analyzing rice trade and price volatility, and examining strategic research and policy issues for food security. Previous research highlights the impact of the Green Revolution on rice production in the region and raises concerns about yield stagnation. Other cited studies focus on future urban land expansion and its implications for global croplands, as well as trends in Asian irrigation. The authors also refer to existing literature on yield gaps in rice-based farming systems, emphasizing the need for closing existing yield gaps and the impact of climate change on rice production.

The study employs a data-intensive approach to estimate yield gaps across six major rice-producing countries in Southeast Asia (Cambodia, Indonesia, Myanmar, Philippines, Thailand, and Vietnam). The methodology follows protocols established by the Global Yield Gap Atlas. Yield gaps were estimated using simulated yield potential (for irrigated crops) or water-limited yield potential (for rainfed crops). The analysis included both irrigated and rainfed lowland rice systems, which represent the vast majority of rice production in the region. The yield potential estimation assumed the absence of water and nutrient limitations, weeds, pests, and diseases (except for water limitation in rainfed systems). The study incorporated both per-crop and annual yield potential, accounting for cropping intensity variations. Subnational-level analysis was also conducted to identify regions with the largest opportunities for yield increases. Three scenarios were considered for projecting rice self-sufficiency and surplus: continuation of current yield trends, full closure of the exploitable yield gap, and half closure of the exploitable yield gap. The exploitable yield gap was defined based on reasonable yield goals achievable with access to markets, inputs, and extension services. Current and future rice demand was estimated using projected population data, per capita rice demand projections from various econometric models, and information from the USDA. The model ORYZA version 3, a well-validated crop simulation model, was used for yield potential estimation. The study also used weather data from meteorological stations and NASA-POWER Agro-climatic databases. Soil properties were specified where necessary (rainfed rice). Data on average farmer yields and rice harvested areas were obtained from official statistics. The yield gap was calculated as the difference between yield potential and average farmer yield. Annual yield gaps were calculated considering cropping intensity. The study accounted for various factors such as water regimes, crop sequences, and soil types, while acknowledging uncertainties related to groundwater depth in rainfed systems. The final analysis involved assessing rice production potential and its impact on rice surplus by comparing projected rice production against rice demand by 2040. The scenarios considered potential yield gap closure at both national and regional levels.

The study found that the average yield gap across the six countries represents 48% of the estimated yield potential, but there is substantial variation among countries and water regimes. Yield gaps were larger for rainfed rice (55%) than for irrigated rice (42%). However, due to higher cropping intensity, the annual yield gap for irrigated rice was larger (7.5 Mg ha⁻¹ per year) than that for rainfed rice (5.2 Mg ha⁻¹ per year). Indonesia and Vietnam showed relatively smaller yield gaps for irrigated rice (37–39%) compared to Cambodia, Myanmar, Philippines, and Thailand (51–60%). Subnational-level analysis revealed significant differences in yield gaps within countries, for example, between the Red River delta and the Mekong delta in Vietnam. The study projected that under the business-as-usual scenario (continuation of current yield trends), the regional self-sufficiency ratio (SSR) would drop to 1.03 by 2040, almost eliminating the rice surplus. Indonesia and the Philippines would fail to achieve rice self-sufficiency under this scenario. In contrast, a complete closure of the exploitable yield gap would lead to a regional SSR of 1.55 and a substantial rice surplus (100 Mt). A more realistic scenario, involving a 50% closure of the exploitable yield gap, would increase the regional SSR to 1.29 and triple the rice surplus to 54 Mt, enabling Indonesia to achieve rice self-sufficiency and significantly reducing import needs in the Philippines. Achieving these yield increases would require annual yield gains ranging from 36 kg ha⁻¹ to 67 kg ha⁻¹ across the countries. The study's findings are consistent with previous studies on yield gaps in specific countries or rice seasons, but the regional scope and level of detail are unique.

The findings highlight the critical need for narrowing yield gaps to ensure Southeast Asia's continued role as a major rice exporter and to guarantee food security within the region. The study emphasizes that relying solely on current yield trends will lead to insufficient rice production to meet future demand, particularly in Indonesia and the Philippines. The required yield improvements are achievable, considering that existing yield gaps in Southeast Asia are larger than in other major rice-producing regions like China and the US. The necessary annual yield gains to achieve a 50% yield gap closure are modest compared to historical yield gains in these countries. The importance of maintaining rice surplus production extends beyond the region, contributing to global price stability and food security in other rice-importing areas. The study acknowledges that future climate change impacts on rice yields are not explicitly incorporated into the model, but argues that the effects within the 20-year time frame are relatively small compared to the size of the existing yield gap. Addressing the yield gap requires targeted investments in agricultural policies, innovation, research, and development to accelerate yield gains. The study notes the importance of improving crop management practices, particularly nutrient and water management, and controlling biotic factors. Reducing production risks, especially in rainfed lowland systems, is also critical. The discussion emphasizes the need to balance yield increases with maintaining grain quality and minimizing negative environmental impacts, highlighting the potential of site-specific nutrient management and integrated pest management.

This study demonstrates that Southeast Asia must significantly narrow its rice yield gap to sustain its position as a major rice bowl. Current yield trends are insufficient to meet growing domestic and global demands. The potential for substantial increases in rice production through yield gap closure is significant, particularly in Cambodia, Myanmar, Philippines, and Thailand. Achieving this will require strategic investments in agricultural policies, research and development, and farmer support to improve crop management practices. Future research could focus on developing more detailed climate change impact assessments and evaluating the effectiveness of specific interventions to close the yield gap.

The study focuses on irrigated and rainfed lowland rice, excluding upland and deep-water rice systems, which may underestimate the overall yield gap. The analysis assumes that the harvested rice area will remain constant, which may not hold true given land conversion pressures. Climate change impacts on yield potential are not explicitly modeled, although the authors argue that the effect within the 20-year time frame is likely small compared to the size of the yield gap. The study relies on data from various sources and may have some inherent uncertainties associated with data quality and aggregation. Finally, the projection of rice demand relies on several econometric models, and uncertainties may exist with the prediction.