Yield dynamics of major crops in Thailand for the period 1918–2023: Regional patterns of growth, stagnation, and climate sensitivity

Context

Understanding long-term yield trends is essential for guiding agricultural policy and climate adaptation, yet major gaps persist due to limited long-term datasets, insufficient analysis of subnational stagnation, and uncertainties in crop responses to policy and climate variability. Although Thailand plays a critical role in Southeast Asia’s agriculture, comprehensive provincial-scale historical assessments remain scarce.

Objective

This study aims to: (1) reconstruct long-term yield trends, (2) detect spatial and temporal stagnation patterns, and (3) assess crop sensitivities to large-scale climate variability for rice, maize, and soybean in Thailand.

Methods

We used national records to compile annual crop yield data from 1918 to 2023 across 77 provinces in Thailand. To capture both long-term trends and sudden shifts, we applied polynomial detrending and dynamic linear models to analyze yield trends and identify breakpoints. We then assessed correlations between crop yield anomalies and major climate teleconnection indices, including the El Niño–Southern Oscillation (ENSO), Dipole Mode Index (DMI), and Southern Oscillation Index (SOI), to quantify climate influence over time and space.

Results

Rice yields declined in the early 20th century but rose steadily after the 1960s. Maize yields accelerated in the 1980s, while soybean trends remained modest and variable. Stagnation occurred in 68 % of rice- and 49 % of maize-growing provinces, especially where irrigation access or economic support was limited. Soybean stagnation was more scattered. Nearly 70 % of rice provinces showed positive ENSO correlations, while maize and soybean responses were weaker or negative. Climate-yield associations were strongest from 1970 to 1999, diminishing in recent decades, possibly due to improved adaptation or evolving teleconnection behavior.

Conclusion

This study provides the first over-100-year subnational analysis of yield dynamics in Thailand. While rice productivity improved overall, maize and soybean exhibited more frequent stagnation and higher climate sensitivity. Long-term teleconnections significantly influenced yield variability, especially before 2000, highlighting the importance of climate-informed agricultural policy.

Implications

The findings support the integration of climate risk monitoring into early warning systems and call for adaptive strategies, including drought-tolerant varieties, climate-resilient practices, and targeted support for stagnating provinces. Future work should incorporate socioeconomic data to refine localized climate adaptation.