Impact of improved crop management practices over the last 20 years on rice productivity in different climatic regions of Sri Lanka

Rice productivity in Sri Lanka has increased from 1.5 t ha⁻¹ in the 1950s to approximately 4.3 t ha⁻¹ at present. This improvement has been attributed to advances in both agronomic practices and the genetic potential of rice varieties. However, the contribution of management practices recommended over the years to rice productivity improvement remains unclear. To evaluate this, long-term productivity data from rice varieties cultivated continuously over several years at the same locations are required. Accordingly, productivity data for the rice varieties Bg300, Bg352, Bg358, and At362 cultivated during both Yala and Maha seasons from 1998 to 2020 at 12 locations were obtained from the National Coordinated Rice Varietal Testing (NCRVT) program. In addition, daily rainfall and daily minimum and maximum temperature data recorded during the cultivation periods were collected. The results revealed that productivity remained unchanged over time in most variety × location × season combinations (>90%), with only a few combinations showing increasing (5%) or decreasing (4%) productivity trends. This widespread productivity stagnation suggests that the management practices recommended during the past two decades have not been sufficiently effective in enhancing rice productivity. Average seasonal maximum temperature and average seasonal temperature difference showed significant positive correlations with crop productivity (p < 0.05), whereas average seasonal minimum temperature was negatively correlated with productivity (p < 0.05). Overall, the findings indicate that crop management practices adopted over the years have contributed little to improving rice productivity, while climate variability has played a significant role. Therefore, identifying and implementing more effective management practices is essential to overcome productivity stagnation and enhancing future rice production.