Trends of agro-climatic variability and multi-year prediction of rice and wheat yields under the changing climatic scenarios using DSSAT crop model in Nepalese western Terai

The rice and wheat yields in the western Terai region of Nepal over the past four decades have been drastically reduced mainly by climatic anomalies such as fluctuating temperatures, decreased solar radiation, uneven and erratic rainfall, drought and so on. NASA-POWER derived weather data of Dumkauli in Nawalparasi (27.68° N, 84.13° E) and of Taulihawa in Kapilbastu (27.55° N, 83.0667° E) districts in western Terai region of Nepal for the past four decades (1984/85-2022/23) were downloaded, validated with the recorded weather data of Department of Hydrology and Meteorology (DHM) and studied the trends of climatic variability. Furthermore, the trend analysis for the grain yield of rice in Nawalparasi and wheat yield in Kapilvastu was drawn with the historical data sets of maximum and minimum temperatures and rainfall. Positive correlations between grain yields and minimum temperature and rainfall each showed acceptable coefficient of determinations (R2) for both of the crops. The correlation between precipitation and observed rice yield estimated was 0.71. Similarly, the correlation coefficient of minimum temperature and wheat yield was 0.272. The multi-year predicted rice and wheat yields using the historical weather data and by the use of the IPCC (2007) scenario embedded in the DSSAT crop model showed that yield of the both crops could be sustained with the use of the current crop cultivars only for a few years. Climatic index, mainly temperature was found to be more sensitive to wheat production, and the rainfall to rice production in the Nepalese western Terai region. This study suggests for the development of high yielding climate change-ready rice and wheat cultivars to feed the increasingly growing Nepalese population.