Abstract
Climate variability is deeply affecting all aspects of human life including agricultural sector. In the present study the CROPWAT model was used to estimate reference evapotranspiration (ETo), crop evapotranspiration (ETc), effective rainfall (ER) and crop water requirement (CWR) of summer-autumn rice crop and its yield during baseline period (2002-2017) and also under representative concentration pathways (RCPs) 4.5 scenario for 2020s, 2055s and 2090s-time scales for Long Xuyen Quadrangle (LXQ) area of Vietnam. It was found that the ER significantly increased by 6.2, 16.9 and 15.4 per cent, respectively in 2020, 2055 and 2090; ETo and ETc increased by 2.1 and 2.3 per cent, respectively in 2020s; 4.4 and 5.8 in 2055; and 5.8 and 7.7 per cent in 2090 compared to baseline. The CWR also increased approximately 4.6, 4.4 and 3.5 per cent, respectively in 2020, 2055 and 2090 and consequent decrease in rice yield by 6.5, 7.9 and 10.4 per cent, respectively. Results showed that if the crop planting date is delayed by 20 days, the rice yield would increase approximately 4.9, 7.9 and 9.9 per cent, respectively in three-time scales of RCP 4.5 scenario, compared to base line period.
Highlights
The results showed that under RCP4 .5 scenario the effective rainfall (ER) increased by 6.2 per cent, 16.9 per cent and 15.4 per cent, respectively during 2020s, 2055s and 2090s while the ETo increased by 2.1, 4.4 and 5.8 per cent and the ETc increased by 3.3, 5.8 and 7.7 per cent,respectively(Table 6)
The crop water requirement (CWR) increased approximately by 4.6, 1.4 and 2.5 per cent corresponding to time scales of representative concentration pathways (RCPs) 4.5 scenario
It was found that under the impact of climate change ETo and ETc were increased leading to increase in crop water requirement, which resulted in rice yield reduction for time scales of RCP 4.5 scenario
Summary
The study area is concentrated to coastal plains of Long Xuyen Quadrangle (LXQ) area of Vietnam stretching from 09o57'-10o42’N and 104o29'-105o29’E (Fig.1) with 85 per cent of rice cultivation area (MNRE 2016). Estimation of crop water requirement CROPWAT model (Version 8.0) FAO (2016) was used for calculating the ETo as,. Future precipitation and temperature data corresponding to time scales 2016-2035 (2020s), 20462065 (2055s) and 2080-2099 (2090s) of RCP4.5 scenario (constructed by Vietnam’s Ministry of Natural Resources and Environment) were used to estimate the rice yield in the future. The statistical indices R2 and RMSE are widely applied to evaluate the model performance based on the agreement of the simulated results and observed data (Deb et al 2015). The farmers grow IR6976 varietyof rice in 93 per cent of the area while in 7 per cent other rice varieties such as IR50404, OM4900 and OM9582 are grown (Deb et al 2015) This IR6976 variety has a mean growing cycle of 100 days from sowing till harvesting depending on the specific cropping season. The model performance was evaluated by statistical methods namely coefficient of determination
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