Utilizing rainfed supply and irrigation as a climate variability adaptation solution for coastal lowland areas in Vietnam
Globally, the agricultural sector continues to be affected by the impacts of climate variability. Lowland regions have frequent drought and saline intrusion, leading to irrigation water deficits as a part of climate variability. This study focused on determining the rainfed use efficiency (RUE) and further establishing a crop cultivation calendar (CCC) for rice paddies across Kien Giang province, Vietnam. The crop yield was simulated in response to the relevant environmental factors based on a crop model. The model performance was appraised using calibration and validation procedures and was considered suitable based on good values for statistical indicators (index of agreement = 0.74–0.89, coefficient of determination = 0.73–0.92 and root mean square error approximately 11–20%). The results indicated that the rainfed use efficiency and crop yield of rice planting seasons notably improved when the CPC (baseline) was altered, specifically, when the first cropping season was around the first week of November, which increased RUE (14.2–17.9%) and the crop yield (1.5–5.9%) at three experimental locations, while the second cropping season in the fourth week of March decreased RUE by 8.8–10.9% and increased the crop yield by up to 6.9 t/ha. An alteration in the CCC of rice paddies across the study area accounted for relevant environmental factors and produced an effective adaptation solution.