Adjusting sowing date to enhance roselle performance and water productivity under water deficiency stress

<title>Abstract</title> Climate change, especially water stress, poses a threat to food production and increases the occurrence of famines worldwide. Adjusting sowing dates to enhance irrigation water productivity is among the adaptation strategies to mitigate the effects of water deficiency stress on crop yields. In this context, a field experiment was conducted during 2021 and 2022 seasons at the AL-Busili Experimental Farm of the Central Laboratory for Agricultural Climate, Agricultural Research Center in Egypt, to assess the effects of sowing dates (T1: May 19, T2: June 19, and T3: July 19) and irrigation rates (I1: 100%, I2: 75%, and I3: 50% of potential crop evapotranspiration “ETc”) on the performance <italic>and</italic> water productivity of roselle (<italic>Hibiscus sabdariffa</italic> L.). The treatments were arranged in a split-plot design with three replications. The results indicated that regular irrigation (I1 at 100% ETc) under the mid-sowing date T2 (June 19) significantly (p ≤ 0.05) increased plant height, branch number, fruit number per plant, and the dry weight of sepals per plant. Adopting I2 or I3 on June 19 enhanced anthocyanin content (AC%). Notably, the late sowing date on 19th July, coupled with the severe water stress (I3, 50% ETc), yielded the uppermost water productivity (1.917 and 1.922 kg/m³). Based on these findings, it could be concluded that the late sowing date can be a viable management strategy in Egypt with limited water availability in terms of water productivity of harvested roselle fruits.