Effect of potassium fertilization on roselle yield and yield components as well as IWUE under deficit irrigation regimes

Abstract

This research aimed to investigate different levels of irrigation water and potassium fertilizer on the yield and yield components as well as qualitative properties and irrigation water use efficiency (IWUE) of Roselle (Hibiscus sabdariffa). For this purpose, in 2019 and 2020, a factorial experiment with a randomized complete block design (RCBD) with three replicates was conducted in a semi-dry region. The experimental treatments included three levels of potassium fertilizer 75 t ha−1 (K1), 112.5 t ha-1 (K2), and 150 t ha−1 (K3) (equivalent to 50, 75, and 100% of potassium fertilizer percentage) and four levels of irrigation water including I1 (40%), I2 (60%), I3 (80%), and I4 (100%) of the plant water requirement. At the end of the experiment, quantitative parameters including plant height, weight and number of capsules, dry yield, and IWUE were measured. Further, qualitative parameters such as level of anthocyanin, protein, carbohydrate, proline, chlorophyll a and b were also measured to investigate the effects of water stress and fertilizer stress on the quality of Roselle. Experimental results revealed that the simple effects of irrigation water and potassium fertilizer became significant at 1 and 5% probability levels on all of the measured parameters. The greatest dry yield (600.95 kg ha−1) was obtained from l3K3 treatment. The maximum IWUE was achieved in l2K3 treatment (0.058 kg m−3). However, no significant difference was observed in this regard between l2 and l3. Qualitatively, with the reduction of the depths of irrigation water up to 60% the plant water requirement and with decline in the potassium fertilizer consumption, the level of anthocyanin, protein, carbohydrate, and proline increased by 85.16%, 19.56%, 15.34%, and 28.35% respectively. However, the values of chlorophyll a and b dropped by 42.75 and 24.54% respectively. On the other hand, no significant difference was observed between K1 and K2 in this regard. Thus, considering the water status of the region and deficit of water resources, application of 80% water requirement (treatment l3) would save water consumption, and consuming 75% potassium content (K2 treatment) would enhance the quality and modify the damages resulting from drought stress in Roselle.