The limitations of water resources in supplying the demands of consumer sectors including drinking, hygiene and healthcare, agriculture, industry, as well as environment well reflect the importance of proper use of water. Thus, it is essential to choose an optimal and superior strategy to use water under water deficit conditions. This experiment was implemented as split plot in a fully randomized block design in a research farm in the southeast of Iran on Roselle plant. The experimental treatments included three levels of potassium fertilizer 75 t ha⁻¹ (K₁), 112.5 t ha⁻¹ (K₂), and 150 t/ha (K₃) (equivalent to 50%, 75%, and 100% of potassium fertilizer requierment) and four levels of irrigation water including 40%, 60%, 80%, and 100% of the plant water requierment (l1, l2, l3, and l4). The main aim of the research was to estimate the production function as well as to calculate the index and optimal depths of consumed water. Regression analyses were done by linear, Cobb-Douglas, Quadratic and Transcendental functional forms of Roselle production. The final production indicators in relation to the water depth and potassium fertilizer, the final rate of technical substitution for potassium fertilizer and water depth, and the final production value in relation to water depth and potassium fertilizer were calculated. The results indicated that the Quadratic function was chosen as the superior function. The final production index in relation to the minimum water depth was 1.4 and for maximum water depth was − 0.86 kg cm⁻¹ of water depth. The final production index in relation to the minimum and maximum potassium fertilizer was calculated as 3.92 and 1.77 kg respectively. The results also showed that by applying deficit irrigation under water constraint conditions, the optimal depths of consumed water in relation to the maximum depth at 75, 112.5 and 150 kg levels of potassium fertilizer per hectare had 13.29, 14.34, and 13.1 cm reduction of water consumption respectively. As can be seen, elevation of potassium fertilizer up to 75% resulted in more saving of water consumption. Use of potassium fertilizer can modify the damages resulting from drought stress in Roselle.

水资源在满足饮用水、卫生和医疗保健、农业、工业和环境等消费部门需求方面的局限性，充分体现了合理用水的重要性。因此，在缺水条件下选择最佳和优越的用水策略至关重要。该实验在伊朗东南部的洛神花植物研究农场中以完全随机区组设计的裂区形式实施。试验处理包括三个水平的钾肥 75 t ha ^-1 (K ₁ )、112.5 t ha ^-1 (K ₂ ) 和 150 t/ha (K ₃)（相当于钾肥需求量的 50%、75% 和 100%）和四个灌溉用水水平，包括植物需水量的 40%、60%、80% 和 100%（l1、l2、l3 和l4)。该研究的主要目的是估计生产函数以及计算消耗水的指数和最佳深度。回归分析是通过洛神花产生的线性、Cobb-Douglas、二次和超越函数形式进行的。计算了水深和钾肥相关的最终生产指标、钾肥和水深的最终技术替代率、水深和钾肥的最终产值。结果表明，二次函数被选为上级函数。^-1水深。与最小和最大钾肥相关的最终生产指数分别计算为 3.92 和 1.77 公斤。结果还表明，通过在水分限制条件下进行亏缺灌溉，最佳消耗水深度相对于每公顷钾肥 75、112.5 和 150 kg 水平的最大深度分别减少了 13.29、14.34 和 13.1 cm 的用水量。分别消费。可以看出，将钾肥提高到 75% 可以节省更多的用水量。钾肥的使用可以改变洛神花干旱胁迫造成的损害。