Water and nutrient management to narrow the yield gap of potato grown in a Mediterranean climate

Potato is a globally important crop, and its cultivation is particularly vital in Iran. However, the area under potato cultivation in Iran has declined in recent years, making yield improvement essential to sustain production and meet food demand. This study aimed to assess the potato yield gap caused by limiting factors in the Dehgolan Plain and to identify effective management strategies for increasing yield with optimal resource use. The research included two parts: first, determining actual on-farm yields through surveys of 50 farmers and field observations; second, evaluating the yield gap caused by water and nutrient limitations via a two-year field experiment (2021–2022). Various treatments combining conventional management, soil-test-based fertilization, organic manure, irrigation at 80% field capacity, and sulfur application were tested. Yield, economic benefits, and productivity indices were measured to assess the cost-effectiveness of closing the yield gap. Results indicated a yield gap of approximately 13 t.ha⁻¹ in both years. Maximum yields reached 37 t.ha⁻¹ in 2021 under CM + W (common management + irrigation at 80% FC) treatment, and 50 t.ha⁻¹ in 2022 under ST + M + W + S ₁₀₀₀ (NPK Fertilizing based on soil test + chicken manure + irrigation at 80% FC + 1000 kg.ha ^− 1 sulfur). Agronomic efficiency of nitrogen fertilizer was highest with 236–284 kg.kg⁻¹, while phosphorus partial factor productivity peaked at 523–661 kg.kg⁻¹. The findings demonstrate that nutrient management guided by soil tests, coupled with adequate irrigation, substantially enhances potato yield. Maintaining balanced nutrient supply and avoiding drought stress during tuber bulking are key for maximizing production. Overall, this study highlights the importance of integrated water and nutrient management to narrow the potato yield gap, improve resource use efficiency, and optimize production costs in the Dehgolan plain.