Optimization of Seed and Oil Yield of Linseed under Semi-Arid Conditions through Balanced Nitrogen and Phosphorus Fertilization

Nitrogen (N) and phosphorus (P) fertilization play a key role in improving the productivity of linseed under semi-arid conditions. This study evaluated the effects of three nitrogen rates (40, 80, and 120 kg N ha⁻¹) and five phosphorus rates (0, 20, 40, 60, and 80 kg P ha⁻¹) on the growth, seed yield, oil content, and oil yield of linseed during two growing seasons under rainfed conditions in Kırşehir, Türkiye. The experiment was conducted as a split-plot design with three replications. Data were analyzed using analysis of variance, mean comparisons, and second-order polynomial regression, and the responses were visualized using three-dimensional surface plots.Nitrogen and phosphorus significantly affected most measured traits, whereas their interaction varied among characteristics. Seed and oil yields increased with fertilizer application up to intermediate rates, with the highest values consistently obtained at 80 kg N ha⁻¹ and 60 kg P ha⁻¹. Oil content tended to decline at the highest nitrogen rate. Quadratic regression analysis indicated that balanced nutrient application was more effective than increasing nitrogen alone. Under the conditions of this study, the combination of 80 kg N ha⁻¹ and 60 kg P ha⁻¹ can be recommended to maximize seed and oil yield of linseed under semi-arid rainfed conditions.