Effects of critical phosphorus doses at different nitrogen levels on yield and yield components of linseed (Linum usitatissimum L.) under rainfed conditions
Abstract
Linseed (Linum usitatissimum L.) is an important oilseed crop with increasing relevance for food, industrial, and bioenergy uses, particularly in semi-arid regions where alternative oil crops are limited. This study aimed to evaluate the effects of nitrogen (N) and phosphorus (P) fertilization on growth, yield components, seed yield, oil content, and oil yield of linseed under rainfed conditions. Field experiments were conducted over two consecutive growing seasons (2023–2024) in Central Anatolia, Türkiye, using a split-plot randomized complete block design with three replications. Nitrogen rates (40, 80, and 120 kg N ha⁻¹) were assigned to main plots, while phosphorus rates (0, 20, 40, 60, and 80 kg P₂O₅ ha⁻¹) were allocated to subplots. Combined analysis of variance indicated that nitrogen and phosphorus fertilization significantly affected most growth, yield, and quality traits, whereas year effects and higher-order interactions were generally not significant, indicating stable nutrient responses across seasons. Plant height, capsule number, seed yield, and oil yield increased with increasing N and P rates up to 80 kg N ha⁻¹ and 60 kg P₂O₅ ha⁻¹, respectively, while higher fertilization levels did not result in further improvements. Moderate nitrogen supply enhanced seed yield and oil yield, whereas excessive nitrogen tended to reduce crude oil concentration despite increased biomass production. Overall, the results highlight the importance of balanced nitrogen and phosphorus fertilization for optimizing linseed productivity and oil yield under rainfed, semi-arid conditions. The identified fertilization strategy provides a practical guideline for improving fertilizer use efficiency and ensuring sustainable linseed production while avoiding unnecessary fertilizer inputs.