Enhancing Linseed Oil Yield using the Synergistic Effect of Seed Priming, Humic Acid and Sulphur under Optimized Irrigation

Linseed, popularly known as flaxseed, is a prominent dual-purpose crop cultivated for both fiber and oilseed crops. It is especially valued for its rich nutritional profile, which includes alpha-linolenic acid, an essential omega-3 fatty acid, along with dietary fiber and lignans, making it more suitable for value addition and sustainable agriculture. Despite its adaptability and uses, it faces challenges such as grain yield followed by oil yield due to moisture stress. In the past few years, it has received special attention due to its industrial application and health benefits. Although the individual impact of seed priming, use of humic acid and sulphur on healthy seedling establishment, crop growth and oil yield under limited water conditions has shown the beneficial impact, their synergistic studies remain to be explored. Therefore, an integrated effort with seed priming, humic acid and sulphur was implemented to mitigate the adverse response to moisture stress.

An experiment was executed using a split-plot design considering the most popular variety of linseed (LC 2063) over the research farm of Lovely Professional University. The main plot treatments consisted of three levels of irrigation: I₀, I₁ and I₂, that is, no irrigation, moderate irrigation and full irrigation, while subplots treatments comprised seven combinations, including seed priming with KNO₃, humic acid and sulphur used as soil application (C₀ to C₆), whereas 15 mM of KNO₃ was used as seed priming and humic acid was used besal application @ 12 Kg ha^-1.

The frequency of irrigations had a significant impact (p=0.05) on the phenological traits in linseed. Out of all the irrigation frequencies, two irrigations (I₂) minimized the days taken to the branching and 50% flowering and maximized the days taken to maturity, number of capsules plant^-1 and oil yield qt ha^-1 as compared to single (I₁) and no post-sowing irrigation (I₀). As for the percent increase or decrease over control is concerned, I2 reduced days by 16% and 13% and increased maturity, number of capsules and oil yield by 7%, 23% and 22%, respectively. The combined application of KNO₃ and humic acid (C₅) was the most effective treatment at (p=0.05), significantly reducing days to emergence, branching, 50% flowering and maturity by 47, 18, 13 and 4% respectively and enhancing maturity, number of capsules and oil yield by 4%, 38% and 32%. A negative relationship was detected between the relative water content (RWC%) and proline content (μmol g^-1) across the irrigation regimes, wherein I₂ showed the highest RWC and lowest proline. Among the chemical treatments, C₅ maintained the highest RWC% and proline, followed by C₄> C₆> C₃> C₂> C₁> C₀. Most of the parameters studied had a significant interaction effect between the irrigation frequency and chemical treatments at (p=0.05), indicating that the combined application of C₅ with I₂ can markedly enhance oil yield in linseed.