Integrating Optimized Intercropping Ratios With Biochar Enhances Land‐Use Efficiency and Seed Functional Quality in a Canola–Oat System

ABSTRACT Ensuring food and energy security under increasing resource constraints requires production systems that simultaneously enhance productivity, improve resource‐use efficiency, and maintain biochemical seed quality traits, including oil content and phenolic compound accumulation. Intercropping and biochar application are promising strategies for sustainable agriculture; however, their combined effects in oilseed–cereal systems remain insufficiently understood, particularly under semi‐arid field conditions. This study provides field‐scale evidence integrating optimized canola–oat intercropping ratios with biochar application to simultaneously evaluate productivity, biochemical seed quality, and land‐use efficiency. This 2‐year field study was conducted in Naqadeh, West Azerbaijan Province, Iran, a semi‐arid region, over two consecutive growing seasons (2021–2022 and 2022–2023). The experiment evaluated three canola–oat intercropping ratios (2C:4O, 3C:6O, and 4C:8O) with and without biochar application (0 and 10 t ha −1 ) to assess effects on yield performance, oil content, phenolic compounds, and land‐use efficiency. Intercropping reduced yields of individual crops compared with monoculture but significantly increased overall system productivity, as indicated by land equivalent ratios (LER) consistently greater than one. Additionally, the relative value total (RVT) index confirmed the economic advantage of intercropping, showing increases from 0.64–0.93 in control plots to 0.84–1.22 under biochar application, with the 4C:8O configuration exhibiting the highest economic return. The 4C:8O intercropping ratio combined with biochar achieved the highest system advantage, with a total LER of 1.69, indicating 69% more efficient land use than monocropping. Biochar improved not only land‐use efficiency but also economic performance (via RVT enhancement) by 26%–31% relative to unamended treatments. Biochar application also increased seed oil content by up to 11% and promoted the accumulation of phenolic compounds. These improvements indicate enhanced biochemical seed quality and improved economic efficiency without compromising overall system productivity. Overall, integrating biochar with optimized canola–oat intercropping simultaneously enhanced land‐use efficiency, economic return, and seed quality traits, providing a viable strategy for sustainable oilseed–cereal production under semi‐arid conditions.