Winter oilseed rape (Brassica napus) as an intermediate crop improves summer-crop yield, soil health, and soil carbon with limited greenhouse gas trade-offs: a meta-analysis

Abstract

Global demand for biofuels is increasing, intensifying concerns about land competition among food, feed, and fuel production in temperate row‑crop systems. Intermediate crops grown during otherwise fallow periods offer a strategy to expand biofuel feedstock supply while limiting indirect land‑use change. Despite increasing relevance, their broader agroecosystem effects remain insufficiently synthesized. Our objective was to assess the agroecosystem impacts of winter oilseed rape ( Brassica napus , L.; WOSR, canola) grown as an intermediate winter crop before a summer crop. We conducted a meta‑analysis examining four outcomes: subsequent summer‑crop productivity; biological, chemical, and physical soil health indicators; soil carbon sequestration; and greenhouse gas emissions. A total of 79 articles yielding 1,469 observations overall, comprising 673 summer-crop yield observations (65 articles), 449 soil-health observations (145 biological, 266 chemical, 38 physical; 22 articles), 156 soil-carbon observations (24 articles), and the greenhouse-gas dataset (14 articles: 68 N₂O, 55 CH₄, and 60 CO₂-eq observations) were included in the meta-analysis. Relative to fallow or winter cereal rotations, WOSR was associated with consistent improvements. Summer‑crop yields increased by 2%, while biological, chemical, and physical soil health indicators increased by 8.0, 5.5, and 7.8%, respectively. Soil carbon sequestration increased by 7.6%. Greenhouse gas responses were gas specific: methane emissions decreased 17.3%, and nitrous oxide increased 51.5%, yielding net CO₂‑equivalent emissions comparable to fallow and lower than wheat‑based systems. Together, these results indicate WOSR functions as a multifunctional intermediate crop that expand biofuel feedstock supply with limited greenhouse‑gas trade‑offs, strengthening sustainable intensification in temperate row‑crop agriculture.