Rowett scientists have been collecting hemp seed samples from growers in Scotland for the past three years, analysing these samples in the laboratory to determine their nutritional and phytochemical composition (phytochemicals are the useful chemicals found in plants that protect them against bacteria, viruses and fungi: many are thought to have health benefits when present in the diet). BioSS has statistically analysed these data, finding important between-year differences and identifying sowing date as having had a statistically significant effect on multiple aspects of composition.

Hemp is an important, underutilised and environmentally friendly crop, which has been grown historically in Scotland. It can be grown to produce food, fibre, drugs and personal care products. Research at the Rowett Institute was pivotal in reintroducing hemp into Scottish agriculture and producing hemp seeds for food consumption in Scotland. In 2022 commercial hemp seed oil from seeds grown in Scotland was produced for the very first time. A current project aims to analyse the macronutrient, micronutrient and phytochemical profile of hemp from three consecutive harvests (2021, 2022 and 2023) and investigate associations with agronomic, geographical and harvest variables. This work will inform and influence future agricultural practices and the food industry.

BioSS has collaborated with Rowett scientists in studying these data. Many factors potentially could affect the composition, and there were issues of confounding between these factors in what was essentially an observational study rather than a designed crop trial. We examined a variety of statistical linear models to assess the overall and marginal effects of the factors that it was believed could affect the composition. These included geographical location and altitude, year, sowing and harvest dates, crop variety, soil type and use of pesticides. We also used principal component analysis as a way to assess the effects of these factors on combined sets of compositional variables, such as minerals and soluble and insoluble fibre components. Between year differences were apparent for most variables, and tended to be seen consistently across all growers. With only three years of data, it is not possible to identify what was driving these differences. The sample size was modest, and while there were indications that several of the other variables had some effect, the only one that generated clear evidence of this was sowing date. Pesticide use also appeared to have effects, though this was potentially confounded with other, unrecorded differences between growers. Growing duration may also affect fibre content. These findings should be of some use to growers planning to produce hemp seed, although further studies will be needed to expand our understanding of the range of factors influencing hemp characteristics.

Listen to the podcast featuring this work: Should you be farming hemp? - with SEFARI and the Rowett Institute - OnFarm - Scottish rural stories | Podfollow

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This work was done in collaboration with Madalina Neacsu at The Rowett Institute and was funded under the Underpinning National Capacity element of the Scottish Government's Strategic Research Programme for environment, agriculture and food.