From breeding to practise : effects of sowing date and pruning system on flower yield and cannabinoid composition in four Slovenian feminized industrial hemp breeding lines

Flajšman, Marko (author), Eržen, Marjeta (author)

our Slovenian feminized industrial hemp (Cannabis sativa L.) breeding lines (G8c, G10c, MERc, CHc), developed within the high‑CBD breeding program at the Biotechnical Faculty, University of Ljubljana, were evaluated in 2024 field trials at Ljubljana and Krško. The effects of sowing date (direct field seed sowing vs. seedlings transplantation to the field, both at density 8,333 plants per ha) and apical pruning (topping) on growth (plant height), flower yield, CBD, and Δ⁹ THC content were assessed. Early- season waterlogging in Ljubljana (heavy soil) caused severe negative effects on plant establishment and growth. Sowing date acted oppositely across sites: direct sowing outperformed transplanting in Krško (medium heavy soil), whereas transplanting increased flower yield in Ljubljana. Pruning reduced plant height but did not change flower yield or cannabinoid concentrations. CBD was primarily genotype dependent, with MERc the highest at both sites (5.02-6.66 %). THC ranged 0.12–0.21 % across treatments. Significant breeding line × sowing date interactions occurred for plant height and flower yield. This study provides the first applied evaluation of Slovenian feminized industrial hemp breeding lines and indicates priorities for subsequent breeding efforts. However, the results represent one year of field data .To draw robust conclusions, multi-year field trials will be required.

• Language: English
• Keywords: industrial hemp, feminized hemp, high-CBD genotype, sowing date, transplanting, pruning, CBD, THC
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: BF - Biotechnical Faculty
• Publication status: Published
• Publication version: Version of Record
• Year: 2026
• Number of pages: 15 str.
• Numbering: Vol. 122, no. 1
• PID: 20.500.12556/RUL-180357
• UDC: 633
• ISSN on article: 1854-1941
• DOI: 10.14720/aas.2026.122.1.26115
• COBISS.SI-ID: 270751747
• Publication date in RUL: 06.03.2026

Record is a part of a journal

• Title: Acta agriculturae Slovenica
• Publisher: Biotehniška fakulteta, Oddelek za agronomijo in Oddelek za zootehniko, Biotehniška fakulteta, Oddelek za agronomijo in Oddelek za zootehniko, Univerza v Ljubljani, Biotehniška fakulteta, Založba Univerze v Ljubljani
• ISSN: 1854-1941
• COBISS.SI-ID: 219581184

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Title: Od žlahtnjenja do uporabe: vpliv datuma setve in rezi na pridelek cvetov in vsebnost kanabinoidov v štirih slovenskih žlahtnjenih linijah feminizirane industrijske konoplje
• Keywords: industrijska konoplja, feminizirana konoplja, CBD konoplja, datum setve, presajanje, rez, CBD, THC

Projects

• Funder: Other - Other funder or multiple funders
• Project number: IO-0022
• Name: Mreža raziskovalnih infrastrukturnih centrov Univerze v Ljubljani (MRIC UL)
• Acronym: MRIC UL

• Funder: ARIS - Slovenian Research and Innovation Agency
• Project number: P4-0077-
• Name: Kmetijske rastline - genetika in sodobne tehnologije