Effect of planting dates and seeding densities on growth, physiology, and yield of industrial hemp

Authors: BAJWA, PREETMAN - Texas Tech University; SINGH, SUKHBIR - Texas Tech University; KAFLE, ARJUN - Texas Tech University; SAINI, RUPINDER - Texas Tech University; TROSTLE, CALVIN - Texas A&M Agrilife

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2025
Publication Date: 3/6/2025
Citation: Bajwa, P., Singh, S., Kafle, A., Saini, R., Trostle, C. 2025. Effect of planting dates and seeding densities on growth, physiology, and yield of industrial hemp. Crop Science. 65(2). Article e70017. https://doi.org/10.1002/csc2.70017.
DOI: https://doi.org/10.1002/csc2.70017

Interpretive Summary: Best planting dates and densities found to optimize crop water productivity of industrial hemp. Industrial hemp is a fiber crop that can reduce water use from the Ogallala aquifer. Texas Tech University Researchers working in an ARS Ogallala Aquifer Program project showed the critical importance of planting dates and seeding densities in influencing the overall crop productivity, including biomass, fiber, and seed production. They also determined the relationships between root morphology, soil water depletion, and water use of industrial hemp. Early planting facilitated longer vegetative growth, improved plant height, stem diameter, and biomass and fiber accumulation. Better root development was also demonstrated. Later planting date led to early transition to reproductive phase, consequently lowering the final biomass and fiber production and crop water productivity (WP). But, due to early flowering initiation, late planting resulted in higher seed yield. Seeding densities affected growth, with higher densities resulting in denser canopies, better light absorption, and eventually higher final production. These results collectively provide farmers with optimal cultivation methods, offering insightful information for increasing crop yield while advancing sustainable agricultural practices in the hemp sector.

Technical Abstract: Industrial hemp (Cannabis sativa L.) exhibits growth potential in water-limited regions due to its deep roots and drought tolerance. However, limited knowledge exists about its agronomic production in semiarid West Texas. A 2-year (2022–2023) field experiment evaluated the effect of planting dates (P1: April 19, P2: May 10, and P3: June 6) and seeding densities (SD1: 84500 seeds ha-1, SD2: 1,408,000 seeds ha-1, and SD3: 1,972,000 seeds ha-1) on the growth, physiology, and yield of hemp in a split-plot block design. In both years, P3 reduced photosynthesis but increased transpiration compared to earlier plantings. In 2022, SD1 increased transpiration during the vegetative stage; however, no significant difference was observed during 2023. Photosynthesis remained consistent among densities throughout both years. In 2022, P2 accumulated 15%, 24%, 33%, and 43% greater plant height, biomass, bast fiber, and hurd fiber, respectively, but 45% lower grain yield than P3. In 2023, P1 and P2, on average, produced 32%, 175%, 149%, and 243% greater height, biomass, bast fiber, and hurd fiber than P3, respectively, while P2 accumulated 36% higher grain yield than P1 and 94% than P3. In 2022, SD3 had the highest bast, while hurd yield did not differ among densities. During 2023, SD3 produced the greatest bast and hurd fiber and significantly greater grain yield than SD1, with no variation with SD2. In conclusion, these findings suggest that early planting at higher seeding density can maximize resource use efficiency and production in West Texas. This makes them a viable strategy for sustainable hemp production under water-limited conditions.