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Elevated Phosphorus Fertility Impact on Cannabis sativa ‘BaOx’ Growth and Nutrient Accumulation
Limited research exists on the fertility requirements for industrial hemp (Cannabis sativa) and the impact of fertility on plant growth and cannabinoids. Optimizing floral production for cannabinoid production and especially cannabidiol (CBD) production, is an economic goal for growers. Phosphorus (P) is an essential nutrient for plant growth and plays many key roles in plant growth and when deficient leads to suboptimal plant growth. Grower P fertility rate recommendations vary greatly, with suggestions of up to 196 mg·L-1 P over part of the production cycle. Four P fertility rates (15, 60, 120, and 180 mg·L-1 P) were evaluated to determine the optimal fertility for C. sativa on a high CBD-type cultivar ‘BaOx’. Plant height, diameter, and total biomass were similar across all examined P fertility rates. Foliar P concentrations increased linearly, with the greatest P accumulation occurring in plants that received the highest fertility rate of 180 mg·L-1 P. Given no differences in biomass production were found, and the luxury uptake of P as fertilization rates increased, the results indicate that rates above 15 mg·L-1 P are not beneficial for plant growth and only add economic cost to the grower and potentially cause waste and pollution to the environment.
Magnesium’s Impact on Cannabis sativa ‘BaOx’ and ‘Suver Haze’ Growth and Cannabinoid Production
Limited research exists on the fertility needs for industrial hemp (Cannabis sativa) and the impact of fertility on plant growth and cannabinoids. Optimizing floral production for cannabinoid production and especially cannabidiol (CBD) production, is an economic goal for growers. Magnesium (Mg) is an essential nutrient for plant growth and plays many key roles in plant growth and when deficient leads to suboptimal plant growth. Six Mg fertility rates (0.0, 12.5, 25.0, 50.0, 75.0, and 100.0 mg·L-1) were evaluated to determine the optimal fertility for C. sativa on two High CBD-type cultivars ‘BaOx; and ‘Suver Haze’. Foliar Mg concentrations increased linearly for all life stages with the greatest foliar Mg concentrations being in the highest rate of 100.0 mg·L-1 Mg. Of the six rates, 50.0 and 75.0 mg·L-1 Mg optimized plant height, diameter, and plant total dry weight as well as having similar cannabinoid concentrations.
Augmenting Nutrient Acquisition Ranges Of Greenhouse Grown CBD Hemp (Cannabis sativa) Cultivars
There is a growing interest in the production of hemp for the extraction of cannabidiol (CBD) due to reported therapeutic benefits. Recent policy reform has permitted state hemp pilot programs, including the land grant research institutions, the ability to investigate the potential of growing and harvesting Cannabis sativa plants (≤0.3% tetrahydrocannabinol) for these purposes in the U.S. There are vast gaps of knowledge regarding the fertility requirements of hemp cultivars grown in a horticultural production setting for floral attributes such as the cannabinoid constituents. Foliar tissue analysis provides an avenue to determine adequate ranges for nutrient uptake and estimating fertilizer requirements prior to visual symptoms of deficiency or toxicity. To facilitate a survey range of elemental nutrient acquisition in hemp cultivars propagated for CBD production, foliar analysis was executed using the most recently mature leaves (MRML) of mother stock plants. All plants were maintained in the vegetative stage for twelve weeks, prior to initiation of cutting for clone harvesting. A total of thirteen cultivars were utilized to broaden previously reported baseline survey ranges. Significant differences were found among all thirteen cultivars in accumulation of both micro and macro essential nutrients, widening the range of the fertility requirements of Cannabis plants grown in this production model for CBD harvesting.
Impact of Phosphorus on Cannabis sativa Reproduction, Cannabinoids, and Terpenes
Many abiotic factors, such as mineral nutrients—including phosphorus (P)—fertility, can impact the yield and growth of Cannabis sativa. Given the economic portion of C. sativa is the inflorescence, the restriction of P fertility could impact floral development and quality could be detrimental. This study sought to track the impacts of varying P concentrations (3.75, 7.50, 11.25, 15.0, 22.50, and 30.0 mg·L−1) utilizing a modified Hoagland’s solution. This experiment examined plant height, diameter, leaf tissue mineral nutrient concentrations, and final fresh flower bud weight as well as floral quality metrics, such as cannabinoids and terpenes. The results demonstrated that during different life stages (vegetative, pre-flowering, flowering), P concentrations impact C. sativa growth and development and yield. Regarding the cannabinoid pools, results varied for the individual cannabinoid types. For the acid pools, increasing fertility concentrations above 11.25 mg·L−1 P did not result in any increase in cannabinoid concentrations. These results indicate that, if a crop is being produced under greenhouse conditions, specifically for cannabinoid production, an excessive P supply did not result in higher cannabinoid production. However, plants grown with a higher rate of P fertility (30.0 mg·L−1) had greater plant width and may result in more buds per plant.
Growing Cannabis with 16 h of lighting in a 24-h period provided by either DE or NI was effective in retaining the vegetative state of mother stock plants. Either photoperiodic lighting strategy can be utilized for producing mother stock plants or during the vegetative bulking of plants prior to flower initiation.
*This publication is a research brief and is not open access.
Expanding Leaf Tissue Nutrient Survey Ranges for Greenhouse Cannabidiol-Hemp*
Recent legislation allows US growers to produce industrial hemp (Cannabis sativa L.) under State Industrial Hemp Pilot Programs. Hemp can be produced for seed, fiber, or cannabidiol (CBD) (Johnson, 2018). Cannabidiol is a non-intoxicating cannabinoid, and products from CBD-hemp are considered to have one of the greatest market potentials due to its pharmaceutical value (Cherney and Small, 2016). There are no researched nutrient recommendations specific to greenhouse CBD-hemp, few resources for diagnosing plant nutrient problems, and little scientific research supporting greenhouse production. While there are Cannabis nutrient survey tissue values reported by Bryson and Mills (2014), it is unknown if these values are applicable for both field and greenhouse CBD-hemp crops or if differences exist among Cannabis cultivars. The purpose of this study was to determine if there were leaf tissue nutrient differences among industrial hemp cultivars being grown as stock plants for CBD-hemp production. In addition, the goal was to provide more precise nutrient survey tissue values that would aid in diagnosing nutrient disorders
*This publication is not open access.
Characterization of Nutrient Disorders of Cannabis sativa
Essential plant nutrients are needed at crop-specific concentrations to obtain optimum growth or yield. Plant tissue (foliar) analysis is the standard method for measuring those levels in crops. Symptoms of nutrient deficiency occur when those tissue concentrations fall to a level where growth or yield is negatively impacted and can serve as a visual diagnostic tool for growers and researchers. Both nutrient deficiency symptoms and their corresponding plant tissue concentrations have not been established for cannabis. To establish nutrient concentrations when deficiency or toxicity symptoms are expressed, Cannabis sativa ‘T1’ plants were grown in silica sand culture, and control plants received a complete modified Hoagland’s all-nitrate solution, whereas nutrient-deficient treatments were induced with a complete nutrient formula withholding a single nutrient. Toxicity treatments were induced by increasing the element tenfold higher than the complete nutrient formula. Plants were monitored daily and, once symptoms manifested, plant tissue analysis of all essential elements was performed by most recent mature leaf (MRML) tissue analysis, and descriptions and photographs of nutrient disorder symptomology were taken. Symptoms and progressions were tracked through initial, intermediate, and advanced stages. Information in this study can be used to diagnose nutrient disorders in Cannabis sativa
Enhancing Rooting of Vegetatively Propagated Cannabis sativa ‘BaOx’ Cuttings
Hemp (Cannabis sativa L.) has recently become legalized in the United States (U.S.). To grow hemp, often propagation occurs via asexual means through rooting vegetative tip cuttings. To produce plants, meristems are excised from stock plants and propagated to produce transplants for greenhouse or field-production. Successfully rooting vegetative cuttings can vary widely among growers due to greenhouse propagation environmental conditions, cultural inputs and practices, and vegetative cutting quality. To overcome rooting challenges, the impact of cutting stem caliper (diameter) and the use of root-zone heating (RZH) on rhizogenesis were investigated. Results indicated that large (2.9 – 3.2 mm) caliper cuttings and the use of RZH of 27.8oC resulted in a higher quality rooted cutting.
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