Paul Cockson

Germination rates of commercial lots of hemp have been highly variable, resulting in poor stand establishment. Germination rates in some seed lots have decreased by 50% after only 1 year of storage. The objective of this trial was to investigate the impact of seed storage conditions on seed germination over time. Industrial hemp (IH) seeds (cv. NWG2730) were harvested from the field. The seeds were cleaned, sorted, and dried to specific moisture contents (MC) 6%, 8%, 10%, and 14%. Seeds were subdivided, placed in hermetically sealed packets, and stored at temperatures of −20°C, 4°C, 10°C, or 21°C for 3, 6, 12, 18, and 24 months. At each increment, seeds were removed from storage and sterilized using hot water and bleach treatment, and subjected to germination tests. A tetrazolium test (1% solution on a sub‐sample of seeds [n = 50]) at 3 and 24 months was conducted. Results indicated an interaction between seed MC and storage temperature over time. At higher MCs (10% and 14%), germination decreased over time with the decline being more rapid at warmer temperatures. For viability, a similar trend occurred with a combination of higher temperature and MC resulting in lower seed viability. These results suggest that optimal storage conditions for intermediate storage of IH seed should focus primarily on keeping seed moisture at <8% and storing seeds at 4°C to10°C. Our data suggest that the variability in germination of commercial hemp seed lots may in part be attributed to loss of seed viability as a result of less‐than‐ideal storage conditions.

Micronutrient accumulation caused by low pH can lead to toxicity and have detrimental impacts on plant growth. In substrates with elevated pH, micronutrients become less available. In the first experiment, industrial hemp ( Cannabis sativa L.) growth was less at pH 3.0 and 4.0 than when pH was ≥5.0. Root growth was also observed to be inhibited at low pH levels. Leaf tissue micronutrient concentrations were higher at the lowest pH level, but no toxic accumulation occurred. In experiment 2, root growth had less mass at the lowest pH (3.1) and highest pH level (7.1). In experiment 3, substrates with three target pHs (3.8, 4.8, and 6.5) as well as three micronutrient concentrations (1X, 2X, and 4X) were examined to determine the impact of pH on micronutrient accumulation in two cultivars Cherry Wine (CW) and Sweetened (SW). Foliar micronutrient concentrations were the greatest in plants grown with pH 3.8, and the lowest concentrations occurred in plants grown at pH 6.5. Susceptibility to toxicity from micronutrient accumulation in plant tissue varied by cultivar. SW plants grown at pH 3.8 and 4X micronutrients resulted in lower leaf micronutrient toxicity symptoms, while CW plants grown under the same conditions did not. These studies suggest that C. sativa does not accumulate micronutrients to toxic levels at low pH when micros are applied within normal growing ranges, but that growth is inhibited at substrate pH < 5.0.

Many abiotic factors impact the yield and growth of Brassica carinata (commonly referred to as carinata or Ethiopian mustard). Very little is known about carinata and how mineral nutrients impact its growth, and more specifically, the sufficiency values for fertility over the plant’s growth cycle and life stages. This study explored the impacts that plant nutrients, specifically micronutrients, can have on the growth and development of carinata over its distinct life stages (rosette, bolting, flowering, and pod set). Plants were grown under varying micronutrient concentrations (0, 25, 50, 75, 87.5, and 100%) of a modified Hoagland’s solution. Data were collected on plant height, canopy diameter, leaf tissue mineral nutrient concentrations, and biomass. The results demonstrated that micronutrient fertility has profound impacts on the production of Brassica carinata during different life stages. Boron (B) exclusion had the greatest impact on the growth and reproduction of Brassica carinata, with the death of the apical meristem that resulted in a lack of siliques or seeds at the lowest rate. Optimal relative elemental leaf tissue concentrations varied among micronutrient fertility concentrations and life stages. Certain elements exhibited linear increases in nutrient leaf tissue accumulation as solution concentration increased without reaching a maximum concentration during specific life stages. Other life stages and/or elements produced distinct plateau leaf tissue mineral concentrations despite increasing fertility treatment concentrations such as B in the rosette stage (47.2–50.0 mg·kg⁻¹), copper (Cu) (bolting stage at 6.62–7.57 mg·kg⁻¹), zinc (Zn) (bolting stage at 27.47–39.87 and flowering at 33.98–43.50 mg·kg⁻¹), molybdenum (Mo) (flowering stage at 2.42–3.23 mg·kg⁻¹), and manganese (Mn) (bolting stage at 117.03–161.63 mg·kg⁻¹). This work demonstrates that Brassica carinata has different fertility demands and will accumulate differing leaf tissue concentrations during its life stages. This work serves as a baseline for further uptake and portioning work for Brassica carinata.

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.

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.

Essential plant nutrients are needed at crop-specific concentrations to obtain optimal growth and yield. Foliar tissue analysis is the standard method for assessing nutrient levels in plants. Symptoms of nutrient deficiency or toxicity occur when the foliar tissue values become too low or high. Diagnostic nutrient deficiency criteria for Brassica rapa var. Chinensis (bok choy) is lacking in the current literature. In this study, green (‘Black Summer’) and purple (‘Red Pac’) bok choy plants were grown in silica sand culture, with control plants receiving a complete modified Hoagland’s all-nitrate solution, and nutrient-deficient plants induced by using a complete nutrient formula withholding a single nutrient. Tissue samples were collected at the first sign of visual disorder symptoms and analyzed for dry weight and nutrient concentrations of all plant essential elements. Six weeks into the experiment, the newest matured leaves were sampled for chlorophyll a, b, and total carotenoids concentrations for both cultivars, and total anthocyanin concentration in ‘Red Pac’. Compared to control plants, the dry weight of ‘Black Summer’ green bok choy was significantly lower for nitrogen (N), phosphorus (P), calcium (Ca), or boron (B) deficiency treatments, and nutrient concentrations were lower for all variables except iron (Fe) deficiency. Dry weight was less in ‘Red Pac’ plants grown without N, potassium (K), Ca, B, or molybdenum (Mo), and nutrient concentrations were lower for all except Mo-deficiency compared to controls. Total chlorophyll and total carotenoid concentrations were lower in leaves from N−, Fe-, and manganese- (Mn) deficient plants of both cultivars. Leaf anthocyanin concentration was lower only for K-, Ca-, and B-deficiencies in ‘Red Pac’. Our results indicate that visual symptoms of nutrient deficiency are well correlated with nutrient disorders. In contrast, changes in dry weight, chlorophyll, and anthocyanin did not show consistent changes across nutrient disorders.

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.