How do pinching and plant density affect industrial hemp produced for cannabinoids in open field conditions?

Abstract

Information regarding agronomic practices for field-scale industrial hemp (IH) production for cannabinoids is extremely limited. The objective of this study was to investigate how pinching practice (i.e., removing the apical meristem) and varied plant density affect yield and cannabinoid production of IH in open field conditions. A field trial was performed in northern Florida in 2019 and 2020. The pinching study included pinch and non-pinch treatments evaluated on two commercially available day-length-sensitive IH cultivars Cherry Blossom (CBL) and Cherry Wine (CW). Four plant densities (3,000, 4,000, 6,000, and 12,000 plants ha -1 ) were evaluated on CW. The experimental design was a randomized complete block design with four blocks. Total flower yield in 2019 was two times greater than in 2020. In 2020, total tetrahydrocannabinol and cannabidiol (CBD) in CBL was significantly greater than in CW. Pinching did not significantly improve flower yield, cannabinoid concentration, or CBD production. Flower yield per plant decreased as plant density increased, but a reversed trend occurred for total flower yield per hectare. Cannabinoid concentration was not affected by plant density, but CBD production increased with increased plant density. Due to the high cost of IH plant material and labor, greater plant density does not always guarantee greater economic return. This study provides valuable information for field-scale cultivation of IH for cannabinoids and supports the development of a large agricultural industry globally.

The Effect of Transplant Date and Plant Spacing on Biomass Production for Floral Hemp (Cannabis sativa L.)

“…Our planting spacing results concur with da Silva Benevenute et al [13], who tested different planting densities (3000, 4000, 6000, 12,000 plants ha −1 ) with the day-lengthsensitive cultivar Cherry Wine. We observed similar trends regarding biomass production, where lower planting densities resulted in more biomass on a per plant basis, while higher planting densities resulted in more biomass produced on a per-hectare basis.…”

“…When compared to all other treatments, our 0.91 m plant spacing, and 11 May transplant date treatments yielded the greatest biomass on a per-hectare basis. Our results, along with those of da Silva Benevenute et al [13] and Anderson et al [26], reinforce the hypothesis that small plant spacing and an early transplant date are both key driving factors for maximizing biomass on a per-hectare basis.…”

“…We did not quantify cannabinoids in our trial; however, da Silva Benevenute et al [13] did not find any evidence of planting density influencing cannabinoid concentration. The cannabinoid synthesis of THC and CBD is primarily regulated by genotype.…”

“…Few scientific studies assessing the effect of planting density on floral hemp biomass production have been conducted. Da Silva Benevenute et al [13] observed flower yield decreasing on a per plant basis with increasing planting density, but yield on a per-hectare base gradually increased. However, in this study, plants were transplanted relatively late in the growing season, and only flower yield was quantified, not the total marketable biomass (leaves and floral material).…”

Effect of High-Tunnel and Open-Field Production on the Yield, Cannabinoids, and Volatile Profiles in Industrial Hemp (Cannabis sativa L.) Inflorescence

“…Other researchers have employed pinching treatment and increased plant density to achieve high total CBC% and observed similar levels ranging from 0.7% to 1.2%. 27,52 Overall, the average total CBC accumulation was higher in plants grown in FD, which contrasted with the patterns observed in total CBD and total THC.…”