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

Abstract

Floral hemp cultivated for the extraction of cannabinoids is a new crop in the United States, and agronomic recommendations are scarce. The objective of this study was to understand the effects of plant spacing and transplant date on floral hemp growth and biomass production. Field trials were conducted in North Carolina in 2020 and 2021 with the floral hemp cultivar BaOx. Transplant date treatments occurred every two weeks from 11 May to 7 July (±1 d). Plant spacing treatments were 0.91, 1.22, 1.52, and 1.83 m between plants. Weekly height and width data were collected throughout the vegetative period, and dry biomass was measured at harvest. Plant width was affected by transplant date and spacing. Plant height was affected by transplant date. Earlier transplant dates resulted in taller, wider plants, while larger plant spacing resulted in wider plants. Individual plant biomass increased with earlier transplant dates and larger plant spacing. On a per-hectare basis, biomass increased with earlier transplant dates and smaller transplant spacing. An economic analysis found that returns were highest with 1.22 m spacing and decreased linearly by a rate of −163.098 USD ha−1 d−1. These findings highlight the importance of earlier transplant timing to maximize harvestable biomass.

Role of Planting Date on Yield and Cannabinoid Content of Day-neutral and Photoperiod-sensitive Hemp in Georgia, USA

“…In that study, the increased plant size corresponded to increased floral yields. It should be noted that the earliest planting in the present study occurred $1 month earlier than in the North Carolina trial (Linder et al 2022). The cooler growing conditions during the earlier planting period in the present study may have resulted in smaller differences in total plant growth among the different planting dates compared with the North Carolina study.…”

“…However, the visual increase in plant canopy did not correspond to increases in flower biomass. Linder et al (2022) reported significant increases in height and width of 'BaOx' plants when planted in May compared with June and July. In that study, the increased plant size corresponded to increased floral yields.…”

“…The impact of planting date on floral yield in photoperiod-sensitive hemp was recently investigated (Linder et al 2022); however, the effects of planting date of day-neutral and photoperiod-sensitive hemp cultivars planted before the critical photoperiod has not been previously evaluated. Flower yields of the day-neutral cultivars decreased as planting date progressed during the year and temperatures warmed.…”

“…However, given the photoperiodic requirements of hemp, planting is recommended for late May and June, when the daily photoperiod in much of the state is near 14 h (Coolong 2020). Linder et al (2022) reported that yield decreased when a photoperiod-sensitive cultivar, BaOx, was planted between 11 May and 7 Jul in North Carolina. Typically, 11 May would be the earliest planting period for growers in Georgia, with a photoperiod-sensitive cultivar.…”

Cannabidiol industrial hemp growth, biomass, and temporal cannabinoids accumulation under different planting dates in southern Florida

“…Planting date effects on crop growth, physiology, yield, biomass, and seed composition have been documented in several crops (Chiluwal et al., 2018; Mourtzinis et al., 2017; Tsimba et al., 2013). A recent study in industrial hemp also evaluated the planting date effect on its floral biomass (Linder et al., 2022b). However, the effect of planting date on CBD and THC accumulation pattern over crop growing season in CBD‐dominant hemp cultivars is still unknown.…”