Optimal Rate of Organic Fertilizer during the Vegetative-stage for Cannabis Grown in Two Coir-based Substrates

Abstract

<jats:p>Cannabis producers, especially those with organic operations, lack reliable information on the fertilization requirements for their crops. To determine the optimal organic fertilizer rate for vegetative-stage cannabis (<jats:italic>Cannabis sativa</jats:italic> L.), five rates that supplied 117, 234, 351, 468, and 585 mg N/L of a liquid organic fertilizer (4.0N–1.3P–1.7K) were applied to container-grown plants with one of two coir-based organic substrates. The trial was conducted in a walk-in growth chamber and the two substrates used were ABcann UNIMIX 1-HP with lower water-holding capacity (WHC) and ABcann UNIMIX 1 with higher WHC. No differences in growth or floral dry weight (yield) were found between the two substrates. Pooled data from both substrates showed that the highest yield was achieved at a rate that supplied 389 mg N/L (interpolated from yield-fertilizer responses) which was 1.8 times higher than that of the lowest fertilizer rate. The concentration of ∆<jats:sup>9</jats:sup>-tetrahydrocannabinol (THC) in dry floral material was maximized at a rate that supplied 418 mg N/L, and no fertilizer rate effects were observed on Δ<jats:sup>9</jats:sup>-tetrahydrocannabidiolic acid (THCA) or cannabinol (CBN). The highest yield, cannabinoid content, and plant growth were achieved around an organic fertilizer rate that supplied 389 mg N/L during the vegetative growth stage when using the two coir-based organic substrates.</jats:p>

Foliar Sprays of Silver Thiosulfate Produce Male Flowers on Female Hemp Plants

“…Increased interest in CBD has led to increased cultivation of hemp, but because hemp has been selected for fiber and seed production, it is generally low in CBD content (2% to 4%) (Mead, 2017). Therefore, the development of hemp cultivars with increased CBD content is a current breeding objective (Caplan et al, 2017;Soler et al, 2017).…”

Cannabis Indoor Growing Conditions, Management Practices, and Post-Harvest Treatment: A Review

“…However, the lower capacity (U2-HP) growing medium produced 11% higher floral dry weight, 13% higher growth index, 20% higher THC yield, and 20% higher CBGA yield than the one with higher capacity (U2) [49]. The increases may be attributed to the higher irrigation frequency (17 times in U2-HP and 13 times in U2), which was necessary for maintaining moisture (30%), and/or high root zone oxygen, which positively affects plant health, nutrient uptake, root growth, and root-bone disease prevention [49]. Hydroponic systems have greater control over the growing environment by delivering a full range of nutrients to the roots.…”

“…Extractable soil P was negatively correlated with CBD concentrations in leaf tissue [48]. Another study showed that there was no difference in floral material yield between two organic coir-based growing media, which had distinct water-holding capacities [49]. However, the lower capacity (U2-HP) growing medium produced 11% higher floral dry weight, 13% higher growth index, 20% higher THC yield, and 20% higher CBGA yield than the one with higher capacity (U2) [49].…”

“…Another study showed that there was no difference in floral material yield between two organic coir-based growing media, which had distinct water-holding capacities [49]. However, the lower capacity (U2-HP) growing medium produced 11% higher floral dry weight, 13% higher growth index, 20% higher THC yield, and 20% higher CBGA yield than the one with higher capacity (U2) [49]. The increases may be attributed to the higher irrigation frequency (17 times in U2-HP and 13 times in U2), which was necessary for maintaining moisture (30%), and/or high root zone oxygen, which positively affects plant health, nutrient uptake, root growth, and root-bone disease prevention [49].…”

“…The study applied liquid fertilizer with a N-P-K ratio of 4:1.3:1.7 at rates of 117, 234, 351, 468, and 585 mg nitrogen per litre of irrigation water (N/L) during vegetative growth and found that the interpolated optimal rate was 389 mg N/L. This optimal rate increased the yield of floral dry weight by 80% as compared to 117 mg N/L [49]. The final yield was positively correlated with growth attributes (growth index [height (cm) × length (cm) × width (cm) × 300 −1 ], leaf number, and branch number) in the vegetative stage [49].…”