2024 Guide to Cannabis Production - 8

LIGHTING
Current's dimmable fixtures
per plot supplementing
sunlight. The L1000 PPB
lighting fixtures delivered
uniform supplemental light
intensities of 150, 300, 500,
and 700 μmol m-2
s-1 for
18 hours, while the Daily
Light Integral (DLI) from
the sun and LEDs were on
average around 18, 30, 40
and 52 mol m-2
; however,
we present preliminary
results for the three highest
light levels. Moreover, the
fertigation system was
triggered independently
at each plot when the
pots' water container
capacities were 80%. This
maintained consistent
water and nutrient levels in
pots regardless of the crop
growth rates. Finally, the
water use was quantified
with load cells (scales)
under the plants.
Figure 1. The top-left
picture shows the
experimental layout
and greenhouse with
two L1000 PPB fixtures
at each plot or light
treatment area (12 plots
in total). The top-right
picture shows a plot
sensor that measures
light from the two LED
fixtures and the sun.
The bottom pictures and
arrows represent typical
cannabis flower and
plant production cycles.
FLOWER PRODUCTION
PLANT PRODUCTION
ROOTED
CUTTING
VEGETATIVE PLANT
Photos courtesy of Cristian Collado
a
IN A PREVIOUS COMMUNICATION
In a recent article, we showed that the light levels
marginally increased the number of primary branches (the
branches on the main stem). However, the light levels strongly
affected the number of secondary branches (branches on the
primary branches/cuttings) as shown in Figure 2a.
The results suggest that increasing the light amount, not
only increased the number of branches or cuttings per plant
but also could increase the water demand (Figure 2b) and
water-use efficiency to produce cuttings (less water per
cutting) (Figure 2b). In other words, plants grown under
an average DLI of 30 mol m-2
d-1
for 21 days produced close
to 29 cuttings per plant while plants grown at 52 mol m-2
d-1
d-1
d-1
produced 4.3 cuttings per the
produced 47 cuttings per plant from new secondary
branches. Furthermore, plants grown under 30 mol m-2
produced 2.5 cuttings per every liter of water while plants
grown under 52 mol m-2
same liter of water. This means the crops were more efficient
at transforming water into branches under higher light
intensities.
IMPLICATIONS FOR GROWERS
The current research highlights the ability of a cannabis
crop to use higher light levels to increase yield and wateruse
efficiency (higher yield per liter of water). As we saw,
the water-use efficiency for cutting production went from
2.5 to 4.3 cuttings per liter of evapotranspirated water when
growing plants under 30 versus 52 moles of light per day,
8 2024 GUIDE TO CANNABIS PRODUCTION
30
20
10
6
4
2
4
3
2
1
30
40
DLI (mol m-2
)
Figure 2a shows the number of secondary branches or cuttings (a) water
use per plant, (b) water-use efficiency (branches or cuttings per liter of
water) and (c) under three light levels (30, 40, and 52 mol m²)
using LED
lighting in addition to the sunlight. Image courtesy of Cristian E. Collado
and Dr. Ricardo Hermández.
respectively. This would mean that to produce 100 cuttings
using 52 moles of light, growers needed 23 liters of water
instead of 40 liters under 30 moles of light.
52
b
c
WUE (SECONDARY
BRANCHES/ L)
WATER USE (L)
SECONDARY BRANCHES
PER PLANT
2024 Guide to Cannabis Production

Table of Contents for the Digital Edition of 2024 Guide to Cannabis Production
