SUPPLEMENTAL INFORMATION Crop Steering Overview WHAT IS IT? Crop Steering is the strategic manipulation of climate and rootzone environment to influence how a plant partitions resources during different phases of growth. At any given time, growth will be somewhere on a spectrum between “vegetative” and “generative”.
This table summarizes a number of vegetative and generative cues. Contact your Front Row Rep for more information on the specifics of irrigation and EC. PARAMETER
GENERATIVE CUE
VEGETATIVE CUE
Irrigation events
Smaller (2-4%), more frequent
Larger (4-10%), less frequent
By manipulating parameters like feed EC, substrate EC, water content, irrigation frequency, and net dryback, we can change how a crop partitions resources and ultimately improve yield, quality, and efficiency.
Irrigation start time
Earlier, 0.5-1 hrs after lights on
Later, 1-2 hours after lights on
Irrigation stop time
Later
Earlier
P3 dryback
Smaller
Larger
Inter-shot dryback
Smaller
Larger
VEGETATIVE AND GENERATIVE CUES
Runoff %
Larger, 20-30%
Smaller, 10-20%
Feed EC
Lower
Higher
Substrate ECpw
Lower
Higher
Temp DIFF
Smaller, 0-5 deg
Larger, 5-15 deg
24hr ave. temp
Warmer
Cooler
VPD
Smaller
Larger
These resource-partitioning effects are accomplished through the use of vegetative and generative cues; changes to specific parameters that signal the plant to shift resources towards vegetative growth (stems, leaves, shoots, roots) or generative growth (fruits and flowers).
VAPOR PRESSURE DEFICIT (VPD) is the difference in water pressure between the inside of a leaf (100% RH) and the air surrounding the leaf. This difference is one of the primary drivers of the “pull” side of transpiration from the leaves and is dependent on leaf temperature, air temp and air RH. It is generally measured in kilopascals (kpa). Keep VPD within these ranges for optimal plant performance. Generally night time VPD should be higher (dryer) to reduce the likelihood of fungal pathogens.
NOTE: Chart assumes leaf temps = air temps
VAPOR PRESSURE DEFICIT (VPD) CHART AIR TEMP
RELATIVY HUMIDITY %
°C
%50
%55
%60
%65
%70
%75
%80
%85
%90
18.9
1.09
0.98
0.87
0.76
0.65
0.55
0.44
0.33
0.22
20.0
1.17
1.05
0.94
0.82
0.70
0.58
0.47
0.35
0.23
21.1
1.25
1.13
1.00
0.88
0.75
0.63
0.50
0.38
0.25
22.2
1.34
1.21
1.07
0.94
0.80
0.67
0.54
0.40
0.27
23.3
1.43
1.29
1.15
1.00
0.86
0.72
0.57
0.43
0.29
24.4
1.53
1.38
1.23
1.07
0.92
0.77
0.61
0.46
0.31
25.6
1.64
1.47
1.31
1.15
0.98
0.82
0.65
0.49
0.33
26.7
1.75
1.57
1.40
1.22
1.05
0.87
0.70
0.52
0.35
27.8
1.87
1.68
1.49
1.31
1.12
0.93
0.75
0.56
0.37
28.9
1.99
1.79
1.59
1.39
1.19
1.00
0.80
0.60
0.40
30.0
2.12
1.91
1.70
1.49
1.27
1.06
0.85
0.64
0.42
31.1
2.26
2.03
1.81
1.58
1.36
1.13
0.90
0.68
0.45
32.2
2.41
2.17
1.93
1.69
1.44
1.20
0.96
0.72
0.48
OPTIMAL
BORDERLINE
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TOO HIGH OR TOO LOW
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