Preliminary Course.
Eco-Physiology
Density effect.
Density effect.
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Plant density greatly affects the overall biomass production due to competition for light, water, and nutrient resources.
In controlled environments (i.e. in greenhouses), competition is mainly for light.
At low density, or early growing stages, competition for light between plants is reduced.
As plants grow, the canopy closes, reducing the light resource, up to reaching complete canopy cover.
At this point, experiments have shown that biomass production reaches a stable maximum.
As a consequence, the variation in overall biomass production is therefore different if considered at plant level or at crop level.
Density effect at plant level
At the canopy closure stage, biomass production is stable.
The weight of each individual biomass increase is therefore proportional to the number of plants per square metre, i.e. proportional to the inverse of the density.
Considering overall individual production, this proportionality remains true if the covert occurs at early growth stages.
Chrysanthemum biomass production at plant level at two densities (Graph: E. Heuvelink, WAGENINGEN UNIVERSITY)
- This experiment, carried out at Wageningen University on Chrysanthemum compared biomass production at plant level at densities
of 32 plants per m2 (in blue) and 64 plants per m2 (in red).
The graph shows that production was similar for both cases up to 60 days.
On that date, canopy closed at high density, leading to lower individual production.
At the mature stage, the individual average weight of the 32 p.m2 crop was nearly twice then the individual average weight of the 64 p.m2 crop .