At low levels of radiation we can learn to accept higher EC levels in the root zone especially if the plants are too vegetative. However as radiation levels rise >400 W/m2 transpiration is stimulated by a significant increase in leaf temperature. As they rise further (>700 W/m2), cooling of crop becomes more critical. At these moments the plants need more water than feed and the substrate EC should be managed by a reduction in irrigation EC as well as a
targeted irrigation strategy so limiting stress on the plant (Table 1).
Table 1: Acceptable substrate EC levels in relation to expected average daily radiation (W/m2) levels.
|EC substrate Tomato
|EC substrate Cucumber
|EC substrate Pepper
The desire to reach an “EC target” will often result in growers over irrigating the crop. Be aware that each time you irrigate the crop will be given a vegetative impulse. Therefore within your irrigation strategy you do not want to be “chasing” substrate EC if you wish to steer in a generative direction on “dark passive” days.
If the crop is described as “too vegetative” steering the root zone to a higher or with an increasing EC and a lower or decreasing WC will provide a generative impulse, especially at light levels below 400 W/m2. Under these circumstances a higher EC level is desirable for controlled growth as more fertilizer will be taken up by the plant. This will result in more dry matter accumulation leading to resilient plants which are less vulnerable to disease.