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EC management

EC management
مدیریت میزان ای سی در کشاورزی

Introduction

EC management is easier in steerable substrates due to better irrigation efficiency. Download our whitepapers for more information.

The issue of EC management is a very vital issue for many greenhouse owners in Iran (especially hydroponic greenhouses). It is also a major issue for people who use different materials such as cocopeat in their culture media. A high percentage of cocopeats in Iran are imported and the reason is the lack of many coconut orchards in Iran. These coco peats are mostly salty and salty (with high EC). Therefore, the farmer or greenhouse owner must eliminate this salinity and prevent damage to the plant and its drying, and this is just one example of the necessities of EC management. PH adjustment is not usually relevant for cocopeat because it is inherently a neutral substance. Instead, pH management is essential to using peat moss because it is inherently acidic. There are materials such as perlite that do not need to neutralize the pH and do not need to adjust the EC.

Achieving drain each and every day and realizing average 24 hour drain figures >30% to manage EC is a thing of the past for the modern greenhouse grower. There are economic and legislative drivers to consider why this philosophy should be adopted to realize Precision Growing:

Economic drivers

Legislative drivers

In this technical article we describe the principle of irrigation efficiency and how this design feature of Grodan substrates makes EC steering easier with lower drain volumes.

What is irrigation efficiency?

Irrigation efficiency is a term used to describe how the applied irrigation water is partitioned in the substrate between re-saturation, and refreshment

Substrates with the highest irrigation efficiency are those which offer maximum EC refreshment with minimal drainage. Irrigation efficiency is an important design feature of modern greenhouse substrates as it allows growers to work with late start and early stop times without the worry of having to “chase” substrate EC. Therefore irrigation strategies can be fine-tuned to the needs of the crop.

Daily change in substrate WC & EC

The way the applied nutrient solution is partitioned within the substrate and subsequently how WC and EC reacts in NG2.0 substrates can be seen in the day dynamic provided by GroSens system illustrated in figure 1.

Figure 1

Day dynamic of water content and EC showing the diurnal fluctuation in WC & EC
in response to applied irrigation. Grodan NG2.0 substrates have higher irrigation
efficiency as shown by greater EC refreshment compared to other stone wool substrates.

Re-saturation

Refreshment

When the first effective drainage is realized the substrate WC will stabilize. Subsequent irrigation sessions immediately preceding this event will have maximum effect on decreasing the substrate EC by displacing the old substrate nutrient solution and refreshing it with new irrigated solution. This reaction is clearly visible in the GroSens graphic (Figure 1). Substrates with lower irrigation efficiency partition more of the applied irrigation water into resaturation, effective drainage occurs later and substrate EC will steadily increase day to day, especially with late start and early stop times (Figure 1). This often results in the grower over irrigating the crop to keep EC within acceptable limits.

Tip:

Direct drainage

Towards the end of the day the applied irrigation water will drain easily through the substrate, the majority of this water can be wasted i.e. it has no effect on WC or EC (direct drainage). This is a common occurrence especially if the distance from dripper to drain hole is too short (<20 cm), the capacity of the dripper is too high (4 l/hr) or too many drain holes have been cut.

Tip:

What is an acceptable EC target?

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).

Radiation (W/m2)
EC substrate Tomato
EC substrate Cucumber
EC substrate Pepper
200
8
5
6
400
6
4
5
600
5
3.5
4
800
4
3.2
3.5
1000
3.8
3
3

Table 1: Acceptable substrate EC levels in relation to expected average daily radiation (W/m2) levels.

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.

What is an acceptable drain percentage?

Continued measuring using the GroSens system in the substrate provides a clear indication of how EC and WC are developing. On hanging gutters capillary substrates (i.e. Grotop Master & Grotop Expert) which exhibit a high level of irrigation efficiency the drain volumes can be reduced depending on light levels to figures outlined in table 2.

Max radiation W/m2
Radiation sum J/cm2
Traditional drain %
Precision Growing drain %
200
500
20-30
5
400
1000
20-30
10
600
1500
30-60
15
800
2000
30-60
20
1000
2500
30-60
25
Table 2: 24 hour drain % in relation to light levels (W/m2) and daily light sum (J/cm2)*.
  • Assuming measured values for substrate WC & EC in line with those provided in 6 phase reference tables.
  • Assuming modern uniform greenhouse and hanging gutters.

Learn more about EC and soil electrical conductivity at Wikipedia

also you can read about peat moss in persian language

cocopeat in persian language

and perlite in persian language