Target crop
Uniform growth and equal development of the stems should continue and the leaf area should increase to enable the plant to intercept as much radiation as possible. Flower development should remain strong and generative with good flower and pollen formation.
Target root zone
The pin roots should grow easily out of the block and uniformly into the growing media. It is important to supply enough water and nutrition to the blocks until the plant can rely on the available water in the slab.
Start of phase
Plants arrive into the greenhouse
End of phase
When the roots have penetrated into the substrate several centimeters and water
absorption is no longer dependant on the moisture content in the block.
Objective phase
Fast and uniform rooting in, so that the roots are penetrating the growing media in line with the plant size.
Good water management is critical for a successful crop. It starts in this growth phase. Please pay attention to how you cut the drain hole.
Following initial saturation leave the slabs full for at least 24 hours before making the drain hole. In this way, the fine pores are also saturated, which enhances uniformity for the rest of the cultivation. The NG2.0 technology used in the slab in combination with Plantop blocks contribute to optimal uniformity over the entire height of the growing media and provides a perfect block - slab connection. This promotes uniform rooting in and thus uniform stem development.
For accurate EC control during the entire cultivation cycle we recommend you cut one drain hole at the lowest point in each slab. Make sure this is done properly, poorly cut drain holes will have a huge impact on your ability to steer the growing media WC% & EC. More than one drain hole will result in an uneven WC% & EC within the slab and will also make steering (WC% & EC) on irrigation session length (ml/m²) harder.
You have two options for cutting the drain holes
Option 1
Pre-draining the slab: Pre-draining the slab involves making a small puncture in the plastic wrapper just above the seam at the end of the slab. A uniform layer of water then remains in all slabs in the greenhouse. Following planting the remaining water is available and will be drawn into the Plantop blocks due to NG2.0 technology. This block - slab interaction means that in the first days after planting only 1 at most 2 irrigation sessions will be required to help stimulate rooting in. After 4 - 7 days when the young crop is rooted into the growing media the final drain hole can be cut. Watch the video below on how to do this correctly.
Option 2
Drain the slabs directly: If the final drainage hole is cut before planting, 3 - 5 irrigations per day will be required until the plant is rooted 3 - 5 cm into the slab. Watch the video below on how to do this correctly.
Irrigation water seeks the shortest route towards the drain hole. Position the irrigation peg on the plant blocks (not too deep) so that they are as far away from the drain hole as possible. Remember the irrigation peg furthest from the drain hole will be the most efficient at replacing the old slab solution.
| Start time | First days during rooting in every 4.0 - 5.0 hrs | ||||||
| Stop time | Not applicable | ||||||
| Target day level WC | For rooting in WC >75% | ||||||
| Moment 1st drain | Not applicable | ||||||
| EC drip | 3.0 - 3.5 mS/cm | ||||||
| EC slab | 3.3 - 3.8 mS/cm | ||||||
| 24 hr drain | Not applicable | ||||||
| Target decrease WC overnight | Not applicable | ||||||
| Night irrigation | If decrease >20% | ||||||
Before planting it is essential to fully saturate the slabs with nutrient solution for at least 24 hours before the drain hole is cut. This ensures that even the fine pore spaces between the NG2.0 fibres are filled with water. There are two ways to cut the drain hole please refer to the video link for more information. You are advised to cut one drain hole per slab. However if your gutter profile is uneven you can make an additional drain hole at the lowest point of the slab. Remember with Grodan Vital Dry it is perfectly safe to recycle the drain water from the moment the drain holes are cut.
Target crop
Work on plant development and increasing the leaf area to capture the available radiation and keep the required vegetative – generative balance in the plant relative to the fruit load and light levels.
Target root zone
Establish complete root penetration in the entire volume of the growing media. This will enable the plant to take up all the water and nutrition it will need for maximum summer production and quality.
Start of phase
When the roots have penetrated into the substrate several centimeters and water absorption is no longer dependent on the moisture content in the block.
End of phase
When the plant starts to feel the effects of the fruit load following first setting.
Objective phase
Set the first fruits at the desired internode and continue their development and the realisation of a root system that fills the entire substrate volume.
The GroSens Sensor should now be inserted into the growing media. Ensure that the stainless steel plate on the sensor is at the correct height. The video below shows you where to place the sensor irrespective of crop type.
When the crop is rooting through the slab the evaporation by the plant is still very low. This means that up to ten days after planting the slab WC% will fall <1% per day even without irrigation. However for every additional 10 days of growth the decrease in WC% will be one percentage point higher so 20 to 30 days after planting the daily water uptake should be between 2% and 3% of the total slab volume.
As a general rule to ensure sufficient decrease in WC% overnight you can use the following formula to judge the start / stop times of irrigation: there should be a minimum decrease of 2% starting from where the stem breaks to produce the final growing shoots and then for every 20 cm growth x 1 %. For example with a total plant height 130 cm with the stem break @ 30 cm = 2% + (5 x 1%) = 7% minimum decrease WC% overnight.
Aim for a slab WC% of 55 - 65% around the time of 1st setting measured at day level (highest value on the day). So plan the decrease now! It is no issue that during this phase the slab EC increases to 5.0 - 6.0 mS/cm as the evaporation by the crop is very low.
In the first weeks of cultivation especially on the dark, inactive days’ irrigation can be skipped for several days at a time. Plan so that you irrigate on the brighter more ‘active’ days or days where higher pipe temperatures are required.
| Start time | +2.0 after sunrise | ||||||
| Stop time | -2.0 - 3.0 hrs before sunset | ||||||
| Target day level WC | Gradually decreasing to stimulate first fruit set. The minimum day level WC% advised for Vital Dry is 60% | ||||||
| Moment 1st drain | If desired 4.0 - 5.0 hrs after sunrise in 3 - 4 irrigations | ||||||
| EC drip | 3.0 - 3.5 mS/cm | ||||||
| EC slab | 3.5 - 4.5 mS/cm 4.5 mS/cm at moment of first setting | ||||||
| 24 hr drain | 10 - 25% | ||||||
| Target decrease WC overnight | Goal > 3% relative to plant size | ||||||
| Night irrigation | When average pipe temp > 60°C | ||||||
The porous and open fibrous structure of Grodan Vital Dry facilitates rapid rooting into the growing media which is required for uniform plant development. For vegetative – generative plant balance irrigation must be applied in line with the climate and screening strategy. To promote optimum horizontal root formation your objective should be to gradually lower day level WC% from 80 - 85% to 60 % by the time of first setting. This will help the crop fully penetrate to entire volume of the growing media providing the basis for water and nutrient uptake in Phase 5, resulting in a stronger plant with more vigour. Accepting a higher EC range in the slab in line with (low)light levels during this phase will contribute towards easier generative steering.
Target crop
Growth should remain constant and uniform. The 24 hrs temperature should be adjusted to the light levels to ensure optimum partitioning of available assimilates for plant and fruit growth.
Target root zone
Root quality and activity should be retained to ensure controlled and uniform re-growth of the crop from the harvest of the first flush until the second flush. The decrease of WC% during the night will provide a good indication for the level of plant activity during the day.
Start of phase
When the plant starts to feel the effects of the fruit load following first setting.
End of phase
Following the first harvest, when the pressure of the fruit load is starting to decrease.
Objective phase
Avoid shocks in development by retaining the right balance in fruit load and growing power in the plant for the second fruit setting. Combination of harvest of the first fruits and new fruit setting (fruit load increases) must be in line with assimilates supply which is variable and strongly depending on the weather.
During phase 2 the WC% of the slabs was lowered. Ideally by not irrigating on the dark ‘passive days’. This strategy should have resulted in complete rooting throughout the entire volume of the slab. The result is good overall crop development with increased generativity and a uniform 1st setting.
Now, at the moment of setting, daily irrigation is recommended it should consist of 1 or 2 ‘fixed’ sessions per day. You can also begin to start working with more structured start and stop times on the basis of radiation sum. However please note that radiation sum used to trigger an irrigation is not pushed too high in the afternoon in order to allow that extra session on sunny days.
The use of a fixed plastic (foil) screen can lead to large differences in climatic conditions and water absorption of the crop which will result in differences in slab WC%. Map these differences per irrigation compartment by measuring a representative number of slabs in each valve section using the GroSens HandHeld Sensor and if necessary adjust the strategy to the observed differences per compartment.
| Start time | +2.0 - 3.0 hrs after sunrise | ||||||
| Stop time | -2.0 - 3.0 hrs before sunset | ||||||
| Target day level WC | Gradually increasing from 65% (start of phase) to 70% (end of phase) | ||||||
| Moment 1st drain | +4.0 - 5.0 hrs after sunrise | ||||||
| EC drip | 2.8 - 3.3 mS/cm | ||||||
| EC slab | 3.0 - 3.8 mS/cm | ||||||
| 24 hr drain | 20 - 30% | ||||||
| Target decrease WC overnight | 5 - 7% | ||||||
| Night irrigation | Only at high pipe temperatures > 60°C and if WC% decrease expected > 8% | ||||||
The growth of new roots and root tips will be encouraged because Grodan Vital Dry will not become too wet, especially on the darker days. The roots in the bottom layer of the slab in particular will remain healthy during this critical Phase of crop development because of the improved distribution of WC% over the height of the growing media due to NG2.0 fibre technology. On the brighter days it is easy to achieve a higher day level WC% by giving more water over a longer period. The drip and slab EC’s are also important steering tools to maintain balance and fruit quality in this phase. Due to the NG2.0 fibre technology and open structure the slab EC reacts quickly to changes in applied irrigation. In periods of variable weather it is therefore easier to maintain the target slab EC in combination with a simple irrigation strategy.
Target crop
Prepare the crop for summer creating the right balance as the plant load and production continue to increase.
Target root zone
To support increasing transpiration levels the root zone environment needs to be prepared. The recommended WC% and EC levels for late spring and summer should now be realised.
Start of phase
Following the first harvest, when the pressure of the fruit load is starting to decrease.
End of phase
When production levels are stable
Objective phase
Realise controlled and uniform re-growth of the crop until harvest of the second flush.
First harvests will have been taken and the solar radiation is increasing rapidly towards the longest day. The warm sunny weather will accelerate crop growth and development but please be aware that the real change from vegetative to generative development comes at quite high radiation levels, (>600 W/m²). Therefore we still need to use tools like EC-level and irrigation start and stop times to steer the crop towards (sufficient) generative development.
Drip EC should be held at at least 3.0 mS/cm. A slight decrease of the set point value based on light intensity can be programmed, especially when drain EC values are trending upwards. However the EC decrease on radiation intensity shouldn’t be more than 0.3 - 0.5 mS/cm.
The first rays of sunlight, right after sunrise may seem very intense on a sunny day, but they do not generate a lot of evaporation. The irrigation start time must be based on water uptake of the plants. The GroSens system is a very good tool to make this visible. Aim for a decrease in WC% of 1.0 - 2.0% after sunrise before the first irrigation is applied.
The stop time of irrigation will vary according to the amount evaporation and thus irrigation should continue until radiation falls below 250 - 300 W/m².
| Start time | +2.0 - 2,5 hrs after sunrise | ||||||
| Stop time | -2.0 - 3.0 hrs before sunset | ||||||
| Target day level WC | 65 - 70% | ||||||
| Moment 1st drain | +4.0 - 5.0 hrs after sunrise | ||||||
| EC drip | 2.8 - 3.3 mS/cm | ||||||
| EC slab | 3.0 - 3.8 mS/cm | ||||||
| 24 hr drain | 20 - 35% | ||||||
| Target decrease WC overnight | 6 - 7% | ||||||
| Night irrigation | Only if vegetative control is required | ||||||
Grodan Vital Dry will provide an adequate water buffer during this phase of the cultivation which is essential for a good summer production. Due to the NG2.0 fibre technology and the open fibrous structure the slab EC will react quickly to changes in applied irrgation volumes during periods of variable weather. It is therefore easy to maintain the target slab EC in combination with a simple irrigation strategy resulting in maximum growth and development of the crop.
Target crop
Vegetative or generative steering will depend on the condition of the crop. The crop should remain strong to cope with large and extreme fluctuations in weather conditions. The set speed should match the harvest speed to maintain constant fruit load.
Target root zone
Water uptake should match the needs of the crop for maximum cooling potential to create a good climate inside the greenhouse. Good root penetration throughout the entire volume of the growing media realised in Phase 2 will help the crop to cope with extreme weather conditions.
Start of phase
When production levels are stable.
End of phase
The last setting
Objhective phase
Maintain maximum plant vigour and production potential by keeping plant and root quality in excellent health.
EC control at this time of year is crucial and the GroSens sensor is an excellent tool to assess if the watering strategy needs adjusting. The standard graphic on which you should base your judgement should contain WC%, EC, radiation sum and radiation intensity. If scaled correctly it is very easy to see relationships between these data points and answer the following questions:
You can check these values with the guidance provided in the reference table.
| Start time | +2.0 - 3.0 hrs after sunrise | ||||||
| Stop time | -2.0 - 3.0 hrs before sunset | ||||||
| Target day level WC | 65 - 70% | ||||||
| Moment 1st drain | 3.0 - 4.0 hrs after sunrise | ||||||
| EC drip | 2.6 - 3.2 mS/cm | ||||||
| EC slab | 3.0 - 3.8 mS/cm | ||||||
| 24 hr drain | 20 - 40% | ||||||
| Target decrease WC overnight | 6 - 7% | ||||||
| Night irrigation | Only if vegetative control is required | ||||||
The open structure and NG2.0 fibre technology of Grodan Vital Dry ensures sufficient water buffer and nutrient supply for the crop in the summer. On days with a lot of radiation this secures the uptake of water. In periods of changeable weather, for example from dark to sunny days it is possible to lower the EC of the growing media quickly with a higher drain volume.
Target crop
Maintain strength and growing power of the plant and limit the ingress of disease in the crop as the light levels diminish towards final harvest.
Target root zone
Maintain a healthy and active root system and to keep the correct nutrient balance in the root zone. Ensure the irrigation strategy compensates for the rapidly changing transpiration levels. Maintain a stable and sufficient decrease WC% during night.
Start of phase
The last setting.
End of phase
When final harvest has taken place.
Objective phase
Keep the crop in a healthy condition and use the vigour to ensure production and quality is maintained right through to the last planned harvest date.
In order to keep the root system healthy good oxygen penetration is important. Therefore lower the irrigation frequency and the day level slab WC% will decrease slowly. To compensate for the lower irigation frequency increase the size of the irrigation volume per cylcle. Ensure the start and stop times coincide with the astronomical clock and gardually lower the day level slab WC%.
Pay attention to dark days with relatively high temperatures as the crop can evaporate more than the anticipated set radiation sum. On a sunny autumn day, the crop will only become active at +/- 100 J/cm². This is the moment for the 1st irrigation.
Often too much irrigation is given on dark days. The advice is to irrigate with minimum volumes on days >500 J/cm² and it is neither uncommon nor detrimental to the crop to achieve zero drain and let the growing media EC increase. On days where the radiation sum exceeds 1000 J/cm² irrigation should be applied 2.5 to 3.0 times the radiation sum. Such days are appropriate for leveling slab EC between 11:00 – 13:00 hrs.
Stop irrigation on dark days up to 3.0 - 4.0 hours before sunset and target a steady decline in slab WC% overnight between 7 - 8%. Overall keep the irrigation EC >3.0 mS/cm especially when radiation <600 W/m² and consider the need for light reduction EC if these settings have been very reactive during phase 5.
| Start time | +2.0 - 3.0 hrs after sunrise | ||||||
| Stop time | -2.0 - 3.0 hrs before sunset | ||||||
| Target day level WC | 65 - 70% at final setting reducing to 60% as the final fruits develop | ||||||
| Moment 1st drain | 3.0 - 4.0 hrs after sunrise | ||||||
| EC drip | 2.8 - 3.2 mS/cm | ||||||
| EC slab | 3.3 - 3.8 mS/cm | ||||||
| 24 hr drain | 15 - 30% | ||||||
| Target decrease WC overnight | 6 - 8% | ||||||
| Night irrigation | No longer required under normal circumstances | ||||||
A stable decrease in WC% during the night is most important to protect the root quality and keep the crop in the right generative balance. The fast drainage of Grodan Vital Dry means that the EC of the growing media can be easily stabilized in the without the WC% rising too high during the day preserving root quality until the final harvest has been taken.
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