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.
NOTE: we now know that the primary cause of internal fruit rot (Fusarium) in peppers is when the fruits become ‘blown-up’ resulting in micro cracking and thin fruit walls surrounding the ‘style’ of the flower which then aids entry of the pathogen. Researchers working for Enza identified that starting irrigation too early, stopping too late & a low EC in the root zone are the primary causes of ‘blown fruits’. This is just one additional reason why root zone management over the 6 phases and especially in changeable weather conditions can help you realize maximum production, quality and shelf life. Keep this focus and take advantage of your Supreme slab which when used in combination with the GroSens system can help you realise benefits of Grodan root zone management solutions.
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 Supreme 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. NG2.0 technology used in Supreme 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.
Supreme is a 10 cm high slab which can exert a considerable suction on the propagation block. It is therefore reccomended to use it in combination with Plantop blocks. Above all be aware that the propagation block should remain sufficiently moist during the rooting in phase.
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. With Supreme we recommend this method of cutting the drain holes. 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.
Once again for Supreme we prefer option 1.
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.
Bright day - Vegetative steering | Dark day - Generative steering | ||||||
Start time | First days during rooting in irrigate every 4.0 - 5.0 hrs (subject to the way the drain hole is configured, see tips) | First days during rooting in irrigate every 4.0 - 5.0 hrs (subject to the way the drain hole is configured, see tips) | |||||
Stop time | Not applicable | Not applicable | |||||
Target day level WC | To stimulate rooting in >75% Upper layer slab >60% | To stimulate rooting in >75% Upper layer >60% | |||||
Target decrease WC overnight | Not applicable | Not applicable | |||||
Moment 1st drain | Not applicable | Not applicable | |||||
EC drip | 3.0 - 3.5 mS/cm | 3.0 - 3.5 mS/cm | |||||
EC block | 3.0 - 3.5 mS/cm | 3.0 - 4.0 mS/cm | |||||
24 hr drain | Not applicable | Not applicable | |||||
Irrigation volume | 100 - 125 ml/block | 100 - 125 ml/block | |||||
ml/joule | Not applicable | Not applicable | |||||
Night irrigation | If decrease >20% | If decrease >20% |
Before planting it is essential that all slabs are fully saturated with complete nutrient solution. Thanks to the NG2.0 fibre of Grodan Supreme this is an easy task. However we would advise that you wait at least 24 hrs following saturation before the drain holes are cut. To facilitate maximum generative - vegetative steering of WC% and EC in the root zone throughout the duration of the cultivation you are advised to cut one drain hole. Cutting along the full width of the plastic seam at the end of the slab is the ideal way to do this. Please see the instruction videos on how to do this optimally. Remember with Grodan Supreme it is perfectly safe to recycle the drain water from the moment the drain holes are cut in the greenhouse. This will help reduce unwanted emission of fertilizer to the environment. Grodan Supreme is designed in such a way that it promotes fast and uniform root growth from block to slab, which will promote strong vigorous growth. Vegetative development at this stage will create a crop with sufficient leaf area facilitating an early first harvest.
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 Supreme slab. Ensure that the stainless steel plate on the sensor is at the correct height (top screws). Watch the video below on how to do this correcly.
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.
Bright day - Vegetative steering | Dark day - Generative steering | ||||||
Start time | +2.0 hrs after sunrise At least 1.0 hour after opening the screen | +3.0 hrs after sunrise At least 1.0 hour after opening the screen | |||||
Stop time | -2.0 hrs before sunset At least 2.0 hours before closing the screen | -3.0 hrs before sunset At least 2.0 hours before closing the screen | |||||
Target day level WC | Decrease to 60% at first fruit set then gradually increase to 70% (by end of phase) | Decrease to 55 - 60% (min 50%) at first fruit set then gradually increase to 65% (by end of phase) | |||||
Target decrease WC overnight | 3 - 5% depending on plant size | 4 - 6% depending on plant size | |||||
Moment 1st drain | Not applicable | Not applicable | |||||
EC drip | 2.8 - 3.3 mS/cm | 3.0 - 3.5 mS/cm | |||||
EC block | 3.0 - 4.0 mS/cm | 3.5 - 4.5 mS/cm (4.5 mS/cm when stimulating fruit set) | |||||
24 hr drain | 15 - 25% | 0 - 15% | |||||
Irrigation volume | 300 - 400 ml/m² i.e. 3-4% growing media volume/m² | 400 - 500 ml/m² i.e. 4 - 5% growing media volume /m² | |||||
ml/joule | Not applicable | Not applicable | |||||
Night irrigation | If average pipe >50°C and decrease WC% >10% | No |
Quick vegetative – generative crop steering
The height (10 cm) and quick drainage properties of Grodan Supreme stimulate the crop to create more roots and show a faster generative crop response. This steering approach is ideal if you wish to transform vegetative growth at the start of the cultivation into generative growth and fruit set. By aligning growing media and climate strategies you will have complete control of how you steer your crop (Precision Growing).
Extra drip session
As the total root volume is created by a total slab height the relative volume of roots at the bottom of the slab is much smaller than a traditional 7.5 cm slab. If in doubt an extra irrigation session after a bright day is no problem. The WC% will decrease faster in the bottom layers enabling oxygen to reach the roots easily.
EC steering
Irrigation efficiency is the key feature of the design of Grodan NG2.0 technology used in Supreme. It allows you to manage growing media EC without the need to create excessive drain volumes. The excellent irrigation efficiency of Grodan Supreme will already be noticeable and by using large irrigation volumes per cycle (4 - 5% of your growing media volume) you will be able to realise optimal EC control without compromising the generative/vegetative balance in the crop.
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, along with climate steering: good overall crop development from the start of cultivation with increased generativity which has resulted in an easier and more uniform 1st setting.
Now, at the moment of setting, daily irrigation is recommended especially when steering with a low slab day level WC%. Key to remember is that Supreme can be irrigated more regularly than other growing media, maintaining vigour, but retaining a good generative balance in the crop.
Because the slab WC% around the time of setting is low there is a lot of room for ‘fresh’ water in the slab. The ‘old’ water is at the bottom of the slab and due to NG2.0 technology is easily replaced.
High EC values in the slab (5.0 - 6.0 mS/cm) are not a problem at this time of year. Certainly not as long as there is no ventilation and the transpiration of the crop is at a relatively low and stable level.
A high or increasing slab EC should not be the reason to lower the irrigation EC. First create additional drain. However remember not to go ‘chasing drain’ and creating excessive drain volumes for EC control.
You will find that the EC in Grodan Supreme due to NG2.0 technology will remain very stable. On the dark days drain is not necessary or at most 10 - 15%. Drain is only desirable on the sunny days and on these occasions it may be high in percentage terms (> 50%).
At the beginning of Phase 3 the day length is already considerably longer than it was when the crop was planted. Now daily irrigation 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.
Bright day - Vegetative steering | Dark day - Generative steering | ||||||
Start time | +2.0 hrs after sunrise 60-100 J/cm² or 200 W/m² | +2.0 - 3.0 hrs after sunrise When WC falls 1.5 - 2.0% from sunrise | |||||
Stop time | Ideally leaving or 60 - 100 J/cm² and a light intensity threshold 200 - 300 W/m² to sunset | -3.0 - 4.0 hrs before sunset | |||||
Target day level WC | During first harvest 65%. At start of second harvest 70% Upper layer slab >50% | 60 - 65% Upper layer slab >45% | |||||
Target decrease WC overnight | 6 - 7% | 7 - 9% | |||||
Moment 1st drain | 400 J/cm² or 600 W/m² | Less than 4 | |||||
EC drip | 2.7 - 3.0 mS/cm | 3.0 - 3.3 mS/cm | |||||
EC block | 3.0 - 4.0 mS/cm | 3.3 - 4.5 mS/cm | |||||
24 hr drain | 20 - 30% | 10 - 20% | |||||
Irrigation volume | 300 - 400 ml/m² | 400 - 500 ml/m² | |||||
ml/joule | 2.5 ml/J (> 800 J/cm²) | Pipe can have bigger influence than light | |||||
Night irrigation | Only if pipe temperature >60°C | No |
The growth of new roots and root tips should be encouraged by adjusting the start and stop times of irrigation, particularly on darker days. The fibre structure and height of the Grodan Supreme slab enable controlled irrigation on darker days. This will result in a fast generative plant response. The drip and slab EC are important steering tools to maintain balance and fruit quality in this phase. The excellent irrigation efficiency of Grodan Supreme will enable you to maintain a high drip EC. The the slab EC can be controlled using longer irrigation sessions in the morning. This strategy enables you to accept higher EC values which results in maximum generative development particularly on darker days. On bright days the good re-saturation characteristics of Grodan Supreme enable the WC% to be steered to a higher value. Combined with a targeted irrigation strategy this will encourage maximum growth and development of the crop.
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 have now been taken and solar radiation is increasing rapidly towards the longest day.
From now on the irrigation strategy can become more structured. Remember there are 4 key irrigation stages during the day:
Optimise start and stop times. Keep the radiation sum used to trigger an irrigation constant throughout the entire day but vary the irrigation volume.
At the start of Phase 4 the radiation sum start will be around 100 J/cm² remembering ventilation is not on summer levels. As the transpiration levels increase the irrigation frequency can be lowered to every 70 - 80 J/cm².
Do not allow the WC% in the slab to fall too far >15% this will be at the expense of growth, vigor and fruit weight.
Bright day - Vegetative steering | Dark day - Generative steering | ||||||
Start time | +2.0 hrs after sunrise 65 - 90 J/cm² or 200 W/m² | +2.0 - 3.0 hrs after sunrise When WC% falls 1.5 - 2.0% from sunrise | |||||
Stop time | -2.0 hrs before sunset ideally leaving or 70 - 150 J/cm² and a light intensity threshold 200 - 300 W/m² to sunset | -3.0 - 5.0 hrs before sunset | |||||
Target day level WC | Gradually increasing to 70 - 75% with increasing light intensity towards summer | Gradually increasing to 65 - 70% | |||||
Target decrease WC overnight | 7 - 8% | 8 - 9% | |||||
Moment 1st drain | 400 J/cm² or 600 W/m² | Less than 5 irrigations | |||||
EC drip | 2.8 - 3.0 mS/cm | 3.0 - 3.3 mS/cm | |||||
EC block | 3.0 - 3.5 mS/cm | 3.3 - 3.8 mS/cm | |||||
24 hr drain | 25 - 30% | 15 - 25% | |||||
Irrigation volume | 250 - 350 ml/m² | 350 - 450 ml/m² | |||||
ml/joule | 2.5 - 3.5 ml/J | 2.5 - 2.8 ml/J | |||||
Night irrigation | If decrease WC% >10% check and correct stop time due to increasing day length | No |
Steering the root zone on dark and bright days stimulates optimal crop growth resulting in maximum production and quality. The design of Grodan Supreme enables the start time of irrigation to be aligned with the plant activity particularly on darker days. This stimulates the roots to form new root tips promoting faster regrowth of the crop after the first harvest has taken place.
The irrigation efficiency of Grodan Supreme enables the growing media EC to be stabilised using minimum drain volumes and without having to decrease the drip EC too far. The start time of irrigation should be related to the light sum (J/cm²) and/or intensity (W/m²). Experience has shown that continuing irrigation for longer into the afternoon on the brighter days with Grodan Supreme is desirable for maximum growth and fruit development. Combined with slightly earlier start times and smaller irrigation volumes until the first drain, the day level WC% will be increased to that desired for Phase 5.
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.
Start and stop times should coincide with plant transpiration. It is best to remove the maximum rest time setting from the first irrigation period and use a light only setting (see advice tables). The second irrigation period should contain a maximum rest time setting. Likewise the final irrigation period of the day should be based on light only starts. In this way on a dark day no starts will be given and on a bright day the starts continue (see advice table) and a stable decrease in WC% will be maintained.
The irrigation EC should remain >3.0mS (especially with radiation <600W/m²). The good irrigation efficiency of the Grodan slabs means you do not have to chase the EC of the growing media and can therefore keep irrigation under control especially in periods of changeable weather. A light reduction EC setting can be used but watch that you do not make the range too reactive, respecting the planned stop conditions.
An increasing EC at midday will have consequences for the plant’s vigour and fruit quality (micro-cracking and blossom-end-rot if it is not controlled). In the morning start with larger irrigation volumes 4 - 5% of the volume of the growing media in order to get drain in time. In the afternoon shorter more frequent irrigations 3% of substrate volume will help keep slab WC% & EC stable and controlled.
The GroSens system is an excellent tool to assess if the irrigaiton strategy needs adjusting. The standard graphic on your climate computer should contain WC%, EC, radiation sum (J/cm²) and radiation intensity (W/m²). If scaled correctly it is very easy to see relationships between these data points and answer the following questions:
Bright day - Vegetative steering | Dark day - Generative steering | ||||||
Start time | +2.0 hrs after sunrise 65 - 90 J/cm² or 200 W/m² | +2.0 - 3.0 hrs after sunrise When WC% falls 1.5 - 2.0% from sunrise | |||||
Stop time | -2.0 hrs before sunset ideally leaving or 70 - 150 J/cm² and a light intensity threshold 200 - 250 W/m² to sunset 75% | -3.0 - 5.0 hrs before sunset | |||||
Target day level WC | 70 - 75% | 65 - 70% | |||||
Target decrease WC overnight | 7 - 8% | 8 - 9% | |||||
Moment 1st drain | 400 J/cm² or 600 W/m² | Less than 4 irrigations | |||||
EC drip | 2.6 - 3.0 mS/cm | 2.8 - 3.2 mS/cm | |||||
EC block | 3.0 - 3.5 mS/cm | 3.3 - 3.8 mS/cm | |||||
24 hr drain | 25 - 35% | 15 - 25% | |||||
Irrigation volume | 250 - 350 ml/m² | 350 - 400 ml/m² | |||||
ml/joule | 2.5 - 3.0 ml/J (depends on use of shading) | 2.5 - 2.8 ml/J | |||||
Night irrigation | If decrease WC% >10% | Not applicable |
The strong root system formed in the previous phases should make the difference in this phase. It is however important to align the start and stop times with the weather conditions and required plant steering. On bright, warm days continue irrigation into the evening for longer in order to achieve maximum growth and fruit size. The required decrease in WC% at night (7 - 9%) can be used as the guiding principle. As the EC in Grodan Supreme is easier to stabilise the set-point drip EC can also be applied for longer with a lower average drain percentage on the darker days. The ability to maintain a higher EC level in this phase will also help you to reduce the risk of production losses in autumn.
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 icrease 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 hrs 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.
Bright day - Vegetative steering | Dark day - Generative steering | ||||||
Start time | +2.0 hrs after sunrise 80 - 100 J/cm² or 250 W/m² or WC decrease after sunrise at 1.0 - 1.5% | +2.0 - 3.0 hrs after sunrise or at WC% decrease 1.5 - 2.0% | |||||
Stop time | -2.0 hrs before sunset Ideally leaving 80 - 100 J/cm² and a light intensity threshold 150 - 200 W/m² to sunset | -3.0 - 4.0 hrs before sunset | |||||
Target day level WC | Decreasing from 65 - 70% (start of phase) to 60 - 65% (end of phase) | Decreasing from 60 - 65% (start of phase) to 55 - 60% (end of phase) | |||||
Target decrease WC overnight | 7 - 8% | 8 - 10% | |||||
Moment 1st drain | Within 4 irrigations before reaching 400 J/cm² or 600 W/m² | If required within 5.0 hrs after sunrise or within 3 irrigations | |||||
EC drip | 2.8 - 3.0 mS/cm | 3.0 - 3.3 mS/cm | |||||
EC block | 3.0 - 3.5 mS/cm | 3.5 - 4.5 mS/cm | |||||
24 hr drain | 20 - 25% | 10 - 15% | |||||
Irrigation volume | First 3 - 4 irrigations 400 - 500 ml/m² then: 300 - 400 ml/m² | 400 - 500 ml/m² | |||||
ml/joule | 2.6 - 2.8 ml/J | Not applicable | |||||
Night irrigation | No | No |
The properties of Grodan Supreme can be utilised exceptionally well during the final weeks of growth. The perfect water distribution over the entire height of the slab, a result of the NG2.0 technology, causes the crop to show a generative response very easily if the start and stop times (larger decrease WC% night) are adapted.
The properties of Grodan Supreme result in the lower part of the slab being drier. This maintains a better air- water ratio benefiting root quality and plant vigour.
An undesirable increase or higher growing media EC is easier to lower in Grodan Supreme using larger (4 - 5% of growing media volume) irrigation sessions in the morning, meaning average drain volumes over 24 hrs can be kept to a minimum.
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