Irrigation – again

Yes, irrigation is hot. In the last 6 weeks, i have seen quite a lot of issues with irrigation. At first sight it should be good: drainpercentages and sum EC totall fine. But:
– Roots quite bad
– Plants just not growing right

The color of these roots are really fine. But the location isn’t. I would like to see the roots from top (2-3 cm below top) till bottom, and eavenly spread.

Then just sit down and check everytyhing. For a good check we have a few tools:
– first irrigation standard 2 hours after sunrise, or better: 60-90 joules after sunrise.
or even better, just 1-2% drydown after sunrise
– last irrigation standard 2-3 hours before sunset, or better: about 125-100 joules before sunset
– the irrigation over the day should be stable. Stable means not in time, but in radiation. The correlation between radiation and evaporation is quite good. Thus stable in ml/joule (officially: ml/lm / joule/cm2). So the amount of ml/joule should be stable between the irrigations within a day, but also between the days.
Normally this is about 1,5 ml/joule. But the number is not very important, it is much more important that it is stable with normal drain percentages (5-35% – depending on plantsize and climate).

With this check (ml/joule) we could find out on several companies, that is was not stable: in most cases in the darker parts of the day too high (for example going in the direction of 3-4 ml/joule), in the sunnier parts of the day too low (going down to 0,7-1,0). That means within one day, plants are drowning or are thirsty.

This caused bad rooting, and bad plant development.
Main reason was in the most cases:
– irrigation on time
– irrigation on radsum, but with a min time interval and a max time interval.

My experience is, that from a certain plant size, irrigation on radsum is way the best system. But it is important to check if the joule and amount settings are correct by:
– drain% measurement and calculation
– drain timing (when do you get the first drain)
– measurement of dry down (between last irrigation yesterday and the first irrigation in the morning); between irrigations; between sunrise and first irrigation and between last irrigation and sunset.

Above a graph with the drydown numbers: 4,09% – quite a lot for strawberries. As you can see in the graph, irrigation started too late. With such a drydown strawberries get easy to generative.

Irrigation – 2

If i would ask all my clients what they see as the hardest issue in growing strawberry, i think about 95% of them would mention irrigation.

It is spring, and in this time of the year i see the struggles again. lots of growers with to wet soil or substrate, and in the meantime enough growers with too dry substrate.
The weather is changing all the time. In the morning it seems to be autumn, and a bit later, summer comes closer and in the afternoon it turns out to be spring.

How to irrigate under such circumstances?
Recently a grower mentioned: “We invest quite a bit of money in a climate controll system, a lot of money in plants, predators, gutters etc. But nothing in the controll of irrigation. It is time to change it…”.

Important to consider:
– The correlation between radiation and evaporation is very high
– Normal evaporation (good developed plants) is about 1,5 ml/joule (or better (ml/m2)/(joule/m2).
– lower LAI (Leaf Aria Index) means also lower evaporation (leaf pruning –> less evaporation, thus changes in the irrigation).

Withgoing a presentation about irrigation for strawberries. It was originally developed for tomatoes, but i was allowed to change the numbers, so it is suitable for strawberries.

New beginning

A new beginning, a new start. Everything ready for the new spring. Days are getting longer, flowerbuds in the hart of the plant promise a new future.

In the same way is Christmas the sign of a new future. God born in a stable, sleeping in a manger. Proof of a future life without war and pain, without tears.
But with fruit, and i hope we will enjoy strawberries as well.

I wish you all Blessed Christmas – a blessed future – a blessed 2024

Irrigation Strawberry dry-down

Irrigation in strawberries seems to be one of the hardest issues. If i ask growers i work with 90% of them will mention this as so.

In my last post on LinkedIn, i had a poll about the dry down for strawberries overnight. Interesting to see 640 impressions, but just 16 votes. An indication for the fact that good irrigation is hard working?

But first, what is dry down? Dry down is the difference in moisture content between the frist irrigation in the morning and the last one of the previous day. In the schedule aboveyou can see the level at the irrigation of the previous day and the level at irrigation of the current day (between the red lines in the graph above).

Interesting to see the answers also: no one voted for 4-6%. Although i didn’t mention the substrate in this poll. I ment to ask for organic substrates like coir or peat.

Most of the answers where on the 9-11%. For Rockwool where dry down is a known concept, i do think 9-11% makes sense. For coir i see 4-6% as the optimum. Reasons:
– Rockwool 9-11%:
* Strawberry is a plant that really likes air / oxygen in the rooting zone. The best soils are still the coarse sandy soils. The best substrates those with a lot of oxygen/air in the rooting zone. The oxygen content in Rockwool is essential lower as in most coir i see. A period with more oxygen in the rooting zone is essential for good root growth. A higher dry down can help therefore.
– Coir / Organic substrates 4-6%:
* Several items are directly related to this percentage:
** Tip burn (or calcium deficiency in the young leafs / flowers)
about more then 90% of the tip-burn i see is not related to fertilizer recipe but to climate. Calcium is passiv taken up by the plant with the sap flow (xylem). This means, Calcium is transported to those places where evaporation is taken place. Only in case of rootpressure it gets everywhere.
Low moisturecontent in the evening means low root pressure and thus higher risk on tip-burn.

** Root health and fluctuation in moisture content. Strawberry generally grow better if the fluctuation in moisture content is not too big. Periods with relative wett substrate seems to influence both rooting as well as browning of the roots, probably because of oxygen deficiency.
** EC / drainage. Strawberry have an optimum EC range from about 1,3-2,0. In case of low drain percentages the EC increases causing mainly yield and quality issues. In case of high dry-down more irrigation water is needed for remoisturing and less time on the day remains for drainage. This can be seen in quite strong increase of drain EC in case of high dry down levels.

LAI = Leaf Area Index

Those experiences bring me to the following numbers:
– optimum drip EC: 1,3-2,0
– optimum drain EC: 1,5-2,0
– optimum dry down:
– coir: 4-6%
– rockwool: 9-11%
-optimum drain percentages:

Important to know, that these numbes are quite general, but differ for individual situations. Irrigation is not easy, it is subject for at least a days discussion if not for a week.

One of the most important basics is, that strawberries don’t handle big fluctuations very well. Both in EC as in Moisture content. They almost always lead to quality issues and sometimes to growth issues.

This means very practicle, that if i have a too high EC, i don’t advice to flush it suddenly, but decrease it steadily, slowely. The same for moisture content, if it is too low, don’t suddenly increase the moisture content.

Bugs wk 38 Beauty

Again several beauties together.

White fly predators: interesting to see the black larvea in stead of greenish colored larvea. 2 growers stopped using insecticides and those predators turned up naturaly.

Interesting: outdoor screening in order to keep the heat out. Works fine so far.


Image 1 of 11

Bugs this week (30)

This time a nice sery of pictures, especially about the lacewing. The adventures of a young lacewing larva entering the big bad world (although – who is bad?).

But also: lacewing larve eating quite a lot more as aphids: spidermites, spidermites eggs, and thrips (in the flower).

I have seen lots of lacewing eggs last 2 week. Essential in all those cases is: no insecticides. One grower with quite a lot of nature around the plot: lots of lacewing, hoverfly, feltiella, andersoni etc all just from the surrounding nature.

Beauty in all its complexity

Bugs this week (wk 26)

This week again a nice couple of good bugs. Especially lots of feltiella showing up in strawberries within some spots with spidermites.
Between these spidermites also a sofar unidentified help.
Especially the Feltiella and the Hoverflies can consume huge populations of Spidermites / Aphids.

The interesting thing in those predators on the picture, is that most of them are native and grew in that crop by themselves. I see more and more, that the area around the strawberries is very important for the development of a natural population of predators.

Below pictures of:
– Feltiella egg. Feltiella is a great consumer of spidermites. It may delete complete colonies of spidermites on leafs.
– Feltiella Larva 2x
– Feltiella pupa
– Hoverfly larva (huge aphid consumer)
– Lacewing egg
– Ladybug pupa
– Ladybug larva
– A type of ladybug: Stethorus punctillum (with thank to Markus Hofmann)

Measuring growth – key to development

One of the biggest issues of growing strawberries is, that you may only experience the yield if you are in the last part of the growth. That doesn’t satisfy me. After 100 days of sub-optimal photosynthesis, we talk about quite a lot of growth thus money.
We love to bring that back to 1 day, or if possible even hours.

Below a system for measuring the growth of Runners. In the picture below you see the system.

On the left the gutter with container where the strawberry plants are growing. you see the runners from the container growing to the right. The tube there is weighing the runners. This tube is connected with electronic measuring cells.

The results are shown in the graph below:

Strawberry growth graph

– left hand ax: weight in kg/10 meter (including pipes etc)
– bottom ax: date
– green line: graph for weight
– reddish: EC
– blue: moisture (scale based)
– yellow: radiation
– Bottom bar graph:
– blue: amount of irrigation (per 2 linear meter)
– red: amount of drain


In the graph above you see the first results:
– Left ax: Radiation in joule and growth (gram/1000 joule)
– Right ax: Weight just before sunrise
– Orange: Radiation (Joule/day)
– Green: Growth in gram/10 meter/1000 Joule
– Blue: Weight just before sunrise

Interesting to see is the differences from day to day. Just these are the reason for measuring: why are the differences there and how can we use them for optimizing the growth and thus the results.

Bugs this week (wk 25) – cryptobug

Several bugs this week: from Hoverfly, to Aphids, Larva of Aphidoletes, Birds, Larva of Lady bug, and some plant reaction of chemicals.
The beauty this week was the Cryptobug. A volunteer, just got in that greenhouse. A little shy, but nice to see.

Bugs this week: 2023 – 22

Or bugs? Quite some different issues i ran in this week.

The first to mention is herbicide damage. Every year i see about 10 cases of herbicide damage. Especially from Roundup. It seems so easy to use, but in my view Roundup and strawberries just don’t combine. Just a little wind, a little movement in the air and there is yellowing and consequences for the crop.
On this picture you only see the consequences for the fruits / flowers. But there was also a slight yellowing of the leafs.

Aphids can be seen this year. But good to see the predators as well. On the pictures you see Aphidius (predated aphid), Aphidoletes at work, Hoverfly adult and Hoverfly egg. The Aphidoletes used to work very fine, at least if they are not combined with a bit more agressive predatory mites.

Mildew and Botrytis
Every year an issue. So far although we had quite some rain the botrytis levels are still very acceptable. In the picture below the very first sign of Botrytis: the red spot on the Sepal.
Mildew: this time the consequences for the fruit: an uneven coloring.