Controlling the EC levels for young tomato plants growing in Coco Fibre

In this article I want to focus on my observations, in regards to controlling the generative/vegetative balance of growing a young tomato plant on coco fibre substrate during January.  Dealing with diverse mixes or grades of coco is a challenge, not to mention the different suppliers, but not unsurmountable.  As long as the figures are accurate finding that balance is achievable.  The difficult task is to achieve the ‘sweet spot’ that suits each tomato variety. 

For young plants, recently planted, that are too long to be cropped, the hardest thing is to not over water or under water.   What we don’t want is to create a situation where we have BER (Blossom End Rot) from running very tight on the irrigation but you also don’t want to be in the situation where you have an overly vegetative plant, which is fine for now but will potentially cause massive headaches in the winter months.    Fat stems, big leaves and soft plants are certainly a funguses dream. 

Even with the technology we have its still tricky finding the correct balance, I rely on the feedback from the growers, via photos, measurements or visiting crops on a regular basis.  The start of the crop is crucial especially at the present time.  As I wrote, a few weeks ago, triple headed grafted plants have made my job a wee bit easier to balance the plant but comes with other challenges such as fruit loading. 

Using high EC on and OFF and tightly controlling the application of water applied is a method I like to use but in coco it is very important to balance this method with measurements. One reason is the variability of the different mixes/grades of coco.   Coco comes in either slabs or bags, again something which needs to be factored.    At this time of the year, with the very warm temperatures, the plants grow, they grow very, very quickly!  In two-four days, without even knowing it, the EC out could increase to undesirable figures.  When the fruit is golf ball size on the first truss your third and fourth truss will probably be flowering and setting accordingly (example large loose tomato variety).  Now you have another pull on the plant.  If you’ve used the methods I use, to control a young plant, to this point then the plant should be in the ‘balanced zone’.  However, it is at this point when caution should be taken not to allow the EC to rise too high and cause unwanted problems.  Sometimes the reaction, to a surprise, is to make a large change and rapidly drop the EC on and off and decrease your intervals between irrigations.

If you drop the EC on and off too quickly you run the risk of a vegetative pulse (as I liken it to) where in several days, plants turn vegetative and all the good work could be mitigated.  I suppose it is about holding your nerve and growing day by day for another week or two.  The older the plant becomes the easier it will be and you can relax, but only a little bit.

Coco fibre is not stone-wool and I would not run EC levels as high in coco fibre substrates as I would in stone-wool.  Just as I would not run EC as high in pumice as I would coco.  I am very mindful I do not want to totally restrict root growth but want to encourage good even distribution amongst the coco without having excessive amounts of water roots at the bottom of the bag/slab.  There is an optimum range I like to see plants grow within and when they exceed that range corrective action should be taken. 

Coco fibre substrates are used by many growers in New Zealand.  As a grower my preference was to grow in stone-wool, I previously worked alongside a stone-wool supplier.  However, as a consultant I deal with growers using coco, stone-wool, sawdust, pumice, NFT and DFT substrates and systems.  I am very familiar with coco as I have used it in the past.  It certainly has advantages for certain products and growers which always need to be considered.  Growers want the best possible return out of whatever they choose to grow in, and it’s my role, as their consultant, to help them achieve this. 

Coco is popular with strawberry growers as it allows for easy penetration of root systems.  The nature of coco allows for vegetative plant development in the initial growth phase, which is desired. 

I appreciate your comments.  Please feel free to comment below or on the grower2grower Facebook page:

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Article Written by Stefan Vogrincic, Consultant, Grower2Grower

Article Edited by Marie Vogrincic, Editor, Grower2Grower

A few tips

I recently visited a customer on the day of planting.  It is the height of summer, temperatures may be reaching up to and over thirty degrees in empty greenhouses during the heat of the day.  With young plants arriving from a nursery they are already mildly stressed, from being picked up and packed onto trolleys.  What they don’t need is any unnecessary additional stress when being planted in such warm conditions. 

The grower I visited uses coco fibre as their media.  What I noticed on arrival was the dry 2-3 cm on top of the coco fibre bags.  The plants had been hydrated over the two days previous to delivery.  However, because of the warm weather the top 2-3 cm of the coco was bone dry.  The spikes could not be laid flat on top of the coco, as they would literally just fall out once the irrigation starts and under pressure, so they have to be spiked into the coco.  NOTE: I would be hesitant hydrating the substrate for too many days before delivery as the bag will become very warm which is counterproductive and potentially cause Pythium issues after planting.

The plants delivered were grown in stone-wool cubes.  They were irrigated the previous afternoon, before delivery, but would’ve dried down overnight to be possibly at 60% water holding capacity.  The issue with planting stone-wool cubes directly on top of the bone dry top 2-3cm of coco will have an effect where the coco literally, like a sponge, sucks the moisture from the cube faster than you can have a cup of coffee. 

There are a few options.   You could manually, with a hose and sprinkler attachment, wet the top of the coco individually, which is both time consuming and unpractical, or you can make sure that as soon as the first plants arrive and are placed onto the substrate that the irrigation starts gifting small shots often.   Preventing the stone-wool block from drying down below 30% of its volume in moisture holding capacity is very important.  Any lower and you are possibly starting to damage roots, which will then lead to potential issues from Pythium.  You will get a lot of runoff but it is really about protecting your plant during a stressful time.  I suggest, in this case, the grower irrigates quite a lot for the first two days after delivery.   For our overseas readers New Zealand and Australia, during January, is smack bang in the middle of summer.  It is hot and very harsh on young plants.  Tomatoes are less forgiving than cucumbers, with cucumbers it is even harder for growers. This is why, at this time of the year, if a cucumber grower can not finish planting his greenhouse by 10am, he should stop planting and come back late in the afternoon to finish. 

Some tomato and cucumber growers have shade/energy screens. These are fantastic for the day of planting to help reduce stress to the plant.  However, I would be cautious and only use the screens for the day of planting.   The plants should be settled and the roots penetrating into the substrate within 24-48 hours. 

The photo above shows the dry layer of coco.  It is not an issue if you know how to deal with it.

I appreciate your comments.  Please feel free to comment below or on the grower2grower Facebook page:

https://www.facebook.com/StefanGrower2grower/

Article Written by Stefan Vogrincic, Consultant, Grower2Grower