What could be the cause of BER considering the cercumstances listed below
 

Good day,


What could be the cause of blossom end rot, in my particular case?

I have the following system and conditions:

I live on the East Coast of South Africa.
Our summers are hot and humid. (Summer has stared here)
My hydroponics system is top feed and drain.
I have 4 varieties of indeterminate tomato plants.
My reservoir is 100l, placed in the ground.
My system is outdoors and exposed to the elements.
I use hydroton as a medium.
I feed my plant 8 times per day for 10min per feed.
My nutrients are the typical A + B nutrient from a commercial supplier.
I have lately been adding MPK.
My plants look healthy and grow vigoursly.
The plant types are, a big paste, hillbilly, giant Belgium and carbon.
I have been feeding quite aggressively.
While feed the plant I check the EC in the nutrient tank and the EC as the system drains. I adjust the EC’s to bring these values close to one another. This is in the region of EC 3.
I check my ph regularly and adjust it between 5.6-6.3
The plants are not shaded.
I have started adding a cup of diluted (1ml / l of water fulvic and humic acid twice a week after the last feed, per plant
Two of the four types are more prone to BER i.e. the paste and the carbon.
The plants are well supported and strung.

I have read up a little on BER, but I am not sure what is causing the BER.
I have upped my B nutrient a little (B has the calcium).

I am keen to hear your input.

Many thanks.........:confused:

Just off the top of my head the heat and "humidity" are a concern especially if they are not heat tolerant variety's. But I'm mostly wondering about the watering schedule. If the roots are drying and then getting moisture repeatedly, that would basically be water stress (a major cause of blossom end rot).

But here are a few links to some info,
Tomato Disease*Identification*Key-Fruit
Blossom End Rot Fact sheet (the blossom ens rot page)

Blossom End Rot - Ripe Fruit Disorders - Tomato Problem Solver | Aggie Horticulture
"blossom end rot is a physiological disorder caused by calcium deficiency induced by water stress"

Tomato Plant Problems FAQ by Kay Klier
"Generally caused by a combination of drought and drown water availability" (water stress)

Blossom-End Rot of Tomato, Pepper, and Eggplant, HYG-3117-96
(they are talking about plants in soil, but the causes are still the same, not the Management part)

Hydroponics:Greenhouse Tomato Culture
"Calcium deficiency as a result of too little calcium, too much potassium and magnesium and possibly ammonium nitrogen in relation to calcium or lack of aeration in growth medium."

Blossom-end Rot in Tomatoes
"You can also reduce blossom-end rot by spraying with a calcium chloride solution. Brand names include: Tomato Saver and Blossom-end Rot Preventer. Follow the label direction. Ideally, you should start spraying when the first green tomatoes are about the size of a silver dollar. Spray once a week for three to four weeks."

Tomato Diseases: Blossom End Rot
What's Wrong with My Tomato Plants

You can have plenty of calcium in the nutrient solution, but as the plant grows it's continually needing water and minerals to grow. As it does this and the plant cells are being formed, periods of low water supply from the roots can result in in inadequate supply of calcium to those forming cells. Because calcium is a immobile element in the plant tissue, once the damage has been done it cant be undone (even if the water supply resumes). Resulting in those cells that got inadequate supply's of calcium to break down prematurely. You can try using a foliar spray of calcium on the plants, but I would still try to make the watering more even.