Tomato Foliage turning yellow

I'd say if there in a raised bed that maybe watering twice a day might be a bit much for them I only water once at night and only if ifs been quite hot if not then once every other day ..before watering stick your finger down in to the soil and just check how moist the soil is deeper down to see if they need watering ..how old is the compost you have in the bed it looks pretty fresh filled to I would assume that wouldn't be the cause unless it's quite old

As Germinater said, I think you're watering too much. What are your raised beds on (concrete, grass, or what). Which brand of compost did you use? If you water too much you will wash all the nutrients out of the compost.

I agree with Rustylady and Germinator.

The green colour in leaves is chlorophyll which comes from the process of photosynthesis which needs sunlight falling on healthy leaves that have the correct nutrients in them.

When either nutrients or sunlight is lacking the plant will take the chlorophyll (green colour) from older leaves that have finished growing and pass it up the plant to the new growth that is unable to make its own chlorophyll.

Assuming the plants are in a sunny place then it must be lack of nutrients that is the cause.

I suggest a feed of a high nitrogen feed and reduce your watering.



Also, there seems to be a chain-link fence behind and I wonder how much wind the tomatoes are getting ?

And lastly, I can't see any stakes or support on the plants - they will need some soon.




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Thanks everybody for taking the time to help me out.
Rusty lady - The compost is a mix of free stuff from the local council ("Croypost" - from Croydon) mixed with an organic compost from a local garden centre (Thatchams Organic) - about 50/50
The raised beds are wood, with a coating of "Ducksback" fence preserver. The "floor" is made of two planks so there's a narrow gap along its length for drainage.
Teakdest - The chicken wire you can see is on an adjacent raised bed. I put that in between two stakes screwed into the bed ends just as an experiment to see if I could use it for support for the plants in place of stakes. Its working a treat for my broad beans.
So its a feed/overwatering issue then. I was thinking a magnesium deficiency but if I understand you all correctly, something like a liquid tomato feed will do the trick, rather than Epsom Salts?
I planted out the seedlings last month when the weather was really unseasonally hot, so I started an extra watering regime and its carried on way past when it is necessary as a habit. I'll reduce to evenings only.
How often should I feed to get the plants back to health do you think? Normally once a week when the fruit has set, but should I perhaps double the frequency to fix this problem, or perhaps double the concentration of the tomato feed and do it weekly?

Ricardo, you shouldn't need to feed until the first truss is set. However, your compost looks a bit "iffy", and if most of it is free council stuff then I believe this is normally classed as soil conditioner and may be short of nutrients. Your plants also look to be very close together, and this may cause problems later on re overcrowding, lack of air circulation. I would give your beds a liquid feed for now, reduce your watering (check whether they actually need watering, not do it on a schedule) and see how they get on.

Rustylady

Can you describe 'liquid feed' further, obviously it is liquid but what should it contain? Is it as Teakdesk says a high-nitrogen feed? Any examples?

Thanks

High nitrogen feed Miracle Grow or an organic equivalent.

Colin

Tomorite or comfrey tea for tomatoes- high potash not nitrogen.

High potash only after the first truss has set fruit.


Colin