Not possible to diagnose a potential problem from a portion of one leaf. Could be short of nitrogen.

Please post an image of the plant.

This post was edited by jean001a on Sun, Dec 15, 13 at 0:27

Lower leaves often turn yellow, because of shade. And eventually may die. I would clip them off.
But if your whole plant looks like that leave then there are several possibilities.
Yellowing, pale green often indicates shortage of nitrogen. Overwatering can also do that (by leaching the nutrients) . Shade is another cause for yellowing.

Your picture looks like Nitrogen Deficiency. Normally as the plants grows it channels most of the nitrogen to the top of the plant to support growth and less is available for the bottom leaves thus the leaves are deficient in nitrogen and turn yellow. See if you can get some Calcium Nitrate from a hydroponics shop and apply to the plant as a soil drench (1-2 tablespoons per gallon of water) and also as a foliar to the leaves which will make it available to the plant more quickly.

Hi, thanks for the replies so far, i have attached a picture of one of the plants....orange cherry.

I think its unlikely to be nitrogen, i've added plenty of composted manure plus some rabbit poo, and i also provide a liquid fertiliser (weak) every couple of weeks.

My initial thoughts were that as the soil is alkaline then perhaps some of the micro nutrients (magnesium, iron etc) may be locked u and not available to the plant.

Any ideas?

another picture.....

try empsom salt

Now that I see the full picture I agree it is not a Nitrogen deficiency. The pH figures you have will not lock up Magnesium. Iron, Manganese, Boron and Copper/Zinc are the only elements affected by alkaline conditions in your range. I think a soil test is in order to nail the problem down.

If you have Molasses down under mix some with water and apply as a soil drench and you can apply as a foliar.

dickiefickle:

i've seen images of magnesium deficient leaves and they do have some similarities to mine, i will look into this.

miesenbacher:

a soil test is logical but I've been quoted $220 ($US200) by a local soil lab, which is not within my budget. Yes we have molasses, seen it at home brew stores.

thanks for your replies!

If you are using a fertilizer formulated for Tomatoes and peppers, It already has magnesium in it. READ THE LABEL>
If not, put one Tspn of epsom salt in 2 gallons of water and water your plants with it. Or simply get some tomato fertilizer.