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Belgium Europe

http://community.webshots.com/myphotos?action=viewAllPhotos&albumID=553364467&security=IGCBWQ
This is how some leaves of two of my plants look.Any idea about the diagnosis?
Thanks
Jos

8/21/2006 2:17:36 PM

Ctpumpkin@optonline.net

This doesn't look fungal but perhaps Belgium has foliar disease that I am not familiar with? I't not too different from Angular Leaf Spot though it seems this would be very late in the year for ALS.

If there aren't any insects or mites causing that necrosis then we need to look at other causes.

Fertilizer deficiencies rarely cause such distinct necrosis.

Have any soluble fertilizers been applied as a foliar treatment in the past 2 weeks? High salts can lead to damage such as this. Where does the irrigation water come from?

8/21/2006 5:01:15 PM

Belgium Europe

Thanks Steve...
I think i have to search in the high salts thing... As i grow in polytunnel,this could be the problem.
I irrigate with rainwater from the roofs .
No foliar feed in the last tree weeks. 13-13-35 soluble once a week in irrigation water.
Irrigation is the same as in the other tunnel, and there i have no problems, and beautifull green leaves, though those two plants there are two weeks older.
Maybe i can let a few thousands of liters of water flow in the tunnel ,to get the salts out of the soil?

8/21/2006 5:22:00 PM

Ctpumpkin@optonline.net

Ahhhh....The tunnel. How is it vented? I have seen leaf tissue damage caused by trapped gasses. Is there any fresh manure in the soil that could be releasing ammonia?

A soluble salts test would be a good idea I think.

8/21/2006 10:33:35 PM

ENGLAND

Jos. I know this may not be of any 'precice' help but i had problems with amonia gas in my polly tunnel when my Buckwheat was at a young growth stage. I then left both doors open 24/7 and within a week the Buckwheat was growing as normal. The manure in the soil was only 3/4 rotted but still 'green' enough to cause a real bad amonia gas problem.

Regards
Mike

8/22/2006 8:11:01 AM

Belgium Europe

Thanks for the imput guys.The problems began a week or two ago,as temps started to drop here in western europe, and i kept the greenhous more closed.In july it was open day and night, so i think the ammonia diagnosis is the right one. I alleady started to ventilate more today.
Anything else i should do to help the plants to recover ?

8/22/2006 1:49:45 PM

ENGLAND

Jos. I don't know what aditional info Steve will bring to this but i think if you just keep the polly tunell well ventilated and see if the plants recover somewhat. Salts issues with us Polly Tunnel owners is something we have to live with in a way but regular irrigation should help keep salts from building up too much. That is why Organic methods used in Polly Tunnels are favourable if at all possible.

Regards
Mike

8/22/2006 3:49:03 PM

Ctpumpkin@optonline.net

There are some Nitrogen inhibitors like Dicyandiamide (N-Serve is one of these I believe) that will stop the release of ammonia by reducing soil bacteria. While this would solve the problem, it does so by causing a new problem (reduced bacteria). Though bacteria do recover I really am not a big fan of nitrogen inhibitors plus they're hard to locate.

Recent research is finding many benefits from the use of Nitrogen Inhibitors however. Protecting the greenhouse atmosphere from Ammonia & Nitrous Oxide as well as Nitrate leaching into ground water is no small matter.

See this link if interested:

http://www.stabilizednitrogen.com/UMAXXResearchSummary.pdf

I'd rather see a creative fan & vent system. Sort of an air handler that would permit moderately warmed air to be exchanged at a controlled rate to get the ammonia out of the tunnel without chilling the plants.

Next year you might try to find an aged manure source or maybe start aging it on-site. Two year old manure should be OK even in a tunnel especially if it's applied in moderation.

8/23/2006 2:05:35 AM