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General discussion regarding the techniques and methods used to successfully grow tomato plants in containers.

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Old May 17, 2017   #16
Join Date: Jun 2013
Location: Wasilla Alaska
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Originally Posted by RayR View Post
50°F or so? Don't you use heat mats or something to keep the soil temperature up? Soil temperature is what matters.
Pythium and other common damping off pathogens are not bacteria, they are not even fungus, they are Oomycetes (water molds). They don't care what kind of nutrients you use or what kind of medium you use. Pythium is the scourge of hydroponics water culture too with no organics. It's true that
Pythium may do better in anaerobic conditions which is one reason why over watering should be avoided Temperature has little to do with whether there are aerobic or anaerobic conditions, it's the level of oxygen in the soil. Yes beneficial bacteria are more active in warm soils but they don't shut down and go dormant unless the soil temperatures are really cold.
Spores can come from anywhere, your water source, on your shoes from walking outside, dirty tools or containers, previously infected dead roots laying around, even through the air. Their spores (called zoospores) germinate in water in the presence of plant roots, they are not immobile like fungal spores, they have flagella similar to what some bacteria have which allows them to swim to plant roots. That's where they infect inside the root, feed, grow and reproduce. They don't eat your fertilizer, whatever that may be.
I've only had damping off once some years ago in a so-called sterile mix. How the spores got there, I have no idea. Haven't had it since I followed the following program. I think your best bets since it is a persistent problem for you is to keep the environment clean and disinfected as possible, avoid bringing in any possible outdoor sources of spores and then inoculate at first with the seed beneficial rhizobacteria and fungi (trichoderma and mycorrhizal fungi) to give the growing roots a defensive shield against those pathogens. Reinforce the microherd with more inoculations maybe in 2 week intervals.

The pro mix rep was over last week and said they are seeing great results when plants are started in the Pro- Mix bio fungicide mix that they sell. Pythium was mentioned rhizo, and others. After the seedlings are started in it, it works as a systemic for the plants life. That is all I can say on it. I am going to try it though.

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Old May 17, 2017   #17
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Join Date: Jun 2010
Location: Cheektowaga, NY
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Originally Posted by Walt B. View Post
I checked the PH before I planted and it was 7ish....but that was with one of those cheap PH testers so who knows how accurate that reading is. I did inoculate the roots with mycorrhizal fungi on planting out. It certainly has been brisk at night the last week or so (mid 40's) that could certainly be a factor. But considering the tomatoes in the other box (cherry tomatoes) and the ones planted in the ground don't seem to be affected I'm not so sure.

There are quite a few tomatoes on the plants already......some golf ball sized already. I do worry about overwatering......and I'm not refilling the reservoir as fast as I did last year allowing things to dry out a bit, but by design you shouldn't be able to overwater these SIPs as the wicking properties are more dependent on the amount of soil media that is in contact with the reservoir (between the landscape piping) and not the amount of water in the reservoir.
I not sure what kind of PH meter you have, hopefully not one of those with the steel probes that you stick in the soil.
I didn't think that temperature had anything to do with it since the visual symptom only occurred with the plant in the SIP.
I've not done a SIP with Raybo's mix but I messed around a lot with custom mixes composed of various inorganic and organic dry components and I can tell you what PH you start with can be vastly different from what you end up with weeks later. It's not something to be taken lightly, it's something you
monitor over time. Manufacturers of commercial potting soils know PH changes over time and have to formulate their mix so that they know about what the gardener's plants are going to live with through their life. As an example, they know if their starting PH is 5.5 to 6.0, weeks later it will end up in a range of 6.5-7.0 in most situations.
The various components that you use are not totally inert, everything has partially soluble chemicals attached to it and these chemicals will react in various ways when water is added. So you have a chemical soup brewing in the soil water over a period of weeks that will ultimately reach a PH equilibrium. Adding dolomite lime itself does not change PH immediately to offset acids, the lime is insoluble carbonates that react with acids over time to raise PH. Too much lime can cause PH to raise into the stratosphere, not enough and PH can end up too low. PH of the soil water will drift one way or the other until it stays somewhat stable.
Besides all that what the gardener adds as a water source can add to the PH issue so it's good to know if you are using tap water what the water PH is. Some city water has excessive amounts of dissolved bicarbonates, and very fast acting at raising PH. Fertilizers can also add to PH change at least temporarily depending on what is used.
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