From out of left field - Diatomaceous Earth and Tomatoes

14 years ago

Hi All -

Our tomato garden is right next to our pool heater/filter here in So. Cal. and I've noticed that compared to the neighbors tomatoes, ours always does extremely well both in foliage and fruit production. I add very little other than bone meal at planting time, and light Miracle Grow once a week when watering.

I'm wondering if this has anything to to with the pool guy cleaning the filter in winter (when the garden is empty) including washing out all the considerable used diatomaceous earth into the garden of which I turn over in the soil before planting. Btw, I've also been fortunate enough to have very little in the way of problems disease wise (possibly due to the additional calcium).

Any thoughts or have I just been lucky?

Good growin' to you -

Will and the Furry Ones in Orange County

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Comments (7)

organicislandfarmer
14 years ago
if its a below ground pool and the tomato plants are near the water heater outflow then you have the heat of the water warming the earth making it nicer for the tomato plants. I would think they would have to be really close though.
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Here is a link that might be useful: chico hot springs greenhouse
susan2010
14 years ago
Just as an aside, the DE that is used for pool filters is not meant for human consumption. I believe (but don't know) that it is chemically treated for use in pool filters. "Food grade" DE is sometimes used in the house and garden for pest control and is considered safe. I'm not sure I'd want the pool filter stuff dumped in my garden. But maybe I'm over-reacting.
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Insecticide usage of diatomaceous earth MUST be a fine dust so that it coats all insects with an exoskeleton and dries them up (kills them). However, if you mix it in your potting mix/soil or even dust once and then spray with water, you have pretty much removed any potential Insecticide use. Livestock caretakers must constantly be dusting as any moisture or even other dust that coats the DE will not allow it to stick to and dry out insects. So if you think you are protecting your potting mix/soil from any insects by mixing a dust DE product into your mix, you are throwing your money away (although it is certainly not harmful to anything, plant or insect). It is actually generally NOT used around farms anymore, it is too time consuming. It is still fed to animals because it is both a good calcium supplement and can actually rid several intestinal worms with prolonged usage. Food Grade (NOT feed grade) is great for people to eat also for those same reasons. The only real distinction of Food Grade is the levels of potentially unwanted metals (think lead). So if you are eating it directly or through a plant you should look for food grade, I believe there is only 1 mine in America that produces Food Grade DE with safe levels of the toxic metals. Others have pointed out the usage as a soil conditioner and so I won't, but I would say there is really no reason to mix in the fine pesticide powder as it is more expensive and won't provide any pesticide usage if mixed throughout. That being said it is not nearly a "broad spectrum" insecticide as even if you powder coated your entire lawn, the next day after a good dew it is mostly inert and will never be actively hurting insects again unless you re-dust daily. Some oil-absorbent material for garage cleanup is also the larger particle DE and cheaper than cat litter. Really, any oil-absorbing silica product for garage spill cleanup could likely do the same job as a soil conditioner, so shop around and see what people are using as a ratio, I honestly was looking for the same thing when I found this post. The big thing that may concern some is whether there are potentially unwanted metals in it, and the only sure way to know is if it is specially labeled "Food Grade". For me personally I would consider "Feed Grade" to be fine. Good luck trying to find oil-absorbent or cat litter labeled "Food Grade"! I thought I should comment, even though I am late to this party, because it is one of the top links in google and yahoo search.
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Thanks so much to everyone for the continued advice. The pyrethrum is a new one to me - if the DE doesn't work, I'll move on to that. I had considered the Sevin dust, in extremis - it's been mentioned several times as the Holy Hand Grenade of critter control in various threads. Honestly, one reason I hadn't gone there is that the label does not identify aphids among the five or six dozen insects that the dust controls, so I figured that the little buggers weren't affected by it. The other is my daughter, just turned three today. While I'm reasonably confident I can keep her out of the garden until the dusts and sprays settle, I'm still a bit reluctant to use anything too potent. I'm not losing my veggies just to stay organic, but I'm not risking exposing my daughter to something nasty just for veggies. Albaby
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LunarSolarPower - Thanks for coming back to my questions, I appreciate your responses. As I'm probably overthinking the CEC impact in my intended use (vegetables in containers), but I do like to optimize systems for efficiency and highest performance, so it was a natural question for me to follow. I'm under the impression that by using CRF and a liquid solution, I'm in a good position to provide what the plants need with little regard for the CEC. My question about the zeolite was to raise the CEC, and in fact, you mentioned in an earlier post about ground basalt, so if I decided to go that route, I could always look more closely there as well. As to getting 10 years out of the media - I can always dream, can't I? :) It appears inefficient (on the convenience and labor sides) to mix new media every spring. It seems wasteful to the product as well - I have limited ground space, and who knows what I would do with the "old" mix. There is always the cost aspect as well. My primary thought was to go fully inorganic and have nothing that decomposes within 5-10 years. But, even if I ended up going with some organics as a fraction of the mix, I'm thinking that if I maintained a reasonable particle size with the inorganics (say Turface/DE/pumice/grit), AND as long as the combo of inorganics comprised the lion's share of the mix (say ~70%), then the organics would be free to decompose and disintegrate their structures without much harm overall. I could simply "top off" the organics (for instance pine mini fines) as needed to keep the overall volume of media to my liking. If CEC value is not critical in my specific scenario (vegetables in containers, using CRF and liquid fertilizers), and assuming I'm able to relatively easily adjust the pH as needed, then I would be able to design the mix primarily on water/air retentiveness. Do you see any faults in the logic so far, or glaring oversights with such a plan?
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homegardenpa
14 years ago
Based on nothing other than observations I've made with pulling weeds where DE had been washed out before, I've noticed that the roots the grow in DE tend to be very large and numerous compared to those weeds I've pulled growing in regular soil.

I had read something a year or so ago that stated that when roots encounter sharp particles in their growing medium, they tend to branch more and DE is made up of very sharp particles (Diatoms) - especially the stuff used for pools. It's possible that the DE is helping to loosen the soil and, at the same time, help to form a more dense root system...

All of this is conjecture, of course.
elskunkito
14 years ago
Diatomaceous earth is an excellent soil additive.

They use that on high grade grass fields.
Very airy. very drainable, very good at holding moisture all at the same time.

I'm not s'prised your tomatoes are kicking butt over those neighbors of yours.

Using it as a filter is probably impregnating it with all sorts of goodness.
MTE417
13 years ago
I was told at Home Depot that DE for pool filters is the same as for gardens. After I applied it, I found out differently.
Is it harmful? What do I need to be aware of?
homegardenpa
13 years ago
From a site about DE:
"... Pool grade DE is Diatomaceous Earth produced for pool filters and it is treated with heat, causing the formerly amorphous silicon dioxide to assume crystalline form... Swimming pool DE ranges from 60% to 70% free silica..."

Basically, when they treat the DE for pool use, you now increase the crystalline silica content. If you Google crystalline silica, you will find there are some health risks, but all of them (that I could find) are related to breathing in the substance.

Crystalline silica is already a natural part of sand and most soils, so assuming the DE is mixed well with the soil, the odds of you breathing in free crystalline silica in significant quantities would seem to be minimal. When working with crystalline silica or products that may contain it, I would definitely wear protection for my eyes, skin and lungs, but if it's already integrated in your garden I would assume very little in the way of health impact.

I've included a link to OSHA's fact sheet about crystalline silica below.

Here is a link that might be useful: OSHA crystalline silica fact sheet
PrestonFarmer
13 years ago
I'm going to agree with elskunkito. Also, check out the linked article.

Here is a link that might be useful: article

From out of left field - Diatomaceous Earth and Tomatoes

Comments (7)

organicislandfarmer

susan2010

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