I have no idea what Auburn University recommends but let's keep in mind that it is just one opinion on what tomatoes may or may not need out of hundreds of opinions out there. 13-0-13 would meet with much disagreement from some of them.

Given that there are so many good, well balanced tomato fertilizers on the market and given that such a small amount is needed in container-type set ups, why go to the trouble and expense? But if you wish, I know of no reason why greensand would cause a problem unless you use too much.

Dave

Here is a link that might be useful: Fertilizing tomatoes discussions

Dave - would the end result of the mixture not be 6.5-.5-9.5?

EG

Techincally if you add the numbers and divide by 2, that's the NPK rating.

However it appears you are mixing a synthetic with a natural material and one thing you may wish to consider is the rate at which nutrients are released. I simply am not all that familiar with greensand so won't say what it's release rate is, but most synthetic ferts are coated to release over a period of time. Generally it's a couple months or so. If the greensand releases over a longer period then the actual ratio of nutrients the plants are getting won't be the same as the NPK ratio suggests.

FWIW I agree with your source that a lower P ratio is appropriate for tomatos (and any other container grown plant).

Jag - thanks for responding. I'll have to do some more research on the release rate of the greensand. A lower percentage of P is what I'm aiming for, because I was taught that tomatoes need almost no P.
According to what I was taught by a professor of horticulture at Auburn, no fertilizer on the market is actually ideal for tomatoes. That's why i'm wanting to create my own.

EG

Hey EG,

Keep us posted on your findings. I have totally given up on the "New" Tomato-tone after they changed the formula last year.

{{gwi:16931}}

I still have a few years supply of the "Old" Tomato-tone which really works well in the 'Tainers - - but when that runs out, I will need to find a new formulation.

Our friend Ami sent me a box of Tomaten Dunger from Germany, and it worked extremely well this past season in the 'Tainer. Wish I could find it here in the States.

{{gwi:45889}}

Perhaps the ingredients list will help you:

Raybo

I could be way off here, but don't you want to promote blossoms?

No blossoms, no fruit.

Cindy

When you look at the ingredients of those little bags and the costs, compare those with the ingredients in dog food, rabbit food, chicken feed and the cost/lbs per bag of cheap feed. Somebody is making a nice return with the "organic" label.

I could be way off here, but don't you want to promote blossoms?

We want to promote healthy plants which blossom as they should ;) The idea that elevated levels of phosphorus increase blooms is a solidly discredited myth that today exists only in the minds of consumers and fertilizer companies catering to their lack of understanding of plant nutrition.

This whole subject of lower P ratio is new to me and I've been a avid reader of this forum for over a year now. Any more elaborating you could do would be much appreciated.
Larry

Larry,

It may surprise you that no plant on earth needs or can use more P than it does N and K. Many 'all purpose' fertilizers are now using a 3:1:2 ratio of nutrients reflecting this. Miracle Grow for example offers a 24-8-16 all purpose fert which is a 3:1:2 ratio.

In the soil one might wish to use more P if the soil is deficient, but in many soils P levels are already excessive and no added P is needed. In Wisconsin it is now illegal to sell a fertilizer with P in it unless a soil test shows the need.

In containers, there is never a valid reason to supply more P than N or K. It is just wasted.

I have some correspondence from the CEO of Dyna Gro, a maker of fertilizer products on the topic of high P fertilizers you might find interesting.

Raybo - That german fertilizer is the closest thing I've seen to what my university suggests. Both old and new tomato tone are WAY off. The ideal fertilizer for tomatoes (according to Auburn University) is 9-3-17, or 3-1-6 for slower results. It's a shame you can't get more of that foreign stuff.

Jag - sorry for dragging you into another tomato fertilizer thread, but I stand behind your comments about exceesive P in fertilizers 100%.

EG

EG,

Yeah, the Tomaten Dunger did outstanding, and if you have seen pictures of Ami's container "farm" in Germany, then you know (one) of the reasons he has such outstanding results. He was even kind enough to contact the Neudorff Company to see if they are planning on exporting it to the States, but no luck, as of this moment.

My son owns a Hydroponics shop in Santa Fe and I will ask him for recommendations on tomato fertilization. I am sure he could come up with a blend that would be more akin to the Tomaten Dunger formulation.

Stay warm over there in NW Alabama tonight!! I understand it might snow near you, after what happened in Houston today.

Raybo

Raybo - it's 23 degrees here now, and I even had to bring the broccoli plants inside for the night.(I'm growing 3 plants in swc's that are 4 gallon)I found a good fertilizer a while back on the internet that was water soluble - and pretty much right on target. I can't remember the name of it now, though. I sure would like to try the 13-0-13 and greensand mixture in one 'tainer, but the closest vendor is about 55 miles away.

EG

Do you have any ammonium nitrate 34-0-0 out in the barn? Combine that with muriate of potash 0-0-60, sprinkle in a little triple super phosphate and you could get pretty close to Auburn's numbers. Couldn't you? Those items might be easier to find locally.

JIM

Next season I'm mixing 1/3 cup old Tomato Tone 4-7-10 with 1 & 1/2 cup Ringer Lawn Restore 10-2-6 plus 1/3 cup of Bonemeal a pinch of Boron and 1/2 cup of Dolomite lime, 1oz of Ironite.

George

Jim - yeah, they're available, but I would still need something to add to it to weaken the potency of the mixture. Hmm....Maybe growing medium?

George - I really feel that there will be alot of people coming up with their own formulation, because the storebought fertilizers just ain't cutting it.

EG

Jim - yeah, they're available, but I would still need something to add to it to weaken the potency of the mixture. Hmm....Maybe growing medium?

Did Auburn supply a recommended rate of application for the 9-3-17? Apply your mixture at 1/2 strength and that should be equivalent to 8.5-0-15. Yes? No? You'll have to do the 'cipherin' on the super phosphate numbers. I could see this working on say 'pounds per 100 feet of row' but I don't know about containers. Good Luck-

JIM

Jim - no they didn't. The info came from a slide that was shown during one of the Master Gardener classes on soil last year. When I saw it, I was like "I have seen the light!"

EG

I believe what people have said about excessive P not being useful.

HOWEVER, my understanding is that you do want to CUT the amount of nitrogen available to a plant that is blooming. In a container where you have total of nutrients (assuming you use synthetic) this is easy, you simply change the nitrogen ration so N is lower than P and K or whatever, and feed it the same amount of total P you were giving it before you cut the N.

So if I were to fertilize my plants with synthetic or organic fertilizer that has no N but equal measures of P and K, and add total amounts the same as what I had been using before I cut out the N, would that not be beneficial to the flowering plants? If my soil is fairly rich and has plenty of compost and other organic matter, will it probably receive the same of nitrogen anyway, regardless of whether or not I cut N from fertilizer?

plantslayer,

Yes, you need to bifurcate the discussion between organically rich dirt, from the relatively "sterile" Potting Mix used in Container gardening. Two totally different NPK requirements, in my view.

Raybo