The fertilizer in the bag isn't going to last 9 months. It's just controlled release fertilizer that at 70F will release nutrients for 9 months. Warmer temps and it releases faster.

Anyway, tomatos use NPK in roughly a 3:1:3 ratio meaning they use nitrogen and potassium in equal amounts. They use much less phosphorus by comparison.

As long as your nutrient supply doesn't have more N than K you should be fine at all stages of growth. The ratio that tomatos use N and K in doesn't change during it's lifecycle.

"I've read to cut back on the Nitrogen now that the plants are setting fruit." [gailo]

Where in the world did you read that?

I've read the same thing about Nitrogen, although I can't remember what book it was, other than it was geared to the UK where I lived at the time. It said to lower nitrogen, raise potash.

I just looked up the tomato fertilizer I used there and it is 4:2:8. Not saying it is wrong or right just that it has been said.

I'm not arguing about the phosphorus and potassium percentages being higher than the nitrogen percentage ... that's a given for tomatoes, in my opinion.

What I want to know is who the heck advised to "cut back on the nitrogen" when the plants are setting fruit? That's not standard advice.

Tomato plants should be fertilized when they first set fruit and most agricultural extension services will actually recommend using nitrogen at this time. Many recommend 10-10-10 or similar. I just happen to prefer 9-12-12 or 10-15-15 for side dressing at first fruit set.

Bill

In reference to the Nitrogen question - I have seen many references to Nitrogen promoting foliage growth, and that if given TOO MUCH Nitrogen at the expense of Phosphorus and Potassium, it can result in less fruit production.

http://www.tomatogardeningguru.com/care-feeding.html

"Avoid high nitrogen when your tomato plants have blossoms as it promotes vine growth rather than fruit growth"

Fish Emulsion typically is 5-2-2. Miracle Grow Tomato Plant Food is 18-18-21. The new Tomato-Tone formulation is 4-7-10. That was the root of my question - whether it is better to use the latter product once fruit production begins to encourage more fruit growth than additional foliage growth.

However, it does seem like there are many different opinions on this topic - and that people have good success with many different fertilizing regimes.

Thanks!

Tomatos use NPK in a 3:1:3 ratio during all phases of growth.

This doesn't mean we need to precisely match this ratio with the fertilizer we use. Matching it does make life easier, but a little less K than optimal such as a 1:1:1 ratio (10-10-10) will just see the tomato taking what it needs and leaving the rest which is why there are a variety of approaches that yield good results.

The only serious problem is when nutrients are presented either in excess or they are deficient. Using a fertilizer in a 3:1:2 ratio isn't going to stop tomatos from yielding well even though it is slightly N heavy and K light compared to what they need, but presenting it in a 6:1:2 ratio likely will have an adverse effect.

A balanced fertilizer (one where the numbers are all the same or close to each other) is fairly safe for most plants.

Still, knowing what the plants actually are using when they are doing well is helpful in fine tuning.

Two things come into play on fertigation. Are you growing in containers or soil and are you using mycorrhizae/beneficial bacteria. The new Tomato-tone is actually 3-4-6 which comes with beneficial bacteria and anytime you are using a product with BF or mycorrhizae you need to keep the Phosphorous (P) no higher than 4 or you make the bacteria ineffective.
I using a 8-2-6 from Bio-Bizz for my containers and I use mycorrhizae.
Here's a link to the Arbico site's organic ferts section. Take a look and see if you find anything interesting and note the N-P-K of the different products.
If it ain't broke don't fix it and from the description of your plants you must be doing it right. Ami

Here is a link that might be useful: Arbico

I've been reading a ton on tomato fertilization. One thing that sort of confuses me is that I inherited two different packages of tomato fertilizer, and they are 4-6-8 and 2-3-4. I'm certainly not attached to this fertilizer so I don't mind getting something more appropriate. But why do manufacturers make a fertilizer for tomatoes that doesn't use the optimal ratio?

In any event, I'm leaning towards MG water soluable 18-18-24 and mixing for weekly/weak waterings.

One thing that sort of confuses me is that I inherited two different packages of tomato fertilizer, and they are 4-6-8 and 2-3-4.

Those 2 are the same ratio. They have different percentages, but are the same ratio. They are both a 2:3:4 ratio, but the 4-6-8 formulation has twice the amount of nutrients in the package.

It would take twice as much of the 2-3-4 to provide the same amount of nutrients as the 4-6-8.

Yes, I realize that. I'm just a bit confused as to why they sell that ratio as tomato food when it sounds like the 3-1-3 ratio would be more appropriate.

Because fertilizer companies are not in the market to educate people as to what nutrition best serves their plants. They are in the market to give people what they think they need/want and make money.

The 2:3:4 ratio isn't going to harm the plant and it will grow just fine. A little more N would be helpful, and less P would be good as it isn't needed in that amount. The K is fine.

If you haven't already seen it, click here to read the CEO of Dyna-Gro answer my question as to why they make a high P fertilizer when there isn't a plant on earth that needs them.

It's all about giving people what they think they need instead of what they do need. It costs too much to go against the tide and try to educate people.

Gailo,

I had my plants in a similar potting mix last year. At first I didn't feed them at all. After a month or so, when the weather warmed, I added in a weekly dose of fish emulsion. They seemed to like it but they were much more productive when I alternated that with a liquid flowering/fruiting fertilzer from the hydro store. It had a lower N, higher P ratio and some additional minerals, although I'm sure the fish emulsion must be mineral rich, as well.

I like liquid fertilizers for container plants precisely because they make it easy to feed them more often with weak solutions. I think this keeps them from going through a feast or famine nutrient cycle.

I also spray them lightly once a week with a diluted tea made of kelp/molasses/eggshells and a ground up potassium pill. They seem to like it. They are green, green, green!

jan

Jan,

The likely reason your container tomatos responded to the hydroponic fertilizer better than they did the fish emulsion is not because of the nutrient ratio, but because one is water soluble and the other is not.

Fish emulsion is commonly believed to be water soluble because it is mixed with water. The fish stuff isn't actually soluble, instead it simply suspends in the water. A hydro fert is water soluble (so is Miracle Grow powder).

What happens with the fish fert is the organic pieces suspend in the water and are added to the container. Initially there are zero nutrients available to the plant because they are stuck inside the organic particles. It takes living organisms digesting those particles and 'pooping' them out for nutrients to become available to the plants. By the time this process occurs much of it has likely been flushed out of the container via repeated waterings.

With a genuinely water soluble fertilizer the nutrients are immediately available to the plants.

In other words by alternating between the two your plants likely went from getting slightly too little to getting adequate to luxury levels of nutrients.

Thank you, justaguy. Now that you put it that way: Duh!

Yes, the difference was noticeable very quickly, as the
kind of results every "hovering mother" gardener hopes for. I dosed them often, saying, "Eat, eat, my darlings!"

I concocted another a new recipe for them tonight...a slug of milk mixed with half strength Schultz Plus indoor plant food, another fertilizer I have come to appreciate after last winter's harvest.

jan

Resurrecting the thread...

JaG, why do you say tomatos use NPK in roughly a 3:1:3 ratio? I understand your reasoning: based on tissue sampling you come to this conclusion.

I did the calculations myself based on the tissue samples in this report: http://edis.ifas.ufl.edu/ep081
(Plant Tissue Analysis and Interpretation for Vegetable Crops in Florida)

But I see a 4:1:5 ratio in tomatoes. What am I missing?

Thanks,
Life

Here is a link that might be useful: Plant Tissue Analysis and Interpretation for Vegetable Crops in Florida