There was a recent discussion about this exact topic really recently, so I thought I would post a link to that thread.

http://forums.gardenweb.com/forums/load/tomato/msg061515192280.html?10

Thanks GTNate...but that thread dealt mostly with kelp/fish emulsion and didn't completely answer my questions. Specifically, is foliar feeding actually beneficial and when is the best time to do it, particularly after fruit is already set. I guess I also wanted to know the benefits of kelp/fish emulsion vs. compost tea. But I do appreciate the link.
Best,
Don

"Right now my plants are doing great." Why mess with
success? I generally consider foliar feeding as a
quick fix for troubled plants. Though I admit to
making sure my fertilizer (Miracle-gro for Tomatoes)
is washed over the leaves! Figure it can't hurt.

As long as things are going fine for you, I wouldn't
make any changes in what you're doing.

I got off track a few years back, trying to do things
differently hoping for improvement. Alas, it had
the opposite effect. I've now gone back to my tried
and true routine.

Agree with qaguy if its working good leave it alone

I have never tried foliar feeding, but it seems to me that if you spray a water soluble fertilizer on the leaves, the vast majority (>95%) would run off the leaves and fall to the ground, where it would feed the roots. So is the perceived benefit of foliar feeding from leaf absorption of nutrients, or the rapid absorption of water soluble nutrients by the roots? Has anyone shown that tomato leaves are capable of directly absorbing water? I thought they had a waxy coating to protect from sunburn.

TomNJ

It has been scientifically proven that their is a benefit to foliar feeding - in that plants can absorb nutrients through their leaves. Please note that it has to be done in a certain temperature / humidity range and at a certain time of day to be most effective.

Sure, some of the fertilizer solution which is sprayed onto the leaves falls to the ground and goes into the roots, but that is not where the perceived benefit is coming from entirely. To what qaguy said, I typically only do it at a time when the plants look like could use a quick boost or are clearly deficient in some way, which is not often.

A time I like to do it is if I feel that the plants need additional nutrients, but we've had a ton of rain. If the soil is already saturated, pouring more water / fertilizer into it doesn't seem optimal - so foliar feeding delivers nutrients, but doesn't soak the soil more than it already is that point. This is a rare case obviously, but worth noting.

Foliar feeding, as far I as see it, it just for a boost and while a decent supplement, shouldn't be used as a primary method for delivering nutrients. As you noted above, it can be damaging if done at the wrong time or at the wrong fertilizer strength - so if you want to try it, make sure you using a very dilute mixture (I do 1/4 strength max) and generally early (sometime time shortly after sun-up) in the morning while temps are in the 65-75 degree range.

Agree with homegardenpa. I am a firm believer in the benefits of foliar feeding IF it is done correctly and at the proper times. I have used the method with diluted compost tea and other nutrient supplements for decades.

It is the "IF done correctly and at the proper times" part that causes the problems for most people - since they don't.

Dave

Great info... I'm going to hold off on the foliar feeding for the time being and maybe wait a bit til the plants look like they can use a boost. But if the plants are already bearing fruit, does feeding them with a nitrogen rich fertilizer like compost or kelp/fish emulsion affect their production? I know that nitrogen is great for plant growth but too much can inhibit fruit production. But what if its already producing fruit?

"A time I like to do it is if I feel that the plants need additional nutrients, but we've had a ton of rain. If the soil is already saturated, pouring more water / fertilizer into it doesn't seem optimal - so foliar feeding delivers nutrients, but doesn't soak the soil more than it already is that point."

This is exactly the situation I'm in! Dave suggested a foliar feed and I just did a search and found this recent thread.

My soil is Medium in P and K and was Very Low in N, I did try amending with UCG, shredded leaves, decomposed bark mulch, mixed with original soil (pH 4.4) and darker screened topsoil (analysis unknown), watered with grass clipping tea after 3 days of no rain, topped each plant with 3 handfuls of finished compost (about 13 gal for 62 plants) but that was all I had.

Some plants have fruit, some are just getting flowers, and some aren't doing much at all. Started seed March 25 (for most, about a dozen were started a month earlier), but just got them into the ground b/t 6/15 - 6/20 b/c of all the rain. We're already an inch over average this month and more rain expected. 3"+ over the past week.

I have some Colorburst packets meant to be added 1 per gallon (I was thinking try 1 per 5 gal), 24-8-16. Would this be something to try as foliar spray or root drench as Dave suggested, or is there something else?

BTW, can someone explain "root drench" since I don't know how this is different from regular watering? Might not be the best thing since ground is pretty saturated right now, but I could try it Wed if Tuesday's storm isn't a big one. We're supposed to see the sun Sunday and Monday.

Thanks

To my understanding, if you can feed your plants via root system, there shouldn't be a need for foliar feeding. But sometimes the soil chemistry (pH and amounts of certain elements) is such that the plants might not be able to uptake certain elements. In this case foliar feeding acts like a bypass surgery system. Or it can accelerate the uptake, as in foliar feeding with Epson Salt. I personally do not believe in foliar feeding NPK as a routine practice. Though I have nothing against doing it .

I am firm believer in foliar feeds. There are very distinct advantages to using foliar feeds, however it is not stand along program nor it is suppose to substitute what is missing in the soil. There is more and more research and field experience about great results foliar feed can have. As Dave mentions, one should rather know what and how to apply.

Here is a link that might be useful: foliar sprays

This year I have started using many things differently and have to say it is very enjoyable ride so far. I would hesitate to separate which one of new things I am using works the best but I distinctly see how EM helps plant to faster repair damage from insects for example. I also have started using Amaze and Texas Tomato Food, Amaze is foliar application with some interesting Ca properties. I use TTF as a soil drench though.
Now if you use Actinovate, for damping off problem you need to use soil drench but for early blight and septoria i.e. fungal leaf problem it is specific foliar application. I add molasses to it as well as Exel LG for improving systemic immune response.

Here is a link that might be useful: Effective microorganisms

Had no idea what Colorburst was as it isn't something normally associated with growing tomatoes so had to look it up.

It is a flower fertilizer and 15-30-15 could easily damage plants if used as a foliar spray. If you want to use it then use it as a root drench as it is intended as it is not at all something I would recommend using as a foliar application. It is a good example of how one can do much more harm than good when using non-floiar products inappropriately.

Especially where soil is already adequate in P and K. It would be a waste of money at least. When all you need is nitrogen then just use nitrogen. Any of the fish or fish/kelp blends make excellent foliar applications.

If your plants were just planted in the past 6-10 days then they haven't even had time to adjust to transplanting much less time to respond to all the other supplements you have already added.

Dave

I personally like to foliage feed once the plants have been established. However, I also foliage feed seedling we start in the cold frame with a diluted very low number kelp solution concentrate, it helps with the development and weather distress if you will.
This AM 6 weeks after the seedlings were transplanted to the garden : (winter squash , tomatoes , potatoes plants and sweet potatoes plants these were foliage fed- as there has been rain and humidity so the foliage feeding was done early in the AM 8 :00 allowing time for absorption. I would agree that the ratio of solution and the time window is very important - We practice organic methods for our gardening

I personally like to foliage feed once the plants have been established. However, I also foliage feed seedling we start in the cold frame with a diluted very low number kelp solution concentrate, it helps with the development and weather distress if you will.
This AM 6 weeks after the seedlings were transplanted to the garden : (winter squash , tomatoes , potatoes plants and sweet potatoes plants these were foliage fed- as there has been rain and humidity so the foliage feeding was done early in the AM 8 :00 allowing time for absorption. I would agree that the ratio of solution and the time window is very important - We practice organic methods for our gardening