I watered with an oscillating lawn sprinkler when my tomato plants were tiny, and after a few weeks I found I would need to water quite frequently to maintain slight soil dampness. Thus I began watering at and around the base of each plant, and I have only needed to water twice at most (per week). This is notwithstanding the fact we have had much rain the past few weeks here in SE Wisconsin. Anyways, my grandfather always watered from the top, and he over-fertilized, with success every year, but his tomato garden never looked like mine.

I think the main issue is that once the plants get big enough (mostly indeterminates), there is so much foliage that very little makes its way down to the roots. Of course there are problems with diseases/fungi etc. There is some logic to the "in nature" argument, but we are trying to maximize the growing conditions, and a lot of times that runs contrary to nature.

Watering overhead is not the same as getting a good rain - I think that's the primary issue.

I could water overhead for hours and not get the soil as evenly moist as a good rain that lasted one hour. I water around the base of plants when I have to water, but I always prefer a good rain, it does a much better job than I can :)

Agree with homegardenpa. It just wastes water, results in shallow watering which encourages shallow rooting, and isn't nearly as effective at balancing soil moisture levels and preventing the problems that come from inconsistent soil moisture as ground level watering does.

Not to mention that wet foliage only encourages more disease problems like Early Blight. We can't keep the leaves dry when it rains but we can the rest of the time by not using overhead watering.

Use sprinklers or sprayers and you can almost guarantee yourself Early Blight will develop on tomato plants.

Dave

Thanks to all for making a good argument to not water overhead.The last thing we need is blight this year after last season's problems up here in New England.I'm going to stick with the watering can. "If it aint broke don't fix it"

I watered everything with a sprinkler last year once it was planted in my garden, and didn't get any diseases that I know of, until I got late blight right at the end of the season. But the slugs made up for it. This year I did some overhead watering of some tomato seedlings, and probably got some kind of fungal thing because of it. I think it'll be alright, but I won't do it again. I got the leaves really wet btw, and I'm pretty sure it was later in the day, so the sun didn't dry it out right away. When I was working in my garden the other day, I was paying attention to the sun and soil moisture. I had a new bed where the soil was still moist after turning the grass over, and once the sun started hitting it, the surface dried out very quickly. So now I know why it's important to water at a time when the sun has a chance to dry out the surfaces of soil and leaves. Especially if you're watering overhead, and going to get the leaves wet. And why morning sun is preferable to evening sun, since the morning sun will dry out leaves that are damp with morning dew.

I water overhead every day and I have beautiful tomatoes this year. But I do live in S. Texas and the high for the day is about 97 degrees. I water between noon and 3 in the afternoon, for 30 minutes. I set a timer so I can be precise. Its so hot that the leaves dry off right away. The soil is evenly moist.

One of the best ways to water tomatoes is with drip irrigation or soaker hoses. It saves time because you can put them on a timer. You can also guarantee a deep watering several times a week, rather than just a superficial watering with hand held hose or even sprinkler.
Soaker hoses or drip irrigation also prevents the spread of diseases. Check out the YouTube link below to see how it works.

Here is a link that might be useful: Watering tomato plants: how to use a drip irrigation system

I also water overhead most days. Not a primary watering,
since I have a drip system for that.

I am in the arid southwest (just outside of Los Angeles)
and you can get away with it.

Steve Goto told me quite a few years ago that in our type
of climate, you can do overhead watering since
the dry humidity dries the leaves quickly.

Overhead watering also helps to wash off most of the
airborne diseases out there.

New England now, that's another story. I wouldn't do it
there. I agree that 'if it ain't broke, don't fix it.

I've had great results over the years and a couple years
ago I tried to 'improve' things with different fertilizing
and watering tactics. Bad move. I tossed those ideas
and went with what worked in the past.