Article on deficit water for tomato: effects similar to stone fruit

I found this article interesting about water and tomato. The effects of deficit water on tomato are similar to those on nectarines and pluots: increased brix and flavor.

Apparently this type of culture for tomatoes started about the time I caught on to the technique in my greenhouse. The article gives water levels for best tasting fruit, 50% or less of full ET. I’d say I run my greenhouse somewhere near that 50% level, maybe somewhat higher.

In a recent post I speculated that nectarines and pluots might benefit from deficit water more than peaches because the former have smooth skin and therefore probably more water loss from the fruit itself. Smooth skinned tomatoes seem to react like nectarines and pluots although I haven’t seen brix numbers for tomato vs water.

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Makes sense. I usually slow watering to prevent cracking. many crack badly. I always harvest before watering too. I’m having a great tomato year, the plants look fantastic. Last year by this time I had some tomatoes. not this year, but I will have a lot more this year. In about a week harvest should begin. We have had little rain and very low humidity, very strange weather for here. Right at this moment it is 84F and 31% humidity. High is 90F. Tomorrow too. Also beacuse we are near the summer solstice, the light waves are long, and the UV index through the roof. Plants are getting a huge amount of light. Incredible response by everything. I expect high brix on everything. The first raspberries are extremely sweet and just good this year. Some so so cultivars really taste better. I think part is maturity, the plants tend to get better with age. Part is the dry weather.

I thought the part about sodium making them more flavorful was interesting. Tomatoes are one of the few foods to which adding a a very slight amount of salt really intensifies the flavor to me. I wonder if it’s the sodium that really brings it out.

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Interesting stuff, I will be curious on how the research develops. Now I fear I’m over watering my own tomatoes but am left without enough info to guide me. I only grow indeterminate tomato types and a very knowledgeable sounding greenhouse grower is quoted here about not recommending deficit irrigation to these tomatoes. They produce much more flavorful fruit than determinate tomatoes anyway- because of a higher ratio of leaves to fruit, I believe. The indy plants that grow most vigorously, produce for the longest season, bearing fine fruit until frost and, if you are alert, even the green tomatoes can be taken inside and provide tasty fruit through Nov here.

The research I’d also be interested in is when during the development of the plants and fruit the true benefit of deficit irrigation begins. From my reading of research, brix improvement in tree fruits doesn’t occur from drought during early fruit development and the best results are achieved by watering for full vigor until summer or a couple months before fruit ripens.

A good place to start is with good tomatoes,and I find somehow they come out ok. Currently I’m just trying to keep them from drying out with temps in the 90’s I have been watering heavy daily. I just finished the backyard, now the front. Everything is dry. I watered my peppers yesterday morning and last night they were all wilting from lack of water. So some plants I need to water twice a day with these temps.

In most places one starts out the growing season with the soil profile full of water. That’s generally what I’ve done. Then begin a deficit irrigation program for the rest of the summer. Most people, even commercial orchardists in WA apple orchards, start watering too early in spring. They over estimate the trees water needs early on. Researchers there suggest that the early irrigation can be detrimental. Better to let the soil dry and warm up in late spring.

On my soil the need for irrigation comes about two months after the trees are fully leafed out. But it’s three months before I go to summer watering which is 3 inches per month, probably 50% of full ET. And I tend, just like the commercial growers, to get started watering too soon.

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That still doesn’t explain the point at which deficit irrigation becomes beneficial. I believe that as long as the fruit cells are increasing you want good vigor but once the cell total is achieved, you don’t want to fill those cells up with extra water. But that is just my hunch.

Well unless you like split tomatoes. Developing tomatoes are still expanding, but ripe ones are not, and as the season progresses you have both on the same plant.

It depends on how much benefit you want/need. If you need full fruit size then you can’t expect max brix. I don’t need max brix which for nectarines has been 30+. I like mid 20s and can get good fruit size in that zone. Maybe not full size but 3 inches plus. You also have to thin enough. So probably give up some yield and size at mid 20s. But I haven’t done the experiments needed to prove anything. Just don’t have near enough room to separate water treatments and root systems.

I was actually thinking about tree fruit when I made that statement, but you make a very good point with indeterminate tomato types. Hard to fine tune timing of deficit irrigation on a plant that has such a long bearing season.

Yes, I like what fruitnut said about brix with nectarines, a balance of size and brix. Hard to do for most of us without greenhouses, but still possible. Right now I watered my trees as they are beginning to droop at the growing points. I didn’t give them very much though. I do want to keep the brix high as possible here. I still have to August before I get stone fruit. I need some earlier cultivars.
Well peaches and nects, my Carmine Jewel cherries are ready for harvest, which is really nice, filling a niche. They are very good too, you can eat them fresh, not that tart.
I have not watered them at all and they are in pots, let me check the brix…
Brix is 16, not bad for tart cherries. About what they said top brix was for this cultivar. Tatse is very good! Size is small though.

If you thin peaches early, it also helps raise brix while making the peaches bigger according to research I’ve seen. I think when cells are dividing deficit irrigation probably doesn’t increase ultimate brix of fruit- I believe it is something that I’ve read, although it wasn’t stated as a cell division issue, but that the brix increase simply comes from water deprivation later in the fruit development.

Have you experimented much with the specific timing of turning off the spigot?

Alan I don’t turn off the spigot before ripening. I’ve got 50 varieties all crammed into a small area and ripening from May to October. I run a deficit all summer. The tree would like 6 inches per month and I give it 3, about 1 inch per 10 days. They get watered before the leaves fall or the fruit shrivels. The tree adjusts it’s osmotic potential so as to draw some water from dry soil.

My feeling is one can’t expect a large increase in fruit quality without some decrease in yield. The tomato article seems to suggest otherwise. Maybe researchers will catch on and give us some good data soon.

I try not to start watering until the tips of nectarine and pluot fire up. That’s what they do just before they quit growing due to drought. Drooping isn’t dry enough for my setup. I’d say you’re falling prey like the rest of us to the watering too soon in spring syndrome. But you do what you think necessary. Maybe you don’t have enough canopy yet.

My trees do grow some all summer. But not nearly as much as they would with full irrigation. It’s sorta like the first 50% of ET grows fruit. The next 50% just grows more wood. So yield may not suffer much with deficit water if a larger percentage of the trees energy goes to fruit vs wood.

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That is probably true, thanks for the tips though. I didn’t water much, maybe 1/2 inch. It’s going to rain tomorrow, so I it is not in my control. It has not really rained here in 3 weeks. Unusual for late spring. I have no rainwater left at all. This usually starts now, so it may be a super dry year. Also I don’t myself wish to stress the trees so much or go for small fruit. I like they way they taste even when wet. It’s more an experiment for me. When friends and family say it’s the best stone fruit they ever had, I think I don’t need to rock the boat. If it’s not broke, don’t fix it.