# How much water do tomato plants need?



## ai731 (Sep 11, 2007)

So I got my drip irrigation system installed, and it's running great. The drought here is still bad and getting worse. Chances are good that they will upgrade form a Level 2 to a Level 3 drought next week.

I want to minimize my water usage, to protect our well, while at the same time watering the tomatoes enough to get a good crop. I have 18 tomato plants, all paste types - mostly Roma & San Marzano. The have all set fruit (currently marble to golf-ball sized) and are still flowering. Each tomato plant has a 1-gallon-per-hour dripper. So - how many gallons per day should I be giving my tomatoes?

Thanks!


----------



## geo in mi (Nov 14, 2008)

ai731 said:


> So I got my drip irrigation system installed, and it's running great. The drought here is still bad and getting worse. Chances are good that they will upgrade form a Level 2 to a Level 3 drought next week.
> 
> I want to minimize my water usage, to protect our well, while at the same time watering the tomatoes enough to get a good crop. I have 18 tomato plants, all paste types - mostly Roma & San Marzano. The have all set fruit (currently marble to golf-ball sized) and are still flowering. Each tomato plant has a 1-gallon-per-hour dripper. So - how many gallons per day should I be giving my tomatoes?
> 
> Thanks!


I think I would let them drip to the saturation point--a mini-barrel of 18 inches diameter and 18 inches deep(you could use a broomstick), then let up and give them enough each day about a gallon a day?? to keep up a basic moisture level. As the fruits ripen, I would then hold back and let the soil get a bit dryer....my opinion. Your soil texture will be the determining factor and you will have to use your own judgment.

geo


----------



## Paquebot (May 10, 2002)

If you are gardening in ground which doesn't have hardpan at 18" or so, then you don't need to give them much water. Tell the plants that the water is down below and that they have to go get it. During 2 months of drought, each of the 150 plants in a field got 1 quart of water and then only so that I give them some liquid fertilizer. The soil is 100% silt and doesn't dry out very quick. If it were lighter soil, I may have had to give them a quart every week during that period. All one need do is scrape away soil until it's damp. If damp 2" down, they don't need water. There is no set formula for how much rainfall will penetrate and dampen a given depth but I know that a half-inch will result in almost 6" of damp silt. And the soil needs only be damp for tomatoes, peppers, and potatoes. 

Martin


----------



## gunnar wordon (Jun 13, 2012)

lots.


----------



## jwal10 (Jun 5, 2010)

I only water when I see the plant droop a little at the top. Then they get a gallon each. They are in well draining potting soil in a 24" dia black tree pot buried 1/2 way in a 3' raised bed covered with 6" of wood chips. The roots go through the drain holes and up to 2' deep into good garden soil below....James


----------



## tomakers (May 27, 2007)

I don't like to water unless I see some drooping from the plants. I have about 6"-12" of leaves, shavings, etc. for permanent mulch and it doesn't dry out often.


----------



## Paquebot (May 10, 2002)

If planted in a garden with normal soil conditions, a tomato plant set out 2 months ago now has roots at least 3' deep and on the way down to about 5' before growth ends. Those are the roots that find the water and bring it up. Commercial growing of tomatoes without irrigation didn't often fail due to lack of water. But also no commercial grower with try planting on a few feet of soil over hardpan. Then irrigation is required during drought periods.

Martin


----------



## ai731 (Sep 11, 2007)

We don't have hardpan - we have about 2 to 3 ft of very rocky topsoil over bedrock. In a "normal" year I don't have to water the tomatoes at all. The last 2 years have been abnormally dry / declared droughts with no rain for 30 days mid-June to mid-July. We've had rain twice in the last 37 days. Wells are going dry all around us and trees are dying.There's no water for the plant roots to get to. 

I'm working to improve the soil by adding more organic matter, but that's a long-term project with the resources I currently have. For now, irrigation is the only way I can have a tomato crop - if I don't irrigate I lose the tomatoes to blossom end rot, and the cucumbers don't grow at all.


----------



## Paquebot (May 10, 2002)

If the overall soil conditions are such that even wells are running dry, and over shallow bedrock, drainage is horizontal and rapid. Rain falls at your place but ends up helping someone several miles away or in a lake. Then you have a problem. It's solvable but not on a large scale basis. Dig holes 2' deep and a little bigger around than a 5-gallon pail. Fill the holes with a mix of 50% leaf-based compost and the original soil. That will serve 2 purposes. The rich portion of the compost will feed the plants and the carbon portion will retain moisture. Feeder roots will remain more concentrated in the loose rich soil and the tap root laterals won't have to work so hard to find moisture. I've done that for up to around 75 plants. Shift a few feet each year and dig new holes, remove the rocks, and you eventually have an entire garden of lovely soil 2' deep. Not easy but worth it in the end if you're intending to garden there for a long time. 

Cucumbers indeed would need irrigation during low rainfall periods. They do have a large root system except that it's shallow. With some vining crops, the root systems are almost as extensive as the surface growth. Thus they are able to take advantage of what little moisture which may exist in a large area. But when they use that up, they go downhill in a hurry.

Martin


----------

