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Irrigation Amount

Posted by misterpatrick 4 (My Page) on
Mon, May 14, 12 at 17:56

Hello all,

I have a garden that is primarily tomatoes and a new dripline irrigation system. I'm using 1/4" dripline with 6" spacing. I have two lines going down each three foot wide row and have one line right next to each tomato plant, but not always near the other stuff (onions, carrots etc) that I have companion planted. I'm trying to determine how much to use and would love some tips. Right now I have the timer set for 3 hours four nights a week. With the amount of mulch that I have on the soil it's hard to tell if this is enough. Thanks for any tips!

Also, I realize that there is an irrigation forum, but as this is mostly for tomatoes and a more active forum I might get more response here.

Follow-Up Postings:

RE: Irrigation Amount

i have similar raised beds to what you describe... my tomato beds are 2'wide though. I planted my tomatoes down the center with onions and cilantro planted on one edge.

I spliced together an irrigation hose and regular hose so it could reach my beds, but only drip in the gardens.

I run the drip hose centered between the tomatoes and companion plats (roughly 6 inches between each) and everybody seems to get enough water, and I think it would work that way in your bed.

I was planning to do companion planting on both sides, but realized I could only run the drip hose on one side. Next season I won't put the tomatoes directly in the center but close to the opposite edge. I will still run just the one drip hose between the two. I think all the plants will get enough water.

I have another beds that is3' wide, but it has garlic, and red onions in it. since there are so many plats I cut my hose a bit longer and serpentined it a bit back and forth.
but I don't it's necessary with the tomato beds.

You can't really see the irrigation hase because it's black, and the grass in pathways is a bit overgrown,

RE: Irrigation Amount

3 hours four nights a week

That sounds like a LOT of watering. Especially that far north. What made you settle on that schedule? Is your soil really sandy and quick draining?

Have you dug down and checked the moisture level at the root level? That's what determines when watering is needed rather than some set schedule. Even just sticking your finger down deep in the soil is a better indicator than some set schedule or you can use the dowel method or even the tuna can method to measure watering need.

What size are your drip emitters? GPH?

My garden is heavily mulched and I use 1 gph emiters on mine and except during the hottest part of the summer I seldom have to water for more than a couple of hours once every 7 to 10 days.


RE: Irrigation Amount

I'm using the 1/4" from Dripworks. Dripline. Their specs are 6" Spacing, 1/2 GPH Flow rate at 15 PSI approx. 100 GPH per 100'. I'm just guessing on how much right now. I'll dig down and take a look. We may be far north, but it's hot here when the summer gets going - lots of 90F and 100F days. Before I set up the drip system I was having to run the sprinklers everyday as the the tomatoes were wilting.

Daytime temps are in the mid to high 70's right now and the seedlings just went into the ground so I'm doing a lot of experimenting.

RE: Irrigation Amount

  • Posted by bets z6A ID (My Page) on
    Tue, May 15, 12 at 1:12


Your tomatoes last year may have suffered during the hot times because you did water them every day. Frequent watering (especially for short time periods) encourages shallow root growth which makes the tomatoes more susceptible to stress and wilting. That is because they have their roots near the surface which has more temperature and moisture fluctuations than the soil deeper in the garden.

Like Dave, I use 1 GPH drippers, I have a single dripper at each tomato plant and water for about 3 hours once a week or so. We get little rain in the summer and like you have some very hot temperatures (often above 100). When we have those hot weeks, I may water every 3 - 4 days. I do keep several dowels poked into the ground at various places in the garden so I can check the soil moisture and adjust as needed.

I hope that helps.


RE: Irrigation Amount

I am going to answer this from the other end. At my old place I watered so that each plant got one half a gallon per day. When it got 100 degree, low humidity in Colorado I had to go to one gallon per day. This was very sandy soil and i had to water every day- that would depend on your soil. Less ofter is better. I would start timing at a low rate and watch for signs of wilting. A little during the heat of the day is OK.

RE: Irrigation Amount

Ok, 100 GPH per 100' and you have 2 rows of tubing, one running down each side of the 3" wide row. You turn that on for 3 hours, 4 nights a week. You don't say how long your rows are but let's assume for purposes of discussion that they are 50" rows.

That means you are delivering 100 div. by 2 X 3 hrs. X 4 day = over 600 gallons of water per week to your garden. That is FAR too much water for anything, even bog plants, regardless of how hot or dry it may be.

With a 100gph/100 ft. system you are getting 1 gph out of each dripper but you have doubled the lines so are actually getting 2 gph out of each. 1 hour 1x a week should be far more than enough unless you are growing in pure sand IMO and yes I have temps just like you describe to contend with.

Over-watered plants are water-logged, shallow rooted, water dependent plants that are prone to root rot, produce less and what they do produce is watery tasting.


RE: Irrigation Amount

I also use 1gph emitters on my tomato plants. I use sliver plastic mulch film and only water at MOST every 5-7 days for about 1 -1 1/2 hour. A LOT of people had horrible harvests in last year's heat because they watered too much. We had one of the best harvests ever in part I think to a consistent, deep watering schedule.

If your plants look wilty during the heat of the day, that's just their normal response to conserve water. If they perk up in the evening and look good in the mornings, they do not need water.

RE: Irrigation Amount

Thanks everyone, this information really helps. Just to be clear, I haven't actually started watering yet, I just set up the schedule. I will reduce it down to once a week and see how things go. My rows are actually only 10' long. I have 20 of them. I actually had a great harvest last year though we got a late start. My watering was erratic.

I didn't know about the dowel method for checking moisture levels and will look into that to keep an eye on things. Thanks all!

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