Watering - Raised Beds w/ Drip Irrigation

Adam SchaefferOctober 19, 2013

Hi everyone - Long time lurker, and first time poster here. I'm managing a community garden in Austin, TX, and we've installed 1/4 dripline irrigation w/6 inch spacing in raised beds that are 16 inches tall.

The irrigation system is relatively new so I'm trying to get the watering adjusted. I've read about the 1 inch per week rule but that doesn't really translate to a drip system that well...at least as far as I can tell.

Now that the weather is cooling in Austin (highs in the low 80s) I'm thinking about watering once a week for 45 minutes but I'm not sure if that's too little or too much. We're using a high quality garden soil w/compost and good drainage in the raised beds.

Thoughts? Should I just start with the 45 minutes and see how it feels after 5-6 days.


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jean001a(Portland OR 7b)

To determine if that's adequate, stick a trowel into the soil to determine how much soil -- wide & deep -- is moist.

Bet you need to run the system longer.

    Bookmark   October 19, 2013 at 8:28PM
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seysonn(8a WA/HZ 1)

I think 1" to 2" per week sounds good. lets take 2". So you gave to figure it out how much time with a given flow rate you will get that.

Lets say that a bed is 4ft by 8ft. That is 32 sqr ft. ONE inch water will add up to 5.3 cu.ft. That is roughly 40 gallons of water.

Now we have to know the flow rate (GPM = gal per min). Roughly, a fully open garden hose will have over 3 gpm. But lets say that your drip line(just the part coming to that bed) has a ONE gpm flow rate . Then you will need 40 minutes. But right now I will cut it in half and if rains, just shut it off completely.

HOW to measure flow rate:
Jut put the hose in a 5 gall bucket and time how long it takes to fill it: flow rat = 5/time (in minutes)

    Bookmark   October 19, 2013 at 8:59PM
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Drip irrigation is one of the watering system that needs a more precise drip hole positioning on certain soil types. For soil that is too clay-ish the water would disperse to area wider than necessary and for soil too sandy the water will go very deep but the wet area will be too narrow than you would like,making it difficult for plants root to reach it if they are too far from the holes.

    Bookmark   October 20, 2013 at 12:45AM
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seysonn(8a WA/HZ 1)

Ceth ... you pointed out to an important issue.
So, in drip irrigation, closer spacing is needes in sandy soil or soil rich in compost and organic matter as they hav a good drainage property. But I thin the 6" mentioned by dmak124 should be fine., AS LONG AS the lines ar also spaced every 6" or so.

    Bookmark   October 20, 2013 at 1:01AM
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Hello Adam, With the compost and good drainage in your soil you might find that 45 minutes is too long and once a week is not enough. When starting out or as the seasons change, it is a good idea to check your soil after watering to see how deep and how spread out the watering is. I like to let the soil rest for 30 minutes after watering before checking. This allows the soil to adequately disperse the water, otherwise known as capillary action. Then before watering again, I repeat but this time I am look for dry soil. By doing this, it gives me a good idea about what is going on below the surface. Hope that helps.

    Bookmark   October 21, 2013 at 9:24AM
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