How much water for Kentucky Blue Grass in Northern New Jersey

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Roland
Posts: 11
Joined: July 18th, 2017, 2:48 pm
Location: Northern New Jersey
Grass Type: Kentucky Blue Grass
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How much water for Kentucky Blue Grass in Northern New Jersey

Post by Roland » July 18th, 2017, 4:05 pm

Good Afternoon,

I just bought a home and am learning a lot while i try and have a nice landscape. I believe I have a Kentucky Blue Grass yard with approximately 2500 sqft in front and 2500 sqft in the rear. Im trying to figure out how long i need to water to put down an inch of water which is what im told is the correct amount. I put out some pint sized chinese food container and had a half an inch of water after two hours and therefor have concluded that I need to run the sprinklers for 4 hrs to get an inch. This seems like a lot of time! Have I made a mistake? My water pressure is 80 psi and my GPM is roughly 8. I've got two rainbird p5r+ which according to this link claim that they put out 7.1gpm at 45 psi with the correct nozzle. I was expecting to be able to water for less time...

Do my observations mesh up with the math?
Is there a quicker way to get down 1 "?
Do I need to put down an inch and if so how often?

Thank you!

Roland

g-man
Posts: 501
Joined: June 29th, 2016, 9:54 am
Location: Fishers, IN
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Re: How much water for Kentucky Blue Grass in Northern New Jersey

Post by g-man » July 18th, 2017, 7:19 pm

The gpm are spread over the coverage area of your nozzles. The p5r+ are impact heads and they will take forever to get an inch, so yes 4hrs.

Quicker, yes. How much you want to spend? In ground irrigation would be the easiest, but cost is a factor. If you want you could buy a hunter pgp head and mount it into a impact head metal spike. With you pressure and gpm, you could run 3 and maybe 4 of these on hoses. Add a bib timer and you could water a large area fairly quick.

An inch of water is the guideline to promote deep roots. In the summer I do 3/4in more every 3-4 days (rachio controller handles this). How often to water? Water just prior to seen the lawn stressed and water deep (~1in). Water in the am not and night.

rtomek
Posts: 554
Joined: March 19th, 2013, 1:55 pm
Location: Northern IL
Grass Type: Elite KBG Sod (unknown cultivars)
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Re: How much water for Kentucky Blue Grass in Northern New Jersey

Post by rtomek » July 19th, 2017, 12:44 pm

If you're at 8 GPM, then there's nothing you can do to speed up the entire process. Your only choice would be to get more smaller sprinklers and do 1/4 of the area for an hour at a time. Also keep in mind that faster is not necessarily better, because there is a limit to the rate you apply water before you start getting runoff - the soil can only absorb water so fast. 4 hours seems perfectly normal, which is why people install in-ground irrigation systems instead of dragging hoses around.

PeterS
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Location: Sacramento, CA - Zone 9b
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Re: How much water for Kentucky Blue Grass in Northern New Jersey

Post by PeterS » July 21st, 2017, 12:57 pm

Four hours seems like a reasonable amount of time based on your maximum GPM. If we convert from cubic feet (2500 x (1/12) = 200 cu ft.) to gallons (Cu ft x 7.48052 = 1,496 gallons) and then divide the 1,496 gallons by 8 GPM we arrive at 187 minutes or a little over 3 hours. That is, of course, making a number of assumptions which aren't realistic including the fact that every single droplet of water is applied to the turf, that none is lost to evaporation, there is no overlap, etc. Even if you were to add two more impact sprinklers and reduce the gallonage from each to 2 GPM, you're still looking at the same time period because the amount of gallons your system puts out is your limiting factor. However, adding more sprinklers (well placed) might cause your distribution uniformity to go up overall even if the aggregate GPM output is static.

If you assume that your irrigation efficiency is around 75%, four hours seems pretty reasonable to get that area covered with a full inch of water.

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