Tuesday, November 3, 2009

Patty Hamilton: Master of Irrigation

 There are few out there who have undertaken a true study of the Art of  Irrigation.  Many gardeners call the creation of a watering system "irritation."   But most of us have personally experienced the sensation of thirst, and know that it is a yearning that will not be abated with anything but that essential combination of hydrogen and oxygen.  Water, and how it is delivered, is at the "root" of everything that happens in our gardens.  Last Wednesday Patty Hamilton from Harmony Farm Supply in Sebastapol, a Master of Irrigation, came to share the top six inches of her wisdom with us.

The class moved quickly, and we did so much math that at times I had to look around to make sure I hadn't been tossed back into college calculus ("Um, excuse me, could you please repeat that last part?"), but in the end we had a good overview of how to approach setting up an irrigation system.  Here I must go back to one of Wendy's favorite garden quotes:  "In general, everything is specific."  That means that we know we start with the basic irrigation building blocks (timer, filter, pressure regulator), then make very specific decisions based on the lay of our own land.

1.  Start with a "Bucket Test" - a five gallon bucket, see how long it takes to fill up so you get you gallon/minute rate.
2.  Filtration system - This decision is based on water quality...are you on city, pond or spring water? do you need a screen filter (basic, if on city water) or a disc filter (26 times more filtration than a screen...needed if you have a lot of particulates in water)
3.  Pressure regulator comes after the filter in your set-up...This is where you begin to make some calculations based on your water pressure and relates to the next step (#4). 
4. Drip, Spray or Combined system.  What type of plants are you watering?  For instance, you don't want a spray system when watering trees because you want to make sure the water gets most directly to the roots....What type of soil do you have?  This relates to the capillary force ( surface tension) and soil structure matters here.  If you have sandy soil, the capillary action is not as extensive and so your water tends to dive straight down...on the other hand, a nice loamy soil means that the water will spread out on its own underground in a nice large ballooning shape.  These, along with questions about the slope of your land,and the length of our rows, are questions we must address to design our systems.

The Harmony catalog has a lot of excellent information about Irrigation, and Harmony will test soil and water before you begin designing your system.

Finally, we moved on to a discussion of Irrigation Tape and an in-depth calculation of emitter spacing on the tape and when you might need "pressure compensating emmitters".  "T-Tape" is what waters the rows at Indian Valley.  It is a flexible, user-friendly option...BUT it requires farmer responsibility.  In Florida, farmers are leaving the tape in the fields and discing it into the soil.  There is no known recycling option for this tape at the moment.

Here's an idea...before the creators of T-Tape (and all the future wonder solutions) receive a patent for their fabulous new product, they must come with the "un-make" plan (otherwise known as "recycling")...and they may receive the patent for that as well.

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