Many of us are looking for alternative low/no energy ways to accomplish things around the garden or farm. One thing every gardener or farmer needs is the ability to irrigate a crop. For some of us it’s as easy as using a garden hose, for others, we are looking at larger drip irrigation systems. The good news is, no matter if you are residential or commercial, you can use gravity-fed irrigation techniques.
While the general concept of gravity-fed, low-flow irrigation is simple, it is a bit more in-depth than a newsletter article can hit on. I’m also no expert on water so, for more info, I will direct you to the publication HO-120 Off the Grid: Ultra-low Pressure Drip Irrigation and Rainwater Catchment by Drs. Rowell and Jacobsen. However, I did want to mention a few key points to maybe spark your interest.
The term psi refers to the pounds per square inch of water pressure. For every 2.3 feet water is raised above the surface of an area, it generates a pressure of 1 psi. Remember that magic number, 2.3 feet! Once you know the psi you need, you can do some simple multiplication to figure out how high your water tank needs to be to irrigate a zone!
For those of you using drip irrigation, you might notice that most drip-tape recommends pressures in the 8-15 psi range. Research done at the University of Kentucky has shown that if a system is designed correctly (maximizing pipe sizing, minimizing the distance from the source) drip-tape can be used at “ultra-low” pressures of only 1-2 psi which would be equivalent to elevating a tank only 2-5 feet off the ground. Totally doable for anything from a rain barrel to a stock tank on a high tunnel! Studies showed that even at this ultra-low pressure a quarter-acre plot could be watered uniformly.
As we continue to see results of climate change and irregular rainfall patterns around the U.S. it is becoming more important to begin collecting rainwater. It always surprises me how much rain water can actually be collected off of a surface. An inch of rainfall on a rooftop only 500 sq. ft. produces about 300 gallons of water. A high tunnel 90ft long and 30ft wide can capture up to 1,620 gallons of water from just an inch of rain. So, really the limit, at least for most KY growers won’t be the rainfall, but having a tank big enough to optimize it.
If you’d like to learn more about low-pressure systems, rigging up gutters or improving drip-tape setups, definitely check out the publication I mentioned above. I’ve also put the link below!
Submitted by Alexis Sheffield, Agent for Horticulture, Boyle County Cooperative Extension Service