Do Microsprinklers Have A Place The Almond Orchard?
When I was a child growing up in an almond family, all of our orchards were watered by flood irrigation. Throwing up levees, opening large valves, and waiting hours for the water to crawl across large blocks were standard practice. Some orchards were serviced by wells and others from surface canal water (it always seemed we got the canal water at 2:00 a.m.). Our biggest concern was making sure no gopher holes ended up flooding out the neighbors.
Fast forward to the 1970s and the orchards were all converted to solid set impact sprinklers. This system was a lot more efficient, easier to control, and provided frost protection in the spring. Start the pump, make sure everything is turning, and you were good for 24 hours. These systems were nice, but required a high initial capital outlay and expensive pumping systems.
Fast forward again to the 1990s and I now have some blocks with low volume microsprinklers. I farm some very sandy soils, and the ability to accurately control small or large volumes or durations of applied water is a distinct advantage. Over the years though, I have come to realize that there are advantages and disadvantages to the various irrigation systems. Without a doubt, the efficiency of micros is a big plus, as is the ability to fertigate. Using them to establish young trees in the first few growing seasons is a big advantage. For those with slower infiltration rates, less ponding and runoff is also a positive.
However, I have learned a lot in the past few years that made me realize the increased amount of maintenance required with micro sprinkler systems. First of all, if you and not one of your employees are responsible for checking all of the micros after starting the pump, your perspective will be much different. At first, I thought plugged emitters or algae in the lines would be my biggest problems. In all honesty, this has been the least of my maintenance problems. I have tried at least eight different brands of micros, including spinning, stationary, pop-up, full coverage, and partial coverage in both pressure and non-pressure compensating types. All have experienced issues with insects and animal damage; some from sources you might not expect.
Insects or their eggs jamming spinners has long been a problem, thus the advent of pop-up or drop-down heads. The insects continually figure out how to plug each new and improved version. Insects getting inside the lines and hoses has also caused grief by plugging emitters. Many growers have to cover all of their pressure relief valves and anti-siphon vents with insect netting to prevent various insects, beetles, spiders, and wasps from getting into these vents and ending up in the hoses. I have found spiders, Assassin bugs, and large gray field ants pinched between the micro housing and the spinner that keeps it stuck in one position. After the sweeper or pickup machine blows dirt on the micros, there are many that are jammed by a single grain of sand that lodges in the spinner or the shaft.
Probably the most troublesome animal damage to sprinklers and hoses is caused by coyotes who love to either chew hoses and sprinklers or bite off the tees at the risers. Sometimes they will go right down the line and chew off several tees in a row. Many growers individually ball valve each tee for differential irrigating of pollenizers so they cannot always be buried to hide the problem. Starting the pump to the fountains of Bellagio is not a pretty site. Gophers can be a problem with buried hoses, and ground squirrels will cut lines both above and below the ground.
While I have experienced all of the above, the two biggest challenges I have battled each year are ants getting in the hoses and meadow voles chewing minute holes in the hoses. The ants will enter large-orificed micros and in-field air vents. I don’t know if they are seeking water or just hunkering down inside the hoses, but when the pump is started, I need to unplug several emitters that are plugged with ants. These are not the fire ants or pavement ants that baits get, but appear to be Argentine or pyramid type ants.
The vole damage is equally frustrating. They use their teeth to scratch these micro slits in the hoses that result in fine mister-like sprays when the lines are pressurized. I always need to keep a supply of blank plugs on hand to fix these holes.
Horticulturally speaking, micros are great, but plan on many hours of maintenance to keep them going.