Blueberry irrigation best practices: Choosing the right system for your field

The best blueberry irrigation best practices depend on what growers want from their systems, said Mark Longstroth, Michigan State University (MSU) Extension small fruit educator.

During MSU’s 2020 Pre-Bloom Blueberry Webinar in mid-May, Longstroth outlined how system design, soil type, and water quality all influence irrigation effectiveness and crop health.

Trickle irrigation: Efficient but demanding

Trickle irrigation remains one of the most common and cost-effective systems for blueberries. The system delivers a slow, steady application rate — ideal for conserving water but less forgiving if growers fall behind on irrigation schedules.

“You don’t have to test the water, but it’s hard to catch up if you fall behind and you don’t have access capacity in your system,” Longstroth said.

Most blueberry growers prefer two irrigation tubes per row, allowing water to reach both sides of each plant. “You want as many emitters close to the plant as possible,” Longstroth said. “Emitter size determines how much water it is putting out with the pressure that you have. Normally, the application rate is measured in gallons per minute and gallons per hour that the emitter will put out in a specific range.”

Soil texture also effects how water moves through the root zone. In heavier soils, water spreads outward, while in sandier soils, it drains more quickly.

“You should look at wetting fronts,” Longstroth advised. “Dig a hole around one of your emitters after it has run for a while to see where the water goes. Does it shoot out, or does it go right back down into the sand?”

He cautioned that it’s easy to over-irrigate blueberries. “You may say I’ve got to put on a lot of water,” Longstroth said. “You’ll turn the trickle irrigation system on and let it run for five or six hours and three-quarters of the water has gone below the roots. You’d be better off cycling your different zones.”

Managing water quality and soil pH

As part of blueberry irrigation best practices, Longstroth emphasized that growers must monitor water quality. Blueberries are highly sensitive to salts, and water containing high levels of calcium and magnesium can gradually raise soil pH.

“If you’ve got hard water, you have a fair amount of calcium and magnesium in the soil,” he said. “When you trickle irrigate, you are going to be liming the soil. I’ve had people with trickle irrigation systems say the more I water, the crappier they look. Often, they have a fair amount of calcium in that hard water.”

Over time, those minerals can increase soil pH, harming blueberry health. To counteract this, some growers add acid to their irrigation water.

“They have a set irrigation schedule,” Longstroth said. “One guy had it set up for a very small planting and he struggled mightily to get a pump that was sensitive enough to be able to just put a drop or two in the flow of water as it went by. He ended up going from fairly concentrated sulfuric acid, to relatively concentrated sulfuric acid to diluted sulfuric acid to match the pump so he could get it correct with the pH of his water.”

Sprinkler irrigation: Versatile but costly

Sprinkler systems can serve multiple functions beyond irrigation, including frost protection and evaporative cooling. However, they require a large water supply and proper water testing, particularly when drawing from surface sources.

“These systems are expensive and require putting a lot of water over the entire acreage, not just on the plants,” Longstroth said. “If you’re pumping out of a surface pond or surface source of water, you have to have the water tested for food safety and figure out whether or not you can or can’t irrigate. There’s also the problem, perhaps, of washoff of SWD (spotted wing drosophila) insecticides.”

Sprinkler irrigation performance depends on nozzle size, pressure and spacing. “Sprinkler irrigation is based on what your nozzle size is, what your sprinkler pressure is, and how far apart the sprinklers are,” he said. “Your application rates are usually measured in inches per hour.”

He provided an example setup. “For a certain type of sprinkler, we use 9/64ths and run it about 45 – 50 pounds. So we’re putting out 4 – 4.50 gallons of water per sprinkler. My sprinklers are spaced at 40 x 60, putting on 0.16 of an inch of water per hour. You should check those rates, not just at the nozzle, but at the pump.”

The takeaway: Match system to site conditions

Whether growers choose trickle or sprinkler irrigation, Longstroth said success comes from understanding the system’s capacity, soil type, and water chemistry. Implementing blueberry irrigation best practices help prevent overwatering, maintain optimal soil pH and ensure blueberry bushes thrive through every growth stage.

— Gary Pullano, managing editor