What To Know About Pulsed Irrigation and Its Potential for Berries

Pulsed irrigation, according to Michigan State University researcher Josh Vander Weide, improves growth, yield, and quality in blueberry plants — which is good news for water-deprived growers in not just his home state but also the entire country.

“Even though we are completely surrounded by freshwater, in specialty crop fields — not just blueberries — the percentage of fields that are irrigating has doubled the last 25 years,” Vander Weide, an Assistant Professor of Horticulture, said at the SE Regional Fruit and Vegetable Conference in Savannah, GA, in January. “We used to be able to rely on rainfall in many fields, and maybe a third to a half of blueberry fields would actually use their overhead sprinklers for irrigation consistently. But now all new fields are putting down drip irrigation. It’s a big change.”

Pulsed irrigation is a method of delivering water to plants in short intermittent bursts with pauses in between. Hypothetically, this leads to better water and nutrient use efficiency and uptake.

“I would equate this to I don’t in the middle of the day or in the morning just drink a really large glass of water and call it for the day. Usually you’re drinking a little bit of water throughout the day,” Vander Weide said. “Plants would hypothetically prefer this as well.”

That they have throughout Vander Weide’s trials the last two years. The results, he added, are “pretty clear cut.”

Pulsed irrigation maintained higher soil moisture throughout the critical blueberry growth stages. At depths of 6, 12, and 18 inches, pulsed irrigation fared better than continuous irrigation. Meanwhile at 24 inches, higher soil moisture was attributed to continuous irrigation. “That’s because all that water is seeping through the soil,” Vander Weide said.

Pulsed irrigation promoted more vigorous growth; both ‘BlueCrop’ and ‘Envoy’ had longer lateral and first-year (whip) shoots. “We weren’t sure if we were going to see effects on both types of shoots, but we did, and that’s pretty cool,” Vander Weide said. “Greater vegetative growth could hypothetically support yield or faster ripening.”

Pulsed irrigation increased plant yield in ‘BlueCrop’ — Michigan’s top variety — by approximately 24%. “Which is pretty massive. Really exciting,” Vander Weide said. “I’m curious to see if it will carry over to the next year.” Meanwhile, plant yield in Envoy was insignificant at 10%.

Lastly, Vander Weide noted that transitioning to a pulsed irrigation system, especially for growers already using drip and an evapotranspiration-based irrigation system, is not that challenging. Required equipment would include a variable frequency drive (VFD), which helps to regulate the pressure by adjusting the pump speed, and an irrigation valve with a latching solenoid to control water being distributed to each zone.

“A small change in setting up your irrigation could hypothetically lead to water savings, potentially nutrient savings, and potentially lead to some of the increases I’ve talked about,” he concluded.