Reasons Fruit Growers Should Invest in Soil Moisture Sensors

Kim Delay can think of at least two good reasons why tree fruit growers in Washington state should invest in soil moisture sensors: 1) every block, let alone farm, has its own soil profile, and 2) every year presents unique weather challenges. He has learned as much the last 20 years while serving as the Manager of CPC International Apple Co.’s operations in Royal City, WA.

While Delay, unlike his tree fruit counterparts in California, has “access to all the water we need” because of the Columbia Basin Project, too much of a good thing can hurt as well. “We’re blessed. You get a base amount of water, you pay for it, and then you have access to extra water,” he says. “But one thing about crops is you can overwater things, too.”

What determines too little or too much? Enter soil moisture sensors. CPC has invested the last 10 years in Semios-deployed probes that allow orchard managers like Delay to determine targets, as dynamic as they might be.

“You wouldn’t think you’ve got different soil profiles within 5 miles apart. But in our 5-mile radius here, we have nine different farms, and they all have different soil profiles. Even in 15-acre blocks you get different soil profiles,” Delay says.

In turn, growers should place probes in “middle areas” that best represent the prevalent soil profiles, Delay says. “If you put them in a rocky area, you’re going to be watering quite often. Put them in an area that’s wet, and you’re not going to be watering enough. You still have to do your legwork,” he says.

Determining soil moisture becomes particularly difficult in June and July when growers apply overhead cooling to prevent sunburn. “We get into cooling at 85˚F and plus,” Delay says. “If you’re doing a lot of overhead cooling, sometimes you’re thinking you don’t need to irrigate: Everything looks good on top, the grass is all green, everything’s nice and wet. But if you’re doing short sets on overhead cooling, what happens is that you’re just getting 4 inches or 6 inches wet, but it’s drying up on the lower part. You still may need to irrigate even though you’re cooling.”

Finally, soil moisture sensors benefit newly planted blocks, Delay says, particularly during the first three years, when drip fertigation is prevalent. “If you get it too wet, then you’re pushing that fertilizer past half the root zone. You’re not getting your best results out of that fertilizer,” he says.