How Frog Hollow Farm monitors fruit trees, carbon storage, and soil tests with Google Earth
By Raleigh Seamster, Senior Program Manager, Google Earth Outreach
As fall begins and farmers finish harvesting the stone fruit at Frog Hollow Farm in Brentwood, California — about 65 miles from Google’s headquarters in Mountain View — workers still have plenty to do. To grow a peach takes not just the actual summer harvest season, but also 12 months of caring for that peach tree.
Frog Hollow Farm relies on year-round work. In the summer, farm workers harvest the fruit. In the fall, they begin pruning 280 acres of trees by hand and also focus on spreading homemade compost on every orchard. Fall is also the time of year that workers conduct soil sampling, so they can understand what’s happening in the ground and decide where they might need to add nutrients.
Farm Operations Manager Rachel Sullivan uses Google Earth to plan the locations from which soil samples will be pulled. She connects her Garmin GPS device to Google Earth so she can make sure she goes to exactly the same points every year when sampling. By linking the satellite images of the farm that are visible in Earth to the USGS Soil Survey, Sullivan and other workers can see the soil sampling sites in a precise and visual way, which helps track progress in maintaining healthy soil.
Why soil health is vital
You may have heard the term “regenerative agriculture.” It’s a new, catchy name for the way Frog Hollow Farm manages its crops, but the farm has been doing this in one form or another since Al Courchesne (“Farmer Al”) founded Frog Hollow Farm in 1976. Regenerative agriculture is different from sustainable agriculture in that farmers are not just trying to continue to produce food for future generations.
“We want to do that, as well as improve the health of the soil, store carbon, and build resilience to extreme weather and climate change — as well as improve the ecological health and diversity of the soil and of the place that we’re farming,” Sullivan says. “There’s a social component too, so we’re thinking about the health of our staff and the people that are growing the food and bringing it to market.”
To understand what’s happening underground, Frog Hollow Farm staff have always tested soil every fall, mostly looking at micronutrients and macronutrients to understand whether they need to add more manganese, calcium, or zinc — whatever the soil might be deficient in.
Five years ago, Frog Hollow Farm started looking beyond traditional soil nutrient analysis and hoped to gain an understanding of how much carbon is actually coming in and being stored in the ground.
“We believe that farming regenerative orchard crops is a great way to sequester carbon and offset high CO2 concentrations in the atmosphere, but we wanted to actually start measuring it,” Sullivan says. “I chose to study areas of the farm that we had taken over from neighboring conventional, annual, heavily tilled, high synthetic-input farming systems. I took baseline soil samples before Frog Hollow began management and planted trees, and then subsequently every year after.”
Creating maps of soil sampling locations
Sullivan goes to each orchard location and to the exact same GPS coordinates every fall to test the soil. She uploads the GPS points into her Garmin device, transfers data to Google Earth, and creates a map of the orchard in Google Earth. “I wanted to establish sites that I’d go back to every year,” Sullivan says. “Since each of the points is already in my Garmin, I can just type ‘G18–7,’ and it will navigate me to that spot.”
Sullivan creates many maps for different purposes. For California Certified Organic Farmers, the farm’s organic certifier, Sullivan produces a farm map so the certifier can see the buffer zones, which help protect orchards from pesticides that might be used in neighboring orchards. Below is an example. This is an old apricot orchard being farmed, so Sullivan needed to create a Google Earth map that would show CCOF how close the non-organic farm is to Frog Hollow Farm.
“Another awesome feature of Google Earth is the ability to add datasets — in our case, the USGS Soil Survey to identify the boundaries between different soil types all over the United States,” Sullivan explains.
In the image below of soil testing sites, there is a soil line that separates the northern side of the orchard from the southern side. The soil on the northern side is Brentwood Clay Loam. By clicking into the map directly, a pop-up appears defining the soil type and summarizing its characteristics — well drained, clay loam, etc. Sullivan can click on the southern side of the field and do the same thing, learning that the soil type there is Capay Clay — a heavier clay that might be only “moderately well drained.”
In this orchard, Sullivan and her colleagues noticed above-ground differences in trees because of the soil differences. On the southern boundary of this orchard, the trees aren’t as vigorous, their canopies are smaller, and there’s not as much foliage. On the northern boundary, the trees are much larger and more vigorous, probably because of the soil type change.
Frog Hollow Farm workers also create new orchard plans with Google Earth. In 2020 and 2021, they planted new orchards with different varieties of trees, planted to allow for staggered harvesting. “We like to have the June 1st nectarine next to the June 10th nectarine, next to the June 20th nectarine, and so on,” Sullivan says. “I use polygons and points to create a map to show Farmer Al my plan for where different trees should go.”
Google Earth maps are also helpful in placing orders for new trees. Sullivan can measure the lengths of the rows in the new orchards, and calculate the acreages. “I know how many trees per acre we want to order,” she says. “Google Earth is always where I go first to calculate the size of the field and then place that order for trees.”
The excitement of tracking increases in carbon storage
The soil samples collected at Frog Hollow Farm show the increased carbon in the orchard soil. Specifically, in the Geddes 2018 orchard, the tons of carbon per acre increased by 90% from 2017 to 2021.
“We know that our older orchards that have been in place since the 1990s can store up to 30 tons of carbon per acre,” Sullivan says. “So to see that difference from 2017, at 12 tons per acre, to about 25 tons per acre in our 2021 sampling, is very exciting.”
In the months and years to come, climate change will play a more important role in how Frog Hollow Farm is managed. Farmers will plant new varieties of trees that don’t require a high amount of chill hours, or a certain number of hours below 45 degrees in the winter to set a good crop. Some of the varieties that farmers and customers love, like Bing cherries, need 800 hours or more. The farm’s leaders are talking to the nurseries developing new varieties like Royal Tioga cherries, which are delicious and only require 600 hours.
“The Google Earth maps help us understand Frog Hollow Farm’s impact on the soil and climate,” Sullivan says. “We expect that we’ll turn to Google Earth again as we monitor the ability of our crops to withstand changes in climate.”
