July 2022 - 16

IRRIGATION & WATER MANAGEMENT
CropManage tool lowers fertilizer, water use
By Vicky Boyd
Contributing Writer
Since the free online irrigation
and fertility decision support tool
CropManage launched in 2011 for use in
lettuce fields, the University of California
has added more than two dozen row and
permanent crops.
Users can typically reduce fertilizer
and water use by 20% to 40% while
maintaining or even increasing yields,
said Michael Cahn, a UC Cooperative
Extension farm advisor in Monterey,
San Benito and Santa Cruz counties who
spearheads tool development.
Mark Mason, a pest control advisor and
farm manager for Nature's Reward based
in Salinas, said he's seen the tool's benefits
first-hand.
Since he began using the program on
Iceberg lettuce in about 2014, Mason
has added Romaine lettuce, leaf lettuce,
escarole, endive and most recently celery.
As a result, it also helped him answer some
pressing questions.
" How do we really know when to
water? " he said. " We always had this
increment and did so every so many days
and so many hours. How do I really know
when to fertilize? "
Working with Cahn, Mason conducted
Zheng Wang, a University of California Cooperative Extension vegetable and irrigation
farm advisor, has been working with two growers the past two years to validate
CropManage for watermelons. Photo: Zheng Wang, UCCE
a number of split block trials comparing
his standard practices to CropManage
recommendations.
" I kind of had to prove out the model
to myself, " he said. In the end, he found
significant savings for both water and
nitrogen applications.
The model helped them reduce
nitrogen use about 30%, depending on
the year, as well as identify irrigation
system inefficiencies, Mason said.
Nevertheless, he still views it as a tool to
aid decision making.
" We don't follow exactly what it says if
we feel like it didn't recognize something, "
Mason said. " There's kind of a strategy and
some communication that has to happen
and some management that has to happen
more than just going out to fertilize. "
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management has taken on new meaning in
recent years as produce buyers increasingly
seek sustainability metrics from suppliers,
Cahn said. In addition, the state's
Sustainable Groundwater Management Act
requires severely overdrafted groundwater
basins to balance extraction with recharge
beginning in 2040. And the Irrigated
Lands Management Program requires
growers to annually report irrigation and
nitrogen (N) inputs and crop withdrawals.
As part of that program, growers along
California's Central Coast from southern
Santa Clara County to Santa Barbara
County will be limited in the amount of N
they can use.
Free user accounts
The CropManage website, cropmanage.
ucanr.edu, can be accessed from a
smartphone, tablet or desktop computer.
Users set up a free online account and
begin entering information for their farm
or specific fields. Cahn said they're also
adding a Spanish version.
To set up a field location, users simply
click on a Google map integrated into
CropManage. The soil type, based on the
Mark Mason, farm manager for Nature's
Rewards in Salinas, California, began using
CropManage for iceberg lettuce in 2014.
He has since expanded the tool's use to
include Romaine lettuce, leaf lettuce,
escarole, endive and most recently celery.
Photo: Nature's Reward
National Resource Conservation Service
Soil Survey Geographic Database, is
automatically populated after the user
chooses the field location.
Then users select a nearby California
Irrigation Management and Information
System (CIMIS) station before choosing
the crop type in the drop-down menu.
The program also allows users to
customize their information by tying in
remote infield soil moisture and flow meter
sensors, for example. In addition, it has an
application programming interface (API)
that can connect with other software,
such as on-farm weather stations or farm
management and recordkeeping programs,
Cahn said.
CIMIS, a statewide network of more
than 145 automated weather stations
operated by the California Department of
Water Resource, provides ET information
based on a well-watered green lawn. To
convert it to the actual ET rate for a specific
crop - known as the crop coefficient
- Cahn said growers would have to do
lengthy calculations. They also would have
to factor in the crop growth stage.
That's where CropManage comes in.
Based on the information supplied by the
user, program algorithms calculate the ET
crop coefficient and recommend optimal
irrigation intervals and run times.
" We've modeled the canopy of the
different crops by taking hundreds of
pictures of the crop, " Cahn said of the
algorithms. " The more leaf area the crop
has, the more water it uses. "
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July 2022

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