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Water Management-Smart Irrigation
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Workers lay subsurface drip
irrigation lines at Colorado State University for a seedless
watermelon crop. Frequent, light applications through drip are
especially suitable for hot, arid areas with limited water.
Photo by Mark Bartolo |
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In Colorado, agricultural educators are working with farmers to
install subsurface drip irrigation systems, which supply controlled
amounts of water to crops with little waste. Drip is especially
suitable for arid, hot and windy areas. Subsurface application of
water to the root zone also has the potential to improve yields
by reducing the incidence of disease and weeds.
Sub-surface drip irrigation is not subject to the amount of evaporation
or runoff that occurs in the more common flood-furrow systems, says
Jim Valliant, an irrigation specialist with Colorado State University
Extension. Some of the more sophisticated systems feature computer-programmed
controllers with an option to apply agri-chemicals.
“You try to fill the crop root zone profile [with water]
at the early part of its growth, then add just the amount the crop
needs plus a little more in case of evaporation or leaching,”
he said. “You can significantly reduce the amount of water
required.”
With a SARE grant, Valliant is working with farmers to perfect
their drip irrigation systems. USDA’s Natural Resources Conservation
Service (NRCS) is partnering on the project by offering cost-sharing
incentives for drip installation, which, because it costs significantly
more than furrow irrigation systems, acts as “a limiting factor
in improving water delivery systems for many farmers,” Valliant
said. The typical cost of $500 to $2000 per acre for materials,
installation and monitoring controls can be prohibitive for growers
of low-value crops.
Drip systems also avoid increasing salinity downstream, a serious
problem with flood irrigation in arid environments. Irrigation water
discharging from furrows carries dissolved solids picked up from
the soil. Farmers near a river’s headwaters who divert part
of the water into furrows multiply the amount of solids –
and salinity – for each farm that follows.
Irrigation Methods
This bulletin takes a holistic view of managing
and conserving resources to improve water availability to
crops. This may involve adapting irrigation systems that
are more water-efficient or protect water quality. Contact
your local Extension office for more information about irrigation
systems, or seek resources specific to your region. (Some
are listed in Resources)
No one set of practices is universally appropriate
to manage water. Growers must evaluate their cropping and
livestock systems, management constraints and water supplies
to determine the right mix of irrigation practices. Some
options listed in the Colorado
High Plains Irrigation Practices Guide: Water-Saving Options
for Irrigators in Eastern Colorado provide ways to improve
irrigation efficiency and conserve water.
Water Delivery Systems.
Unlined ditches lead to significant seepage losses, typically
25 to 40 percent. Lining ditches with impermeable materials
can decrease water loss and improve efficiency. Consider
a variety of underground or portable piping systems.
Irrigation Systems.
With proper design and installation, a center pivot sprinkler
system can achieve high irrigation efficiency and uniform
application. Consider a variety of packages and operating
methods. Contact Extension or the appropriate state agency
to learn about furrow irrigation strategies, such as tailwater
recovery, irrigating every other row and polyacrylamide
application. USDA’s Natural Resources Conservation
Service offers many cost-share programs to encourage water-saving
systems, such as its Agricultural Management Assistance
Program. (Resources)
Irrigation Management.
Determining the amount and timing of irrigation for efficient
water use can play a huge role in conservation. Monitoring
water application for crop needs and soil moisture content
remains a key strategy. Consider a variety of low-cost,
user-friendly electronic devices.
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Improving irrigation efficiency was also a goal of The New Entry
Sustainable Farming Project, a Massachusetts- based nonprofit organization
that works with immigrant farmers, primarily Hmong and Cambodians,
to access land and hone their vegetable-growing and marketing skills.
With a SARE grant, New Entry staff tested a combination of trickle
irrigation systems and plastic mulch to improve water delivery and
reduce labor. They emphasized irrigation scheduling to counter the
farmers’ traditional daily watering practices.
The farmers, who grow and sell ethnic vegetables popular with
Boston-area Asian Americans, used to plant in bare soil, then weed
and hand-water their crops from a farm pond. They lost moisture
to evaporation, drew down the pond and spent up to three hours a
day irrigating vegetables.
“Due to their experience in tropical climates, where during
the growing season it rains each day, they continue to be convinced
that certain plants will die without daily water,” said Jennifer
Hashley, project coordinator with The New Entry Project. “They
tend to produce fast-growing greens that their customers want to
be succulent and tender, requiring more irrigation than other crops.”
Working with New Entry staff, about 16 vegetable farmers installed
drip irrigation tape under black plastic. Since the work occurred
as a demonstration, their work was shown to at least 15 other active
immigrant farmers.
Most of their crops, such as bitter melon, okra, tomatoes and
eggplant, grew faster and fruit matured earlier with the trickle
irrigation/mulch system. They realized reduced weed pressure thanks
to the plastic mulch and decreased the time they spent weeding and
irrigating. While there were upfront costs for drip tape and plastic,
those costs were offset by savings in labor and increased sales
from earlier and larger yields.
In New Mexico, many farmers irrigate from ditches called acequia,
named by the Spanish settlers who dug them. When an area was settled,
new residents dug
acequia first and built homes later. Today, many farmers in central
New Mexico rely on old rock-and-brush dams that divert water onto
their crop fields and pastures. Like the old name for ditches, water
laws are based on history and state who has water rights (usually,
the oldest systems) and who can lose them (those who don’t
irrigate regularly for three years).
The widely used ditch/dam method, however, directs water unimpeded
onto fields and pastures, with an estimated 60 percent lost to seepage
and evaporation. Members of the Tierra y Montes Soil and Water Conservation
District, with a SARE grant, sought to help farmers do better.
Stephen Reichert, project facilitator with the conservation district,
demonstrated conservation-oriented irrigation methods, including
drip irrigation, corrugated pipe and above-ground gated pipes. Gated
pipes, favored by many because they are less expensive and easy
to use, contain holes covered by slide gates that control water
flow.
“The more farmers hear about this and see how a better distribution
system makes it easier, the more they’re interested,”
Reichert said. However, while “irrigators are sold on these
improvements, in many cases they require financial assistance to
change.”
Gil Gallegos was among a handful of farmers to test the gated
pipe system after siphoning water from a ditch dam for years.
“It wasn’t working because if you don’t have
a constant, sustainable supply of water, the tubes will go dry,”
said Gallegos, who grows alfalfa, oats and sorghum and runs 120
head of cattle on three parcels near the Pecos River. “Now,
I conserve water, I’m more precise, and I can move it as I
need.”
Similarly, across the state, Milford Denetclaw used to flood-irrigate
his 28-acre pasture from a San Juan River canal. Yet, his soil is
so sandy that the practice was wasteful. “I could irrigate
the whole day and, once I shut it off, within a day it would be
like I never had the water on,” said Denetclaw, a member of
the Navajo Nation who raises certified “Beefmaster”
beef and received a farmer-rancher grant from SARE to improve his
pasture and conserve water. (See profile)
With help from his local Extension agent, Denetclaw built a head
gate that brought water from a San Juan River canal, then regulated
its flow with gated pipe.
Along with his improved irrigation system, Denetclaw planted four
varieties of cool- and warm-season grasses in his pasture and was
able to graze his cattle there through the winter. He demonstrated
his renovations to other Navajo ranchers and presented a slide show
during the annual conference of the Navajo Nation Soil and Water
Conservation District. “As far as water delivery goes, I couldn’t
ask for anything more,” Denetclaw said.
Water Cycling/Aquaculture
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