Water Management-Smart Irrigation
|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
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.
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.