Salt-tolerant alfalfas can help in saline-damaged areas
Salt-tolerant alfalfas won’t solve the problem of saline soils. Yet they’re helping Western growers produce crops where, in cases, they weren’t able to grow any. That’s the consensus of researchers working to develop or identify varieties that can grow in soils damaged in part by irrigation water drainage and dryland saline conditions.
Salts accumulate in soils through excess salty water from abundant rainfall or irrigation that moves through the soil profile to evaporate in low-lying areas. Salts left behind gradually accumulate, making it hard – or impossible – for many crops to grow.
Paul Johnson knows too well the damage that salt causes. The Conrad, MT, grower has worked to reclaim 500-600 acres of high-salinity land, and says salt-tolerant alfalfas and grasses help.
“We can actually get alfalfa to grow in places. We’ve grown salt-tolerant grasses in the discharge and alfalfa in the recharge and reclaimed some of it,” he says.
Johnson is trying to make a living farming in a high-desert area with an average yearly rainfall of 13” while salvaging soils that he says weren’t meant to be irrigated in the first place.
“We call him our poster child because he had one of the worst saline problems we’ve ever seen,” says Jane Holzer, program director of the Montana Salinity Control Association (MSCA).
One of Johnson’s dryland saline seeps, areas with extremely high salt accumulations, couldn’t be driven over, he says. “You’d lose a tractor.”
“The water wasn’t seeping, it was flowing,” adds Holzer. “After he planted alfalfa and Russian wildrye in the upslope recharge area, he put this land into a 10-year CRP contract to use the stored soil moisture and annual rainfall. The saline area was gradually reclaimed.” As salt-tolerant alfalfas and grasses became available, Johnson added them to some saline areas.
The Conservation Reserve Program and the Environmental Quality Incentives Program (EQIP) offer cost-share funds for salinity control that have helped spur reclamation efforts like Johnson’s in Montana, Holzer says.
This year, about 13 years after MSCA helped him identify the cause of the seep and how to reclaim the area, Johnson brought some of the land back into production.
“We’re monitoring now to see if I can control it with annual cropping instead of crop-summer fallow,” says Johnson, who runs a feedlot and more than 10,000 acres, growing dryland and irrigated alfalfa, malt barley, wheat and canola.
“It’s a success story,” Johnson says of his and Holzer’s reclamation efforts. “But we’re not done by any stretch of the imagination.” He’d like to see higher salt tolerance in varieties that yield well in saline and non-saline conditions.
Researchers across the West would love the same thing.
Mike Peel, USDA-ARS research geneticist, runs a salt-tolerant variety selection program at Logan, UT. That state has some “very salty areas,” especially in the east.
“Developing salt tolerance is very difficult, because the salt concentration in the soil is so variable.” One part of a field may have a salt concentration of 15 EC (electrical conductivity); another spot a few feet away may be down to 2 EC, which won’t restrict plant growth, he says.
Peel’s solution? He tests varieties on uniformly salty ag land watered with high-salt byproducts from a nearby power plant. The same varieties are being tested on non-salty ground and will be compared for performance. He hopes to have results next year.
North Dakota has a lot of areas where nothing will grow because of salt accumulations, says Marisol Berti, North Dakota State University forage and biomass specialist.
“In the Carrington area, there’s a lot of salt and saline seeps.” When farmers try to establish alfalfa there, bare low spots, and then weeds, appear. Berti planted three salt-tolerant variety trials this year, but wet weather kept all from succeeding. She says she’ll try again next year.
Salt is also an issue in West Texas’ Pecos-Fort Stockton area. But alfalfa growers are actually using irrigation as their main management strategy, says Calvin Trostle, a Texas A&M University Extension agronomist who tests salt-tolerant alfalfas’ performance. Some growers began using center pivots because they were more water-efficient than flood irrigation.
But some found salt accumulations in the soil surface “and they were finding that their yields were starting to tail off, so several returned to flood irrigation,” the agronomist says.
Flood irrigation water flushes salt down, preventing a surface-salt buildup. “I wish that we didn’t have to do it that way, but the salt issue makes it a necessity,” Trostle says.
He believes about 10% of acres planted in that area have salt-tolerant varieties; some growers are still planting common seed. “That’s ridiculous – you need to know what you’re putting in the ground. With common varieties, you don’t know what you’re getting.”
“You would think that Arizona, with these very high evaporative demands, high temperatures and high water-application rates, would be a great place for salinity to accumulate. It’s really not,” says Steve Smith, University of Arizona plant scientist. He also evaluates salt-tolerant varieties.
“Most of our alfalfa is grown on soils that drain fairly well. Most of the irrigation water is fairly high quality.”
Yet, Smith says, irrigated agriculture is still relatively young in his area. “Salinity the world around, and for the history of agriculture, has been a problem in arid environments where irrigation is used. We’re just hitting that duration where it’s going to be a problem.”
California’s Imperial and San Joaquin valleys are good examples of that. “They have a lot of soil issues that cause salinity to be much more of a production limitation than we see here in Arizona,” Smith says.
Salt accumulations are causing problems for California and the rest of the irrigated West, says Dan Putnam, University of California Extension forage agronomist, who has salt-tolerance trials in the works.
But, he adds, there are more reasons why alfalfa research and breeding efforts should be done on salt tolerance.
Over time, alfalfa will end up on marginal land with marginal water sources as irrigated regions produce more high-value crops. “That has happened in California and other irrigated regions.”
Salt-tolerant alfalfas may also be able to use degraded water from municipal wastes, dairy wastes and food processing wastewater. “You could put degraded water on grasses and other crops, but alfalfa has higher value, generally speaking, than some of those other forages,” Putnam says.
Yet, reminds Smith, salt-tolerant alfalfas aren’t a solution. “It’s an opportunity to maintain some level of productivity as that salinity increases. It allows you to buy time until you either deal with the quality of the water coming in or with the drainage issue that may be leading to the salinity.
“The long-term solutions are about engineering and water management – not biology.” He advises growers to work with professionals to find out what’s causing the salinity problems and then find out if there’s a solution to them.
For more on soil and irrigation salinity management, contact your state Extension service. Or check this publication online: Irrigation Water Salinity and Crop Production.