Soil Salinity: An Expanding Issue
Monday, March 28, 2011
filed under: Optimizing Plant Development/Yields
The recommendation for dealing with too much saline in the soil comes down to three simple words: “Dry it out,” says Ron Meyer, extension agronomist with Colorado State University, Burlington.
The words may be simple, but the task can sometimes be complicated. Drainage is not always an easy option, so growers need to turn to a cropping system to deal with high-saline soils. Since no one can control Mother Nature’s rainfall, the best way to do it is with rotation that includes a salt-tolerant, high-water-using crop.
The worst thing a grower can do for saline soil conditions is to repeatedly employ a cropping strategy that allows soil water to continue to accumulate, Meyer notes. Excess soil water rises to the soil surface, carrying salts with it. When the water evaporates, saline particles are left on top of soil surfaces. Employing correct cropping strategies will address the free-water issue. Including a crop like sunflower in the rotation will assist in “harvesting” excess soil water, keeping salts below the soil surface.
Sunflower is one of the better crop choices to consider on saline soils. “Sunflower will accept that kind of condition nicely. It’s more tolerant than many other crops, and close behind barley — which is the top —when it comes to salt tolerance,” Meyer explains.
Management of saline soils must somehow balance seasonal water needs with salt reduction. In dry regions like the High Plains, where seasonal water often does not meet the crop’s needs and irrigation is key, saline soil can also be an issue. This is especially true when irrigation involves high-salt water. Joel Schneekloth, regional water resource specialist for Colorado State University at Akron, says the first priority for excess water should be a drainage system. Then the grower should look at saline-tolerant crops. “Sunflower is a good choice because it is able to mine soil water deep, making room for excess soil moisture drainage or slowing down the up-seep. The crop can also handle salinity,” Schneekloth says. “But sometimes, in wetter areas, no matter how much water the crop uses, Mother Nature may give you more than the soil can take. With some environmental conditions and soil types, the battle gets tougher.”
Some farmers in eastern North Dakota may feel like they are fighting a losing battle. Mother Nature has given them more than they can handle in terms of precipitation in recent years, and water drainage from the Red River Valley only compounds the problem.
The situation is becoming critical. This ongoing public concern is being addressed by the Eastern North Dakota Soil Salinity Project, which was developed by coordinators from the Natural Resources Conservation Service’s RC&D Program (Resource Conservation and Development) to focus on the salinity issue in depth. It is a joint effort between NRCS and the North Dakota Department of Health, working closely with many different partners on the salinity issue.
The project area encompasses the entire Sheyenne, James, Devils Lake and Red River basins. Jessica Beard is a NRCS resource soil scientist managing the project, located in the NRCS Fargo field office. Beard’s position was created to focus exclusively on this problem. She will share information and resources about practices that may improve saline soil conditions, working to support development of new and innovative approaches to salinity management.
Beard kicked off the project in mid-2010 and has been pulling together ideas and results of local efforts by Soil Conservation Districts and other public and private entities. She’s spent a great deal of time with growers, hearing how salinity soil issues are affecting them. This is the first year of a three-year project.
The salinity project’s overall goal is to increase public awareness of the economic and environmental impacts to soil and water resources in eastern North Dakota. Beard has organized a number of demonstration plots in the region. The plots are agricultural fields currently being farmed that will install new and established management practices that attempt to reduce salt levels, increase soil health and stop the salt levels from increasing or affecting more land. Beard is working closely with the landowners and operators, because she feels these approaches should be practical and economical for producers to put in place. The efforts will be monitored to measure success and shared at future plot tours. The results will also be available on the project website.
Arnold Woodbury, a Wyndmere, N.D., farmer and NSA board member, says that the issue is getting worse in his area where water drainage comes to a head. The solution with the most potential in the area is diversifying the cropping systems. “We’re looking for research on using sunflower to prevent soil salinity,” Woodbury states. “This NRCS study is a good start, because the problem needs to be addressed. Too many farmers wait until it’s too late.”
Salinity is a complex issue, but it has always been around. “Some soils are just not suited for intensive crop production and are better managed growing forage. And this project is not attempting to fix that problem,” Beard notes. “The salinity we are looking at is the direct result of the wet cycle we have been experiencing since the early 1990s.” The water table is close to the root zone, affecting crops. “The salts occur naturally in North Dakota soils. But with so much moisture the past 20 years or so, the dissolved salts in the water are coming to the surface. When the water evaporates, the salts are left behind. With time, the salts become increasingly concentrated and more of a concern.”
Woodbury says a major factor regarding saline problems is the trend toward rotations with only shallow-rooted crops. “You can use sunflower to lower a shallow water table, lower in the soil where the salt zone increases — and then come back in your rotation with a shallower-rooted crop,” he notes. “Too many farmers stick to what they know and are reluctant to try sunflower; but that’s what’s gotten us into this situation.”
This is not a new problem, and it continues to get progressively worse. The wet cycle in the Northern Plains has brought it to a whole new level.
“I have heard how years ago people would put a portion of their land in alfalfa for a couple years, work up the soil and plant sunflower and then wheat. Planting that deep-rooted, high-moisture-use vegetation helps maintain the water balance and combat salinity,” Beard says. “The excess moisture is the cause of multiple problems growers face, such as salinity, water-logging, drown-out and topsoil runoff.”
Salinity impacts soil health in many ways. It causes drought stress in plants because salts are drawing water away from the root zone, causing reductions in seedling emergence, poor establishment, stunted growth and reduced yields.
North Dakota State University soil scientist Dave Franzen points out in the bulletin “Managing Saline Soils in North Dakota” (http://www.ag.ndsu.edu/pubs/ plantsci/soilfert/sf1087-1.htm) that excessive salts injure plants by disrupting the uptake of water into roots and interfering with the uptake of competitive nutrients. Several factors contribute to the development of saline soils in North Dakota, but a high water table is a prime requirement. Recognizing how and why salts accumulate is the first step in farming profitably on land interspersed with saline soils. Preventing further encroachment of salinity and addressing remediation strategies are other steps.
The NDSU bulletin outlines how late-maturing crops with deep rooting properties are important for saline soil management:
• Late-maturing crops provide a mulching soil cover until frost, reducing the potential for late summer and early fall surface evaporation.
• Deep-rooted crops leave the soil drier at deeper depths going into the winter, increasing the potential for salts to leach away from the soil surface.
• Deep-rooted crops can use more water at the capillary water boundary, preventing further upward movement.
As growers know, not all sunflower hybrids are created equal. Some hybrids perform better on salty ground than others. It’s usually best to consult with a seed company representative about what might work for a particular salinity issue.
Research is being conducted in the area of identifying a reliable screening method for determining salt tolerance in specific plant lines. Texas A&M researcher Dr. Steve Hague and graduate student Laura Masor are working on singling out specific plants that show traits for salt tolerance to be introduced into breeding lines. This research project is in its second year and is partially funded by the National Sunflower Association.
“We are making great progress, both in our greenhouse and the lab,” Hague says. “The data there [are] matching with our field data, so we are thinking we will be able to screen a lot of different lines in a short period. Genotypes identified as having superior salt tolerance can then be integrated into breeding populations.”
The Texas A&M work will also build upon research findings that genes related to salt tolerance are also linked to drought tolerance. Some of Masor’s field work is being conducted at Pecos (far western Texas), an area that generally receives less than 10” of rain per year and has high saline soils.
This ongoing research at Texas A&M, along with the document released by NDSU, are information resources that the Eastern North Dakota Soil Salinity Project will use to provide a “toolbox” for salinity management, sharing a variety of approaches fit to different regions and producers. The presence or lack of practical, economic ideas will make or break salinity management.
The number-one recommendation Beard gives producers is to keep something growing on the soil throughout the season. What are you growing, and when is that crop using that moisture? Cover crops and rotations can be utilized to use up moisture. She notes that deep-rooted, high-moisture-use crops like sunflower and alfalfa have many advantages. They use up excess water in the soil, break through compacted layers to alleviate compaction, find and utilize nutrients that may have leached deeper into the soil.
If your soil is suited for it, switching to a no-till or strip-tillage system may be an option. Also, leave more residue on fields as a mulching practice. It may seem counter intuitive, but by reducing evaporation you can prevent concentrating more salt within the root zone.
Beard also recognizes that, in some cases, there is no easy fix. “But if we can slow or stop the encroachment of salinity on productive land currently in production, to me that would make this project a success.”
It is an issue that certainly needs to be addressed on a widespread scope in different geographical areas — and something must be done to fight it. Increasing interest and effort by many different groups with different interests will help to ensure the issue is addressed over time. — Sonia Mullally