Growing Turfgrass on Salt-Affected Sites

Introduction

Frequently, high levels of soluble (saline) salts in the soil cause problems in Colorado lawns. Salts may be from natural processes and mismanagement. Salts can accumulate when soil evaporation is greater than rainfall. Attempting to leach salts and using salt-tolerant turfgrasses may remedy this problem. In instances where irrigation water is high in soluble salts or exchangeable sodium, a salt-tolerant grass may be the only solution to the problem.

Turfgrasses

Grass subjected to high soluble salt levels can suffer from root damage, more disease problems, and poor drought resistance. Kentucky bluegrass, the most common turf grass in Colorado, does poorly where salt levels are high (greater than 6 mmhos/cm). Bluegrass can turn a blue-gray color, which indicates drought stress due to excessive soil salts dehydrating the plant’s roots even in moist soils. 

A soil test will determine the salt level in the soil, enabling the homeowner to select the best grass species for the salt-affected site. Less familiar, salt-tolerant grasses for home lawns include:  

• Perennial ryegrass 
• Tall fescue 
• Fine fescues 
• Alkaligrass 
• Bermudagrass 

Perennial ryegrass and alkaligrass are fine-textured and should be mowed, fertilized, and watered like a Kentucky bluegrass lawn. Turf-type tall fescue, a bunchgrass, has a coarser texture than Kentucky bluegrass and will require as much water. Hybrid bermudagrasses result in high-quality lawns that use less water than Kentucky bluegrass – these include Tahoma 31, Latitude, and Iron Cutter.  Bermudagrass greens up late in the spring (May) and turns brown with the first hard frost in the fall. 

If the quality of the irrigation water is unknown or is suspect, submit a water sample to a lab to check it for soluble salts and sodium. Avoid irrigation water with a sodium adsorption ratio (SAR) exceeding 10. 

Table 1: Approximate salt tolerance of turfgrass species. 

Turfgrass Species	Salt Tolerance* (mmhos/cm)	Growth Habit
Kentucky bluegrass	3-6	Sod-forming grass
Buffalograss	3-6	Sod-forming grass
Blue grama	5-6	Bunchgrass
Perennial ryegrass	8-10	Bunchgrass
Turf-type tall fescue	8-10	Bunchgrass
Fine fescue (Chewings, creeping red, sheep)	8-12	Bunchgrass
Bermudagrass	16-18	Sod-forming grass
‘Fults’, ‘Fults II’, ‘Seasalt’ alkaligrass	20-30	Bunchgrass
*Salt levels above which noticeable plant growth reduction and management problems normally occur; mmhos/cm is an expression of the salt content of the soil. This number increases as the salt content of the soil increases and is easily determined by a soil test.

Higher Quality Grasses for Salty Sites

Salty sites can be planted with a single species or mixes of different salt-tolerant grasses. In lower salt areas, buffalograss and blue grama can be planted together, but may not work with other grass species. These are warm-season grasses that green up in May and go dormant (turn brown) with the first hard frost in the fall. Do not use them above 6,500 feet elevation. 

Bermudagrass is a warm season grass and can be used successfully in most parts of Colorado below 6,500 feet elevation. Perennial ryegrass mixes well with Kentucky bluegrass and has similar management requirements; it will not persist under low maintenance or drought stress. The fine fescues provide a fine-textured lawn and do best in cooler temperatures, so could be a good choice for mountain communities. Alkaligrass does best where it is well-watered. 

Do not confuse the turf-type tall fescues with the older forage-types, such as Alta, Fawn, Goar, Kenmont, Kentucky-31, and Kenwell. The newly developed cultivars generally are darker green, have finer and smoother leaves, and are more tolerant of shade than older cultivars. While tall fescue is typically a bunchgrass, there are cultivars that have short rhizomes that recover better from foot traffic and form more of a sod.  

It’s best to purchase grass seed from a nursery, garden center, or directly from a grass seed dealer. Grass mixes (two or more species mixed together) may not contain all salt-tolerant grasses, which can lead to management challenges and dieback.

Grasses for Naturalized or Low Maintenance Areas 

For areas of the landscape that receive lower maintenance (irrigation, mowing, and fertilization), grass selection will be important. Wheatgrasses (tall, western, and crested) and bromegrasses can do well if left unmowed. Grasses that receive lower irrigation will naturally space themselves out between plants and be less “turf-like” but will persist and provide a good soil cover. Without irrigation, these grasses become dormant during extended drought. Bromegrass can be used alone or with the above species if soil salt levels are only moderately high. Where salt levels are relatively low, blue grama and buffalograss (both native to Colorado) are excellent choices for naturalized or low maintenance lawns.

Internal Drainage 

Washing salts off the soil surface is not sufficient to prevent damage to grass roots. Internal drainage usually needs to be improved to allow the leaching of the salts below the root system. Sometimes a layer of clay in the soil will prevent proper drainage. Breaking through such layers can increase drainage and the downward movement of salts. 

The “white alkali” (soluble salts) seen in many areas of the state are chlorides, sulfates, carbonates, and sometimes nitrates of calcium, magnesium, potassium, and other minerals. These salts are mostly soluble. They can be leached out of soils with good internal drainage when good quality irrigation water is used. Good drainage and good irrigation water can provide a permanent solution to high soluble salt problems. (See Table 2.) 

Table 2: Good quality water needed for salt reduction. 

Amount of water	% salt reduction
6 inches	50%
1 foot	80%
2 feet	90%

Soluble salts generally are a serious problem in poorly drained soils where adequate drainage does not exist. To improve drainage, add organic matter at the rate of 3 to 6 cubic yards per 1,000 square foot area, and thoroughly mix this with the existing soil to a depth of at least 6 inches. Avoid excessive use of fresh cow, horse, or steer manure because it may be high in salts.  

Adding sand as a soil amendment to loosen clay soils is seldom recommended. Sand mixed with heavy clay soil frequently sets up like concrete. However, a sandy soil may be used as topsoil provided good subsurface drainage exists. Partially mix topsoils with the subsoil to prevent the reduced drainage that often occurs when soils are layered. 

For white alkali, the addition of gypsum (calcium sulfate) is not recommended. A high percentage of white alkali in Colorado is gypsum. Adding gypsum only increases its concentration, increasing the salt problem. 

In some cases, a tile drain system may be needed to carry salty water to a drainage ditch or sump. In other instances, trenches filled with gravel or coarse sand may be used to help move salt-laden water off a problem site. 

A high water table, less than 48 inches below the soil surface, can aggravate a soluble salt problem and create a hydraulic connection with the soil surface. This allows the pumping of soluble salt to the soil surface. If an outlet is available, use a tile drain system to reduce a high water table problem. In addition, place a layer of coarse sand above the water table, and below the water table, place a layer of good, sandy soil to stop upward water and salt movement. Then plant grass in the sandy soil. Impervious barriers of plastic, blacktop, and concrete placed under lawns have caused serious salt buildup problems resulting from improper fertilization and poor quality water. 

In many instances, it may not be practical to amend, drain, and leach the soil for salt intolerant turfgrass species. However, a salt-tolerant grass may provide an acceptable solution. This is especially true where a lawn is in a low, poorly drained area with a high water table, or when salt moves from an unlined irrigation ditch into a lawn area. There are some areas in Colorado where the combination of high salts and heavy clay soils preclude the planting of any turf variety without excessive costs.

Sodic Soils Differ

Sodic soils (black alkali) contain an excess of sodium and are very difficult to manage. They often need to be amended before planting any turfgrass species. Leaching sodic soils that contain high salt levels will deteriorate drainage and create an even worse problem. Before leaching, always test the soil with a reputable lab to determine if amendments, such as gypsum, are required. Leach the soil only after the addition of a required amendment. 

A soil test through a soil- and water-testing laboratory can determine whether you have a saline (white alkali) and/or sodic salt problem. A soil test to determine salt levels can save time, effort, and money by helping determine the best adapted grasses for these areas.

Fire Mitigation 

Many mountain homes are surrounded by wildfire-susceptible forests, so fire resistance should be considered when landscaping. In general, flammable plant materials such as conifers should be removed within 15 feet of the home, and nothing should be planted within 3 to 5 feet of the house, particularly if it is sided with a flammable material. 

Reference: CSU Fact Sheet 7.227