What Grasses Grow in High pH and Low Nitrogen?

Ideal Grass Life

• The majority of lawn grass seed varieties do well in slightly acidic soil with regular applications of nitrogen-rich fertilizer. The pH scale, which describes the acid or alkali content of soil, would show readings of 5.5 to 6, with 7.0 being neutral on a scale of 14, for soil in which most grass varieties do well. Nitrogen fertilizer governs healthy cell formation and therefore growth; results are visible in a strong green color. If, in addition, you have good sun, plenty of water and good soil drainage, a wide range of lawn grasses will flourish.

Alkaline Soil

• Some regions of the U.S. naturally contain alkaline soils. "White alkali" soils are also classified as saline soils, excessively rich in water-soluble salts of several kinds. Concentrations of salts can be affected by excessive dryness or excessive moisture if the water table is high and water sources are salt-rich. "Black alkali" salts are excessively rich in sodium compounds that are not water-soluble. While high alkali levels can be found in soils close to salt water, Northern U.S. plains and Western mountain areas also have highly alkaline soils. High-pH soils adversely affect plant water uptake and, because they affect the adhesion of soil particles to each other, can also make it difficult for grass plants to stay securely rooted.

Low Nitrogen Soil Content

• Low nitrogen content is often a predictable corollary to saline or sodic soil conditions. Organic matter content is low, and nitrogen absorption is blocked by high salt conditions. The heavy watering that can leach soluble salts out of soil and reduce pH can also wash away added nitrogen-containing fertilizer. Without good nitrogen levels, cell growth is affected and grass becomes spindly and sparse.

Grasses That Survive

• A small number of turf grasses can survive moderately high pH levels, from neutral 7.0 to 8.0. From Accurate Building Inspectors' extensive list of lawn grasses, beachgrass, blue gammagrass, buffalograss, dichondra and wheatgrass are possible candidates, depending on climate. The University of Rhode Island Cooperative Extension adds alkaligrass to the list, noting that it is tough enough to tolerate roadside salt. The Colorado State University Extension includes tall and red fescues, perennial rye grass and Bermudagrass among high salt-tolerant grasses. Some wheatgrasses show good tolerance. Suggestions vary regionally and are determined by exact local soil conditions. All those suggesting grasses note the importance of getting soil tested.

High pH and Low Nitrogen

• Several grasses can be eliminated when confronting both high pH and low nitrogen levels. University of Illinois Urbana-Champaign fertilizer specialists rated a number of turfgrasses by nitrogen need, pounds per 1,000 square feet per year. Of those tested, perennial rye grass, with a level of 2-4, and buffalo grass, with a rating of 0-2, met both criteria. While not tested, alkaligrass, which can tolerate being planted along highway medians and roadsides, could be an excellent candidate for no added fertilizer. Regional natives in general are likely to show better soil tolerance and lower needs for added nitrogen than nonnatives.

Changes and Amendments

• Although it can be difficult, county extension agents in varied parts of the country suggest ways to alleviate saline and sodic conditions, as well as knowing good varieties to plant in your area. Opponents of added nitrogen fertilizer, including Nitrogen Free, have further suggestions to enhance naturally occurring nitrogen. Tips include leaving grass clippings on the lawn after mowing, to return nitrogen to the soil, and growing clover or other low-profile legumes with nodules that fix nitrogen in the soil, mixed in with your grass. They also note the importance of soil testing in making any decisions about your lawn and other plantings.