Understanding the Soil Environment

A basic understanding of soils allows the gardener to work with natural processes to enhance plant root growth and overall vigor. Turfgrasses are as demanding of proper soil conditions as all plants - healthy soil grows healthy plants.  Soil is an amazingly complex, living ecosystem requiring a balance of organic, inorganic, living, and nonliving components.

Recent soil science research has demonstrated that the most productive soils are loaded with a variety of microbial life; beneficial fungi, bacteria, yeasts, and other microorganisms work to decompose organic matter into humus. Humus directly influences both the assimilation of nutrients and plant resistance to disease, insects, drought, and other stresses.

Physically, the soil should be composed of fifty percent solids and twenty-five percent each liquid and air, with an organic matter content of three to five percent. On this side of Iowa, the "ideal" soil is seldom found in the native habitat. Here in the West, we are required to amend the soil to provide the optimal growth environment. The various fine-particle clays and silts of our region benefit greatly from the addition of organic matter.

Alkaline clays (high pH) should also be amended with gypsum. The addition of organic matter to sandy and gravelly soils is also beneficial, increasing water retention and providing essential nutrients. Initial expense for organic matter and other amendments pays for the continued beauty and health of the planting. New lawn installations should start with basic soil considerations; physical and chemical soil analyses may be desired.

Marginal soil conditions in existing lawns can be improved with cultural programs designed for the specific site. Regular aeration, vertical mowing, top dressing with compost or rich soil, proper fertility management, and applications of foliar and soil biostimulants are all proven techniques for rejuvenating a poor lawn. A properly balanced soil will support deep, extensive root systems, allowing plants to assimilate all available food and moisture. The result is a thick turf that resists drought, weeds, and disease.

For basic physical soil analysis, use a soil probe or large, strong knife to cut samples at least six inches deep. Examine for thatch layer thickness, particle size, distribution, compaction, and topsoil depth. A minimum of six inches of properly balanced soil is required to grow a healthy lawn. A thatch layer thicker than a one-half inch will act as a sponge to limit the penetration of water and nutrients to the root system. If necessary, consult with a qualified landscape professional for help with soil testing.

Basic chemical soil tests (nitrogen, phosphorus, potassium, and pH) can be handled through the county extension service. For a very thorough soil analysis with written interpretation and recommendations, contact Integrated Fertility Management at (800) 332-3179. What occurs below ground, unseen, largely determines what we see above ground. The knowledge of basic soil conditions is essential to proper cultural decisions and practices. Again, healthy soil grows healthy plants.

Preferred Organic Matter Amendments

1. Commercial compost - bulk or bagged
2. Well-aged manure - our favorite is a horse manure
3. Blood, bone, and cottonseed meals
4. Bagged products - steer manure, chicken compost, etc.
5. Well rotted sawdust
6. Grass clippings - with no herbicide residue!
7. Chopped straw or hay.
8. Decomposed pine needles (for acid-loving plants) and hardwood leaves(#'s 5-8 are best when first composted with manure, or worked into the soil well ahead of planting)