WE KNOW TURF: Fertilizing

A dense green carpet of grass is the basis of most home landscaping plans. Without this rich green, even the most perfect tree and shrub specimens will not show to the best of their ability, nor will the house itself. In addition to its aesthetic value, a well-kept lawn has many practical functions. It holds the soil in place and reduces dust and mud tracked into the house. It provides a cooler setting for the house by reducing glare and reflected heat from the sun. It serves as a family recreation area and reduces the risk of injuries.

A regular lawn fertilization program is necessary to maintain a good quality lawn. Dollar for dollar, proper fertilization will do more to improve poor quality lawns or maintain good quality lawns than any other single management practice.

The best approach to the establishment of an adequate fertilization program is to have a soil test made, although soil tests must not be regarded as a panacea for poor quality lawns. Soil tests are one of the tools for determining an intelligent fertilizer program. For instance, it is impossible to look at turf and determine if it has a phosphorous or potassium deficiency, even though it is obvious that the grass is not growing satisfactorily.

The best indicator of plant nitrogen status is the appearance of the plant. A thin, chloratic turf stand often results from lack of nitrogen; and dense, green turf indicates ample nitrogen. A fast-growing, dark green, very dense turf stand may mean excessive nitrogen.

When corrective measures are undertaken, do not expect to correct the deficiency immediately. In some cases, regular fertilizer application may be required for several years. Usually, however, nutrient balance can be achieved in a much shorter time. By correcting soil nutrient deficiency problems through proper fertilization, you can develop a more balanced maintenance fertilizer program.

Cool season grasses (Kentucky bluegrass, fine-leaved fescues, tall fescue, perennial ryegrass, and bentgrasses) make their maximum growth during periods of cool, moist weather and may become dormant or semi-dormant during hot weather months.

Warm season grasses (bermudagrass, centipede grass, carpet grass, bahia grass, St. Augustine grass and zoysia grass) make their maximum growth during periods of high temperatures and normally go dormant during the cooler periods of the year.

Fertilizer requirements will vary with the species and/or variety of turf grass; the soil physical and chemical conditions (texture, structure, compaction, PH, inherent fertility), climatic conditions (temperature, rainfall, length of growing season), the use to which the turf is subjected, and other management practices.

Among the cool season grasses, turf-type perennial ryegrasses, Kentucky bluegrass, and especially some of the improved cultivars, have high nutrient requirements, whereas slower growing, fine-leaved fescues (red, chewings, hard and tall fescue) have lower needs for many nutrients. Bermuda grass, especially the improved cultivars, has a very high nutrient requirement especially for nitrogen; St. Augustine grass and zoysia grass have medium requirements; and the centipede grass, carpet grass and bahia grass are slow growing, low fertility, warm season species.

FERTILIZING MATERIALS

An ideal fertilizer program should provide uniform grass growth over the entire growing season. Although the ideal is seldom reached due to temperature and moisture fluctuations, proper choice of the right type of nitrogen material in a fertilizer, along with the correct rate and frequency of application, are important in moving towards this ideal.

Basically, nitrogen materials are divided into two broad groups - those which are quickly available to the plant and those which are slowly available. It is important to note that quality turf grass can be produced with either type of nitrogen, provided that the nitrogen is applied in the proper amounts and frequencies.

The quickly available nitrogen materials are water soluble, and, once in the root zone, the nitrogen is readily available to the plants, provided there is adequate soil moisture. This fast release action allows weak turf top recover quickly. It may be necessary to make frequent, light applications of the quickly available nitrogen fertilizers in order to maintain a uniform growth over the growing season.

Slowly available nitrogen fertilizer materials which contain IBDU or SCU release a portion of their nitrogen over relatively long time periods. These materials depend upon physical and/or chemical process to provide nitrogen in a form available to the plant.

As a general rule, cool season grasses require approximately four pounds of nitrogen per 1,000 square feet per season.

Warm season grasses have a much wider range of nitrogen requirements than do cool season grasses. The difference in length of growing season in regions of warm season grass adaptation accounts, in part, for the wide range of nitrogen requirements, especially for Bermuda grass and St. Augustine grass.

Efficient use of nitrogen fertilizer can be achieved only if the turf manager knows the growth habit and needs of his turf, understands the characteristics of the different nitrogen carriers, reduces any possible nitrogen losses and evaluates each application to make any necessary adjustments. In short, a systems approach is necessary when dealing with the interrelationship of plants, soil and fertilizer.