January 30, 2004 | General

Measuring Compost Impact On Turf Growth

Michael Rainey
BioCycle January 2004, Vol. 45, No. 1, p. 28
In February 2003, the New Hampshire Compost Association (NHCA) requested permission from the state’s Department of Administrative Services, General Services Bureau to conduct a compost use demonstration on state grounds outside the Health & Human Services Building in Concord. The goal of the project was to show that use of good quality compost would improve turf growth around state buildings when compared to the typical turf management currently employed.

Construction of the demonstration area was done on May 5, 2003. The pilot area in total was about 51 feet long by 14 feet wide. This plot was divided into four smaller treatment plots, each 12 feet by 14 feet. Three plots were treated with different soil amendments/fertilizers (biosolids compost, chemical fertilizer, and leaf and yard trimmings compost) and then seeded with a perennial rye grass. One plot received no amendment/fertilizer, but was seeded. Between each of the smaller plots, a one-foot buffer of untreated turf was maintained.
In order to determine the appropriate application rates for compost and fertilizer, a composite sample of the soil in the plot area was collected and sent to the University of New Hampshire’s (UNH) Analytical Services laboratory in Durham. After completion of the analysis, a lab report was sent with detailed nutrient recommendations for nitrogen, phosphorus, potassium, and lime requirements. Based on the soil test results, no lime was recommended. Application rates for the three plots receiving fertilizer or compost were based on nitrogen need. The recommendation from UNH for nitrogen was 1 lb of nitrogen per 1000 sq.ft. The area of each treatment plot was 168 sq.ft. Rounding to an area of 200 sq.ft., 0.2 lbs of nitrogen would be needed for each treatment plot. For the chemical fertilizer plot, about 1 lb of a 29-3-4 fertilizer was applied (about 0.29 lbs). For ease of application, it is often recommended that one-quarter to a half inch of compost be applied to lawns. Assuming 0.15 percent available nitrogen, and using the application guidelines of one-quarter to one-half inch, between 0.19 to 0.38 lbs of nitrogen was applied to the leaf and yard trimmings compost treatment. Assuming 0.30 percent available nitrogen, 0.36 lbs. to 0.72 lbs. of nitrogen was applied to the biosolids treatment.
After the fertilizers and compost were applied, these amendments were incorporated into the soil to a depth of two to three inches, eliminating any existing grass. Since no amendment was added to the control, no incorporation was necessary and the existing turf was preserved. Perennial rye grass seed was applied to all four treatments according to application recommendations on the label and raked into the surface of the soil.
After amending the soil and seeding the area, stakes and string were used to prevent foot traffic while the turf was being reestablished. Posters also were put on display to explain and identify components of the demonstration.
This demonstration did not attempt to quantify the potential differences in growth response between the different treatments. Instead, visual observation was used to assess the relative efficacy of each treatment. The costs for each type of treatment also were compared. Finally, an evaluation of the ease of application is offered.
Between May 5th (the day of application) and June 17th (the day of observation), there was no mowing or foot traffic across the plot. During this six week period, all four treatments were managed in an identical manner, affording each the same potential for grass germination and growth. The control plot had a slight advantage in that some grass already was established at the start of the demonstration as opposed to the other three treatments in which all turf was destroyed during the incorporation process when these plots were initially established. Photos 1-4 show the amount of grass growth on each treatment over the six week period.
In comparing the “before” and “after” photos, it is obvious that all plots benefited from being reseeded. It also seems that both the biosolids and yard trimmings composts were superior to chemical fertilizer for establishing turf. The compost plots have both denser and higher growth. Using grass height as an indication of grass production, Photos 1-4 seem to show that the control produced the most grass. However, careful observation would suggest denser growth in the compost treatments, particularly for biosolids. While not discernible from the figures, the amount of newly germinated grass was clearly greater in the compost plots than in the control. The appearance of greater production in the control can mostly be attributed to previously established turf.
Table 1 shows the material costs for managing turf using the four treatments discussed. Costs have been equalized to show the cost per 1000 sq.ft. for each management regimen. These expenses do not reflect labor costs necessary to have a professional landscaper, turf manager or groundskeeper perform the work. As would be expected, the cost of reseeding is less than the cost of reseeding combined with the addition of a soil amendment. Among the amendments, chemical fertilizers were the least costly. Although the leaf and yard trimmings compost appears to be the most expensive option, the actual cost of using various composts may vary depending on the quality, quantity ordered and trucking distance.
With regard to the comparison of ease of application, clearly simple reseeding or reseeding coupled with chemical fertilization were the easiest options. Because composts are far more bulky than seed or chemical fertilizer, transporting and handling them requires far more time and effort. In addition, home lawn spreaders are adapted to spreading commercial seed and fertilizer and may not be able to handle many types of compost.
Although cost and ease of application favor reseeding or reseeding with chemical fertilization, compost use seems to enhance germination and grass production. Compost use has other advantages not readily apparent from such a short demonstration, e.g., it is a slow release nutrient source and supplies a wider array of macro and micronutrients compared to most lawn fertilizers which predominately supply nitrogen, phosphorus, and potassium. Most importantly, compost adds organic matter to the soil, which can improve soil structure, soil aeration, water holding capacity, nutrient retention and compaction resistance. Reseeding and chemical fertilizers will not improve these soil properties. There also is significant evidence that compost provides resistance to turf diseases. If turf health and production are the primary goal, compost is a superior soil amendment for overall soil health and enhancement of plant growth. When all the benefits of compost use are considered, the cost and handling advantages of other turf management options may not be as attractive. The benefits to soil properties and plant growth from compost use are difficult to quantify. Consequently, Table 1 may not accurately reflect the value of amending the soil with compost.
Mike Rainey is with the New Hampshire Department of Environmental Services, and a founding member of the New Hampshire Compost Association. For more information about NHCA, log onto

Sign up