These last few weeks, we have been looking at organic lawn care practices, and today’s blog examines the benefits of applying top dressings to lawns. There has been a considerable amount of university-based research on the improved performance of turf with the use of top dressings of compost. Today, the practice of top dressing is used by many who prefer a more organic approach to lawn maintenance as well professional turf managers of sports fields and golf courses.
What is a top dressing? Simply put, it is a thin layer of material, ¼ to ½ inch that is spread over the top of the turf. The materials used for top dressing can include sand, soil, composts or a mixture of any of these. The best times of year to top dress are in the fall before frosts are expected or in the spring after the first mowing. Adding a top dressing is a way to slowly add organic amendments to the soil and improve it without disturbing the growth of the grass. The improvements in the soil might not be immediately visible, but following a routine over a period of several years, the following list of benefits is attributed to top dressings of compost:
- Provide nutrients
- Increase organic matter
- Improve soil structure
- Reduce irrigation
- Reduce thatch
- Improve surface irregularities
- Add beneficial microbes
- Reduce winter damage
- Reduce weeds
- Reduce nutrient loss to surface and ground water
Composted material is easily added to gardens or beds where the large clumps are usually left to further breakdown. But with grass, it’s helpful to sieve the compost so that the large clumps are removed and put back into the compost bin. A homemade screen can be made from 2 x 4s and made to fit over a wheel barrow. Use a piece of hardware cloth that has ½ inch openings, and secure the piece to the wooden frame. The organic material to be placed on the lawn should be dry and easily pass through the screen. Once you have the material screened, you can spread it by using a large drop spreader, by dumping small piles and then raking it out, or by simply using a shovel and flinging the material over the lawn. Typically only ¼ to ½ inch of top dressing is applied. At least half of the leaf height should be visible or the grass may be killed by a lack of sunlight. Except for areas in the turf grass that are already thin with soil exposed, a top dressing should not be visible.
Top dressings can be used to even out bumps and swales. In this case the top dressing may be a mix of soil and composted material, and the depth may be deeper. The area can then be over-seeded with grass seed. Lightly rake the seed into the top dressing and keep the area moist for good germination and establishment. Lawn overseeding should be done when the soil temperature is optimal for your specific area.
Core aeration can be done before or after top dressing, and it helps to incorporate the organic material into the soil. Irrigating after the application of top dressing also helps integrate the compost down into the turf.
If you do your own composting, you know exactly what is in the compost and how well-processed it is. Many home owners find themselves looking for compost to purchase. When purchasing compost, it is important to find a reputable supplier who can provide an analysis of the product. How do you know how much to purchase? First, determine the amount of surface area to be covered then multiply the area by the depth of compost desired (in feet).
For a 5000 square foot lawn being covered with ¼ inch of compost, the math would be 5000 feet2 lawn x 0.02 ft compost = 100 feet3. Usually, compost is sold by the cubic yard. Divide 100 feet3 by 27 = 3.7 yards3. So, for a 5000 square foot lawn, 4 cubic yards of compost would cover it at a depth of ¼ inch.
Many homeowners have replaced synthetic fertilizers with a yearly top dressing. It may involve more work, but as composted materials continue to breakdown into the lawn and add nutrients to the soil the results begin to become obviously visible and rewarding. A healthy lawn is better able to recover from dormancy, tolerate a summer drought, resist a disease outbreak, or repair after heavy wear and tear from foot traffic, and top dressing definitely results in a healthier lawn.
Question for the week: Have you ever top dressed your home lawn?
By Kimberly Bell
Photo from: http://www.compostjunkie.com