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It is said that if any of the billions of organisms inhabiting the soil had hands, the fate of the world would be in them. An important soil function is the harboring of a diverse community of organisms that includes bacteria, fungi, protozoa, nematodes, mites, springtails, millipedes, sowbugs, earthworms, and many others.

This community drives the decomposition of organic residues; recycles important nutrients like carbon, nitrogen, phosphorus and contributes to the formation of new soil and soil structure. With these activities, soil organisms contribute to other important soil functions, such as supporting the growth of plants and absorbing, neutralizing, and transforming compounds that might otherwise become pollutants in the environment. Basically, soil organisms play a critical role in shaping and maintaining terrestrial communities and ecosystems.

As the Superintendent at North Shore Country Club in Glenview, IL, I became interested in applying compost as a soil amendment after reading about research suggesting it’s many agricultural benefits. Dr. Michael Boehm, Ohio State University and Dr. Eric Nelson, Cornell University have done helpful work, specifically about the effects of compost on turfgrass. Generally, researchers and practitioners recognize that incorporating high-quality compost does several things:

  1. Adds food and nutrients for plants and organisms,
  2. Adds a diversity of organisms to the soil,
  3. Encourages plant growth promoting substances in soils. Compost can also have an effect on soil structure, nutrient cycling, disease suppression, nematodes and other biological activity.

In fact, the use of composts on turf is not new. A book given to me by my Grandfather, Frank Dinelli (retired Greenkeeper at Northmoor Country Club), titled Turf For Golf Courses, by Charles V. Piper and Russell A. Oakley printed in 1917 has a chapter devoted to “Manures, Composts and other Humus Materials”. Yet because compost is not widely used on golf courses, I wanted to participate in further research prior to investing in the process at North Shore Country Club.

Phase I: Experimentation

In 1996, we got just that opportunity by participating in a two-year study of various composts and organic materials under the direction of Dr. Michael Cole of the University of Illinois and GreenCycle, Inc. (operator of several composting facilities) of Northfield, Illinois. The study was a replicated 10’ X10’ plot design on our 5th fairway comprised of creeping bentgrass and Poa annua maintained at 1/2” mowing height. During the field evaluation, all observations were noted. However, our main objective was to observe any disease symptom differential between the various plots.

Our first application was in the fall of 1996 to observe snow mold (Gerlachia nivalis, Typhula spp.) suppression. None of the materials demonstrated any noticeable snow mold suppression. However, plots treated with compost had a notably earlier green-up and recovery rate verses the control plots. We then repeated applications late spring of 1997. Observations through the remaining growing season showed strong dollar spot (Sclerotinia homoeocarpa) suppression — up to 80% reduction; improved turf color and density, and increased earthworm castings. Thus, while our initial objective of snow mold suppression was not observed, our experiment to test organic products to improve overall turf ecology proved quite successful.

Phase II: Implementation

Based on favorable results after 2 seasons of field evaluation of compost topdressing, we implemented the strategy on all our fairways. During our normal coring of fairways, the process involves the following steps:

  1. Coring with hollow tines,
  2. Breaking up the soil cores with a vertical mower,
  3. Topdressing with compost,
  4. Mixing the soil with compost as it is matted into the surface with a section of chain-link fence,
  5. Blowing the remaining tufts of turf and thatch into rough via a three-point hitch blower,
  6. Picking up debris in the rough with an out-front rotary mower fitted with a bagging attachment,
  7. Irrigate the area well.

We have been coring fairways like this for several years. Adding the extra step of compost topdressing has not significantly impacted the workload. The cleanup is about the same and we can still get our targeted 9 holes (15 acres) done in one day. (Note: Part of our IPM cultural program is poling, by dragging a chain over the fairways each morning to remove leaf moisture and guttation. This process also manages earthworm casting buildup).

The results so far are much the same as in the test plots: improved turf density and color; rapid healing of cored turf; Dollar spot (Sclerotinia homoeocarpa) suppression; increased earthworm castings; and thatch reduction have been observed. We continue to monitor the impacts of compost use on turf and maintain computerized spreadsheets to evaluate our results. In time and continued applications, we hope to document improved soil structure and suppression of other diseases.

Selecting quality compost is key

Selecting quality compost is very important; you have to do your homework. Compost products are not yet standardized, so the challenge is in obtaining consistent, high quality compost. The procedure we use to assure the compost we obtain is optimal for our turf involves a series of tests. We analyze chemical, physical and biological activity.

Chemical Analysis:

In the chemical analysis we look for:

  • Carbon : Nitrogen ratio <20:1, best at 15:1
  • pH at 6.5 – 8.5
  • None to trace amounts of ammonium, sulfide and nitrite
  • Low concentrations of soluble salts, especially sodium

We strive towards elemental balance and recommended ratios favoring the high side of potassium and calcium. Biosolids need to meet US EPA’s Part 503 technical rule for biosolids. All biosolids tested for coliform and other diseases. Biosolids composted properly have been heated sufficiently to kill viruses, coliform and other diseases. Metals in biosolids are often high and should be considered.

Physical Analysis:

Physically we look for:

  • Fine texture < or = 1/8”
  • Light, crumbly structure, parent material non-visible
  • Moisture at 30-40%
  • Dark brown to black in color (caution, dark black compost might indicate the compost was too hot)

Microbiological Analysis:

A great diversity of bacteria, fungi, protozoa, and beneficial nematodes occur in good compost. Healthy compost has been hypothesized to have between 10,000 to 20,000 species of bacteria per gram. The DNA analysis required to establish the set of species in highly diverse compost awaits study by molecular microbiologists. The study of microorganisms is very complex and dynamic. Many of the billions of organisms that exist have not yet been described or their functions understood. It is a frontier ready to be explored. Several laboratories and universities are exploring methods to assess soil and compost microbial activity. Soil Foodweb Inc. has done testing for us, including bacteria, fungi, protozoa and nematode counts. Some feel nematodes could be used as a biological indicator. Four basic types of nematodes occur: bacterial-feeders, fungal-feeders, root-feeders and predatory nematodes which feed on other nematodes. When organisms increase, an increase in those nematodes that feed on them occurs, thus giving an indication of relevance. BBC Laboratories has also done testing for us (see charts).

They analyze concentrations in six groups of organisms, which they feel are ‘key players’ in soil ecology. The following six functional groups tested are:

Heterotrophic (Aerobic) bacteria

Finished compost should have 100 million to 10 billion Colony Forming Units/gram dryweight (CFU/gdw). Compost with less than 100 million CFU/gdw will not perform as well as soil inoculants and may not be effective in suppressing plant diseases.

Yeasts and molds (fungi)

Finished compost should have between 1 and 10 thousand CFU/gdw. These organisms are important for breaking down organic compounds, soil nutrient cycling, stabilizing soil aggregates, and controlling plant disease.

Nitrogen-fixing bacteria

The number of free living nitrogen-fixing bacteria in compost varies a lot depending on the available nitrogen concentration but may be in the range of 1 thousand to 1 million CFU/gdw. The populations of these free-living nitrogen-fixing bacteria will proliferate as the available nitrogen in the compost decreases. As a consequence, there is typically an inverse relationship between biologically available nitrogen in the compost and the concentration of free living nitrogen fixing bacteria.

Actinomycetes

Finished compost should have at least 1 million to 100 million CFU/gdw. Compost made with woody materials may have more. These organisms are important for many functions including the break down and nutrient cycling of complex chemical substances such as chitin and cellulose, improving soil crumb structure, and assisting in the reduction of plant pathogen pressures. They are particularly efficient in alkaline soils.

Anaerobic bacteria

Ratio of Aerobes to Anaerobes in the compost should be at least 10:1 or greater. An overgrowth of anaerobes indicates the compost was not turned with sufficient frequency. It is important that anaerobic by products in the compost be degraded prior to use with plants of germinating seeds.

Pseudomonads

Finished compost concentration should be between 1 thousand and 1 million CFU/gdw. Depending on starting materials, this number could be lower, but is rarely higher. Pseudomonads are important in nutrient cycling, assisting plants with phosphorus availability, and some have been linked to the biological control of plant pathogens.

In addition, compost needs to be free of contaminants, such as weed seeds, plant parts, pathogens, stones, plastic, glass, wood, nails, etc. Compost also needs to be ‘mature’, testing >50% on the maturity index, by BBC Labs. In house maturity tests can be performed by planting grass seed in a pot, utilizing the intended compost as the growing medium, to observe seedling health and establishment. Another method is to fill a plastic bag with intended moist compost and allowing it to sit sealed in the sun for a few days. Upon opening the bag, the compost should have an earthy smell, not an offensive smell from ammonia or sulfur.

Following these procedures will help insure favorable results. Adverse effects can result when utilizing poor-quality compost. Starting slow and testing small areas first is always helpful. Developing a working relationship with local composters will help in understanding their product.

Additional Uses for Compost with Turf

In addition to our fairway compost topdressing program, we also use compost in our ‘soil and seed’ mix for divot repair. Compost is used as topdressing while over seeding turf. In 1998, a 7,000 sq.ft. experimental putting green was constructed having 20 different root zone mixes. Each mix used USGA approved sand in a USGA root zone profile with various organic and inorganic amendments. The 90/10 sand/compost plots out performed the others considerably in seedling establishment and development. We continue monitoring other effects as the putting green matures. Compost tea is made and applied as a protective biofilm on the phylloplane and to deliver plant growth promoting substances.

The Bottom Line

To apply compost topdressing to fairways we purchased a TY-Crop MH-400 for $20,000. This material hauler/topdresser is used for other tasks as well, such as rapid refill of materials while topdressing greens and tees and applying sand in bunkers. The compost we currently use is a 50/50 mix of yard trimming compost and biosolids. Our cost for yard trimming compost is $14.00/cubic yard. For us now, biosolids are freely available (EPA permits are needed). The rate used is approximately 17 yards (7 tons)/acre = 1/8” layer. Total material cost $119/acre. We offset some costs by reducing our other fertility inputs and decreasing fungicide treatments as part of our IPM program.

All composts are not created equal

Understanding the chemistry, biology and science of compost is complicated. Parent material used, how it’s managed during composting, and storage can all have a huge effect on the finished product and results. Yet our efforts to understand compost, particularly its microbial benefits, have paid off. Results using composts have been positive and the turf ecology is improving under our growing conditions.