Using composts to improve turf ecology
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…Posted Jan 28, 2009
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.
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.
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.
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.
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.
Dan Dinelli is Superintendent of the North Shore Country Club in Glenview, IL.
To find out more about the composting practices at North Shore Country Club, contact Superintendent Dan Dinelli, CGCS at 847-724-4963, or via E-mail at firstname.lastname@example.org.