This is the second post in a three-part series. Click to read the first post, Weeds Taking Over Your Lawn? Try Compost.

The soil food web consists of a multitude of creatures, from microscopic bacteria to earthworms and moles (see Figure 1). At the bottom of this web are bacteria and fungi. These microbes form the base of the pyramid of all soil life, and by extension, all terrestrial life. By breaking down organic matter and dissolving minerals for their own consumption, they provide the basis for nutrient cycling in soils. The larger food web organisms, such as protozoa and nematodes, eat the bacteria and fungi, and then excrete many of the nutrients into the soil in plant-available form.

The Soil Food Web (U.S. Dept. of Agriculture)

The contribution of these microbes does not end there. Bacteria and fungi are largely responsible for soil structure. Bacteria secrete glues that bind tiny particles of soil together. The fungi grow threads (called fungal “hyphae” – see Figure 2), which bind these smaller aggregates into larger ones, giving soil its porosity and loose, crumbly structure.

Without a good proportion of both bacteria and fungi, soils tend to become compacted, with less oxygen and reduced water-holding capacity, creating the hard-packed, stressed soils in which weeds thrive.  Since many home owners don’t add organic matter to their lawns and often eliminate the only major source by removing grass clippings, fungi are starved of available nutrients. Bacteria, on the other hand, can thrive under all kinds of harsh conditions. Accordingly, many of our lawns are unbalanced and “bacterial dominated,” deficient in beneficial fungi. This situation constitutes an open invitation to weeds, who are nature’s “first responders” when soils are damaged or stressed. Their job is to grow rapidly, die, and decay, and by doing so increase the organic matter in the soil, so that the fungi can slowly come back into balance. Weeds are by their very nature suited to bacterial soils because they are the first vital step in nature’s long-term remedy for disturbed ecosystems.

Fungal hyphae under a microscope (jollyfarmernursery.com)

By adding compost, we can quicken the process of bringing a damaged turf soil back into equilibrium. Compost raises the level of organic matter in soil, making it better for grasses and less hospitable for weeds. What would ordinarily take nature decades to accomplish, we can do in a season or two with compost.

The ECO would like to see the provincial government supporting the optimal use of compost by helping those who make it and use it to understand how important the biology can be for the compost’s effectiveness. A piece in this year’s Annual Report, entitled “Compost: Understanding Nature’s Sense of Humus,” provides considerable background information on compost’s nature and benefits, as well as some inspiring examples of how well compost works when used within the scientific framework provided by soil ecology.

Watch for the third blog in this series, where the ECO will provide a few practical tips for home owners on how to use compost to effectively control weeds.

First in a three-part series.

(photo by flickr user arimoore)

Ontario’s ban on the cosmetic use of pesticides has made a lot of people nervous about weeds. Letters to editors of the province’s newspapers often carry laments from home owners regarding weed invasions and the despoiling of lovely green lawns, parks and sports fields. Many people are at a loss for how to cope with weeds.

The ECO would like to suggest that the solution is close at hand. The application of well-made compost, with the occasional help of a few additional organic inputs, can reduce weeds to the point where a few minutes of hand-pulling from time to time is all that is needed to maintain a green, healthy, weed-free lawn. This is not a matter of just adding compost and hoping for the best. This is science that works.

The Town of Wolfville, in Nova Scotia, provides a good example. David Slabotsky, who manages the parks, gardens, and recreational sports fields for the Town, had been using organic methods of turf management for years but was still having problems with weeds. After attending a workshop where he heard a scientist talk about the importance of beneficial fungi in turf soils, he decided to get some training in the biology of compost and soil and apply his new knowledge to his job.

Within a couple of years of introducing some new methods, weeds have all but disappeared and the soil in Wolfville’s parks and soccer fields is healthy and productive. David uses no pesticides and only a small amount of organic fertilizer. His main tool for this successful program is well made, mature compost. (Read more about this project, and more, in Compost: Appreciating Nature’s Sense of Humus from this year’s ECO Annual Report.)

With respect to weed control, it is important to realize that not all composts are created equal. In general, for a compost to provide optimum benefit, it must have high levels of microbial diversity (there are millions of different species of microbes in a handful of good compost). Properly made, well-aged composts generally meet this requirement.

For fighting weeds in lawns, however, microbial diversity is not enough. This diversity should include significant levels of beneficial fungi. But what are beneficial fungi, why are they important, and how do you know when there are enough fungi in your compost? This blog is the first of a series on how compost – your own, the municipality’s, or commercially produced product – can be used to develop and maintain a lush, healthy and weed-free lawn.

The next blog will look at the science of soil ecology and how the management of the “soil food web”Âť can provide an effective, low-cost, environmentally superior alternative to the use of chemical fertilizers and pesticides. The third and last blog will provide some practical tips on how you can apply these principles to your own lawn.