The Garden Blogger's Book Club selection for January - Teaming with Microbes: A Gardener's Guide to the Food Web by Jeff Lowenfels and Wayne Lewis - is not a book I would ever pick up on my own. My ability to avoid all things related to math or science was well-developed by the time I was a freshman in college, and I've found that (my) adult life doesn't require much knowledge beyond the basics (and even those seem fuzzy sometimes).
So it was with some trepidation that I started reading Teaming with Microbes. As I read, I found that the authors made the chemistry and biology palatable and understandable to this die-hard English major, and I found myself drawn into the world beneath our feet.
Rather than writing a typical review, I'm going to describe some of the things that I learned that have some practical application to my own garden. Some people may find these concepts useful, some may not, but these are ideas and techniques will influence the way that I garden this year.
To learn more about the Garden Blogger's Book Club, visit Carol over at May Dreams Gardens.
Bacteria and fungi are at the bottom of the soil food web, and feeding them will help to attract other good organisms to the garden. The bacteria and fungi "hold" nutrients until they die - or are eaten by other things - at which point the nutrients are released to the soil through the higher organisms excrement. Thus, feeding bacteria and fungi is the key to healthy soil (pp. 21-22).
Perennials, trees and shrubs prefer higher fungi levels in the soil. Vegetables, annuals and grasses prefer higher bacteria levels (p. 26).
Anaerobic bacteria live in the absence of oxygen and smell bad (i.e., rotten meat). Aerobic bacteria live in the presence of oxygen and smell good (i.e., the smell of earth). (p. 46)
Bacteria create bacterial slime, which "glues" the bacteria to the soil. Thus, when bacteria die, the nutrients they have accumulated - especially nitrogen - stay in the soil. Artificial fertilizers are only available as nutrients at the time they touch the soil. Once they wash through, they're gone. Thus, feeding the bacteria creates more nutrients than adding artificial fertilizers (p. 50).
Fungi grow into long strands and collect nutrients that are not available until the fungi die. However, when they die those nutrients are immediately available to the soil. Strands of fungi also create tiny tunnels in the soil, allowing oxygen and water. "Fungi are the primary decay agents in the soil food web" (p. 56). Fungi feed from several sources (leaf litter, soil, plant exudate) so are widely available in the soil. (pp. 54-57)
Mycorrhizal fungi are those that live in a symbiotic relationship with plants' roots. The plant provides nutrients via the root exudate, and the fungi bring back other nutrients from the soil to the plants. It is estimated that 90-95% of plants form mycorrhizae. Fungi are very fragile. Compaction or rototilling breaks up and crushes the fungal tubes (p. 60).
Protozoa eat bacteria and fungi and their wastes make minerals available to the soil. ". . . [A]s much as 80% of the nitrogen a plant needs comes from the wastes produced by bacteria- and fungi-eating protozoa. Since bacteria and fungi are attracted by plant exudates to the rhizospere [the area directly around the plants' roots], and that is where protozoa consume them, a huge source of plant food is delivered, right around the roots." (p. 73)
Nematodes eat bacteria, fungi, protozoa and each other, thus releasing more nutrients into the soil. Because nematodes need less nitrogen than protozoa, they release more than protozoa. Nematodes need porous soil in which to live, so will not be present if the soil is compacted (p. 76).
Arthropods are food in the soil food web and "are important to the community as shredders, predators and soil aerators" (p. 79). "Most soil arthropods, particularly those that reside on the soil surface, are shredders. They chew up organic matter in their constant quest for food, creating smaller pieces. As a result, fungal and bacterial activity is increased because shredding exposes surfaces on organic litter that give bacteria and fungi and easier avenue of attack" (p. 81).
Forest soils are more acidic because the bacteria cannot keep up with converting wastes into nitrate. So, more wastes are ammonium (which are more acidic) and the bacteria leave (p. 85). Earthworms cannot live in acidic soil, so there will be fewer (or none) in a forest setting. This means - at our house - that our woods will be much more fungal (and thus acid) than bacterial and won't have a lot of worms.
". . . [A]n acre of good garden soil contains 2 to 3 million earthworms (anywhere from 10 to 50 per square foot); this is enough to do a bulldozer's amount of work and indeed, this crew is capable of moving an astonishing 18 tons of soil a year in search of food" (p. 85).
"They [earthworms] are intimately involved in the shredding of organic matter , the aeration of soil, the aggregation of soil particles, and the movement of organic matter and microorganisms throughout the soil. They also increase microbial populations and aid plant root growth" (p. 86). "Worms can deposit a staggering 10 to 15 tons of castings per acre on the surface annually" (p. 87). Worms also shred and burrow, which both have obvious benefits to the soil.
Early succession communities (and vegetable gardens) are bacterially dominated. As more organic litter accumulates and later succession communities end up being dominated by fungi. There is the same amount of bacteria in all types of soil, but fungi increases along each step (pp. 101-102).
Compost can be made to be either dominated by either bacteria or fungi, depending on the plants you want to feed (vegetables, annuals and grasses like bacteria, perennials, trees and shrubs like fungi). Brown material has more carbon and thus feeds fungi, green material has more nitrogen and thus feeds bacteria. The book then goes on to describe how to make compost. To feed the soil, put 1/4 to 1 inch of compost around the plants. (pp. 117-128)
Most brown mulches are fungal, and one of the best is leaves. If the leaves are shredded very fine, then they become bacterial (more edges for them to eat). Buried leaves are also more bacterial as they hold more moisture. Peat is biologically sterile so it needs to be mixed with something else that will feed the soil. Leaves or shredded bark on the surface is fungal; ground leaves, green material, wet or dug in is bacterial. If using wood chips, maker sure they are 3/8" or smaller to encourage fungal growth. (pp. 129-133)
To make the most effective use of mulch, make your own "protozoa soup" - application will help to start the feeding process immediately. "Soak fresh grass clippings, alfalfa, hay or straw in dechlorinated water for three or four days. It is a good idea to bubble the water with an aquarium air pump and air stone . . . to keep the mix aerobic. . . . Pour this protozoa soup on mulches and you will increase the nutrient cycling power . . . ." (p. 133)
Compost Tea (pp. 134-147): The authors are really into this (see El's comments at Fast Grow the Weeds for a humorous take on this). I'm sure this works great, but it's way more work than I know I'm going to do. However, I know it's there if I ever change my mind.
The Lawn (pp. 148-157): Spouse and I have never used pesticides or fertilizers on any lawn we've had. At this house, we live in a very natural area where none of the neighbors worry too much about the perfect lawn. There are some handy tips in this chapter, but other than perhaps trying some corn gluten meal for the dandelions (which I've been meaning to do for years), we will just leave it be.
The authors show some awesome pictures comparing plants that were inoculated with myccorhizal fungal spores before planting (p. 162, p. 169), and I'm definitely going to do it this year. I've always used inoculants for peas and beans, but I didn't know how helpful they were for almost all other plants. You use ectomycorrhizal fungi for conifers and hardwood trees. You use endomycorrhizal fungi for most shrubs, softwood trees, perennials, annuals and some vegetables (p. 162). Vegetables that don't form mycorrhyzae are brassicas (including cabbage, mustard and broccoli) and the Chenopodiaceae family (spinach and beets) (pp. 169-170).
In the vegetable garden, the keys to success are no rototilling (p. 166), using green mulch to foster bacteria (p. 167), apply protozoa soup to speed up feeding (p. 168), and using endomycorrhizal fungi where appropriate (p. 169).
With raised beds in the vegetable garden I've never needed to rototill, but I have been "digging in" compost. Ironically, I've never "dug in" compost for the perennials - I've always just dug a hole and threw a handful of compost on the bottom of the hole before sticking the plant in. I think maybe I baby my vegetables too much.
I've also used some green mulch on the veggies, but because our scraggly lawn doesn't grow very fast, the few grass clippings we have stay on the lawn. I'll definitely be looking at how I can do more green mulching. And I'm really excited to try protozoa soup and mycorrhyzal fungi.