BU-07403 2000Organic Matter Management main page
Several guidelines for managing soil biology were introduced in this chapter - encourage diversity, feed organisms frequently, donít destroy habitat with excessive pesticides or tillage. But there were no strict numbers for how many arthropods you need, or a list of species that are essential, or a precise set of practices that will generate the "ideal" mix of soil organisms. This means that good observation skills are important to assessing the effects of practices on your farm.
Each farmer notices a unique set of changes as soil biological activity rises. One might notice more birds picking out earthworms behind the plow. Another might see manure pies disappearing more quickly, or reduced ponding after a rain. It takes practice to observe the activities of soil organisms. Observations such as these are essential, but there are also more systematic ways to monitor soil biology.
Assessing soil life on your farm
Soil life can be measured in three general ways: the amount of organisms, their activity, and the soil processes they influence.
The amount of organisms can be measured by directly counting them under a microscope or by estimating biomass using several laboratory methods. Activity is often monitored by measuring soil respiration (the amount of carbon dioxide given off) or decomposition rates.
The biomass (amount of organisms) does not change drastically from day to day, but activity levels respond rapidly to changes in temperature, moisture, and food. Because activity levels can change quickly, it is important to note temperature and moisture conditions when sampling.
In addition to directly measuring the organisms or their activity, it can be useful to monitor the processes they influence. These include the stability of soil aggregates, rate of water infiltration into the soil, the rate of decomposition, pest activity, and soil nitrate levels.
The Monitoring Tool Box describes a soil respiration test that measures carbon dioxide, and a cotton strip test that measures the rate of degradation of a buried piece of cloth. The Tool Box also describes tests of aggregate stability and percolation (infiltration).
A simple on-farm respiration test is available from Woods End Research Laboratory (207-293-2457, http://www.woodsend.org/).
Biological activity can be observed more informally by noting how long it takes for manure or residue to disappear from a field.
A few commercial labs will test the number or activity of organisms in your soil. Some consultants are developing recommendations based on such tests, but the research basis for interpreting biological measures is still weak.
The future of soil biology management
There is much to learn about managing soil biology. Researchers are only beginning to understand the specific biologic mechanisms of many management practices. As research accumulates, farmers may increasingly use practices such as:
Practice seeing soil organisms.
Take half an hour for a little investigation. If you have a wooded lot, go there. Or go to an unpastured, untilled fence line or meadow. Take along a shovel or spade. Kneel down on the leaf mold. Maybe youíll see a frog, toad, or shrew. Youíll probably see small spiders and beetles immediately. Peel away a few leaves. Youíll probably see more spiders, beetles, and a millipede or two. These creatures are busily devouring each other and the dry leaves. They are carrying out life functions such as breeding and defecating. Dig a little further and youíll find white fungus roots or mycelium wrapping around skeletonized leaves and little chunks of wood. As you gently dig deeper youíll find earthworms and their burrows. The material you find now will begin to look like soil but will be in little crumbly balls and pellets. Some of it will be earthworm castings, which will be further broken down by fungi and by organisms too small to see, and some of it will be glued together by mucous from microbes. Among all this you will no doubt see threads of plant and tree roots taking advantage of the rich chemical environment that is generated by the teeming life on the forest floor.
In a few square feet of forest floor and leaf mold there are spiders, millipedes, snails, slugs, beetle larva and pupae, and countless other small creatures. Scientists say that a single gram of soil from the forest floor can contain up to a kilometer of fungal hyphae. Without all this crunching, munching, and processing of living things down to the basic elements, plants simply couldnít grow.
Now take a trip to one of your farm fields. What do you see thatís different?
Copyright © 2002 Regents of the University of Minnesota. All rights reserved.
In accordance with the Americans with Disabilities Act, this material is available in alternative formats upon request. Please contact your University of Minnesota Extension office or the Extension Store at (800) 876-8636.