If we set a microscope in the soil, we could see tiny, one-celled bacteria devouring the remnants of leaves and root hairs. We would see fungi disintegrating the larger, hard-to-digest roots and stems. We would see protozoa dining on bacteria and fungi and, in the process, releasing nitrogen and other nutrients needed by plants.
We would see roots releasing substances into the soil to attract and fed bacteria. In return the bacteria would release compounds that stimulate plant growth and help defend the roots from pathogens.
We would see other bacteria attaching themselves to roots, taking nitrogen from the air and then supplying the host plants with the essential nitrogen; we would see the plant giving to the bacteria, simple carbon compounds to encourage them to keep feeding them nitrogen.
If we were lucky we might see a fungus shaping itself into a noose lying in wait to snag a nematode for dinner or a nematode puncturing the cell wall of a fungus and sucking out the internal contents. We might see a nematode gulping down a whole protozoa. Plant-invading nematodes have gotten a lot of attention, but they are only a small fraction of total nematodes. The vast majority of nematodes are beneficial to plants and play a critical role in the soil foodweb. They dine on bacteria, fungi, protozoa, and other nematodes. In the process of eating and excreting, they release many nutrients that are readily available to plants.
To our amazement, we would see stands of fungal hyphae pushing their way between soil particles and binding soil particles together, creating soil aggregates.
We could see earthworms, springtails and a myriad of arthropods, feasting on plant residues and other soil life and leaving behind trails of supercharged soil.
With all this already happening in the soil, is tilling really necessary?
In a teaspoon of rich, fertile soil are hundreds of millions of living organisms. They form an interdependent web of life within the soil. We are just learning how this soil foodweb works. We do know that, if the web is properly taken care of, it will provide all the nutrients needed for optimum plant growth.
Tillage disrupts this foodweb. The obvious example is the cutting in half of earthworms. The myth many of us learned as children, is not true. When you cut an earth worm in half, you do not get two earthworms.
Tillage also destroys the long strands of mycorrhizal fungi. These fungi exist in a symbiotic association with plant roots. Mycorrhizae attach themselves to the roots and act as root extensions, allowing plants to access more soil. They can be yards long.
Tillage also destroys soil aggregates. Aggregates give soil its crumbly structure. They are small clumps of many soil particles, that contain open space. Sticky gums and gels, produced by soil bacteria, loosely hold together individual grains of sand, silt, clay and humus. Strands of filamentous fungi and actinomycetes also helps hold the aggregates together. The open spaces between soil particles are called pores and contain water and air. When aggregates are broken apart into individual particles, many pores are eliminated. Plant roots need the empty space between soil particles through which to easily extend their roots. Also, without adequate air in the soil, anaerobic conditions exist which cause root diseases. In addition, most organisms need abundant air in the soil to carry out their many functions.
Imagine a suburban community with all its houses, streets, underground water pipes, and electrical wires. Now imagine a mile-wide rototiller with 500 foot tall blades rumbling through. Is this the effect tillage has on the community that live in our soils?
Hundreds of years ago, before the native grasslands of this country were first put to the plow, tall, green, nutritious grass grew without the help of man. The soil was deep, rich, and dark brown. How did it get that way? The soil had not been plowed or fertilized. How did nature do that?
We till the soil to loosen it and introduce air. But then, we drive over it with tractors and other farm equipment, smashing it back down and squeezing the air out. By the time harvest is over, the soil resembles a concrete slab. To plant our next crop, we need a huge tractor to loosen it back up, and all kinds of implements to pulverize it into submission. Then during the next growing season, we smash it back down again only to work it back up again. This scenario repeats itself year after year.
Is there a way out of this vicious cycle? This is what I am trying to discover with my conservation tillage experiments.
If you are interested in the details of the techniques and results of the no-till and strip-till trials, please E-mail Helmut. Helmut.