Why Soil Health Matters

By Greg Bowman
January 1994, The New Farm

Editor's Note: The more you know about soil, the better you can care for it. Beyond stopping erosion, you can significantly boost the productivity and quality of soil by improving its health. In this panel discussion, four soil scientists share what they've learned about the links between soil life and regenerative farming.

: How can regenerative farming benefit soil health?

Dr. Marianne Sarrantonio
SARRANTONIO: By cycling organic matter and nutrients. Regenerative farming is all about improving soil health. Face it - farming is not a natural process. It's disruptive to the soil. When we monocrop, we decrease the diversity of life forms above and below ground. When we till repeatedly, we destroy soil structure, promote loss of organic matter and disrupt nutrient cycles. These practices cripple the soil's ability to respond to stress and leave it unable to function the way it should.

Regenerative farming practices try to mimic nature. Diversity is increased by rotations, by multiple cropping and by creation of hedgerow habitats. Organic matter is returned to the soil. Nutrient release from the breakdown of organic materials is more gradual and should coincide better with changing crop needs.

WEIL: By increasing water infiltration. When we start a side-by-side comparison of crop rotation with monocropping, one of the first differences we notice is in the structure of the soil surface. Especially after continuous corn or heavy tillage; you see crusting and loss of porosity in the soil, faster runoff, less infiltration and more erosion. Surface condition is tremendously important in how much rainfall your field can hold.

If you're testing infiltration in a field that has recently come out of alfalfa, it takes only minutes. You may spend hours waiting in a field that's been in continuous corn.

GOLDSTEIN: By improving soil structure, which also improves crop root health. These benefits come hand in hand when farmers use really sustainable practices.

Farmers who expand crop rotations to include perennial forages and leguminous green manures, and who add livestock, begin to restore soil health. The contributions of these practices were learned in the '30s through the '60s, but were then forgotten with the influx of cheap nitrogen, herbicides and monotonous cash-grain farming.

Our observations in the Midwest indicate we have soil compaction and unhealthy roots at epidemic levels as a consequence of excessive cash-grain production.

DORAN: By showing its we have to balance the demands that profitable food production makes on soil today with the improvement of soil and environmental resources for the future.

The Dust Bowl era in North America provided a vivid example of this. Early pioneer farmers reaped the benefit of stored fertility in grassland soils when they used monocropping and inversion tillage. The loss of soil organic matter, surface cover and drought resulted in crop failures and in tremendous erosion losses. The burst of activity with chemicals and monocropping which started in the '50s is showing up as excessive erosion and water contamination today.

We must study the way things are structured in nature, but this is a new approach for many traditional agricultural scientists. It's alien to much of what we've been trained to do. Our past marching orders were to produce maximum crop yields to feed ever-increasing populations. However, in the last two decades, we are learning to balance the good things about production with its consequences to the environment.

: What's the most important concept to learn?

Dr. Ray R. Weil

WEIL: Soil is not a hydroponic medium.

You can't spoon feed fertility to roots, even if you apply all the fertilizer a corn crop needs. In a corn-soybean rotation on most soils, if you put on 15C pounds of N, less than 50 percent is likely to end up in the corn plant. It can be as little as 10 percent. The N that does reach the plant may come from last year's fertilizer or from the last decade's. Adding new fertilizer may cause more N uptake, but even that is mostly "old" nitrogen that enters the plant because the nitrogen cycling system kicked into a higher gear.

It's like a biological banking system. The dollars you get out are not the same dollars that you deposited.

DORAN: Soil is a living, dynamic organism. It functions most effectively when the physical, chemical and biological components are in a state of dynamic balance - a balance between the "living" and the "dead." Whenever we manage the soil to produce crops, we upset the natural balance, especially when little plant residue is returned to the soil surface.

GOLDSTEIN: Soil responds strongly to how we treat it. As Ray alluded, the old thinking was that soil is an inert sponge for holding nutrients and water for plants. Now we know that soil has living and mineral parts, and that we can build up its strength or run it down.

Teaching about soil fertility in terms of soil chemistry has had a paralyzing effect on our sense of what "healthy" soil is. Everything became abstract. To do the soil justice, we need to put chemistry in the context of living processes. In reality, the carbon in cornstalks has a different significance - and less beneficial effect - for soil fertility than the dynamic weaving activity of carbon in grass roots. Similarly, the living nitrogen process of legumes has a totally different effect on soil animals than does mineral nitrogen from a bag or tank.

We can learn to recognize a soil's health by its form and by its living qualities. Certainly, tillage that fluffs up soil can fool us. But if we make observations on a soil that has settled well, the amount of soil crumbs between 1/32and 1/3 inch in size can give us a good idea of its structural quality and its potential for microbial activity and nitrogen release. The more particles in this range - and the more stable they are - the better. Abused soils tend toward the extremes of forming massive clods or powder.

SARRANTONID: Keep your sense of humus! Maintaining active soil organic matter is the key to keeping almost everything else healthy in the soil. Cycling active organic matter maintains soil structure, provides nutrients, helps retain and recycle added nutrients, and provides habitat plus water-holding capacity.

: So how can farmers best improve soil health?

Dr. Walter Goldstein
GOLDSTEIN: Maximize soil builders. Use crops that will build your soil, such as fine-rooted grasses, deep-rooted perennial and biennial legumes, and cover crops. Use animal manure. These resources can he raised on your farm. They stimulate soil microorganisms, improve nutrient cycling and availability, and enhance the soil's fertility.

Manage soil depleters. Be careful how many grain crops you grow - especially sorghum, corn and wheat - because they destroy soil structure and fertility. Their repeated use leads to accumulations of soilborne, disease-causing microorganisms that live partly on cereal straw, partly on crop roots. Cash-grain farmers can build up their soil structure by underseeding or overseeding legumes such as sweetclover, red clover or hairy vetch as green manures. This practice also makes the soil environment less supportive of disease-causing organisms.

Learn from your roots. Dig them up, wash them, study them. If they aren't white, ask yourself "Why?" Roots need oxygen to grow. Look at your soil in the middle: of summer and ask yourself if oxygen can get down into it. If you were a plant, would you like to root there? The trick to growing crops with good yields using few or no chemical inputs is to grow healthy crops with healthy roots. These crop plants can compete strongly with weeds for moisture and nutrients.

SARRANTONIO: Take full advantage of cover crops. Continually improve vour system to better use covers to supply nitrogen, protect soil from wind- or rain erosion, add organic matter, take up excess nutrients, create a nice crumb structure, or act as a food source or habitat for the tons of soil organisms we want to encourage.

WEIL: Compact and till as little soil as you can. Ridge tillage involves minimal soil movement, yet provides for incorporation of organic matter, greatly cuts down erosion and keeps soil biological activity at a high level. Permanent ridges make it easier to have controlled-traffic lanes where you run all your equipment, leaving most of the field's root zone uncompacted.

Recognize which types of tools cause compaction. ones that lift topsoil by pressing down on soil below - such as a moldboard plow or disk - tend to compact. Less prone to create tight layers are tools, such as a spring-tooth harrow, where tractor or implement tires support the weight of the engaged topsoil.

DORAN: Use crop rotations to reduce pest problems and increase biological diversity. Growing the same crop every year sets the stage for a buildup of plant disease, weeds and insect populations.

We break these trends by incorporating grass sod or cover crops in a rotation. These practices protect the soil surface for more of the year. In the soil, the variety of roots and residue from covers helps to increase beneficial species of soil life that compete with weeds and disease organisms.

The diverse mixture of plant materials also creates a more hostile environment for pests. Rotations help take away the crop-specific overwintering sites that pathogens and insects need to survive.

: Why should farmers work for healthier soil?

SARRANTONIO: So we can keep on farming. Farming without keeping soil health in mind is like painting over termite holes in the frame of your house. We can kid ourselves for only so long. Healthy soil should not be considered a "luxury" that we work toward only after we meet our immediate economic needs. It is an absolute necessity. This amazingly thin, fragile layer of material coating less than half the earth is the key to human existence. Doesn't it make sense to take care of it?

DORAN: To achieve global environmental balance. The soil plays a critical role not only in supporting crops, but also in acting as a living buffer and filter. It completes the carbon and N cycles on earth and influences the quality of the air we breathe and water we drink.

Sometimes the imbalance affects farmers directly. In parts of Nebraska, rural communities have gone to drinking bottled water because their groundwater has a nitrate level of more than 30 parts per million of nitrate-nitrogen. (EPA drinking-water guidelines for infants set a nitrate limit of 10 ppm.) The 30-ppm level amounts to about 81 pounds of nitrogen per acre-foot of water.

Some farmers, who are over-irrigating to maximize yields, put on 3 acre-feet of water in a season. A lot of the N in that water will leach. Even in this situation, building healthier soil can help. It holds more water, so there's less leaching and less need for irrigation. To maintain a "healthv" soil, farmers should monitor nitrate in soil and water to reduce unneeded nitrogen inputs.

WEIL: To improve long-term productivity. It is possible to improve your soil's health, rather than have it go downhill over time. Healthy soil is more stable. That doesn't mean it's neutral or static, but that it has a complex, dynamic equilibrium that keeps its systems from crashing. It keeps functioning even under adversity, because those systems are self-regulating.

GOLDSTEIN: To avoid disaster. Soil health contributes enormously to longterm yields and crop reliability. Crops in unhealthy soil are more dependent on chemical inputs, even though they are unable to use them as efficiently. Conventional fields that farmers convert "cold turkey" to non-chemical systems show the results of unhealthy soil and roots: Crops look poor and weeds look great.

: If you had only 5 minutes to evaluate soil health in a moist, harvested wheat field in July, what would you do?

WEIL: I'd brush away the residue and take a close look at the soil surface to see if it was crusted, which would tell me something about tillage, organic matter and soil structure. I'd push a probe down about 12 inches and lift out the soil to feel its texture. if there was plowpan, I'd feel it as the probe went in.

I'd break the soil cores into depth intervals: the top 2 inches, then two 5inch sections. I'd measure each with a pocket pH meter. Often in reduced-tillage situations, pH problems are concentrated near the surface.

I'd turn over a shovelful of soil. If I didn't see any earthworms or their holes, I'd be worried. I'd smell the soil for that rich, earthy scent that comes from the presence o£ actinomycetes (moldlike microorganisms that help to compost and stabilize decaying organic matter).

It would be a busy 5 minutes.

Dr. John Doran

DORAN: I'd use a soil auger to probe down about 4 feet. I'd check depth and color of the topsoil, the presence of soil insects or earthworms and the filth in various levels. I'd look at root depth to see the ability of the soil to support plant growth and to find if anything is inhibiting root growth. If the soil didn't look biologically active, I might run a quick test for soil pH and electrical conductivity using pocket meters.

SARRANTONIO: Ha! Trick question! The whole idea of soil health is to go beyond the superficial, instant analyses we thought were adequate in the past — the old N-P-K mentality. We need to look at all kinds of different things and how they interact — soil organisms, soil structure, soil fertility. And that takes more than 5 minutes.

GOLDSTEIN: These all are good. One little fact should be added. Farmers often pick up some soil and come to a quick judgment: this soil is dead, burned out; or, this soil is rich, alive, fertile or has good filth. What do such common experiences mean? Qualities of soil speak intimately to us as humans because we feel something of them in ourselves. We need to appreciate such experiences, and even train our capacity to have them, because they can be of great practical significance.

: Are resources better used to develop computer-based "expert systems" in soil health or in sharpening farmer expertise?

DORAN: Regenerative farming will likely use computer-based "expert systems" to monitor the soil health in quantitative terms. But the "experts" in regenerative systems will have to be farmers who are managing the land. They must have simple tools for assessing soil health and incentives for improving soil health. What we need is a stronger partnership between researchers and land managers, and increased government support for "onfarm" research.


WEIL: Expert systems can make a pretty graph for fertilizer recommendations. But we don't even know enough about soil health to really have experts, let alone expert systems. A farmer's gut feeling about soil is worth as much as a computer model.

SARRANTONIO: I don't think computers will ever be able to substitute for personal experience, a keen eye or creative mind. Computers can handle lots of information, but they are incapable of original thinking, and that' what's needed for regenerative farming.

GOLDSTEIN: Expert systems will be useful only if they give farmers the right ideas of what to look for. It takes a human being with training and experience to properly assess soil health because health is not a tangible "thing" that any instrument can measure. Just as valuable as chemical analysis is the knowledge of an attentive farmer who knows how a soil works and crumbles, and how it and the crops it grows have responded to good or poor management over the years.

NEW FARM: What has been your most significant soil-health insight?

WEIL: Take your own soil samples—as often as you can. Stop long enough to put your hands in the soil and remember what you feel. Set aside days when that's going to be your first priority.

Soil really breathes! When we began to measure the rate of carbon dioxide release from soil, I was astounded at how it responded almost instantaneously to changes in tillage, residue or moisture. It really reinforced the concept that the soil acts as an organism - that it's alive and needs to be nurtured.

DORAN: Look at the big picture. Be aware of all the effects of agricultural management on the physical, chemical and biological components of the soil environment. We have to adjust practices to seasonal changes in the availability of nutrients - particularly N - and in the potential loss of nutrients through erosion, leaching and microbial conversion to gasses.

GOLDSTEIN: The best soil research tool is a shovel in the hands of a farmer who knows a field's history. Farms are living storybooks. They tell us a lot if we pay attention to the present signs and past management.

A soil records its past, often how much it has been abused. Look at the soil under grass in fencerows. Compare its topsoil depth and earthworm holes to that of soil in the fields. Remember that the life of the soil varies with the seasons. Gain a sense of that dynamic.
The soil itself will teach us significant things if we pay attention.

Greg Bowman, THEN: When he wrote this, Bowman was working in Emmaus, Pennsylvania, as managing editor of The New Farm magazine. NOW: Bowman is on-line editor of The Rodale Institute's NewFarm.org, and he's as fascinated as ever by healthy soil.