|
Introduction
Used to be anybody could farm. All you needed
was a strong back. . . but
nowadays you need a good education to understand all the advice
you get so you can pick out what'll do you the least harm.
Vermont saying, mid-1900s
One of our truly modern miracles is our agricultural
system, which produces abundant, affordable food. High yields come
from the use of improved crop varieties, fertilizers, pest control
products, and irrigation. At the same time, mechanization and the
ever-increasing capacity of field equipment allows farmers to work
increasing acreage.
Despite the high productivity per acre and per person,
many farmers, agricultural scientists, and extension specialists
see severe problems associated with our intensive agricultural production
systems. Examples abound:
- Too much nitrogen fertilizer or animal manure sometimes causes
high nitrate concentrations in groundwater. These concentrations
can become high enough to pose a human health hazard.
- Phosphate in runoff water enters water bodies and degrades
their waters by stimulating algae growth.
- Antibiotics used to fight diseases in farm animals can enter
the food chain and may be found in the meat we eat. Their overuse
has resulted in outbreaks of human illness from strains of disease-causing
bacteria that have become resistant to antibiotics.
- Erosion associated with conventional tillage and lack of
good rotations degrades our precious soil and, at the same time,
causes the silting up of reservoirs, ponds, and lakes.
The food we eat and our surface and ground waters
are sometimes contaminated with disease-causing organisms and chemicals
used in agriculture. Pesticides used to control insects and plant
diseases can be found in foods, animal feeds, groundwater, and in
surface water running off agricultural fields. Farmers and farm
workers are at special risk. Studies have shown higher cancer rates
among those who work with or near certain pesticides. The general
public is increasingly demanding safe, high quality food that is
produced without excessive damage to the environment and many are
willing to pay a premium to obtain it.
Farmers are also in a perpetual struggle to maintain
a decent standard of living. As consolidations and other changes
occur in the agriculture input, food processing, and marketing sectors,
the farmer's bargaining position weakens. The high cost of purchased
inputs and the low prices of many agricultural commodities, such
as wheat, corn, cotton, and milk, have caught farmers in a cost-price
squeeze that makes it hard to run a profitable farm.
Given these problems, you might wonder if we should
continue to farm in the same way. A major effort is underway to
develop and implement practices that are both more environmentally
sound than conventional practices and at the same time more economically
rewarding for farmers. As farmers use management skills and better
knowledge to work more closely with the biological world, they frequently
find that there are ways to decrease use of products purchased off
the farm.
With the new emphasis on sustainable agriculture comes
a reawakening of interest in soil health. Early scientists, farmers,
and gardeners were well aware of the importance of soil quality
and organic matter to the productivity of soil. The significance
of soil organic matter, including living organisms in the soil,
was understood by scientists at least as far back as the 17th century.
John Evelyn, writing in England during the 1670s, described the
importance of topsoil and explained that the productivity of soils
tended to be lost with time. He noted that their fertility could
be maintained by adding organic residues. Charles Darwin, the great
natural scientist of the 19th century who developed the modern theory
of evolution, studied and wrote about the importance of earthworms
to the cycling of nutrients and the general fertility of the soil.
Around the turn of the 20th century, there was again
an appreciation of the importance of soil health. Scientists had
realized that "worn out" soils, where productivity had
drastically declined, resulted mainly from the depletion of soil
organic matter. At the same time, they could see a transformation
coming: although organic matter was "once extolled as the essential
soil ingredient, the bright particular star in the firmament of
the plant grower, it fell like Lucifer" under the weight of
"modern" agricultural ideas (Hills, Jones, and Cutler,
1908). With the availability of inexpensive fertilizers and larger
farm equipment after World War II, and of cheap water for irrigation
in some parts of the western United States, many people working
with soils forgot or ignored the importance of organic matter in
promoting high quality soils.
As farmers and scientists placed less emphasis on
soil organic matter during the last half of the 20th century, farm
machinery was getting larger. More horse power for tractors allowed
more land to be worked by fewer people. Large 4-wheel drive tractors
allowed farmers to do field work when the soil was wet, creating
severe compaction and sometimes leaving the soil in a cloddy condition,
requiring more harrowing than otherwise would be needed. The use
of the moldboard plow, followed by harrowing, broke down soil structure
and left no residues on the surface. Soils were left bare and very
susceptible to wind and water erosion. New harvesting machinery
was developed, replacing hand-harvesting of crops. As dairy herd
size increased, farmers needed bigger spreaders to handle the manure.
The use of larger equipment created new problems. Making many passes
through the field with heavy equipment for spreading fertilizer
and manure, preparing a seedbed, planting, spraying pesticides,
and harvesting created the potential for significant amounts of
soil compaction.
A new logic developed that most soil-related problems
could be dealt with by increasing external inputs. This is a reactive
way of dealing with soil issues you react after seeing a "problem"
in the field. If a soil is deficient in some nutrient, you buy a
fertilizer and spread it on the soil. If a soil doesn't store enough
rainfall, all you need is irrigation. If a soil becomes too compacted
and water or roots can't easily penetrate, you use an implement,
such as a subsoiler, to tear it open. If a plant disease or insect
infestation occurs, you apply a pesticide.
Are low nutrient status, poor water-holding capacity,
soil compaction, susceptibility to erosion, and disease, nematode,
or insect damage really individual and unrelated problems? Perhaps
they are better viewed as only symptoms of a deeper, underlying
problem. The ability to tell the difference between what is the
underlying problem and what is only a symptom of a problem is essential
to deciding on the best course of action. For example, if you are
hitting your head against a wall and you get a headache is the problem
the headache, and aspirin the best remedy? Clearly, the real problem
is your behavior and not the headache, and the best solution is
to stop banging your head on the wall!
What many people think are individual problems may
just be symptoms of a degraded, poor quality soil. These symptoms
are usually directly related to depletion of soil organic matter,
lack of a thriving and diverse population of soil organisms, and
compaction caused by use of heavy field equipment. Farmers have
been encouraged to react to individual symptoms instead of focusing
their attention on general soil health management. A new approach
is needed to help develop farming practices that take advantage
of the inherent strengths of natural systems. In this way, we can
prevent the many symptoms of unhealthy soils from developing instead
of reacting after they develop. If we are to work together with
nature, instead of attempting to overwhelm and dominate it, the
buildup and maintenance of good levels of organic matter in our
soils is as critical as management of physical conditions, pH and
nutrient levels.
This book has three parts. Part One provides background
information about soil health and organic matter: what it is, why
it is so important to general soil health and why some soils are
of higher quality than others. Also included are discussions of
soil physical properties, soil water storage, and nutrient cycles
and flows. Part Two deals with practices that promote building
better soils with a lot of emphasis on promoting organic matter
buildup and maintenance. Following practices that build and maintain
organic matter may be the key to soil fertility and may help solve
many problems. However, other soil-management practices also are
needed to supplement soil organic matter management. Practices for
enhancing soil quality include the use of animal manures and cover
crops; good residue management; appropriate selection of rotation
crops; use of composts; reduced tillage; minimizing soil compaction
and enhancing aeration; better nutrient and amendment management;
and adapting specific conservation practices for erosion control.
Part Three deals with how to combine soil-building management strategies
that actually work on the farm and how to evaluate soil to tell
if its health is improving.
Source
Hills, J.L., C.H. Jones, and C. Cutler. 1908. Soil deterioration
and soil humus. pp. 142177. In Vermont Agricultural Experiment
Station Bulletin 135. College of Agriculture, University of
Vermont. Burlington, Vermont.
Top
|