by Joel Simmons,
EarthWorks, Inc.
Man's survival has always depended on his ability to work the
land.
As man became more civilized, so did his skills at agriculture
Simmons: "Use synthetics after soil biology problems are
solved."
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and horticulture and his understanding of the importance of proper
soil management. Today, many farmers, fruit growers and turf managers
are re-evaluating the importance of the soil and gaining an understanding
for the concepts of biological soil management.
Rediscover the basics - Biological soil management is based
on solid agronomic principles that date back decades, if not centuries.
Dr. William Albrecht, the former head of agronomy at the University
of Missouri, wrote in the late 50s and early 60s of the importance
of maintaining a healthy soil. Today, the agriculture industry
is making major changes in its outlook toward the importance of
soils, as farmers continue to lose topsoil at alarming rates.
The practice of eco-agriculture is being led by government and
universities in the U.S. and the world over.
Many in the turf industry are starting to realize the advantages
of natural programming. An effective program depends on an understanding
of the agronomic principles behind biological soil management.
For years now, we have been focusing on plant growth and have
ignored the soil. We must build a healthy soil first, which allows
for ample nutrition, and a healthier plant.
The principles - There are four basic agronomic principles
that have to be considered to build a healthy soil. Those are,
in descending order of importance:
- Air management
- Water management
- Decay management
- Nutrient management
The relationship between these four principles is significant.
Without good air management, the other three cannot produce healthy
soil. If water management is not up to par, proper air, decay
and nutrient management is difficult. Most of us in the business
of growing plants have over emphasized the focus of nutrient management
(i.e. fertilization) without considering the interdependence that
exists among air, moisture, decay and fertility.
A program that keeps all four of these principles in mind assures
you of good results; lessens plant stress; and reduces the need
for pesticides. This may sound simplistic, but it works.
Unfortunately, our industry is focused on products that are designed
to manage nutrients, often at the expense of air, water and decay
management.
The breathing soil - Air management insures that there
is ample oxygen in the soil. Soil compaction strangles air movement
and depletes oxygen availability. A well-balanced turf program
must first address compaction. Too often this is done by aeration
or top dressing, short-term treatments which ignore the fundamental
causes of the problem.
Usually, the soil needs to be physically changed by adding composts,
natural/organic fertilizers or other organic materials.
These can be worked in over time, or in combination with aeration.
Managing oxygen in the soil also requires the proper ratios of
cations (positively-charged nutrients) and anions (negatively-charged
nutrients).
Measurable imbalances, due to either excesses or deficits of particular
plant foods, will cause the soil to take on adhesive characteristics.
Water: easy to waste - Water management addresses the problems
of too much or too little water availability. Too much water creates
an anaerobic environment, which depletes oxygen from the soil,
and affects microbial activity and nutrient release. Too little
water can produce the same results: poor microbial viability and
limited nutrient uptake. Again, soil structure will have a significant
effect on water mobility. A richly organic soil will provide both
the pore space to allow water to drain through, and the sponging
properties that will hold water.
From decay comes life - Decay management is a concept that
few of us understand, but it is here that more of our focus should
be placed, because it is here that biological soil management
has its greatest impact.
The soil's micro-organisms decompose the organic compounds which
release plant available nutrients. Humus is the final phase of
decomposition that includes the use of organic matter, synthetic
and natural plant foods and the remains of soil organisms themselves.
It provides a significant buffering effect for excess moisture,
temperature, acidity, alkalinity and salts. This reduces plant
stress and increases insect, disease and weed tolerance.
Air and water mobility must be available for sustainable microbial
activity. Soil micro-organisms need very much the same kind of
environment that we need: air, water and nourishment. Nourishment
for soil microbes is supplied by organic matter: carbohydrates,
sugars, proteins, vitamins and minerals, just to name a few.
Plant foods vary - Without proper microbial activity, synthetic
nutrients are not mobilized and assimilated to plants. As one
example of microbial involvement in plant food availability, the
urea molecule is transformed to nitrate, one of the forms that
plants can utilize, due to the urease enzymes that are produced
by these organisms. To generate these enzymes, energy from soil-available
carbohydrates is necessary (humus).
Lime - which is simply calcium and/or magnesium carbonates - is
often ignored as an important element.
Adjusting pH is critical because most soil organisms thrive in
a limited range of acidity or alkalinity. Perhaps even more important
is the need to provide calcium - and a smaller percentage of magnesium
- as primary plant foods for soil microbes and landscape material.
Calcium/magnesium content and ratios in the soil are also essential
for building soil structure because of the valence or electrical
attraction that exists between soil colloids and these two nutrients.
The over use of synthetic fertilizers eventually destroys soil
aggregates due to excessive salt accumulation. Simple and complex
carbohydrates found in humus are oxidized or broken down, and
used as an energy source in order to accommodate overloads of
non-protein nitrogen. As the soils die, air space or granulation
is reduced, creating compaction.
Compacted, low oxygen soils no longer retain moisture or support
adequate life forms to stimulate digestion. The interdependent
cycle has been ruptured, plant stress leading to insect and disease
pressure has begun and subsequent "rescue chemistry,"
in the form of pesticides, is needed. The soil and the plants
become dependent on chemicals, like plants in a hydroponic medium.
Formula for success - "Biologically friendly"
turf care programs improve the soil structure with organic matter:
Build up a healthy soil to allow for ample nutrition and a healthier
plant.
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compost, natural organic fertilizers or even grass clippings.
When synthetic products are used, proper IPM practices should
be followed. Biological soil management will greatly enhance IPM
and may be the "missing link" in truly making IPM work.
Use those synthetic fertilizers that have the least harmful effect
on the soil.
For example:
- Use fertilizers with lower salt indexes. Chlorine, found in
some plant foods, is very detrimental to microbial life.
- Increasing the amount of organic matter allows for a reduction
in total nitrogen for the year.
- Consider natural organic based bridge products.
- Use less reactive sources of phosphorous such as colloidal/rock
phosphates.
With these four agronomic principles in mind, you'll get the most
out of the soil. There will be more available nutrients, less
plant stress and less dependence on pesticides.
Joel Simmons is president of Earth Works, Martins Creek, Pa.
This article was first published in Landscape Management, March 1993
