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 Soil
Analysis Reports May Be Incomplete, Misleading
Sample, Combine, Bag, Mail, Wait,
Read, Apply as directed; fairly standard practices on the farm as producers have
become aware of the value of soil samples. But what if the information was
incomplete? If the information is incomplete, then the conclusions would be
faulty. Unfortunately, in many circumstances that is the case. The fact is, that
even though libraries could be filled based on what we know about plants,
comparatively little is known about soils. We know that healthy soils have
certain components like NPK, and trace elements like boron and manganese. We
know that under ideal conditions plants work with the soils to replenish them.
When that fails we fertilize, either based on ‘best guesses’, habit, or
professional recommendations. But we are learning new things about the
environment in which the roots of plants grow: the rhizoshpere. We are also
learning more about how plants access and utilize different nutrients to
optimize the genetics intrinsic to those plants. As our body of knowledge
increase one thing is becoming clear. Standard soil tests may not be telling us
everything that is going on in the soil profile. As a result decisions are being
made regarding fertilization and soil amendments that are, at best, needless,
and, at worst, detrimental.Good
Soil, Bad Test
Almost 90% of soil tests solicited by farmers are standard acid-tests and they
are okay as far as they go. Where they fail is in their inability to tell you
what is available for your plant to use. They will indicate how many units of a
given mineral or nutrient are available, what they will not show you is how many
of those units are actually in a form that are useable by the plant. In the Ohio
Valley, for example, nature has given us vast limestone deposits very close to
the surface. That should mean that calcium deficiency is not a problem. However,
‘liming’ the fields is a common practice because the calcium released gets
locked up in a form that is unusable or by the presence of other elements. A
traditional soil test will show a heavy concentration of calcium in the soils,
because it is there. However it will not indicate that it will not be utilized
by the plants. Traditional soil tests generally cost about $10-15, for an
additional $10 a more extensive test, known as water soluble extraction can be
conducted. This test not only will indicate what minerals and nutrients are in
your soil but what percentage of those elements can be taken up by the plants.
This is crucial for two reasons. First, it can indicate that you only have 80
units of nitrogen in your soil, but that 90% of them are usable. In this case
you would be better off that a farmer that had 150 units of nitrogen with only
50% accessibility. Second, it can show you the opposite, that your soils contain
enough nitrogen, but that the plants will need additional product in order to
maintain maximum performance. The point is to get as accurate a picture of your
soils condition as possible before you start adding soil amendments. By
maintaining the proper balance of needed elements you can foster a favorable
environment for the growth of your plants. When everything is in balance you can
maintain proper pH and 4% organic matter. This combination will provide for very
desirable rich soils regardless of your location. Without the proper balance,
input costs will continue to rise, yields will level off or decline and many
soil amendments will be discarded through leeching, run-off, evaporation, or
degradation into the environment. That balance is not only determined by what is
in the soil, but at what quantities, and in what ratio to other necessary
elements.
Limiting Reactants
The best way understand limiting reactants in your soil is to think of fire.
Fire requires three things to burn: Oxygen, Fuel, Heat. If you remove any of
those items the fire will die. That is why smothering a fire is possible; it
robs the fire of needed oxygen. So even though there is enough fuel and heat,
the fire starves and eventually goes out. The fire will only consume the fuel it
has enough oxygen to utilize. In this case Oxygen is the limiting reactant: The
effect of the heat and fuel is limited by the availability of oxygen. The
nutrients needed by your body follow the same principals: You can only utilize
the calcium which you have enough vitamin D to process. That is why so many
calcium supplements are now containing vitamin D. Without it, the product would
be useless. Likewise, your soils don’t just need potassium or nitrogen, calcium
or boron, they need them in the right proportions. Without the proper balance,
some nutrients will go unused and stay ‘locked up’ in the soil profile. Rendered
useless, these nutrients might as well not even be present. For example, if your
phosphorous levels are too high it will lock up copper and boron. Likewise
calcium and magnesium have to be at a 10:1 ratio, respectively, or the bulk of
your calcium will not be accessible to your plants. Unless you supply all of the
necessary ingredients many of your amendments will go unused. One of the key
things to remember is the end-user of all of these amendments. It is not the
soil, it is the plant. So the question needs to be “What does my plant need?”,
not “What does my soil need?”.
Feeding the plant v. Amending the soil
By treating the soils, not as an end to themselves, but as a medium in which to
grow plants producers are noticing two benefits. First, their plants are
emerging better, are healthier, and have better root systems. Second, the soils
are not being over-treated with chemicals, they are returning to a more natural,
healthy state, and they are improving and becoming sustainable. Traditional
chemicals, though effective, tend to worsen the problems they are trying to
correct. If we are assume that the soils are not fertile, typically we boost
that by applying fertilizer. The main problem with this is approach is that most
granular fertilizers are salt-based compounds. When we place the fertilizer in
the row or side-dress our crops with it we are actually forcing the water toward
the fertilizer as nature tries to dilute the product before it burns or kills
the plants. As moisture is drawn toward the fertilizer it is drawn away from the
plant. This is why fertilizer recommendations always suggest planting ahead of a
known rain event. If the rain does not come, traditional fertilizers only worsen
the impact of drought. |
