This course will cover the agricultural and urban water quality issues in Florida, their bases, land and nutrient management strategies, and the science and policy behind the best management practices (BMPs). Students will learn to evaluate BMP research and analyze its role in determining practices and policies that protect water quality.
Soil Testing, Part 2
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來自 University of Florida 的課程
农业可持续土地管理
50 個評分
從本節課中
Nutrient Management
In week 6, we will continue talking about soil testing and then cover proper nutrient management.
與講師見面
George J. Hochmuth, Ph.D.Professor
Urban and Agricultural Environmental Sciences
Okay, hello everyone again, I want to continue our discussions about, soil
testing. In our previous lecture we looked at soil
test procedures and how they're developed and what they can do and, and what they
can't do. And I alluded to the fact that there are
some philosophical variations out there on how we interpret those index numbers, and
how we convert them into a fertilizer recommendation.
And I want to continue that discussion here today.
And I guess I ought to give you a little bit of a warning, you know, we're, this,
this is one of our longer lectures. I don't think it's going to go too much
more than 30 minutes, so you know, if you need to have a drink or something with you
go ahead and be my guest. Also this area of soil testing and
fertilizer recommendations, is a little bit controversial, there are differences
of opinion about how to go about this and these phil-, philosophical do, do lead to
some fairly healthy discussions. And, just remember I'm the instructor, I'm
the teacher and I'm the messenger. And I, I think it's going to be
interesting to say how everyone out there on the discussion, in the discussion world
discusses and looks at these, these differences in philosophical approaches to
making fertilizer recommendations. Okay so last time we talked about the
fertilizer recommendations, here's a exampel of a kind of report, that would
come out of a lab. And I want you to look at this, so we
won't dwell on it, otherwise the lecture will be, way too long.
But just notice that for phosphorous, this is the, the big line right here is the
phosphorous, you see that it's very high. So the number over here, the index, the
125 parts per million, milligrams per kilogram was interpreted by this lab using
this procedure as being very high. The other part to go along with that is
down here and you see the fertilizer recommendations.
This particular lab is saying that the middle number is the phosphorous.
The first number is the nitrogen recommendation and the middle number is
the phosphorous and the potassium. You know that the middle number is zero.
So this lab says this soil has enough phosphourius to supply that phosphorous
nutrient requirement. So when you look at soil test reports,
they generally have the soil test index, the interpretation of the index and the
fertilizer recommendation. And as we get done today you'll be able to
make some determinations about the lab as to what philosophical approach they make,
they use when they make a fertilizer recommendation.
So when we do soil testing we know something about the fertility level of our
soil, they were going to grow corn in or tomatoes.
And the lab is going to give us a recommendation for how to supplement that
native fertility with fertilizer. So then the question is how do you go
about making that final recommendation for, for that farmer.
And there have been several approaches developed over the years, and typically,
you know, I would have to admit to you that the private sector testing labs and
the Land Grant universities take a little bit of a different approach.
There is some crossover between the two for sure but generally there is
differences in the approaches in which of these philosophical approaches the
different labs take a look. And In my mind, it comes down to these, to
a couple of ideas like this. There's differences in whether you
approach the soil testing. And the recommendation, the fertilizer
management part, fertilizing the soil or the plant as a, as a priority.
And are you, probably even more importantly, are you comfortable with
recommending or using a zero amount of nutrient.
For example, as we saw, under a high or a very high Index are you comfortable with
omitting the phosphorous in that scenario. So, the discussion about philosophies,
again just like soil testing, it really revolves around these non-mobile
nutrients. We're using a pre-fertilization soil test
to Predict the, the nutrient requirements, that would re, we would apply as
fertilizer under different, soil, test, scenarios.
And so we'll talk, we'll, we'll focus most of our discussion on, phosphorus.
And, as I said before, nitrogen is mobile. In most of our agriculture soils and in
the United States, we do not do it pre, most labs do it pre-fertilization soil
test for, for nitrogen. Okay, so here are the three, probably the
three most widely used approaches to making a fertilizer recommendation.
I'll call them philosophies. The build up and maintenance approach.
The percent sufficiency ranges. It also goes by a couple other names
depending on where you are in the country. The crop nutrient requirement approach or
the sufficiency level of available, nutrients.
All of them basically revolve around the idea, that's there's an index above which
you do not need to fertilize the crop. And then there's another, probably older
and, and less used, becoming more and more less used, the basic cation saturation
ratios. So you'll need to recall your the
information that we talked about on cation exchange when we get to that.
So the soil test is a, is a starting point, and then we come to the point of
making a fertilizer. My recommendation, do we simply just say
no fertilizer when the soil is high or very high or do we hedge a, a little bit?
And that's basically you know, what, what's happening here with these
different. The philosophical approaches.
It gets down to the comfort zone of the person making the recommendation or the
farmer using the recommendation. Also fertilizer costs are coming more and
more to the front in this decision making process because you'll see when we're done
today that there are differences in cost associated with the these differences and
philosophical approaches. And as we all know there's more and more
emphasis now a days then there was 40 or 50 years ago, or 60 years ago when these
philosophies were gaining ground there's more emphasis on the environmental impacts
of different fertilizer recommendation strategies.
And again, I want to present each of em to you and then I, I, I think it's healthy to
have a good discussion about these approaches.
So let's start with build up and maintenance philosophy.
Under this philosophy you add fertilizer until you achieve your desired soil test
level. So, for example, you want your soil to
test high in phosphorus, so you're going to add fertiziler.
Some promote adding it, building it up over a short period, two or three years.
And then you grow your, your crops on this, and you're going to add back, each
season, an amount of, of phosphorous in this case, let's say, that the crops,
removed. So if you, if you sell your corn grain off
the farm it's going to take some phosphorous away.
It's going to remove that from the soil, bank, as it were.
So under this, scenario, this approach relies on some very accurate and very
important crop removal values. How much phosphorous was taken out of your
field, given a certain yeild level? And that's a real tricky part.
You have to have good numbers reliable numbers.
This approach more or less treats the soil as a bank.
So you hope that the, the phosphorous that you put into the bank, your bank account's
going to stay relatively level over the years.
So as you remove money from the bank, or phosphorous from the soil you need to add
it back. So under this scenario, you usually are
going to be adding phosphorous every year. Now, some proponents suggest not testing
every year, because if you're always adding a little bit of phosphorus, chances
are once you get away from that critical level between medium and high on the soil
test, then perhaps you can back off of the need for a soil test every year.
And maybe some farmers that own their own land may be they don't mind building up
or, or may be they like building up the phosphorus for example in their soils.
If they are renting landing and the chances are they are not going to have the
land more, or for more than a short time, then there might be a little reluctance to
practice this particular approach to fertilizer management.
So I mentioned crop removal values, here is a chart of some, and there's many, many
of these, kinds of charts, out there. Here's corn grain, and you can see that,
for this certain level of yield. It was expected that 66 pounds of P205.
Again, you know, that's, what, 20 or 30, pounds of, or, kilograms of, p, was
removed from the from the field. If you are in, you know, producing using
your corn stalks for bio-fuel, then you may remove another 40 pounds.
So somewhere around 100 pounds of P2O5 would be a removal value that a farmer
might add back, if they were practicing buildup and, and maintenance.
So for these crop removal values, as I said, they're very important.
You need to know where they came from. How were they developed?
Do they reflect luxury consumption? So when they were developed.
When the researcher was developing these numbers, did they apply a lot of
fertilizer? Fertilizer such that the plant took up a
lot of nutrients and therefore these numbers might be a little bit on the high
side so you need to know a little bit about the crop removal values that the lab
or the person making the recommendations where they cam from, In this regard if we
just step aside a little bit The and, and touch on nitrogen.
Typically for, for this procedure, for this philosophical approach nitrogen is
recommended based on a yield goal. So a farmer would say I think I can
produce. So many bushels per acre of corn, or so
many pounds of potatoes in my crop. And I know that the matter of nutrients
are associated in, in that amount of crop. And so for nitrogen the recommendation
Might be 200 pounds per acre because that correlates with a particular yield goal.
And so yield goals are used very commonly to make nitrogen recommendations.
So again here, you need to Ask if you're not familiar with how the lab is, or the
person making the recommendations if they're using yield goals.
Where did those yield goals numbers come from?
What research was used? The challenge here is to really have a
good realistic yield goals. If your fertilizer recommendation is going
to be based on yield goals Then, you need to think about what would be realistic for
you. The average of the last five years, the
average of the last ten years some people say you know, my average is 200, but I
really would like to produce, 300 bushels of corn per acre is that realistic, for
that farmer and for your growing region. There's been some research on yield goals
and I've given you one of the citations here.
These researchers studying yield goals and evaluating farmers found out that very few
farmers, in fact about 20% of them were successful in achieving their yield goals.
So that's another reality check that we all need to do with ourselves when we're
using yield goals to set our nitrogen fertilizer rate.
Here's the results from some studies evaluating yield goals over four years and
many, many farms. You can see the numbers of farms that were
involved in this. And you see that, on average depending on
the year, farmers were overestimating their yields.
In this particular year here, you can see that the overestimation was, you know,
modest, only 16 bushels per acre. But also that year they had really, really
good yields compared to the other year. So weather may have played a bigger role
in the yields across these years than fertilizer nitrogen, for example.
So again just to drive home the point, that yield goals, need to be, set
realistically. So in the build-up and maintenance
approach, is building up the soil nutrient level okay?
Where might this work? Think about soil texture, Where might this
be a challenge? Think about soil texture.
Again, why, some people will ask why add fertilizer, even a little bit, if a soil
is already at a level where it can supply the requirements for that crop.
I think that's a valid question, why would you add more fertilizer, particularly in
today's age with the extra cost, increasing cost of fertilizer.
And also the potential that extra fertilizer that's not used by the plant is
going to end up in, in someones water body.
So that's a valid question. Also, if you remember as you change from
medium to the high on the. The, soil test, calibration.
If you're far out to the right of the high in the very high category.
Maybe you have enough phosphorus in the soil to grow several crops years.
You can essentially mine the phosphorus. So, again, a question as to why you might
be inclined to add more phosphorus, in that situation.
Environmental and economic considerations, as I said can have, should have an impact
on this decision making process. And even though traditionally labs have
recommended to add back 100% of the crop removal value, some labs are starting to
back off of that. And recommending under those high and very
high soils to add back only a portion of the crop removal value.
So if you remember our example, where we talked about possibly adding 100 pounds of
P 205, maybe some labs would back off and say Add half of that.
Or maybe even a quarter. I saw some labs, recommendations that are
for adding back a quarter, of the crop removal value.
So we're moving in that direction of, reducing the amount of fertilizer that's
recommended, by this, philosophical approach.
And what we'll, we'll, I'll have a few more words about that as we get, towards
the end. The other, major approach, or phi-,
philosophy is that percents/g efficiency or the crop nutrient requirement approach.
This relies on the idea that there is a soil test index there in a well
correlated, calibrated, soil testing procedure.
Above which we can, we can be sure we do not need to add fertilizer, in our case
phosphorus. And so if our soil tests at or above that
index then the recommendation under this philosophical approach would be zero
phosphorus. This relies very heavily on a well
calibrated Soil test procedure and it relies particularly or if you're in the
high, just into the high category is going to rely on more frequent testing to make
sure that you're remaining in the high category and that you haven't slit, your
soil hasn't slipped into the, the medium category which is where you might start
adding some fertilizer. This particular approach is generally
favored by the land grant institutions who are still in the, the soil fertility
testing and, and recommending business. The percent sufficiency, many people say
it fertilizes the crop, because now we just add the nutrients that the crop needs
to make up for those nutrients that Are already there in the soil, so we focus
more on the crop with this approach. And some argue that other soil testing
philosophies focus more on the soil. We need to build the soil up to a level
And even though that level is higher than the critical level and the crop would do
just fine without fertilizer. So here for the example, the University of
Florida and I've highlighted in green, the high and the very high So here, this
example happens to be for vegetables and as you can see our fertilizer
recommendations for P2O5 go all the way from 150 to 0.
And so once we've crossed that threshold and our soil is high then We recommend
zero phosphorous to the farmer. And so you can see that for watermelon,
potato, and tomato for, for phosphorous, we're confident that the soil test can
predict no crop No crop increase or advantage to adding more phosphorus.
There's been lots and lots of studies comparing these philosophical procedures.
Here's our philosophies, here's one here done in, in Kentucky where they had eight
years of trials and in this column here they had the percent sufficiency and over
here the buildup in maintenance. And you can see the fertilizer
recommendations, and in this particular case, the soil tested high and phosphorus
and potassium so, they recommended 0. Over here under the maintenance philosophy
these farmers had a recommendation to add some amount of phosphorus and potassium
and you can see that resulted in a difference in the, the total cost of the
fertilizer program and the interesting aspects to this is that the corn yields
over all of these trials were exactly the same.
With these 2 philosophical approaches. So under one approach more money was spent
for fertilizer but it did not return an increase in, in yield.
So it's interesting that in this particular case in one of those studies
there was a significant difference and it was towards the advantage of the percents
efficiency approach. The third philosophical approach is basic
cation saturation's ratios and so you think back to your discussion on cation
exchange capacity, you can see where this one is built from.
So here is cation exchange capacity illustrated.
Here's our colloid either organic or clay, and it has calcium and mag-, magnesium,
and sodium associated with it. And in the soil solution, the blue, that
can be exchanged, in the soil solution. Under this, basic cation exchange,
capacity, which was developed, a long time ago.
It's an idea that says that there are certain favored percentages of our cation
exchange capacity that will be occupied by these various cations.
So therefore we can develop a ratio of one cation to the other.
And the idea here is, is that you can modify those amounts, those percent
saturation or those ratios by changing your fertilizer.
And new analytical lab equipment that can analyse a lot of different cantions.
And computers that can cacluate these ratios and make recommendations has made
this approach easy to do. So here's an example of some of the
original research promoted that the cation exchange capacity of a, a soil should be
roughly in these kinds of percentages. And this is used for, obviously for
potassium, magnesium, calcium, some of the other cations for making fertilizer
recommendations. So if your soil is sort of not in these
kinds of, of numbers or is so-called out of balance, then you would change the
amounts of fertilizer that you added. And so you can think back to our soil
textural triangle, and you might think that, well, you know, in these kinds of
soils up here that have some significant, cation exchange capacity, maybe this could
be managed. But think about out sandy soils, with low
cation exchange capacity. Maybe you have the ratio and the balance
correct but the amount that, that low[INAUDIBLE] exchange capacity could
hold maybe in, in sufficient to supply the nutrition for the crop.
And in fact in those kinds of scenarios potassium for example could be leached.
If you added a lot of potassium in an effort to achieve a, a certain balance or,
or ratio. So I hope you see that.
That this, this particular approach is, is rather cumbersome and, and rather
difficulte to manage particularly when you go to our south eastern coastal plain
soils and here in Flordia where we're dealing with sandy soils this approach or
this phylisophical apprach is probably very difficult to It's, to justify.
Again here's some research that's been done with this approach.
In this particular study, this scientist, looking at corn and soy beans over several
years, took the highest, the highest five, sites and the lowest five sites in terms
of yield. And then looked at the ratio of calcium to
magnesium in the soil. And you can see that for the highest
yielding site and the lowest yielding site this range and ratio is almost exactly the
same. You know, as you go from year to year so
the take home lesson here is that the ratios were the same in the low and the
high yielding sites. So there must have been some other factor
going on there, controlling yield across those sites rather than the basic cation
saturation ratios in the soil. So why the lack of relationship, that more
modern researchers, have determined about this, philosophical approach?
Well, it turns out that most plants are pretty good scroungers.
I use the word scroungers because, plants can do a pretty good job of To obtaining
nutrients if they're, if they're out there in the, in the neighborhood.
They can do a, a very good job over a wide range of ratios on the on the cation
exchange. And we've eluded to some of the problems
with this approach particularly for sandy soils with low cation exchange, capacity.
Well, what about calcareous soils that are high, very high in calcium?
Could you ever achieve, a desired, ratio in those soils?
What about farming scenarios like we have in Florida where we're irrigating with
high calcium carbonate irrigation water, we're adding calcium every time we
irrigate. So we might start out with what we might
think will be our ideal or desired ratio, but pretty soon, as soon as we start
irrigating, that ratio is gone. And this approach like in large way, like
the build up in maintenance typically results in adding a fertilizer, because
you rarely have that ideal. Ratio when you do the soil test and you
start. So in summary, with these philosophies,
the buildup and maintenance. You determine a point a soil test index,
high or very high that we, you would like to get to, if your soil isn't already
there, and then you're going to maintain that level of fertility.
You may allow some draw-down if you're out at the very high, periodically, maybe not
so attest, maybe reduce greatly the amount of fertilizer that you add, but you
typically, in accordance with this philosophical approach, you're going to
add back fertilizer based on what the crop, the previous crop, removed.
So many people say that this approach fertilizes the soil.
Because you're more concerned about the soil test, result and situation, so you
typically always add, some fertilizer. The research with this particular approach
compared to say for example the percent sufficiency.
You know, shows rarely where there are differences and/or enhancements in, in
yield by following this approach but the fertilizer costs typically went up, what
about soils with erosion we talked about rolling topography and soils that might
erode and think about continually building up phosphorus in those soils if you are
not also controlling soil erosion and using good soil conservation techniques,
then this approach which might risk at putting larger amounts of, of phosphorus
and risking it to, to erosion. The basic cation saturation ratio, again
is that there's some best ratio or amount or balance of cations occupying the cation
exchange in the soil. This usually results in adding fertilizer
to change or to recalibrate those ratios to some desired levels.
And it usually results in adding fertilizer and we've eluded to the fact
that this has problems with very sandy low cation exchange capacity soils, for
example, what we have here in Florida. And again you know, we pointed out the
idea that plants are pretty good at obtaining nutrients over a wide
concentration in the soil. And also the fertilizer research comparing
this technique, or this philosophical approach does not document that it has a
benefit over say for example the crop nutrient requirement or percent
sufficiency. In the crop nutrient requirement or
percent sufficiency philosophical approach we have a calibrated, a good calibrated
soil test procedure, that will tell us when and how much we need to add
fertilizer to. We may actually end up.
Over years following this philosophical approach with soils that are higher or
maybe even a little bit higher than high, very high.
But at least we're going to move that soil test index from the medium to the high
category because that's where we need it to be to get a maximum yield fertilizer in
this particular situation, is seen as a material to supplement the native
nutrients in the soil, and that's a very, very important distinction and concept
with this particular philosophical approach.
We're looking at both of those sources, the native soil fertility and fertilizer
to supply the nutrients that the, the crop needs to give us the, the good response.
And most of the research that's done comparing these philosophical approaches
shows that this is typically the most appropriate one, particularly when you
factor in environmental issues and costs. So just a few more points to, to make
here. You know the percent sufficiency and the
build up may end up in the same place sooner or later.
That is soils that test high in phosphorous for example.
So at that point these two are, are fairly similar in that regard.
They have, in, in essence, built the soil up to a, a high category.
We're not going to use percent sufficiency or crop nutrient requirement and always
farm soils that are in the medium or medium-low category.
Because we know that they need fertilization.
The main difference between these two is what happens after you get to that high
category. The percent sufficiency would say we're OK
for now, we can confidently grow that crop without added PTO5.
And the other approach would say maybe we're not quite that confident and we're
going to add what we remove because we want to keep our bank account full.
And those are decisions that. Farmers and people making recommendations
need to confidently and, and, and with a lot of good science behind them make those
decisions because they do have implications for.
The return on investment and the economics of the farm, and also, potentially, and
environmentally. These so attest philosophies came along
when fertilizer, was increasing in use, synthetic fertilizer back in the 40s and
50s. Many of these soil test procedures, these
extraction solutions and these philosophical approaches to making
fertilizer recommendations were born out of that time of the last century.
That's when large benefits were seen by Making fertilizer applications and no one
wanted to be on the low side of fertilization of our crops because we saw
the drastic improvements in yield and quality by adding fertilizer.
And fertilizer, you know, during those years was a fairly small, maybe a few
percent of the total cost of producing a crop, so it was seen as relatively
inexpensive insurance to make sure that we had enough fertilizer out there.
And the research had not progressed, enough to really show farmers and help
them get confidence that when the soil tests said high we could get by with no,
with no, fertilizer. So this was all prior to more recently in
the last, say two decades, when fertilizer costs have been increasing and, more and
more emphasis now on. The environmental, implications of this,
and in the 70's and 80's, we had far enough, we'd come far enough along that
scientists were very interested in comparing soil test, extracting solutions
and philosophical approaches, and there's been a fair amount of, Research done on
that. Unfortunately we have not done very many
of those kinds of studies in the last say decade really so word about yield goals.
Some degree of measured yields needs to be incorporated in this whole process.
So, if you're going to use yield goals, those numbers need to be based on some
good experience that the farmer has in terms of the productivity level on their
farm or some good research. The goals should be to have realistic
yield goals because if your yield goals are not realistic then chances are you're
going to be applying more fertilizer than your crop could, could use.
And our studies of the fates and flows of nutrients, particularly nitrogen, which is
where yield goals really come into play very heavily.
You know, we've learned now what can happen to nutrients that are beyond the
capacity of the crop to, to assimilate and return in terms of yields.
So in today's world, the, the idea of yield goals needs to be really more, more
thoughtfully approached. I'm not saying that yield goals do not
constitute an important part of making a good fertilizer recommendation.
I think in many cases, they do but they need to be very carefully considered.
I want to finish with just a minute here to let you know that, you know, over the
years there has been some studies done on comparing these different philosophical
approaches. There's one fairly detailed and complete
study, by Doctor Olson, and his colleagues.
Unfortunately it's the early 80's, and we just have not done very many of these
studies. But it involved growing corn over several
years. And what the scientists did was to take
samples from several sites, and they split those samples.
And sent some of them to various labs including private soil testing labs and
also the University lab and they followed those recommendations coming out of those
labs for fertilizer explicitly for their crops.
So the treatments in these experiments consisted of the fertilizer programs that
were recommended by the, the crops. The commercial labs and one way or another
use the canine exchange, capacity, the ratio approach, or the buildup approach.
The University Lab subscribed to the percent sufficiency approach.
And when they got done, and manage the fertilizer according to the lab
recommendation they. They found no differences in grain yield.
Amongst the different philosophical approaches with the different, resulting
in different fertilizer amounts. They were great differences in the amount
of fertilizers used to grow the corn crop but, but no difference in the yield.
So the scientists concluded and I've added a few words to this but basically they
concluded the conservative approach with the percent sufficiency and most people
recognize or put the moniker on the percent sufficiency as being very
conservative. And depending on how you define
conservative maybe, maybe that's, maybe that's a good thing But the conservative
approach with the percents efficiency no fertilizer for soils that tested high seem
to be the most appropriate given considerations for social economic and the
environment and I've inserted. As I have warned you all, uh,[LAUGH]
through this course, the Triple Bottom Line, because that's very important and I
think, comes out, shining, clear in studies like this, because the economics
and the potential, impacts on environment, are very important.
So still today, these, philosophies are out there.
There in terms of making fertilizer recommendations.
But as I said, there's been some changes and some moderations to some degree and
some amalgamations, if you will, between different approaches, and so I think we're
moving forward with understanding a little bit more about making fertilizer
recommendations, and How our philosophical approach, should, will impact, those.
And particuarly you know with regard to over fertilization, we surely don't want,
to make, fertilizer recommendations based on a philosophy that results in, excessive
fertilization. Because the economic impacts on the farmer
even though fertilizer today is still relatively small compared to other
impacts, it's still not, it, it is not a trivial part of the overall production
costs and budgets. Fertilizer might still be seen in some
sectors as relatively inexpensive insurance against low yields.
So, if I put a little extra on, I can sleep at night based from my fertilizer
aspects. I can worry about other things on my farm
like weather disasters and, and labor costs and, and pest management and
marketing and things like that so sometimes that plays a role in the
decision making process. As I said before, fertilizer, you know,
Twenty or thirty years ago demand was few percent but now increase in cost of
fertilizers hmm, it becoming a non trivial part of our cost of production and I am
giving you some papers on this subject if you want to do little bit more reading on
this subject hmm, you know again there. You know, they're 20 years old now.
And I wish that we had the wherewithal and the, the resources to continue to study
these kinds of aspect with soil testing, because we all say that its an important
BMP for nutrient management. And as we move forward as crops change, as
variety change, as production practises change and become more intensive We really
need to keep up with doing research on fertilizer and nutrient requirements and
calibrating soil testing. So a couple take home pages here for you.
Soil testing is still a very important first step in a nutrient management BMP.
With all its potential problems and challenges that we've talked about now
it's still very important because without it we really are moving in, in the dark.
We need to have an idea, of the nutrient supply and capacity of our soils.
Even though you have a good soil testing result and a recommendation, you need to
think about, the, basis for the recommendation and you need to, to do
some, spend some, some time, quizzing the, the lab and the person making those,
recommendations. So that the farmers can understand the
differences, amongst those approaches, and also the potential economic and maybe even
environmental implications. Not all philosophical approaches are, are
going to apply to your farming situation. The environmental part of the triple
bottom line in this regard is becoming increasingly important and is going to
continue to drive decisions about fertilizer use and management.
Cost of fertilizer today, much more expensive than it was two or three decades
ago. These two aspects at least in my mind,
seem to be driving the decision more towards a sort of percents efficiency
approach, applying less fertilizer at least on those soils that are high and
very high. But soil tests, you know, in the final
analysis, soil tests that are properly developed and properly executed and
properly interpreted can, can, can go a long ways to helping us manage nutrients
on the farm. And we'll talk a little bit more next
time, you know we'll get a little more detailed about some of those nutrient
management procedures but I thought it was very important to really cover this aspect
of soil testing fairly thoroughly because it is so important, to our understanding
of best management practices and being able to move forward, with managing
nutrients, on our farms.
