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 Management, Part 2
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來自 University of Florida 的課程
农业可持续土地管理
66 個評分
從本節課中
Soil Management
For week 5, we will look at soil management in detail and begin to discuss soil testing.
與講師見面
George J. Hochmuth, Ph.D.Professor
Urban and Agricultural Environmental Sciences
Hello everyone again. In our last lecture, we talked a little
bit about soil tillage. And some of the things that lead to the
development of soil conservation practices that now we actually take for granted in
this country. Those experiences during the dust bowl
years made a big change in this country and the way we practice farming.
And we talked a little bit about one of the first practices that Mr.
Bennett tried to get farmers to adopt was terracing.
And you can go around this country in area in the Midwest and even in the other areas
in the country. And you can see terrace farming being
practiced now when you ride around you will know what you're seeing.
There are other soil conservation best management practices that are been
developed over the years. Methods for conserving mostly directed at
conserving the soil. Some of these fall under a general
classification called conservation tillage.
No-till, Ridge till, and Strip till are a few three of them that I'd just like to
call your attention to. In these pictures, you can see Strip
Tillage and it is kind of what it looks like.
We have specialized equipment that tills a small strip of the soil, not the whole
breadth of the soil. And you can see the refuse from the
previous crop still on the surface of the soil.
But in some situations, we need to till and loosen the soil so that you get better
seed soil contact for improved germination.
And you see corn being planted in the upper picture, this is called strip
tillage. Ridge tillage is a variation on this, but
in this particular case, we're actually are building slight, small ridges or hills
across the field that we're going to plant into .
Again, this one relies on leaving the refuse from the previous crop on the
surface. In this case, ridge tillage is used
because in some soils that tend to try out a little bit slowly.
We can probably guess based on our soils lecture what kinds of soils those might
be. But building a small ridge allows that
soil to dry out and warm up a little bit faster and in some, for some crops,
that's, important. So, when you see fields that have small
ridges or marsh board or a ripple across them that farmer is likely practicing
ridge till. No-till is just what the word indicates.
We do not till the soil in preparation for planting.
Here is a crop of soybean that was planted after a crop of corn from the previous
year. And you can see these soybeans have been
planted directly in the refuse from the, the old crop.
No-till takes special equipment rather heavy equipment to cut through the refuse,
particularly if it's something like corn. So, that you can cut through that refuse
and open up a seed furrow for the seeds to be deposited in.
But as you can see, these pieces of equipment can plant right over the top of
the old, crop refuse. In the bottom right-hand picture, here
behind me, were planting small grains into another small grain apparently.
Maybe it's soy beans being planted into a small grain field, but directly through
the old crop refuse. Here are the soy beans growing up through
the corn refuse. And over the years, there's been a
considerable amount of research comparing conventional tillage where we till the
soil with plows and disks and plant compared to no-till.
And this is just a, a capture of some of the data that can be that can result from
some of the studies showing that there's very little differences, if at all between
the yields for several crops between conventional tillage and no-till.
Even though no-till has been practiced most widely for agronomic crops such as
corn and soy beans and, but it can even be used on vegetables.
Here's a picture of transplanting vegetables.
I believe this was a cold crop like broccoli or cauliflower.
Here, they're using a variation of ridge tillage and they're planting or
transplanting their vegetable crop in the top of those ridges.
And you can see the old crop refuse, in this case, it was a cover crop of rye.
They're planting directly into that. And, of course, this leaving the refuse on
the, on the surface helps conserve moisture and prevents in many, many ways
wind blowing of the sand. And it adds organic matter to the into the
soil. There are some other conservation best
management practices that farmers use. Some of these might be classified as more
bigger picture types of approaches, windbreaks grassed waterways, grass filter
trips riparian buffers or riparian strips. And I remember, remembered I, I asked you
to, to pay particular attention to the curvy rows that are typical to contour
farming. This particular farmer has rolling land
and if the farmer planted up and down the hills then during a rain storm you have
easy pathways for the water to run off of that field and erode.
And so, contour farming involves planting perpendicular to the contour of, of the
land. You also note in this particular field a
grassed waterway and we're going to come back to that to, to show you how those are
used and can be used in conjunction. It, it might be worth noting at this time
that many of these practices can be teamed up in what is called a BMP train.
Several of these practices used in one for one crop on one, one particular farm.
Here is a picture that I think is particularly interesting, because they're
using plastic mulch. This happens to be strawberries in
California. But you can see the contour of the land
and how this farmer has planted those rows against perpendicular to the contour of
the land. And so, the field directly in front of us
with the rows going right and left. You can see that we're up on the high part
of that slope looking down and the rows are planted crossways.
And this helps protect minimize erosion, at least in the field.
Erosion can still happen and we see it happening in the roadway to the edge of
the roadway. But at least in our field we're not having
wholesale gullies formed as the water runs down the slope of the land.
Contour planting and perhaps even in this picture terracing can make for a very
spectacular view from the air. Here's a midwestern picture of alfalfa and
probably some small grains fields that have been planted on the contour.
Serial windbreaks or wind breaks for that matter.
Typically, cool season cereals cereal crops like rye Secale cereale are used
very commonly for windbreaks particularly in vegetable fields.
Here is this picture of the farmer putting out plastic mulch and drip irrigation.
But you'll note the green strips in the field in this particular case, this farmer
planted in the fall rye to get it established, so that it would grow during
the winter time. And then, in the spring, when the, the
plastic mulch beds were formed and the crop would be planted, it would look more
like the picture here on the, on the bottom, except we do not have the plastic
mulch here. But you can see how tall, by the time the
spring time comes around, you can see how tall the windbreak is.
And now, it can be effective in protecting that crop from moving soil from, from
winds. Windbreaks work by slowing down and
deflecting the wind up and over. In this particular case here, the wind is
moving this direction and it's deflected up and over this windbreak, and then
eventually, comes back down. And there's a zone of protection in here
that roughly is ten to 30 times the height of the windbreak.
So if you have a windbreak that's, say 2 meters tall, then somewhere between, you
know, ten, 20 30 times, that would be your effective protected zone in the field.
And then it would time to have another windbreak to repeat the process.
So that's why you saw in the previous picture with a small farmer laying down
plastic mulch had regular windbreaks across.
Those windbreaks were fairly close maybe more on the order of ten times the height.
Here is the windbreaks being used again. A type of windbreak is called a
shelterbelt. These, remember back to our discussion
last time with the Civilian Conservation Crops.
This is what they were planting, rows of trees at periodic intervals across the
land to break the wind. Here is a row of pine trees.
This happens to be in the Central Area of Wisconsin.
Those of you that might be familiar with Wisconsin know that the central part of
the state is very, very sandy, and those sands are very subject to blowing, in the
springtime. So that was one of the areas that these
shelter breaks were planted. Another soil conservation practice is
called cover cropping. In this collage of pictures, I've given
you several different scenarios where cover crops are being used.
The one on the top left is our winter rye, Secale cereale, and you can see how tall
this gets and how effective it would be, either as a green manure crop to add
organic nutrients back to the soil or as a windbreak.
On the right-hand picture, upper right-hand picture, you see a cover crop
being used in the alleys and a fruit orchard.
The lower right-hand picture down here is a cover crop that a farmer has planted.
It's probably a winter rye to protect that field during the winter from erosion or
blowing soil. On the left, you see Crimson clover.
This is an interesting cover crop, because it fixes nitrogen.
So it can take nitrogen out of the air and fix it in forms in mineral forms that then
plants can use through a process that we call biological nitrogen fixation.
So a couple of crops have a lot of different benefits, and in fact, it's hard
to deny their usefulness on most farming situations.
They reduce soil erosion from either wind or rain.
That's one of the major emphasis that we have for cover cropping.
Cover crops can also take up nutrients that have been left over from the previous
crop. Remember, we talked about the fact that
most of our, our crops do not, are not 100% efficient in using the fertilizer
nitrogen. So some is going to be left in the soil.
Cover crops are very effective at scavenging, and taking up those nutrients,
and capturing them if we can plant the cover crop as soon as possible after the
main crop and before leaching rains for example.
Cover crops add organic matter whether we till them back into the soil as a green
manure crop or if we leave them on the surface when we practice strip tillage or
no tillage. And, as that cover crop organic matter
decomposes, it adds those nutrients back into the soil that the plants can then
use. Cover crops and green manure crops are
particularly favored by those practicing organic agriculture because these crops
can fix the nitrogen. If, if they're a legume those crops can
fix the nitrogen from the air and add it to the soil.
So that minimizes in those systems about the alternative that you have would be
animal waste. But I think that it's important to just
remember that in biological nitrogen fixation, we are taking nitrogen out of
the air and fixate it in forms that plants can use.
When that plant is finished, when that crop is finished, that organic matter goes
back to the soil and those, those nitrogen forms are then mineralized.
And as far as managing nitrogens, nitrogen in our soils the approaches become similar
between conventional crops and organic crops, because the nitrate that forms from
the decomposition of the organically produced crops.
If, if, if they're a legume would be need, we would need to manage it the same as if
that nitrate came from synthetic fertilizers, when it, so when that
nitrogen enters back into the into the nitrogen cycle our management strategies
are, are, then become very similar. Here is a cover crop on a very, very sandy
farm in northern Florida and you can see how uniform the person has planted this
crop. Another approach to protecting our soil is
called a grassed waterway. Here, you'll see where grasses have been
planted in a depression going across the field and in this depression is where the
run off mostly is captured from this field.
And if we plant grasses in this in this waterway then we can slow down the water
for one thing and prevent or minimize erosion.
And as we slow down the water, we give it a chance to infiltrate it into the soil,
so this is very important for soil, for water conservation.
And also, those plants if they're actively growing, they can take up nutrients that
might be in that runoff. So grassed waterways is a very important
way to conserve soil and many other things like nutrients and water.
Here is a picture from the air of how grassed waterways are being used on a
farm. I think this farm is from maybe from
Pennsylvania. But nonetheless, you see there's some
topographic relief to this fields and those low spots have been planted in grass
so that they will not erode. Here is an idea of a filter strip.
Filter strips are typically areas of plants, maybe grasses that are planted
along the edge of a field between the field that we're growing crops and say, a
stream or a pond. And the idea is that, as runoff moves from
the field towards the stream or waterbody, it passes through this filter strip and
can be filtered. Sediment falls out and is collected in the
filter strip, and, ad the plants in the filter strip can take up nutrients and
keep the sediment and nutrients from entering the waterbody.
Filter strips do need to, to be thought about before they're planted.
In the bottom picture, you see a filter strip.
Bright idea. The execution leaves a little bit to be
desired, because this filter strip was too narrow and the runoff, the volume of the
runoff was too great for that filter strip to slow down.
And in fact, it eroded the filter strip away.
Filter strips and grassed waterways as I've mentioned already, have several
advantages. They slow down the water flow, slow down
the speed, and so, erosion is greatly reduced and that gives time for the water
to infiltrate into the soil. It filter strips and, and grassed
waterways, also because, they have plants in them can trap the sediment.
They hold the soil in place and those plants can take up nutrients if there's
new, if the resonance time of the water in the filter strip or the grassed waterways
is long enough, so those plants can take up nutrients.
And that's particularly true in the warmer times of the year when plants are actively
taking up nutrients. Some research shows that filter strips and
waterways can remove half of the nutrients that are flowing through them.
That's a significant reduction in the amount of nutrients that would leave that
farm. And most of the sediment can be trapped in
these filter strips and grassed waterways. They can be used on deep, sandy soils, or
on more heavy, clayey soils. On deep, sandy soils, you need to think a
little bit about the type of plant that you're going to grow there, because
remember, sandy soils tend to be low in nutrition.
And so, you may need to actually manage that filter strip or grassed waterways to
make sure that it gets nice uniform coverage and it needs to be a grass that's
fairly deep rooted. So filter strips and grassed waterways and
some of these techniques that we're talking about that involve plant materials
using plants will need some degree of, of maintenance.
A riparian buffer system sometimes we hear the word riparian buffers or buffer
systems. This again is a system where we're trying
to protect the waterbody from nutrients and sediment that would move off of the
off of the land nearby. In this particular, particular case, we
have a waterbody and then we have various degrees of agroforestry going on, I guess
you could call it. Here is some managed timber, and then
eventually, we get out to the grassed system.
This, this can be native grasses or it can be planted grasses, and then eventually,
we get out to the agriculture fields. So when we talk about a riparian buffer
system, we're buffering that waterway from any possibility that nutrients and
sediment could move from our agriculture area.
Here is an interesting picture, because you might want to take a look at this and
see how many of these conservation, conservation practices that we've talked,
not only today and the last lecture, but even earlier in the course.
For example, here we have a stream that's flowing through a farm.
Some of these ideas, we're not, we're not going to have time to cover in this
course, such as rotational grazing that keeps that keeps the animals from totally
destroying and wiping out the, a coverage in a certain area.
You rotate around and give the grass a chance to recover.
But we had talked about constructed wetlands.
Remember when we talked about, and see here right by my finger the tile drain
coming off the agricultural area. We talked about constructed wetlands as
being a place where that runoff from those farms could be deposited.
And then, the plant materials in that constructive wetland would then take up
and use the, the nutrients. What else do you see in this, in this
picture? There's lots of other ideals that, that
we've talked about. For example, here's our multispecies
buffer, with the trees, maybe a grass, although, it looks like a stylized grass
to me and then our crop finally. What do you notice about the crop,
particularly the way it's planted? Those don't look like straight rows to me,
so probably the idea of contour planting is, is being depicted here.
So there's a lot of different ideas that you can see in some of these some of these
cartoons, cartoons. Here is a real picture of a riparian
system in an agriculture area. Again I would ask you to maybe stare at
that for a, a little while and see what kinds of conservation practices that we've
talked about do you see. I mean, I see filter strips.
I also see grassed waterways and they might be a little bit difficult to see,
but if you look really carefully in, in one of the fields in the back, you'll see
grassed waterways. So maybe take a look at this pictures and
see what kinds of conservation practices you can you can see.
Hopefully, when you travel around if you're not that intimately familiar with
all of these conservation practices. When you travel around, particularly in
the springs of the year during as farmers are getting ready to plant you, you can
start to see some of these conservation practices.
Going back to the, the dust bowl was a major wake up call in this country for
farming practices and many, many farmers have adopted these, these practices and
more on their farms. And research is continuing to develop new
ideas and new applications for these conservation practices.
It's all done with the effort of trying to keep the soil and the nutrients and the
water on the farm. Because remember, those nutrients probably
eventually represent a cost that, that farmer put into growing crops and that
farmer wants to make as much keep as many of those nutrients on the, on the farm as
possible, as well the water and the soil. The soil is the greatest asset, I think,
that farms have. I wanted to close with sort of a, maybe a
little bit of a different idea that we, in Florida we, we do call this or count this
as a best management practice. Because it does have a lot of benefits
from an environmental standpoint and also an economic standpoint.
This is polyethylene mulch used very widely on, for vegetable production in
this country. Particularly in states like Florida and
California and also used all around the world now.
It's basically plastic mulch that has been formed over a raised bed and then the crop
is planted through this plastic mulch. Again, here's our small farmer in northern
Florida has applied plastic mulch to some raised beds.
This farmer is using drip irrigation as well.
Plastic mulch is a good method to conserve the soil.
The soil doesn't erode from a heavy rainstorm that would knock down the beds
if they were not covered with the plastic mulch.
The fact that we have the polyethylene over the soil can conserve moisture from
evaporation from the soil surface. And it also protects our fertilizer, which
is under that plastic mulch protected from the rainfall and protected from leaching.
But, think back to the picture that I showed you dealing with contour planting
and the strawberries in California. If you don't plant your, your plastic
mulch correctly with the contour, you can actually have even worse erosion.
This is a picture that I shot a few years ago on a tomato crop that was growing on
rolling land, but the rows had been placed in such a fashion that during this heavy
thunderstorm ,which is ongoing as you can see the water was rushing down those
alleys and eroding soil from that field. Plastic mulch in many cases farmers are
looking at this because of its other impact on the agriculture system.
If you look at this picture, here is watermelon planted on plastic mulch versus
watermelon planted on the bare ground, and you can see the drastic difference in the
growth of those crops. So with plastic mulch, it warms the soil.
Not only does it conserve moisture and protect our fertilizer, but it also warms
the soil and helps the crop get off to an earlier start, which in most seasons is an
economic benefit, to the farmer. Plastic mulch is very important.
You can see how yh, tightly that plastic is fitted to the bed so that the warmth is
transferred from that black mulch. That black mulch heats up from the radiant
energy and transfers that heat to the soil.
And so, that is a major benefit particularly in our cool season uh,uh,
season cool season times of the year. The advantages are early crops, less fruit
rot because our fruits are not resting on the soil.
It protects fertilizer from leaching and it protects our soil from erosion.
But as I said before, there's a double-edged sword associated with that.
Again, its a good technology. We need to be careful about how we
implement or execute that technology. Of course, plastic mulch is a, a product
that needs to be removed from the field. There are ways to get it out of the field
and bale it, and it can in fact, be recycled.
I just thought maybe to show you that kind of a technology.
There's not too many times you get to talk about a technology that might look kind of
strange to, to some of us that are more in, more attuned to row crops agronomic
crops like corn and soybeans. But just to know, just to not leave out
the vegetable side of things there are lots of techniques and technologies that
we can use to help return investment for the fertilizer that the farmer spends to
grow vegetables and also help him or her protect the environment.
Just a few take-homes from this section. We learned greatly from problems in the
past. We always do this.
Hopefully, if we have problems, we can identify the problems come up with fixes
for the problems and adjust to new ideas and new approaches.
In this particular case, no-tillage and planting and soil management technologies
have made a big, big difference in runoff and erosion in many areas of this country.
And if it weren't for the challenges that we had during the early part of this
century and those scientist and agriculture experts and interested parties
like Hugh-Bennett, we've been able to come a long way.
There are many, many choices for effective soil management.
We've touched on a few of those soil management techniques conservation
practices and we've developed a lot of programs in this country for managing
soil. For coming up with new ideas, and for
helping farmers adopt through incentive cost-share programs to help farmers adopt
some of these technologies that might cost a little bit of money to get them
instituted. And if you can help out financially, then
growers are more likely and can then afford to adopt and that's, that's in
everyone's best interest, I think. I tell our students that it is in our best
interests to help agriculture adopt these best management practices.
In our country the NRCS and our land grant universities, are very active with
research and education programs to assist farmers to adopt best management
practices. Not every farm is the same and not every
farmer is the same. And so, different ideas and different
approaches are required. And it takes a very large knowledge base
to help farmers adopt these practices. And we're going to talk about a lot of
other BMPs pertaining to nutrients and water management where education
information and large amounts of effort from the agencies and also from the
educational institutions are, are very, very important.
These management practices do constitute as BMPs and in this state, if farmers
adopt these best management practices then, as we talked about several lectures
ago with our rules and regulations on water quality they can qualify for cost
share to, to help institute these. And then, if those particular best
management practices are deemed effective for water quality, then those farmers get
that presumption of, of compliance with water quality standards.
So there's a lot of incentives, and not only economics and environmental but also
those farmers can, can go a long ways to protecting themselves in terms of water
quality issues.
