IMPS
Activity
Activities to Accompany
Improving Old
MacDonald's Farm
For Grades 6-8
Objectives:
This exercise is designed to further explore topics
addressed in the accompanying article. Students work
through calculations to determine how much fertilizer is
needed to meet a plant's nutrient requirements. From these
calculations, students draw conclusions about the most
cost-effective and environmentally sound farming
practices.
Exercises:
Exercise I. Old MacDonald's Farmland Fertilizer
Dilemma
Exercise II. Mooooving Those Cows
Time Required:
Individual exercises are designed to be approximately 1A
hour to 45 minutes long. These exercises are also ordered
progressively: each builds on concepts introduced in the
previous.
Curricular Standards and Skills:
Math:
word problems
addition
subtraction
multiplying decimals
working with money
order of operations
Thinking Skills:
deductive reasoning
Language Arts:
reading comprehension
Vocabulary:
dead zone
eutrophi cation
pesticides, herbicides, and fungicides
sedimentation
Improving Old MacDonald's Farm
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IMPS Classroom Activities
Exercise I.
Old MacDonald's
Farmland Fertilizer
Dilemma
Why Worry About Old MacDonald?
Old MacDonald has some big decisions to make. In this exercise, you will help him
decide how much fertilizer his crops need. At the same time you will help him to keep
costs down and prevent nutrient runoff into nearby lakes and streams.
Old MacDonald's Farm
Verse 1: Old MacDonald had a farm. . . E-I-E-I-O
And on this farm he had 900 chickens. . . E-I-E-I-O
with a cluck-cluck here and a cluck-cluck there,
here a cluck,
there a cluck,
everywhere a cluck-cluck
Old MacDonald had a farm. . . E-I-E-I-O
Verse 2: And on this farm he had 10 pigs
Verse 3: And on this farm he had 12 cows
Old Macdonald has a small farm. The cows graze in a 15-acre pasture, and he grows
corn to feed his chickens, pigs, and cows in a 35-acre field. Altogether, Old
MacDonald's animals produce about 170 tons of manure every year! That manure
contains 1,200 pounds of nitrogen and 800 pounds of phosphorus.
Old MacDonald knows that manure is an unbalanced
fertilizer for corn because it has too much phosphorus and
not enough nitrogen. Corn plants use 5 to 20 times as
much nitrogen as phosphorus, and there is less than twice
as much nitrogen than phosphorus in manure. Farmers
usually apply manure to fulfill the nitrogen requirements
for crops. Because crops do not use up the phosphorus in
the manure, the result is an overapplication of phosphorus.
This phosphorus then builds up in the soil until a rainstorm
washes it into nearby streams or rivers, where it can cause
water quality problems and threaten aquatic life.
Improving Old MacDonald's Farm
Exercise
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IMPS Classroom Activities
Solving the Problem
Old MacDonald wants to fertilize his pasture and cornfields with the manure that his
cows, chickens, and pigs produce. After all, it's free, and he doesn't have to haul it from
somewhere else! And commercial fertilizer is expensive—nitrogen costs 150 per pound
and phosphorus costs 500 per pound.
However, his choice is not easy. Either he spreads enough manure so that the crops get
enough nitrogen (leaving large amounts of leftover phosphorus that could run off into
streams and lakes), or he spreads only enough manure so that the crops get the right
amount of phosphorus (but not enough nitrogen).
After testing the soil, Old MacDonald is able to determine
that the pasture requires 80 Ib/acre of nitrogen and 5 Ib/acre
of phosphorus for the best growth. He also discovers that his
corn crop needs 125 Ib/acre of nitrogen and 25 Ib/acre of
phosphorus for the best growth.
Fill in the table below with information from the preceding
paragraphs.
Pasture size
Corn field size
Manure produced
Nitrogen in manure
Phosphorus in manure
Cost for extra nitrogen
Cost for extra phosphorus
Nitrogen needed to fertilize
pasture
Phosphorus needed to
fertilize pasture
Nitrogen needed to fertilize
corn
Phosphorus needed to
fertilize corn
Number
Units
Improving Old MacDonald's Farm
Exercise
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IMPS Classroom Activities
Doing the Calculations ...
Parti.
Find the amounts of nitrogen and phosphorus required on the farm:
I. How much nitrogen does Old MacDonald need to fertilize his farm?
| acres pasture x
I acres cropland x
| Ib nitrogen per acre =
I Ib nitrogen per acre = +
ib
Ib = nitrogen requirement
Remember your order of operations.
Multiplication is done before addition.
2. Now compare the amount of nitrogen required on the farm to the amount of nitrogen in
the manure. Is there enough nitrogen in the manure to fertilize both the pasture and corn?
3. How much more nitrogen does he need?
4. How much phosphorus does Old MacDonald need to fertilize his farm?
| acres pasture x
I acres cropland x
| Ib phosphorus per acre =
I Ib phosphorus per acre = +
[Ib
Ib = phosphorus
requirement
5. Now compare the amount of phosphorus required on the farm to the amount of
phosphorus in the manure. Is there enough phosphorus in the manure to fertilize both the
pasture and corn?
6. How much more phosphorus does Old MacDonald need?
Improving Old MacDonald's Farm
Exercise
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IMPS Classroom Activities
Part II.
Option 1: Fertilize with enough manure to meet nitrogen needs
From the calculations in Part I, we discovered that the pasture
needs 1,200 pounds of nitrogen. This is exactly the amount of
nitrogen contained in the manure produced on Old
MacDonald's farm. So, let's assume that Old MacDonald uses
all the manure to fertilize his pasture. This will completely
satisfy the pasture's need for nitrogen and phosphorus.
However, he still needs to fertilize his corn crop.
Because Old MacDonald used all the manure produced on his
farm to fertilize his pasture, he must buy commercial fertilizer
for his corn. He needs to buy both nitrogen and phosphorus.
7. How many pounds of nitrogen would Old MacDonald need to buy? Hint: Look at
your calculations in #1.
8. How much would Old MacDonald have to pay to buy enough commercial nitrogen?
9. How many pounds of phosphorus would Old MacDonald have to buy? Hint: Look at
your calculations in #3.
10. How much would Old MacDonald have to pay to buy enough commercial phosphorus?
11. How much would Old MacDonald spend in all on commercial fertilizer for Option 1?
Improving Old MacDonald's Farm
Exercise
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IMPS Classroom Activities
Option II. Fertilize with enough manure to meet phosphorus needs
Old MacDonald does not have to use all the manure from his farm to fertilize his pasture.
From the calculations in Part I, we found that if Old MacDonald puts some of the manure
on the pasture and some on the corn field according to the amount of phosphorus each
field needs, he will need to buy only 10 pounds of phosphorus. However, he will then
have to put nitrogen on both his pasture and his corn field. Will this method of
distributing fertilizer be worth it? Let's find out.
12. After spreading manure according to the phosphorus needs of each field, how many
pounds of phosphorus would Old MacDonald need to buy?
13. Find the total price that Old MacDonald would have to pay for commercial phosphorus.
14. How many pounds of nitrogen would Old MacDonald have to buy? Hint: Subtract
the total amount of nitrogen Old MacDonald needs from the amount of nitrogen in the
manure that he spread.
15. Find the total price that Old MacDonald would have to pay for commercial nitrogen.
16. How much would Old MacDonald spend in all on commercial fertilizer for Option 2?
Improving Old MacDonald's Farm Exercise
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IMPS Classroom Activities
Making the Right Decision
17. Which is cheaper for Old MacDonald, Option 1 or
Option 2?
18. How much would Old MacDonald save if he used
the cheaper method?
19. Which method of fertilization would lead to less
excess phosphorus accumulation in the soil? (Remember
that excess phosphorus in the soil is washed away by
rainwater and leads to pollution in nearby waterways.)
Other Farmer-ly
Considerations-
Manure also contains other
nutrients such as
manganese, calcium,
sulphur, boron, and iron that
plants need to survive. If Old
MacDonald applies manure
only to his pastureland (as
was the case for nitrogen-
based application), he might
still have to buy and apply
these additional nutrients to
satisfy crop needs.
Manure application will also
increase the health of the soil
because manure contains
organic matter that is used as
food by worms and other
organisms in the soil. The
result is a healthier soil that
grows healthier crops while,
at the same time, reducing
the environmental damage of
excess nutrient runoff into
lakes and streams.
Improving Old MacDonald's Farm
Exercise
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IMPS Classroom Activities
Exercise II.
Mooving Those Cows
Old MacDonald has a second dilemma. A small stream runs
between the cow pasture and the barn, as shown in the picture
below. Your job is to draw a plan that will allow the cows to
roam between the barn and the pasture and will also provide
water for the herd. Label any devices that you use and their
purpose. When you are finished with your drawing, write a
paragraph about the benefits and drawbacks of your design.
Things to think about
• How would you get your cows water but keep them out of the stream?
• What problems can you cause for the stream if you let the cows drink directly from it?
• How else can you get water from the stream to the cows?
• How will the cows get across the stream to their barn?
• What streamside practices would you use to make sure water quality, the physical stream structure, and the
fish and organisms living in the stream are protected?
Improving Old MacDonald's Farm
Exercise
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IMPS Classroom Activities
Some Examples
For years, farmers have been working on new ways to keep cows out of nearby streams.
They have come up with a number of practices that help reduce the damage cows can do
to a stream. You can use some of these practices to help Old MacDonald with his cows,
or you can come up with some practices of your own.
Wire fences (left) keep cows from walking on streambanks and digging them up with their
hooves. Planting vegetation (right) along streambanks can help filter out nutrients and bacteria
from rainwater that runs off cow pastures.
A watering trough is a place where cows can drink away from the stream. Use a
water pump to get water out of the stream and into the trough.
Wherever cows gather together in a large group, they dig up the ground with their
hooves. Rainfall washes the loose dirt down the stream as sediment. Use cement in
places where cows are expected to gather to keep this from happening.
Put up a wire fence to prevent cows from getting into the stream or breaking up
mud along streamside areas with their hooves.
Plant grasses or bushes to protect the stream from mud and sediment washing into it
off the banks.
Remember that cows poop wherever they stand around for a long time. If rain falls
on these high-use areas, it will wash manure down into the stream. Plant grasses,
shrubs, and trees along the streambank to capture and filter some of that runoff.
Catch water from high use areas in a settling pond. This practice allows bacteria
and pollutants from the manure to settle out of the water before it runs into the
stream.
Ever heard of a cow path? Cows typically find a path and stick to it. They will find
their way back to the barn from the stream. But they might crowd around trying to
get back into their pens! Create an outdoor holding area/exercise area outside the
barn door that is fenced off.
You can expect cows to poop in the exercise area. A water ditch can divert water to
wash manure out of this area. Then the water should be directed into a settling
pond before flowing back into the stream.
Create a bridge over the stream so that cows will be able to cross over the stream
without trudging in it or pooping in it.
Improving Old MacDonald's Farm
Exercise
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