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Forage Crops HCS 412 |
Homework
Question 1
(5 bonus points)
a) Which of the following fertilizers provides the cheapest source of nitrogen?
| Fertilizer |
%N
|
$/ton
|
lbs
N in
1 ton fertilizer |
cost per lb N |
|
| 28% |
28%
|
$224
|
|||
| urea |
46%
|
$299
|
|||
| ammonium sulfate |
21%
|
$175
|
|||
| 19-19-19 |
19%
|
$375
|
|||
| 8-25-3 (liquid) |
8%
|
$266
|
|||
| 14-14-14 |
14%
|
$326
|
|||
| 24-8-16 |
24%
|
$379
|
b) Alfalfa can fix 200 lb N/acre/yr. How much would this cost if it were applied as fertilizer (state which fertilizer you used)?
A hayfield produces 4 alfalfa crops, each of 1.5 ton/acre.
a) How much hay is removed from the field?
b) How much K is in that hay? (hay is 2.8% K)
c)
How much fertilizer would be required to replace the removed K?
(K20 = 83%K)
[0.83 lb K/lb K2O or 1.205 lb K2O/lb K]
d)
What might the hay be worth, and what might the fertilizer cost?
| Fertilizer |
%K2O
|
$/ton
|
lb
K2O in
1 ton fertilizer |
cost
per lb K2O |
| 19-19-19 |
19%
|
$375
|
||
| 24-8-16 |
16%
|
$379
|
||
| 0-0-60 |
60%
|
$236
|
Calculate
a farm P balance
A confinement dairy farm has 500 cows each producing 20,000 lb milk. The
farm has 90 acres in forage (alfalfa & corn silage) producing 12,000
lbs/acre/yr. No P fertilizer is used.
a) Calculate how much purchased forage is required, and how much P is imported onto the farm (assume each cow consumes 10,000 lbs forage/year and forage = 0.3% P)
b) Calculate how much P is exported as milk (assume milk = 0.1% P)
c) Effluent from the cows is collected and spread over the farm. What is the P application rate? (assume all imported P ends up as effluent P, with no leaching losses)
d) What would the soil P level be after 20 years (assume 9 lb/acre of applied P will increase soil P by 1 lb/acre, initial soil P = 22 lb/ac, no leaching losses)
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