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Natural Resources Extension Program
Step 7. Total Cropland Required -
Using two different approaches, this worksheet
estimates the total cropland required for manure application.
Example Information:
| Method
#1
This is the preferred method, when
a soil test has been performed and P is below
25 ppm. |
| 1. Total nutrients produced per year
from solids: amount of nutrient/year
(step 1) x amount of plant available
nutrient in manure (step 4) =
| Nitrogen: 1174.5 T/yr x 8.53 lbs N = 10,018.5
lbs N/yr |
| Phosphorus: 1174.5 T/yr x 18 lbs P2O5
= 21,141 lbs P2O5/yr |
| Potassium:1174.5 T/yr x 26 lbs K2O
= 30,537 lbs K2O /yr |
|
2. Total nutrients produced per year
from solids and sludge:
amount of from solid + amount from sludge (step
5) = total amount produced
| N = 10,018.5 lb + 328 lb = 10,347 lbs
N/yr |
| P2O5 = 21,141 lb
+ 842 lb = 21,983 lbs P2O5/yr |
| K2O = 30,537 lb + 362 lb =
30,899 lbs K2O/yr |
|
| 3. Total crop acres based on soil
fertility needed for 100 bushel barley crop:
Total nutrients produced divided by nutrient
required/ac (step 3)
| Nitrogen: 10,347 lbs N/yr divided by 160
lbs/ac = 65
ac for N |
| Phosphorus: 21,983 lbs P2O5/yr
divided by 50 lbs/ac = 440
ac for P2O5 |
| Potassium: 30,899 lbs K2O /yr
divided by 75 lbs/ac = 412
ac for K2O |
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Method #2
This is the preferred method, when a soil
test has NOT been performed.
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| 4. Total crop acres
based on nutrients used by 100 bushel barley
crop
(See
page 24. Fertilizer Guidelines for Montana Crops,
EB 161, 2003)
One bushel of Barley grain use:
0.87 lbs N
0.36 lbs P2O5
0.25 lbs K2O
One ton of Barley straw uses:
14 lbs N
4.1 lbs P2O5
30 lbs K2O
Barley Grain to Straw
Ratio is 1 to 1.3
(48 lb/bu x 100 bu) x 1.3 divided by 2000 =
3.12
Grain:
N = 0.87/bu x 100 bu/ac = 87 lbs/ac
P2O5 = 0.36/bu x 100 bu/ac = 36 lbs/ac
K2O
= 0.25/bu x 100 bu/ac = 25 lbs/ac
Straw:
N = 14 lbs/T x 3.12 T/ac = 44 lbs/ac
P2O5
= 4.1 lbs/T x 3.12 T/ac = 13 lbs/ac
K2O
= 30 lbs/T x 3.12 T/ac = 94 lbs/ac
Total Nutrients used
by 100 bushel barley crop
N = 87 + 44 = 131 lbs N/ac
P2O5
= 36 + 13 = 49 lbs P2O5/ac
K2O = 25 + 94 = 119 lbs K2O/ac
Acreage needed based
on nutrients produced per year from manure
N = 10,347 lbs divided by 131 lbs/ac = 79
ac for N
P2O5
= 21,983 lbs divided by 49 lbs/ac = 449
ac for P2O5
K2O
= 30,899 lbs divided by 119 lbs/ac = 260
ac for K2O
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