88 188
Effect of single large doses of P fertilizer
Large doses were applied in 1979 at various rates, then wheat yields were added up for the next five years.
Pounds P2O5 per acre — applied once in 1979
5-year total
wheat yield (bu./ac.)
Increase due to P Cost of P ($/acre)
Cost of P ($/acre)
Wheat $ 4/bus Wheat $ 6/bus
Wheat $ 8/bus
Wheat $ 4/bus Wheat $ 6/bus
Wheat $ 8/bus
0
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144
* **
Total gross profit for the 5 years (Value of yield increase minus cost of P, given as $ per acre)
P2O5 at
35 a pound/
P2O5 at
50 a pound
40
158
14 $14
$20
42 70
98
36 70
92
80
175
31 $28
$40
96 158
220
84 146
208
160
190
46 $56
$80
128 220
312
104 196
288
320
194
50 $112
$160
* $0.35 /lb P205 ($401 per tonne of 11-52-0)
**$0.50 /lb P2O5 ($573 per tonne of 11-52-0)
This is from a study by Wagar, B. I., Stewart, J. W. B. and Henry, J. L. 1986. Comparison of single large broadcast and small annual seed-placed phosphorus treatments on yield and phosphorus and zinc contents of wheat on Chernozemic soils. Canadian Journal of Soil Science , Volume 66; Pages 237-248. Note, the third author is me. My role in the study was very small, but that is the way multi-authored scientific papers are. The grad student does all the work and various profs tag along for the ride.
288
40 140
240
