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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

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

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