Phosphorus should be applied before planting when the soil test level is below 50 ppm. Actual phosphorus recommendations are determined by the yield goal and soil-test level (Table 5). Phosphorus and fall-applied nitrogen are often applied as diammonium phosphate (DAP) or monoammonium phosphate (MAP).
| Table 5. Phosphorus Recommendations for Wheat at Various Yield Potentials and Soil-Test levels. | |||||
| Yield Potential (bu/A) |
Soil test (ppm)
|
||||
|
15
|
20
|
25-40
|
45
|
50
|
|
|
lb P2O5/A
|
|||||
|
60
|
90
|
65
|
40
|
20
|
0
|
|
70
|
95
|
70
|
45
|
20
|
0
|
|
80
|
100
|
75
|
50
|
25
|
0
|
|
90
|
105
|
80
|
55
|
30
|
0
|
|
100
|
115
|
90
|
65
|
30
|
0
|