Understanding Phosphorus In Minnesota Soils
Table 1. The effect of banded and
broadcast phosphate on corn yield
when soil test levels for P are low. |
Phosphate Applied
lb P2O5/acre |
Placement |
Yield
bu./acre |
| 0 |
- |
122 |
| 40 |
starter |
146 |
| 100 |
broadcast |
148 |
Soil test P (Bray and Kurtz #1) = 6 ppm; study conducted
at the Southwest Experiment Station, Lamberton |
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Table 2. Soybean yields as affected by the rate
of phosphate applied (1986-1988 ave.) |
|
Location |
| Phosphate Applied |
Waseca |
Lamberton |
| lb./acre |
- - - - - bu./acre - - - - - |
| 0 |
31 |
27 |
| 23 |
33 |
29 |
| 46 |
35 |
30 |
| 69 |
36 |
30 |
| 92 |
37 |
32 |
| Soil Test P (ppm): |
5 |
3.5 |
| (Bray and Kurtz #1) |
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| Table 3. Interpretation of plant analysis values for phosphorus. |
| Crop |
Plant part and sampling stage |
deficient |
low |
sufficient |
high |
|
|
- - - - - - - - - % P- - - - - - - - - |
| corn |
whole plant; 12 in. height |
- |
- |
.40 |
> .80 |
|
ear leaf at tasseling |
< .16 |
.16 |
.25 |
> .50 |
| small grain |
Top leaves, boot stage |
< .16 |
.16 |
.21 |
> .50 |
| alfalfa |
upper 1/3 of plant, early bloom |
< .16 |
.16 |
.25 |
> .70 |
| sunflowers |
5th leaf at flowering |
< .15 |
.15 |
.30 |
> .50 |
| Adapted from Soil Testing and Plant Analysis, Soil Science Society of America (1973). Values subject to modification as research develops. |
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