The Ohio State University Extension Crop Nutrient program is another method of calculating crop nutrient needs. In our example, the analyzed biosolids from page 4 are being applied to the following crop, and the fertility recommendations were based on soil samples from this field.
| Table 1. Range and median of N, P and K contents of digested sewage sludge | |||
|---|---|---|---|
Component |
Range Percent |
Median | |
| Percent | lb/Ton | ||
| Total nitrogen |
1.5-4.5
|
3.3
|
66
|
| Organic nitrogen |
1.5-3.0
|
2.0
|
40
|
| P (phosphorus) |
0.5-4.0
|
2.5
|
50
|
| P2O5 (phosphate) |
1.1-9.2
|
2.5
|
114
|
| K (potassium) |
0.1-2.0
|
0.3
|
6
|
| K2O (potash) |
0.12-2.4
|
0.4
|
7
|
| Source: Ohio State University Extension fact sheet, HYG-6010 | |||
| Corn 125 bu/A | N/lb/A | P2O5/lb/A | K2O/lb/A |
|---|---|---|---|
| Crop needs from soil test: |
145
|
45
|
70
|
| Convert lb P2O5 to lb P needed | P2O5 x (0.44 conversion factor) = P (elemental) |
| 45 x 0.44 = 19.80 lb P/A |
| Convert lb K2O to lb K needed | K2O x (0.83 conversion factor) = K (elemental) |
| 70 x 0.83 = 58.1 lb K/A |
You may choose to convert nutrient values to the same terms (i.e., elemental). The soil test may differ from the forms of the nutrients measured in the biosolid analysis, and conversion may be necessary. The steps above demonstrate the process of converting P2O5 to P, and K2O to K.
| Soil Values from soil test report | pH | 5.9 |
| CEC | 10 |