Miss. Code. tit. 11, pt. 8, ch. 2, app 11-8-2-A, 11-8-2-11-8-2-A-Q
Rules 2,4,5
When test plots and reference plots fall on different soil series, adjustments must be made to compensate for the productivity difference. Section II of the NRCS Field Office Technical Guide shall be used for this purpose. For ease of calculation, this adjustment shall always be made to the reference area yield.
Example 1:
| area | soil series | productivity index (PI) |
| test plot | Barzo Sil 2-5% | 76 |
| reference area | Zoko Sil 1-4% | 60 |
In this situation, the test plot has a 26.6% higher productivity index than the reference plot, so the reference plot yield is adjusted upward by 26.6%.
Example 2:
| area | soil series | Productivity Index (PI) |
| test plot | Zoko Sil 1-4% | 60 |
| reference area | Barzo Sil 2-5% | 76 |
In this situation, the test plot has a 21.0% lower Productivity Index than the reference plot, so the reference plot yield is adjusted downward by 21.0%.
These adjusted reference yields become the standard against which the test plot yields are compared.
In the case where several soil series are mixed during reclamation, or a reference plot contains more than one soil series, a weighted average productivity index must be determined. Weighted average productivity indices should be calculated as described in the following example:
| Premine Soil Mapping Units | Productivity Index | soil acreage in reference or release area |
| Barco loam, 2-5% slopes | 60 | 15 |
| Barco loam, 2-5% slopes, eroded | 50 | 25 |
| Deepwater silt loam, 2-5% slopes | 84 | 10 |
| total acreage | 50 |
(15/50)(60) + (25/50)(50) + (10/50)(84) = 59.8 (weighted ave. prod. index)
The adjusted release area yield is determined by multiplying actual release area yield by percent yield adjustment.
Miss. Code. tit. 11, pt. 8, ch. 2, app 11-8-2-A, 11-8-2-11-8-2-A-Q