Agronomic Services — Soil Testing

Mehlich Buffer Acidity

Table 1. Factors for calculating lime rates*

Current Soil pH	Target pH
	6.5	6.2	6.0	5.7	5.5	5.0
3.2	.971	.882	.824	.735	.676	.529
3.3	.970	.879	.818	.727	.667	.515
3.4	.969	.875	.813	.719	.656	.500
3.5	.968	.871	.806	.710	.645	.484
3.6	.967	.867	.800	.700	.633	.467
3.7	.966	.862	.793	.690	.621	.448
3.8	.964	.857	.786	.679	.607	.429
3.9	.963	.852	.778	.667	.593	.401
4.0	.962	.846	.769	.654	.577	.385
4.1	.960	.840	.760	.640	.560	.360
4.2	.958	.833	.750	.625	.542	.333
4.3	.957	.826	.739	.609	.522	.304
4.4	.955	.818	.727	.591	.500	.273
4.5	.952	.810	.714	.571	.476	.238
4.6	.950	.800	.700	.550	.450	.200
4.7	.947	.789	.684	.526	.421	.158
4.8	.944	.778	.667	.500	.389	.111
4.9	.941	.765	.647	.471	.353	.059
5.0	.936	.750	.625	.438	.313	0
5.1	.933	.733	.600	.400	.267
5.2	.929	.714	.571	.357	.214
5.3	.923	.692	.538	.308	.154
5.4	.917	.667	.500	.250	.083
5.5	.909	.636	.455	.182	0
5.6	.900	.600	.400	.100
5.7	.889	.555	.333	0
5.8	.875	.500	.250
5.9	.857	.428	.143
6.0	.833	.333	0
6.1	.800	.200
6.2	.750	0
6.3	.667
6.4	.500
6.5	0
* The factors in this table are derived from this formula:         FACTOR = [(target pH - current pH) ÷ (6.6 - current pH)]. The lime requirement (LR) in U.S. tons per acre = (acidity × FACTOR) - residual credit.   Residual credit = 8% per month for MIN soils and 16% per month for M-O and ORG soils.         Example: If soil pH = 5.0; desired pH = 6.0; acidity = 1.2; and residual credit = 0,         then LR = (1.2 × 0.625) - 0 = 0.76 ton/acre. Acidity is calculated from the formula: (6.6 - BpH) × 4 = meq Ac/100 cm³, where BpH = the buffer pH reading determined in the lab.