Excess sodium can cause soil to be hard and cloddy when dry, to crust badly, and to take water very slowly. Clangor, P.M., and Fillet, R.C. Colorado State Cooperative Extension Publication No. 0.502 . When the SAR test indicates an excess of sodium, the addition of gypsum to free the sodium and allow it to be leached from the soil, may be necessary. The pounds of nutrient reported per acre therefore must be divided by 2 to produce the ppm of that nutrients. The next step converts ppm to meq.
Equivalent weight is determined by dividing the molecular weight by the valence.
The next step in this process involves the determination of the SAR of the soil. Based on the SAR, the addition of gypsum for this soil is not necessary. Not all soils laboratories provide quality results. In this case, the laboratory was in error. If the SAR was determined to be such that plant damage would result, the soils laboratory must determine the amount of gypsum present in the soil prior to recommending the addition of gypsum.