SO4 High Mg Amendment Calculator
Estimate an SO4 Product Rate to lower magnesium saturation by displacing exchangeable Mg with calcium. Enter CEC, current Mg, and desired Mg, and the calculator will convert inputs as needed.
Inputs
Summary
The calculator first normalizes magnesium to a % Mg basis, then estimates how much exchangeable Mg must be displaced to reach the desired level.
That displacement is converted to an SO4 Product Rate using the amendment factor built into the calculator.
Yearly application rates should be based on economic and operational considerations. In general, rates in excess of 600 lb/acre will not be practical for economic and logistical reasons. Rates in excess of 600 lb/acre can be split over multiple years.
Caution should be taken with soil CEC values less than 10 meq/100g as excessive application rates of gypsum on low CEC soils can result in cation imbalance.