Articles by Jim Gainan

As published in the Billings Gazette

Gardening Today: Gypsum

Gypsum additions are food for improving clay and alkali type soils. Clay soils often contain high magnesium levels and little organic matter. This condition tends to make the soil particles so tight that air and water cannot penetrate it. Alkali soils have high sodium levels which prevent plant, crop or turf production. By the proper use of gypsum, these soils can be returned to production. By adding gypsum to soils, an ion exchange results which dramatically improves soil friability and tilth. Once active, gypsum will give at least three benefits. One, is conditioning of sticky-clay loam soil. This will greatly improve water and air penetration, promote root growth and improve plant vigor where it was previously limited. It will loosen up and improve soil structure and workability of clay, gumbo and compacted soils. Second, is the direct addition of the secondary plant foods sulfur and calcium. Third, the removal of sodium from the clay and silt particles. It also may reduce the ph of the soil.


It Will Not Cure Saline Seepage
Gypsum's effect on soil conditioning and addition of sulfur and calcium will require only a few days, but the removal of the sodium does require up to three years. Gypsum is a mined product, which is a form of hydrated calcium sulfate. There are vast natural deposits of it in Montana, including Carbon and Stillwater counties. Other materials which will have the same effect are iron sulfate, aluminum sulfate and any form of elemental sulfur (rock, powder, flakes). These do require more time than gypsum in order to condition the soil. Use about one ounce of these materials per square yard or three feet by three feet area. Gypsum may be applied anytime of the year, when the soil is workable.


Application Rates for Gypsum
Heavy clay soil 20 to 30 pounds per 100 square feet. May be applied every four years till desired results are achieved.

Lighter clay soils 20 to 30 pounds per 1,000 square feet. may be applied every other year till desired results are achieved. These previous rates may be applied to established lawn areas After application, irrigate for one hour. Water regularly afterwards to continue the movement of the gypsum into the soil. Gypsum may be tilled or worked into the garden area during spring preparation.

Alkaline Areas 30 to 40 pounds per 100 square feet. After application, flood area about four times before planting. May be applied every four years till desired results are achieved.

Shrubs 2 pounds around each shrub, then water in. May be done annually.

Roses 1 pound mixed with well rotted manure. May be put around roses up to four times a year.