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Is it time to begin to ‘rethink how we think’ about soil calcium, or do we just continue on with our old, conventional thinking that the soil has enough?
One of the ingredients in building the ‘perfect soil’ is routine application of gypsum, or calcium sulfate. My general practice is to apply 1 ton of synthetic gypsum every 3 or 4 years, and in some fields 300 to 400 pounds of pelletized gypsum annually.
But don’t expect to see immediate changes in tilth or soil health. Change takes time and it may take 5 or 6 years to notice.
I’m a fan of gypsum and have realized its benefits, which include improved soil structure, nutrient benefits through added calcium and sulfur, and remediation of salinity and sodic soils.
But an overlooked factor, in my mind, is how additional calcium might benefit the soil and if we’re even measuring the right factors. Agronomists don’t track calcium and take it for granted that most soils already have plenty. I wonder if our thinking is wrong?
A routine soil test measures exchangeable calcium in parts per million (ppm). That is the calcium cation held on the soil exchange complex. Soils on our farm routinely measure about 3,000 to 4,000 ppm, so that is obviously a lot of calcium in the soil.
But I question how available it is to the soil, and if I’m getting the true benefit of calcium to improve soil structure — and if the crop is…