By Brent Rouppet, Ph.D.
(Part 2 of a 3 Part Series)
Gypsum. Gypsum is invaluable is since it the only natural product on Earth that serves as an (1) amendment, (2) a soil conditioner, and (3) a fertilizer; and this unique and essential product should not be confused with limestone, dolomite, and other liming materials. Gypsum typically is neutral with a pH.
- Improves water use efficiency (WUE). Twenty-five to 100% more water is available in gypsum treated soils vs. untreated soils; therefore, less irrigation water is required to achieve the same results.
- Improves soil structure and loosens compacted soils. Reduced water infiltration causes ponding and runoff and can waste irrigation water. Improved soil structure reduces erosion and soil crusting.
- Amends and reclaims soils high in destructive sodium and magnesium. Sodium and magnesium (to a lesser extent) act the opposite of calcium in soils by deflocculating structure and reducing water and air movement, and root growth. Preferably, here should to be 16 times more calcium in the soil than sodium, and 8 times more calcium than magnesium.
- Counteracts acidity in subsurface soils. Calcium moves into the subsoil displacing aluminum and other acidifying ions from the exchange complex.
- Improves water penetration at the soil surface. Gypsum is necessary when irrigation water doesn’t contain many minerals and when soils are low in total salts.
- An excellent fertilizer source for calcium and sulfur. There are 16 nutrients required or essential for plants. Calcium and sulfur are two of the essential nutrients.
Growers must be aware of which soil amendment product is needed for application for each specific use. Limestone and dolomite are used to amend soils that are too acidic for optimum plant growth and production; and gypsum is used primarily to correct soil structure-related problems, and to help with any water penetration problems.
From the standpoint of plant nutrition and as a soil conditioner or soil amendment, gypsum uniquely helps soils be more productive and more fruitful than any other single product on earth. Worldwide gypsum’s usage is largely underutilized, yet routine and frequent application of this essential amendment is required for the sustainability of all irrigated soils.