Effects of the calcium in gypsum on reducing phosphorus pollution
The calcium in gypsum reacts with phosphorus leading to calcium phosphate precipitation. This property of gypsum is used to improve the quality of running water. In Iran also, phosphorous concentrations are high in some of the northern regions and it enters surface waters. Consequently, gypsum can be used in agricultural lands to reduce the amount of phosphorus that enters surface waters from agricultural lands. This may decrease Azolla plant density in surface waters and rice fields. Of course, more accurate research must be conducted before taking this step.
Distribution of Azolla filiculoides Lam. in surface waters and agricultural lands