Effect of mined gypsum on physico-chemical properties of sodic soils and yield of wheat in Ramjerd region of Fars province.

Management of sodic soils and water play a decisive role in increasing crop production. amendment of sodic soils is based on replacing the calcium instead of sodium in ions exchange complex, leaching excess salts, reducing pH value and neutral carbonate and bicarbonate ions in the soil solution. Mined gypsum (CaSO4.2H2O) was used for this purpose. This project aimed to assess the effect of gypsum content, method of application of gypsum and gypsum particles size to achieve the maximum wheat yield and minimum soil exchangeable sodium percentage. For this purpose, a sodic soil which irrigated with sodic water was selected from the Ramjerd district in Fars province.The experiment was carried in a randomized complete block design with 8 treatments and 3 replications. Treatments included three levels of gypsum requirement (50%, 75% and 100%), 2 levels size particles of gypsum ( 0.05 mm and 20 mm). in addition, a plot for the dissolution of gypsum in the irrigation water and a plot as for control were considered. Experiment continued for three years. The results showed that adding gypsum to the increased soil EC. However, the soil salinity in all treatments was lower the salinity tolerance threshold of wheat. SAR of soil surface decreased by adding gypsum to the soil, While SAR of lower layer increased compared to control treatment. Wheat yield was affected by adding gypsum to the soil. However, water applied gypsum had no significant effect on wheat performance. Effect of coursed gypsum was more compared to fined gypsum. Yield increase can be attributed to improved soil chemical and physical conditions. Generally it is recommended add coarse gypsum (less than 20 mm) and 50 percent gypsum requirement. Keywords: Sodic Soil- Sodic Water- Mined Gypsum- Soil Reclamation- Fars Province