Gypsum is the most commonly used amendment for sodic soil reclamation. Use of gypsum as a sulphur fertilizer to enhance crop production in sulphur deficient soils has been proved for many crops.
Gypsum (calcium sulfate) + sodic soil = calcium soil + sodium sulfate (leachable with water) Sodium sulfate is then leached out of the soil by rainfall or heavy irrigations. Gypsum does not change pH nor improve drainage in non-sodic situations.
|Sr. No||Original Soil pH||Gypsum (Tone)|
|1||8.5||5.0 – 6.5|
|2||8.0||3.5 – 5.5|
|3||7.5||2.0 – 2.5|
Gypsum is broadcasted on the soil surface. Where gypsum is applied to improve soil structural characteristics, apply it as early as possible prior to sowing a crop. After application, it should be thoroughly incorporated into the soil.
Rain (or irrigation) is required to leach these soluble salts out of the topsoil deeper into the soil profile, away from zone in which crop roots will be growing.
Some precautions should be considered; the rate and season to apply gypsum will vary by location and soil type.
Over application of gypsum may result in seedling damage and nutrient imbalance.