Alkalinity in soil can be addressed by the following methods:
1. Using Sulfur or Sulfur Compounds: Sulfur fertilizer (S) reacts with soil water to form sulfuric acid (H₂SO₄), which then reacts with sodium compounds (NaCO₃) to form soluble sodium sulfate (Na₂SO₄). The alkalinity of the soil can be reduced if sodium sulfate is removed through the extraction process. Since organic matter increases soil fertility, the pH value of the soil does not easily decrease or increase.
2. Using Organic Fertilizers: Organic fertilizers play a crucial role in correcting alkaline soils. Common organic fertilizers include cow dung, compost, farmyard manure, and green manure. Modern biofertilizers like Rhizobium biofertilizers, Azolla biofertilizers, Bau-bacterial fertilizers, Trichoderma biopesticides, and algae fertilizers are also effective. Fungi, especially Trichoderma fungi, are important for decomposing organic matter. These fungi are used in composting processes to accelerate decomposition. The application of organic fertilizers enhances soil fertility without significantly altering soil pH.
3. Application of Chitagur: Adequate quantities of sugar mill effluents, known as Chitagur, can be applied to alkaline soils to reduce alkalinity.
4. Salinity Control: Soil salinity can be managed by reducing water evaporation. Applying moderate amounts of water and calcium sulfate to saline soils reduces salinity, thereby lowering soil alkalinity. This helps improve water infiltration into the soil.
5. Irrigation and Drainage: In soils with relatively low sodium content, the application of good quality water through irrigation, followed by proper drainage, can help reduce soil alkalinity.
6. Application of Gypsum or Calcium Compounds: Applying gypsum fertilizer (CaSO₄) to the soil can replace sodium ions (Na⁺) attached to clay particles with calcium ions (Ca²⁺) from the gypsum. This reaction forms soluble sodium sulfate (Na₂SO₄), which can be removed from the soil through drainage. As a result, soil alkalinity is reduced.
CaSO₄ + clay (Na⁺) → Na₂SO₄ + clay (Ca²⁺)
Irrigation under these conditions will flush out the soluble Na₂SO₄ with the drained water, reducing the soil’s alkalinity.