Effect of Modified Lignin Sulfonate on Controlled-Release Urea in Soil

The present study reports an economically attractive improvement in fertilizer, using lignin sulfonate as a waste product in the pulp and paper manufacturing process. Lignin sulfonate was extracted by precipitation with calcium hydroxide. To achieve hydrophobicity, some modifiers were tested, and oxalic acid successfully met the required purpose. FTIR analysis indicated the changes in the functional groups of acetylated lignin. Then, lignin sulfonate acetylated with oxalic acid was coated on urea through a fluidized bed column. The released amount of different concentrations of fertilizer in water and soil was measured. Sulfur-coated urea fertilizer was used to compare with the product. The results showed that acetylated lignin sulfonate coated urea could properly control urea release. The amount of released acetylated lignin sulfonate coated urea after 18 days was 79 %, while for sulfur-coated urea, 93 % was released after 11 days. To add, the power model could predict the release pattern of acetylated lignin sulfonate coated urea accurately.