Controlling the release of high-consumption nitrogen, phosphorus and potassium fertilizers using hydrogels based on sepiolite clay nanostructure and starch

 The emergence of nanotechnology and the use of nanoscale materials has made it possible to take advantage of the potential and novel applications of this technology in various fields of agriculture. Therefore, this research aims to make fertilizer for high-consumption nutrients such as nitrogen, phosphorus, and potassium (NPK) by hydrogels based on the sepiolite (Sep) clay nanostructure and starch (S).

 In this study, the physical inhibition method was used to control the release of high-consumption nutrient elements of fertilizer. For this purpose, appropriate amounts of NPK salt were inserted in the structure of Sep-S hydrogels. Then, the release level of nutrients was investigated by the column elution and measuring the conductivity of the outlet solution of the column.

 The elution profile of the NPK fertilizer shows that the salts quickly leave the end of the column so that the conductivity of the solution at the end of the column in the first washing after consumption of 250 mL of water reaches about 12000 µS/cm. On the other hand, the elution profile of the slow-release fertilizer containing NPK salts shows that the release profile of the fertilizer in 4 times of washing with the same volume is almost similar (range 1400 µS/cm to 2300 µS/cm). Results show that the placement of fertilizer salt inside the proposed hydrogels leads to the slow release of highly consumed nutrients.

 The release of nutrients from the structure of slow-release fertilizer based on Sep-S hydrogels has a delay, which is vital to prevent the excessive release of nutrients, and minimize negative environmental effects and excessive consumption of chemical fertilizers. Also, the materials used to make the slow-release fertilizer have a relatively low cost.