Slow-release fertilizer special for saline alkali soil improvement and preparation method thereof

The invention provides a slow-release fertilizer special for saline alkali soil improvement, and the fertilizer comprises the following components by weight: 18%-20% of large granular urea, 35%-40% of slow-release coated urea, 12%-15% of an organic granulated fertilizer, 15%-18% of monoammonium phosphate and 12%-15% of potassium sulfate. The low-release fertilizer special for saline alkali soil improvement combines nutrient slow release and salt and alkali resistance, effectively reduces alkalescence of soil, effectively increases the aggregate structure of the soil, increases fertilizer retention properties of the soil, increases soil porosity, reduces soil bulk density, changes the saline alkali soil compaction structure, creates the good soil environment for crops, is comprehensive in nutrient and lasting in fertilizer efficiency, and reduces environmental pollution caused by fertilization, the nitrogen utilization rate can reach more than 45%, the input total amount of the fertilizer can be reduced, low c