Micro-nano selenium-enriched controlled-release microbial fertilizer and preparation method thereof

The invention discloses a micro-nano selenium-enriched controlled-release microbial fertilizer and a preparation method thereof, belonging to the technical field of fertilizers. The micro-nano selenium-enriched controlled-release microbial fertilizer is prepared from the following raw materials in parts by weight: 5-15 parts of urea, 20-30 parts of ammonium sulfate, 10-20 parts of ammonium dihydrogen phosphate, 10-20 parts of potassium nitrate, 0.5-1.5 parts of sodium selenite, 15-35 parts of humic acid, 4-8 parts of nano microspheres of natural polysaccharide, 1-3 parts of a coated controlled-release agent and 0.5-1.5 parts of a microbial additive. The micro-nano selenium-enriched controlled-release microbial fertilizer is good in controlled-release property, capable of releasing nutrient elements for a long term, high in utilization ratio, and capable of reducing loss of fertilizer nutrients in soil and increasing the utilization ratio; and the fertilizer is rich in selenium, so that the content of organic