TECHNOLOGY FOCUS - POLYMERS - Preferred Process: The pre-sulfurized latex is obtained by grinding (in mass parts) sulfur (8-12.05), Accelerant PX (RTM: zinc diethyl dithiocarbamate) (8-12.05), Antioxidant 264 (RTM: 2, 6-di-tert-butyl-4-methyl phenol) (6.03), zinc oxide (4.82) and soft water (143.24) by colloid mill or sand mill for 24-48 hours, heating the compounded latex at 55 degrees C for 50 minutes, slowly agitating at 52-58 degrees C, controlling the natural latex to reach the desired sulfurizing degree with respect to sulfurizing reaction time, measuring the sulfurizing degree by chloroform value, filtering with 250 meshes of sieve mesh, distilling by adding water in the filtered latex, and adjusting the concentration of the latex to 35-45 mass%. The primary package of the fertilizer is obtained by adding dissolvable fertilizer such as urea, potassium chloride and ammonium chloride in chitosan acetic acid solution, agitating, controlling the concentration of the fertilizer and chitosan to be 5-10 mass% and 1.0 mass%, respectively, obtaining solution (A), then adding glutaric dialdehyde solution and dissolvable fertilizer in sodium alginate solution, supplementing a certain amount of water, agitating, dissolving, controlling the concentration of the fertilizer, glutaric dialdehyde and sodium alginate to be 5-10 mass%, 3-5 mass% and 3%, respectively, obtaining solution (B), pumping few solution (A) by water pump to a round disc whose bottom has several pores, making solution (A) pass through the pores having diameter of 4-6 mm, adding solution (A) in solution (B) drop by drop, curing small, after the solution (A) is added in the solution (B) drop by drop, continuously adding solution drop by drop for 5-10 minutes, stopping adding solution (A) drop by drop, maintaining for 20 minutes, filtering out small ball by nylon mesh, obtaining flexible small ball containing fertilizer, and drying small ball in air. The secondary package of fertilizer is obtained by adding Operegal O (RTM: stabilizing agent) or Emulsifier OP (RTM: emulsifying agent) (0.5-1) with rubber mass in natural latex with different cross-linking degree and pre-sulfurizing concentration of 35-45 mass%, adding anti-bonding parting agent (1-2 mass%) chosen from talcum powder, mica powder or magnesium stearate to prevent the package particle from bonding in drying process, agitating, obtaining package film coating material, putting the primarily dried small ball containing fertilizer on a dish, spraying the film coating on the small ball, separating out small ball after 2 minutes, putting small ball in oven, dispersing the balls and drying at 80 degrees C. The rest film coating can be recycled. The release time of the obtained slow release fertilizer is 30-50 days. The chloroform value is from primary sulfuration at the second grade to the highest sulfuration at the fourth grade. The sulfurizing degree is degree of cross-linking, which is the key factor to control the release speed of the fertilizer. The cross-linking speed is higher and effective release time is longer. ACTIVITY - Fertilizer.