NOVELTY - A synergistic sodium ammonium hydrogen carbonate fertilizer comprises 0.15-0.80 wt.% sodium alginate synergistic agent, 98.20-99.85% ammonium hydrogen carbonate and 0.0375-0.2 wt.% alginic acid.    USE - Synergistic sodium ammonium hydrogen carbonate fertilizer.    ADVANTAGE - The synergistic sodium ammonium hydrogen carbonate fertilizer has better yield-increasing effect and high nutrient utilization rate, and avoids secondary pollution and utilizes simple production technology, and is environment-friendly, low in cost and easy to operate.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a method for producing a synergistic sodium ammonium hydrogen carbonate fertilizer which involves mixing 800-1200 pts. wt. natural alginate raw material powder, 100-200 pts. wt. corn flour and 30-80 pts. wt. sucrose, glucose, fructose, galactose, lactose or maltose, uniformly stirring, adjusting the pH value of the mixture by utilizing hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate or potassium bicarbonate inorganic base aqueous solution, obtaining a natural seaweed fermentation material, adding 0.1-2.0 pts. wt. effective microorganisms (EM) bacteria fermentation liquid and 0.1-2.0 pts. wt. sucrose, glucose, fructose, galactose, lactose or maltose sugar into 0.5-20 pts. wt. water, mixing uniformly, putting in a sealed container for 20-30 hours to obtain a fermenting EM bacteria stock solution, diluting the fermenting EM bacteria stock solution to obtain the fermenting EM bacteria stock solution diluting liquid, spraying 10-100 pts. wt. fermenting EM bacteria stock solution diluting liquid on a natural sodium fermentation material, stirring uniformly at room temperature, composting to ferment for 5-10 days to obtain fermented natural alginate, adding the ferment natural alginate material into aqueous solution of sodium hydroxide or sodium carbonate, stirring at 70-100 degrees C, extracting for 6-12 hours, filtering, followed by drying to obtain the synergistic sodium bicarbonate fertilizer.