NOVELTY - A special biological potassium fertilizer comprises (pts. wt.): mixture of cow dung and straw (600-800), turf (100-300), sugar (15-30), and Paenibacillus polymyxa strain fermentation liquor (60-120).    USE - Special biological potassium fertilizer for potato (claimed).    ADVANTAGE - The fertilizer uses industrial wastes of cow dung and straw to replace traditional microorganism absorber turf, thus fully using agricultural waste resource and reducing environment pollution. It has yield increase effect after applying to potato (yield is increased for 11-15.4%). The quality of the potato is improved (starch content is improved for 3.3-7.5%).    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for preparation of the fertilizer which comprises (A) fermenting P. polymyxa strain, (B) stacking, fermenting and processing cow dung and straw, and (C) preparing fertilizer. The step (A) includes culturing strain with fermentation culture medium having pH of 6.5-7.5, where air flux of fermentation tank is 4-5 NL/minute, stirring speed is 250-350 revolutions/minute (rpm), culture temperature is 28-32 degrees C, culture time is 39-72 hours; and obtaining strain fermentation liquor and standing for use. The step (B) includes uniformly mixing (pts. wt.): fresh cow dung (800-200) and straw (200-800), stacking into a pile having width of 1.7-4 m, height of 1.1 to 2.5 m and unlimited length; turning with turning machine each two days and controlling temperature of high temperature fermenting; keeping temperature of pile at 50-70 degrees C for more than 7 days and fermenting for 25-35 days; and ending fermenting after cooling to normal temperature, airing and crushing, sieving with 80-mesh sieve to obtain mixture of cow dung and straw, and standing for use. The step (C) includes taking mixture of cow dung and straw, adding turf, sugar, uniformly mixing and stirring, microwave sterilizing and inoculating with strain fermentation liquor; and storing at room temperature for 2-4 days and packaging to obtain desired fertilizer.