NOVELTY - Microbial bacterium with an acid-producing function comprising bacterial strain WSA061, which is Bacillus amyloliquefaciens with preservation number of CGMCC10070, is new. Morphological, physiological and biochemical characteristics of the bacterial strain WSA061 are as follows: bacterial strain WSA061 is gram-positive bacterium, the cells are rod-shaped, can produce spores on lysogeny broth agar flat plate with fast growth speed, colonies are circular, intermediate small projection (grow at 37 degrees C for 36 hours), white opaque, colony diameter is 3-7 mu m, and cells are rod-shaped.    USE - The microbial bacterium is useful for preparing organic fertilizer used in lettuce and corn cultivation (claimed).    ADVANTAGE - The microbial strain: is capable of producing acid under different fermentation conditions; can durably produce acid when compared with an inorganic salt; is derived from maize rhizosphere soil in sterile soil and can obviously promote tolerance to alkaline soil of crops including lettuces and maize; improves urease activity of the soil and provides an excellent liquid strain fertilizer for the growth of the crops including lettuces and maize in the alkaline soil. The organic fertilizer: does not need to be frequently applied; solves the problem of the soil cakes due to the gathering of anions; can optimize micro-ecological environment of the growth of root systems of alkaline soil crops; is prepared by microbial strain, which is capable of improving the content of chlorophyll in leaf tissues, the content of vitamin c in leaves and the yield of crops including as lettuces and maize, and has excellent effect of improving quality and yield.    DETAILED DESCRIPTION - Microbial bacterium with an acid-producing function comprising bacterial strain WSA061, which is Bacillus amyloliquefaciens with preservation number of CGMCC10070, is new. Morphological, physiological and biochemical characteristics of the bacterial strain WSA061 are as follows: bacterial strain WSA061 is gram-positive bacterium, the cells are rod-shaped, can produce spores on lysogeny broth agar flat plate with fast growth speed, colonies are circular, intermediate small projection (grow at 37 degrees C for 36 hours), white opaque, colony diameter is 3-7 mu m, cells are rod-shaped with end flagellum, and the size is 2.8-4.2x 1.5-1.8 mu m. The optimum growing temperature is 28-37 degrees C, and the optimal growing pH is 6-8. During facultative anaerobic process, taking as dextrin, D-glucose, D-galactose, sorbose, L-fructose, D-fructose, fiber disaccharide, trisaccharide, cellobiose, trehalose, mannitol, L-arabitol, D-arabitol, D-sorbitol, inositol, galactitol, sorbitol, sodium gluconate, sodium succinate, sodium lactate, malic acid, glycerol, D-sodium glucuronate, butanediamine, N-acetyl glucosamine, L-glutamine, L-alanine, L-glutamic acid, L-histidine, L-tryptophan and L-cystine as unique carbon source of a culture medium, growing pH range is wide, can be resistant till 3-9 pH, is sensitive to sodium chloride, and may grow when the sodium chloride concentration is less than 1%, can be resistant to 300 mu g/ ml ampicillin, streptomycin, tetracycline and erythromycin, has gentamicin-resistance up to 100 mu g/ml, has show poor tolerance to kanamycin, chloramphenicol and neomycin, can inhibit their growth at low concentration of (50 mu g/ml) of many antibiotics, indole reaction is positive, and can secrete growth hormone indole acetic acid (IAA). INDEPENDENT CLAIMS are also included for:    (1) microbial organic fertilizer containing microbial bacterium, comprising 1.5x 108 colony forming units/ml or more bacterial strain WSA061, 3-7 wt.% total nitrogen, 5-11 wt.% total nitrogen, phosphorus and potassium (NPK), where the mass ratio of organic matter content is not less than 40%; and    (2) use of the organic fertilizer in lettuce and corn cultivation.