TECHNOLOGY FOCUS - AGRICULTURE - Preferred Method: (a) - (f) are prepared by culturing the yeast cells in a first to sixth electromagnetic field having frequencies of 860 - 870 MHz, 360 - 370 MHz, 250 - 260 MHz, 1087 - 1097 MHz, 1382 - 1392 MHz and 1690 - 1700 MHz, respectively and an amplitude of 1000 - 5000 mV. (a) is prepared by culturing the yeast cells in an electromagnetic field having a frequency of 865.522 MHz, and an amplitude of 1250 mV for 24 hours and an amplitude of 4656 mV for another 24 hours. (b) is prepared by culturing the yeast cells in an electromagnetic field having a frequency of 366.243 MHz, and an amplitude of 1230 mV for 24 hours and an amplitude of 4570 mV for another 24 hours. (c) is prepared by culturing the yeast cells in an electromagnetic field having a frequency of 255.425 MHz, and an amplitude of 1340 mV for 24 hours and an amplitude of 4850 mV for another 24 hours. (d) is prepared by culturing the yeast cells in an electromagnetic field having a frequency of 1092.387 MHz, and an amplitude of 1530 mV for 24 hours and an amplitude of 4720 mV for another 24 hours. (e) is prepared by culturing the yeast cells in an electromagnetic field having a frequency of 1387.556 MHz, and an amplitude of 1620 mV for 24 hours and an amplitude of 4830 mV for another 24 hours. (f) is prepared by culturing the yeast cells in an electromagnetic field having a frequency of 1694.365 MHz, and an amplitude of 1470 mV for 24 hours and an amplitude of 4780 mV for another 24 hours. (m1) involves culturing the yeast cells in the presence of an electromagnetic field having a frequency of 1387.556, and an amplitude of 1620 mV for 24 hours and an amplitude of 4830 mV for another 24 hours. (m2) involves culturing the yeast cells in the presence of a first electromagnetic field having a frequency of 1694.365 MHz and an amplitude of 1470 mV for 24 hours and culturing the yeast cells in the presence of another electromagnetic field having a frequency of 1694.365 MHz and an amplitude of 4780 mV for 24 hours so that the yeast cells can overproduce adenosine triphosphate. (m1) and (m2) further involve inoculating a fermentation medium comprising a starch solution at a concentration of about 400 gram/liter with the yeast cells and fermenting at 20 - 30degreesC until at least 90% of the fermentation substrate has been fermented.    TECHNOLOGY FOCUS - BIOLOGY - Preferred Composition: The composition further comprises a fourth yeast cell component (d) containing several yeast cells which convert complex carbon compounds to simple carbohydrates; a fifth yeast cell component (e) containing several yeast cells which overproduce growth factors; and a sixth yeast cell component (f) containing several yeast cells which overproduce adenosine triphosphate. The fertilizer comprises (wt.%) (a) (0.1 - 0.2), (b) (0.1 - 0.2), (c) (0.1 - 0.2), (d) (0.1 - 0.2), (e) (1), (f) (3), organic substrate (65), inorganic substrate (19) and starch (14).Preferred Components: The yeast cells belong to a genus selected from Saccharomyces, Schizosaccharomyces, Sporobolomyces, Torulopsis, Trichosporon, Wickerhamia, Ashbya, Blastomyces, Candida, Citeromyces, Crebrothecium, Cryptococcus, Debaryomyces, Endomycopsis, Geotrichum, Hansenula, Kloeckera, Lipomyces, Pichia, Rhodosporidium, and Rhodotorula. The cells of the components are derived from yeast strain Saccharomyces cerevisiae Hansen deposited at China General Microbiological Culture Collection Center as given in specification. The yeast cells are dried.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The composition further comprises an organic and/or inorganic substrate. ADMINISTRATION - The composition is applied on soil (claimed). No dosage given.    SPECIFIC MICROORGANISMS - Use of 75 species of yeast is specifically claimed for preparation of biological fertilizer, e.g. Saccharomyces cerevisiae, Schizosaccharomyces pombe, Candida lambica.    EXAMPLE - A fertilizer comprised (wt.%) nitrogen-fixing yeast AS2.502 (0.2), phosphorus-decomposing yeast AS2.5356 (0.2) and potassium-decomposing yeast AS2.441 (0.2).