PROBLEM TO BE SOLVED: To provide mixed microbial cells for permanently neutralizing or weakly acidifying water in acidic or alkaline soil, to provide a method for neutralizing water in soil with a material for improving water quality, and to provide a deodorizing effect and an insect control effect associated with them.SOLUTION: The mixed microbial cells comprise lactic acid bacterium L1 (accession number: FERM AP-22138), lactic acid bacterium L2 (accession number: FERM AP-22139), bacillus B1 (accession number: FERM AP-22136), bacillus B2 (accession number: FERM AP-22137), and yeast Y1 (accession number: FERM AP-22140). An aqueous solution containing the mixed microbial cells is scattered or sprayed on soil.【課題】酸性又はアルカリ性の土壌中の水分を恒久的に中性又は弱酸性にする混合菌体及び水質改良用資材を用いた土壌中の水分を中性にする方法を提供し、此れに伴う消臭効果と防虫効果がある。【解決手段】乳酸菌L1(受領番号:FERM AP-22138)、乳酸菌L2(受領番号:FERM AP-22139)、桿菌B1(受領番号:FERM AP-22136)、桿菌B2(受領番号:FERM AP-22137)及び酵母Y1(受領番号:FERM AP-22140)を混合してなる混合菌体を含有する水溶液を土壌に散布又は噴霧する。【選択図】図1