A crop growth improving agent, comprising an aq. soln. of an electrolytic liq. compsn. obtained by 1) mixing and stirring paper and a vinegar soln, leaving the mixt. in a temperature range wherein the bacteria originally existing in the mixt can remain active, 2) filtering the mixt and mixing the filtrate with polyester polyol at a temperature which is in the above-mentioned temperature range, followed by maturation to obtain a three-phase mixt (wherein first phase: a liq. phase, second phase: a viscous phase of an ion exchange semipermeable membrane soln, and third phase: viscous liq. phase), and 3) separating the above-mentioned first phase from the mixt..    Also claimed is i) a process for growing crops wherein the above-mentioned crop growth improving agent is scattered on leaves of the crop; ii) a fertilizer which is a residue obtained by filtering the mixt of paper and vinegar after it is left in a temperature range wherein the bacteria originally existing in the raw material can remain active.    ADVANTAGE -   The crop treated with the growth improving agent increases the amount of the crop, and allows the growth of the crop in a cold region.    PREFERRED MATERIAL - The crop pref. includes rice, wheat, corn and beans.    EXAMPLE - Shredded waste paper (7 kg) was added to 3000 kg of vinegar and the mixt was stirred for 3 hours to obtain a pulp like substance, which was then matured for 3 days at 40 C. The mixt. was filtered and the filtrate was matured for further 3 days at 40 C. In the mixt. Bacillus-felsineus, Bacillus-mesentericus etc as well as Candida Utilis, Debaryomyces etc. were recognized. The matured mixt was filtered and the filtrate was matured for further 3 days at about 40 C. The bacteria and derived enzymes were added to it and stirred for 3 hours, then matured for 3 days to provide a polyester polyol modified substance made of 3 phases. The first phase (pale yellow, transparent electrolytic soln) was separated and diluted with water to 800 - 3000 times to provide the crop growth improving agent.