PROBLEM TO BE SOLVED: To obtain soil for raising seedling causing little loss of soil with water during the seed raising period and exhibiting sufficient soil-reinforcing effect in transplantation by adding a specific polymer to a soil. SOLUTION: A polymer produced by a W/O-type polymerization is added to a soil. The polymer is preferably an acrylic polymer. When the carboxyl group in the polymer molecule takes the form of a salt of a metal such as sodium, the water-solubility is increased to increase the flow-out loss of the soil by irrigation and, accordingly, the neutralization degree of the polymer is preferably <=50%, more preferably <=25%. Especially preferably, an essentially non-neutralized polymer is used as the polymer. The problems such as the flow-out loss of the binder in irrigation can be suppressed by using a polymer having the above neutralization degree.
