Method for controlling decomposition of corrosion-resistant paper

A method for controlling initiation of biodegradation of a base paper for a raising seedling pot or a base paper for an agricultural paper mulch sheet made from a corrosion-resistant paper, by which the method allows compatibility between corrosion resistance and easy degradability of the base paper,

• the method comprising a step of alkali treatment of the corrosion-resistant paper with solution having pH 9 or more so as to provide easy degradability,
• wherein the corrosion-resistant paper contains a cellulose fiber-containing paper and a carboxylic acid crosslinking agent;
• the cellulose fiber is at least partially bonded to the carboxylic acid crosslinking agent;
• the carboxylic acid crosslinking agent is contained in an amount of 5.0 to 20.0% by mass relative to a dry mass of the cellulose fiber-containing paper;
• and
• an enzyme corrosion resistance index derived from a formula of [tensile strength (enzyme treatment)/tensile strength (water treatment)]×100 is 75 or more,
• where the tensile strength (enzyme treatment) is measured by which a test sample of the corrosion-resistant paper is continuously treated for 72 hours at 45° C. in an incubator containing an enzyme liquid prepared so as to arrange cellulase at a concentration of 1% with pH of 5.0, the test sample then washed with water and measured by a method according to JIS P8113:1998 “Paper and board—Determination of tensile properties—Part 2:
• Constant rate of elongation method,” and
• the tensile strength (water treatment) is measured by which a test sample of the corrosion-resistant paper is immersed in water having 20° C.±5° C. at room temperature for 24 hours and measured by the method according to JIS P8113:1998.