PURPOSE: To enable the culture of peanut with saved labor without deteriorating environment by closely covering a ridge face with a photo-degradable mulching film having planting holes, sowing seeds of peanut and, after blooming, introducing the gynophore formed from flower into the ground.

CONSTITUTION: A mulching film is produced from a photo-degradable resin such as a modified PE composed mainly of ethylene and produced e.g. by copolymerizing ethylene with carbon monoxide or ethylene with carbon monoxide and an ethylenic unsaturated compound. A ridge face is closely covered with the mulching film and seed of peanut is sowed into a planting hole opened on the film to grow peanut. After blooming, a gynophore formed from flower is pierced from the aboveground side of the photo-degraded mulching film toward the underground side and introduced into the ground to enable the culture of peanut while efficiently keeping warn and suppressing the growth of weeds. The mulching film can be produced also from a resin composition produced by compounding a polyolefin with a photo-degradation promoting agent such as benzophenone.