Effects of polyethylene mulch ridge coverage and coverage period on tuberous root characteristics and characteristics of “hoshi-imo” steamed and dried sweetpotato slices during sweetpotato (Ipomoea batatas L.) cultivation

The effects of mulch ridge covering during sweetpotato cultivation for “hoshi-imo” steamed and dried slices on soil moisture, properties of sweetpotato tuberous roots, and processing characteristics were investigated for five years by late planting in four treatment plots: mulch ridge covering plot, removal plot one month before harvest, removal plot two months before harvest, and no mulch plot. It was confirmed that the variation of soil moisture content in the ridge caused by rainfall and drying was suppressed by covering the ridge with polyethylene mulch during sweetpotato cultivation. In the late planting culture, the yield of tuberous root was increased by the mulch ridge covering. The dehiscence rate of “Tamayutaka” without mulch was significantly higher than that of other test plots, and it was considered that the dehiscence rate was lower by mulch ridge covering in the initial growth stage. And, in “Tamayutaka”, the increase of the dehiscence was recognized in the year with much soil moisture, but this tendency was not recognized in “Hoshikogane”. The texture of the “hoshi-imo” tended to be the most viscous in the non-mulching plot, and it was indicated that the texture of the “hoshi-imo” became a little viscous when the mulching coating was removed about 2 months before the harvest. However, when it was removed about one month before harvest, the effect on the texture of the “hoshi-imo” seemed to be small.