Effect of mulching of plant materials on the growth of ground cover plants and emergence of weeds on levee slope

Ground cover plants are useful for weed suppression on levee slopes. However, weeding is necessary until the slopes have covered with ground cover plants. In farm village, plant organic matter such as bark, chaff and wood chips are not used effectively. In order to elucidate the effects of the mulching of organic matter on levee slopes planted ground cover plants, the growth of ground cover plants and weeds were investigated. The number and dry weight of the emerged weeds in the organic matter mulch treatments were fewer than in the non-mulch treatments. The growth rates of ground cover plants (Eremochloa ophiuroides (Munro) Hack., Verbena tenera Spreng. and Phyla nodiflora L.) in crushed bark mulch treatment was equal with geotextile mulch treatment. On the slopes, the chaff and wood chips washed away by rain and wind, but the bark was stable. Therefore, it was thought that bark was suitable for mulch treatment at the slope. The number and dry weight of emerged weeds which were mainly made from Echinochloa crus-galli and Digitaria adscendens were decreased 5 cm in thickness by mulch treatment with the bark of Japanese cedar (Cryptomeria japonica) mixed with Japanese cypress (Chamaecyparis obtusa). On the slopes of levees mulched with bark composed of mixed Japanese cypress and cedar, the growth of weeds was suppressed, however, the growth of transplanted ground cover plants (E. ophiuroides, P. nodiflora and Thymus serpyllum L.), which spread over the bark, is not affected.