Improvement of Understory Vegetation by Seeding of Herbage Plants in a Wasted Mulberry Plantation under Cattle Grazing

摘要

Our previous study conducted in a wasted mulberry plantation showed significant decline of leaf productivity of mulberry (Morus sp.) by cattle grazing in three years (Ogura et al., 2009). This means that improvement of understory vegetation is essential to use such wasted areas as grazing lands. In this study, the mixture of seeds (Dactylis glomerata, Lolium perenne, Poa pratensis and Trifolium repens, 15∶15∶5∶2) was seeded on 18 Sep. 2007, in nine experimental plots (6 m ×6 m each) with different seeding rates (L: 37 kg/ha, M: 56kg/ha and H: 74kg/ha, three replications) in the wasted mulberry plantation described in the previous paper (paddock A) (Ogura et al., 2009). Two cows were grazed in the paddock for 42 and 54 days in 2007 and 2008, respectively. No fertilizer nor herbicides were applied in the paddock. The coverage of the sown species and weeds, and the proportion of bare area were recorded on 19 Sep. 2007, 16 Nov. 2007, 21 May 2008 and 21 May 2009. T. repens rapidly covered the understory; the coverage ranged 49.4-71.7% in 2008-2009 (Fig. 1). D. glomerata and L. perenne also increased to 10.6-18.3% and 20.633.9% in 2009, respectively, regardless to the seeding rates. In contrast, the proportion of bare area rapidly decreased. The quick establishment of the sown plants probably due that defoliation and trampling of cows suppressed the growth of native plants. In conclusion, the seeding rate of 3.7 kg/ha is sufficient to establish herbage plants in wasted mulberry plantations under cattle grazing.