Abstract
In order to find out the most effective method of seedbed preparation suitable for oversowing, an improvement trial was conducted on Miscanthus-dominant grassland with seeds of 5kg/ha white clover and orchardgrass 25kg/ha under 2^4 split plot design involving hoof cultivation, disking, rate of basic fertilizer and pelleting seeds. Lime was applied at the rate of 5t/ha and N, P_2O_5 and K_2O were applied 49, 92 and 46kg/ha respectively for low fertilizer treatment and 3.5 times of these for high fertilizer treatment. The results obtained are as follows ; 1) plant density Plant density of two months after seeding were in the order of HC-D, hc-D, hc-d, HC-d, where HC signifies hoof cultivation, hc control of HC, D disking and d control of D, respectively. Orchardgrass seedlings increased than white clover if the seedbed was well prepared as HC-D and hc-D treatments one month after seeding though they decreased gradually thereafter. Seedling emergence was lower in other treatments and the density did not decrease as the former treatments. Establishment could be judged two months after seeding though the seedlings still decreased thereafter. 2) yield High yields were harvested in the following order ; [table] Vegetation could be improved if the newly developed pasture was properly managed and utilized under high topdressing. 3) effect of disking Disking was most effective as the seedbed preparation and establishment was guaranteed under high fertilizer placement. Vegetation could be even improved successfully with seeding and fertilizer placement in proper season without hoof cultivation nor disking, which shows that the breakdown of vegetation was not always necessary for surface sowing. 4) effect of hoof cultivation Hoof cultivation was effective in breaking the vegetation with grazing and treading wild grasses, but it was not considered to be effective in promoting emergence of sown seeds by treading them into soil. 5) effect of fertilizer High amount of basic fertilizer was not very effective in promoting the emergence of white clover seedlings under disking treatment probably because of fertilzer burn. Orchardgrass seedlings were tolerant to the high rate of fertilizer. Nevertheless higher fertilizer was indispensable for the seedling growth and early production of the sown species. 6) effect of seed coating Though it was not clear whether pelleting seeds of orchardgrass and white clover could be effective in seedling emergence and insuring seedling density thereafter, it was considered promising if the weather condition was unsettled or in a longer spell of dry weeks.
