Abstract
Effects of lime nitrogen application on the establishments and yields of several warm-season grasses in a serial non-tilled sowing were investigated by pot and field experiments. And another pot and petri dish experiments were also conducted to find out the best condition for controlling the survival of Italian ryegrass (Lolium multiflorum, abbr. as Ir) and for preventing the inhibition of the germination of oversown grasses with the higher rate of lime nitrogen application. 1. In the field, Ir swards were treated with 12, 24kg/10a using lime nitrogen or ammonium sulfate on June 17 and in the pot experiments, 0, 0.2, 0.4, 0.6gN were applied to each pot using lime nitrogen or ammonium sulfate on July 4. Then Sweet sorghum (Sorghum vulgare, abbr. as So), African millet (Eleucine corocana, abbr. as Am), Rhodes grass (Chloris gayana, abbr. as Ro) and Green Panic (Panicum maximum, abbr. as Gp) were oversown on June 20 and July 7 respectively. The residual growth of Ir which received the higher rate of lime nitrogen was extremely suppressed comparing with that treated with the ammonium sulfate. Then the better establishment and growth of So, Am, Ro, Gp were found on the field which received N ; 24kg/10a of lime nitrogen and on the pot received 0.4g/pot N lime nitrogen. However, in the pot experiment, the heavier lime nitrogen application caused the suppression of the germination of oversown grasses. Yields of warm-season grasses were increased with improving their establishment. The establishments and yields of oversown grasses on the lime nitrogen plots were ranked as Am>Ro>Gp. 2. The suppression of the residual growth of Ir was proceeded in case of supplied lime nitrogen to the soil surface or to the root stumps of Ir after cutting of Ir swards. Furthermore, the residual growth of Ir was suppressed by lime nitrogen application in cultural solution. Therefore, it was considered that the residual growth of Ir was more effectively suppressed when Ir swards were cut as lower as possible and treated with lime nitrogen onto the root stumps of Ir and/or the soil surface near to stumps. 3. The effects of the concentration of lime nitrogen on the germination and establishment of Am were investigated under the different soil temperatures and soil moisture contents. The suppression effects of lime nitrogen on the germination and establishment of Am were decreased extremely at the higher soil temperature (above 28℃) and at the middle (18%) or high (25%) soil moisture contents.
