Abstract
To clarify the effects of insufficient precipitation stress on the growth of timothy ageing plants, we applied artificial irrigation simulating daily precipitation in several drought years (1990, drought after first cutting; 1995, drought at first crop; 2005, drought at first crop and after first cutting) and in an average year as the control, in northern district of Hokkaido, Japan. When precipitation was insufficient at first or second crop, dry matter yield (DM) decreased in both. Drought after first cutting especially brought about, in second crop, obvious delay of regrowth, decrease of new tiller emergence and depression of DM (1990, 2005). And in 2005, which drought continued from first crop to second one, DM of second crop decreased to 19% of an average year, 27% of plants had died. So it was guessed that tiller density of timothy after the first cutting can be disadvantageously affected by the drought stress. However, it was also suggested that if suitable precipitation were carried out from then to the next year, tiller density and DM in the next year would be improved to the same level as an average year. Concentration of TDN, CP and mineral (Ca, Mg, K, P), if anything, tend to become higher than an average year in case delay of growth caused by severe drought stress.
