Abstract
We thought that subterranean clover (Trifolium subterraneum) has the greatest potential of any annual clovers as a cool season cover crop. So we attempted to investigate the relationship between the persistence of sub clover seedling emergence after seed maturing and seed survival in the soil on the supposition that seeds are buried by tillage.
The seeds of sub clover both of Mt. Baker and trikkla which set at the soil surface germinated little during the summer, as these seeds immediately after seed maturing germinated little at high temperature. These seeds sprouted simultaneously in the early autumn, as the decrease of the hard seed ratio of sub clover seeds was effected by fluctuating temperature at soil surface. On the other hands, almost sub clover survived seeds buried at 5-10cm showed hard seeds, so these seeds germinated little in early autumn and will survived for several years in the soil.
Therefore we thought that the fields tilled by rotary after sub clover seed maturing, these seeds at soil surface will distribute within the depth of rotary share, over half of the seeds at the soil surface will emerge in early autumn and will reestablish the good stands. Other seeds which were distributed to lower depths by rotary tillage will remain in the soil to make a seed bank. The hard seeds in the deep soil layer will survive for several years, and if these seeds are redistributed to the soil surface by rotary tillage, they may soften rapidly and emerge. These seedlings will be useful to success for good stand. So rotary tillage will make an adequate soil seed bank of sub clover.
