Experimental design
The experiment was started in early rice of year 1998
and ended in late rice of year 2003. The primary hybrid
varieties with early rice Xiangliangyou 68 (from
the end of April to the end of July) and late rice
Peiliangyou Teqing (from the end of July to 15-25 of
October) were planted. The transplant density was
20 cm × 20 cm.