Abstract
In this experiment, the dry matter production of Alfalfa was studied with the method of growth analysis, concerning the weather of high land region of Central Japan. The experiment was carried out, one in June-July and another in Sept.-Oct., the former was for 59 days from June 4th and the latter was 57 days from Sept. 4th in 1968. These were started after Alfalfa was clipped at two levels of height namely, 7cm and 15cm, from ground level, and the growth was examined 8 times at the interval of 7-14 days in each experiment. The results obtained were summarized as follows ; 1) For 57 or 59 days after clipping, the dry matter increased about 500-515m/m^2 in June-July, and 210-340g/m^2 in Sept.-Oct. Both RGR and CGR were higher in June-July. 2) This difference between two seasons was mainly caused by the fact that NAR in fall was lower about 30-60% than it was in June, also RLGR was low in fall and LAI reached a maximum earlier than June, and decreased rapidly because of defoliation. 3) The reason of low NAR in fall was considered to be caused partly by the low temperature of daytime and short duration of sunshine under the short days compared with those in June and July. 4) Comparing with high clipping at 15cm, dry matter in stubble and root decreased more severely by low clipping at 7cm in June. Also leaf area in stubble at clipping date was less and the regrowth after clipping was inferior in 7cm clipping. But the dry matter yield in both 7cm and 15cm clipping differed only a little because RGR of regrowth was higher in 7cm clipping and dry matter amounted nearly to the same degree. So, if Alfalfa is clipped with long interval, the regrowth and dry matter production would not be inferior in low clipping.
