Abstract
Clipping winter crop in autumn promotes the snow damage in snowy district. In this report investigations were made on definition of snow damage and regrowth in spring in relation to the prosperity and decay of TAC (total avilable carbohydrate) and total nitrogen after clipping Italian ryegrass in autumn. Tottorizairai variety was seeded Septmber 2. Whole plots were clipped October 25 for the first time, and plot II, III and IV were clipped November 10, November 26 and December 10 respectively for the second time to differentiate the days from clipping to continuous snow cover. In spring whole plots were clipped two times. Duration of continuous snow cover were 84 days. The results obtained are shown below. 1. Snow damages were different clearly among plots. There were little snow damages (area rate) on plot I, 40-60% on plot II and IV, and the most heavy snow damage on plot III, above 80%. 2. Snow damage has a direct influence on yields of each plot and both fresh and dry yields were I>II≒IV>III. 3. TAC in stubble has reduced after clipping and reached minimum about 5-10 days after clipping on plot I, II and III. Two or three weeks elapsed before TAC recovered on the level with that of clipping time, but on plot III clipped at the lower temperature, recover of TAC was insufficient in about a month after clipping. TAC in stubble just before continuous snow cover were I>IV>II>III and this order was the same as that of yields. 4. Total nitrogen in leaf was higher than in stubble. Total nitrogen in stubble tended generally to decrease after clipping and its order among each plot just before continuous snow cover was I<IV<II<III and symmetrical with that of TAC. 5. There was high negative correlation between TAC and total nitrogen, especially in stubble. There was more TAC and less total nitrogen on plot I with light snow damage. On the contrary, there was less TAC and more total nitrogen on plot III with heavy snow damage. Plot II and IV were in the middle of them. 6. According to the above mentioned, clipping in autumn must be done about a month and a half before continuous snow cover or just before continuous snow cover, but it is in danger to put the latter to practical use because it is difficult to estimate the first day of continuous snow cover correctly. 7. As there is high positive correlation between dry weight rate and TAC, dry weight rate must be index of snow resistance.
