Abstract
This experiment was conducted in order to clarify the regrowth behavior after defoliation at the internode elongation stage in forage crops. Oats were selected for this purpose. In heavy density plots 100 plants per box and in light density plots 15 plants per box were grown. The size of each box was 43×15×17cm. The heavy density plots showed earlier development than light density plots. Defoliation were made on March 9th at 5cm levels above the ground. After defoliations, growing points remained uncut were 28.0% and 83.8% of the tillers in heavy density plots and light density plots respectively. Regrowth of plants was classified into two kinds. The first kind of regrowth was regrowth of already existing tillers and second kind, growth of new tillers. In heavy density plots, regrowth of already existing tillers was not seen, but in light density plots it was observed in about 30 tillers per box. The growth of new tillers took place in both of the plots. In heavy density plots it was. vigorous at first and then fell down considerably and in light density plots it showed more or less a steady increase. On 44th day after defoliation the dry weights of the plant materials resulted from the growth of new tillers were 9.5g (45.7 tillers) and 4.6g (32.0 tillers) in light density plots and in heavy density plots respectively. The total available carbohydrate (TAC) contents at the time of defoliations were more in the light density plots in comparison with the heavy density plots and hence it could be assumed that better regrowth in light density plots were due to their high carbohydrate contents. In this experiment it could be concluded that the regrowth of plants mainly depended on two factors. One was the conditions of growing points at the time of defoliation and the other was the quantity of reserve materials at the time of defoliation.
