Abstract
In order to contribute to the establishment of the stable highyielding cultivation of barnyardgrass (Echinochloa Crus-galli BEAUV. var. caudata KITAGAWA) as a forage crop, an experiment was conducted to know the relation between the growth state at cutting time and the regrowth after cutting. The results were summarized as follows: 1) The weight of dry matter on the process of regrowth increased following "S shape growth curve". The rate of dry matter production in the initial stage of regrowth was slower than that before defoliation. The bigger the state of growth at cutting time, the larger was the decreasing tendency of that rate. 2) Dry weight and total available carbohydrate content of the stubble did not correlate with "regrowth indexes", such as the ratio of regrowth tillers in whole defoliated tillers, plant height, tiller number and dry matter production in the initial stage of regrowth. But a close positive correlation was found between the total nitrogen percent of the stubble and those indexes. 3) In this experiment, barnyardgrass grew to about 140cm in height and to about 80kg/a of dry matter yield without lodging, and continued to regrow without wilting after defoliation. Since the regrowth with the low ratio of regrowth tillers was consisted of new tillering after defoliation, that caused to delay the regrowth. The regrowth after cutting used to be delayed in the case of the over-growth (i.e., higher than 70cm in height or heavier than 30kg/a in the dry matter yield). 4) In order to raise the high yield during a season, it was discussed in this paper that the cutting interval and time should be decided in a consideration to rise "average productivity" dry matter yield regrowth/duration) during whole growing season, avoiding to delay the regrowth as less as possible.
