牧草の混播に関する研究 : III. 種子の定着におよぼす播種法と土壤水分の影響

抄録

In a mixture of some pasture plants, it was observed that the number of established seedlings was less than expected theoretically from numbers of seeds and their germination percentage (Table 2), especially legumes showed much difference (Table 1). The experiments were conducted in order to make clear the causes of this phenomenon and obtained following results. 1. Effect of soil covering treatment upon the seeds of two grasses and three legumes was examined with pots in a green house. The water level was regulated so that the soil moisture content may be kept at about 100% (plot A), 110% (plot B) and 120% (plot C) of maximum soil water capacity (Fig. 1). The effect of soil covering was distinct at plot A, but no effect was found at plot C which contained high soil moisture (Table 3). In the case of alfalfa, however, the effect of soil covering was remarkable even at plot C, and extremely poor establishment was observed at non soil-covering plot. On the contrary, Italian ryegrass was not influenced by soil covering and red clover, ladino clover and orchard grass showed intermediate. It was observed that under non soil-covering condition the seeds could not put their roots into the soil, although they could germinate. When the clear vinyl sheet was covered over the plot, establishment was well even in alfalfa sown under non soil covering condition. From the above test, it was considered that air humidity might be closely related to the establishment. 2. Effects of soil covering and soil packing on an establishment were studied under the fields condition. From the result of this examination (Table 4, 5, 6, 7), it was cleared that grasses (orchard grass, Italian ryegrass) were not influenced by soil covering, while legumes (ladino clover, red clover, alfalfa) were significantly affected. Soil covering did not affect on the establishment of grass on the field in spite of the remarkable influence in green house. It was supposed that above difference was because the field test was conducted under high air humidity (Fig. 2). Effect of soil packing upon each species was not found owing to no difference in soil moisture content between soil packing plot and non soil-packing plot, because of high precipitation during this experiment (6 mm per day). It was supposed, however, that the soil packing may have the effect under the case of low precipitation from the view point of soil moisture trend at Fig. 3. 3. It is necessary to cover the seeds with soil, because soil covering promotes not only their establishments but also their subsequent growth. Especially, legumes (alfalfa, red clover and ladino clover) need soil covering treatment, because of their impossibility to establish under low humidity condition.