Abstract
The author tested the influence of the frequency of mowing on the growth of orchardgrass and Ladino clover grown in mixtures in the same sward. For that purpose, both species were grown in pure and mixed sward, and three cutting plots were set up in two swards respectively, i.e., Plot A: the plot cut at 6 times a year (in late April, late May, late June, late July-early August, late August-early Sept., and Oct.); Plot B: the plot cut at 4 times a year (mowings in late June and late July.early Aug. were saved as compared with the case of plot A) ; and Plot C: the plot cut at 3 times a year (in early May, late July and late Sept.). In mixed sward, Ladino clover has become extinct in case where the two species covering the mixed sward were cut less frequently, while orchardgrass had a tendency to become extinct in case where they were cut more frequently. Namely, the yearly changes of yield of the two species corresponded to the yearly changes of population of the two. All the stolons of Ladino clover died out by early May in the first year in case of plot C, and by mid-June in the second year in case of plot B. While the stolons of clover per unit length of string (the number of stolons was shown by the frequency of stolons crossing the unit length of string setting in the sward at random) in plot A began to increase after June in the first year and reached the maximum in June in the second year. After that it showed no appreciably great changes. The number of hills of orchardgrass per unit area decreased temporarily for the first year, but after that it showed little or no changes in case of plot B and C, while the number of hills of orchardgrass per unit area in case of plot A showed a marked decrease in sumrner (June and July) and showed a tendency to decrease year after year. In pure sward, it was not observed the extinction of clover in case of plot B and C, and a tendency of the extinction of orchardgrass in case of plot A. Namely, the number of stolons of clover per unit length of string has been increased in all plots, but the increasing rates were higher in case of plot B and C than that in case of plot A. The number of hills of orchardgrass per unit area decreased temporarily for the first year, but after that it showed little or no changes in case of plot B and C as with in that case in mixed sward. While the number of hills of orchardgrass per unit area in case of plot A showed slowly decrease every summer, but has highly maintained comparing with plot B and C. The data for the mixed and pure sward showed that the extinction of clover or orchardgrass in mixed sward can be ascribed to the competition between the two species led by the mowing rather than to direct influence exerted by the mowing itself.
