Abstract
A field experiment was conducted to study the mechanism of competition by seed mixtures which were made of timothy and red clover under combinations of various seed ratios and fertilizer treatments. Following seed ratios (total number of germinable seed being 8,000) of timothy vs. red clover were adopted in this study, viz. 10:0, 7:3, 5:5, 3:7 and 0:10. Further six fertilizer treatments were taken: 2 NPK, NPK, NP, NK, PK and none. Both factors were combined in all possible ways. Results obtained over 3 harvest years were summarized as follows: 1. Each fertilizer treatment and seed ratio gave a respective effect on rise and fall of plant vigor of both species in the mixture over 3 years. 2. Total cured hay yields over 3 years were higher in the mixture than in single sowing and 5:5 seed ratio showed the highest yields at respective fertilizer treatment except PK treatment which gave the highest yields at 3:7 seed ratio. The order of high yields by fertilizer treatments was 2 NPK>NPK>NP, NK and PK>none by means of Duncan's test. 3. Red clover, regardless to plant vigor in the mixture, gave somewhat beneficial effects on the yields of timothy and as the ratio of red clover to timothy increased, the yields of timothy became higher. Red clover conversely suppressed by timothy in the 2nd and 3rd crop year in the plots where the seed ratios of red clover were higher. In the plots where PK treatment was given, such a phenomenon was not observed. 4. The botanical composition in the plots of 7:3 seed ratio was more stable than the other ones shown by the value of coefficient of variation of timothy content in the hay through each cutting of 3 years. 5. Generally speaking, customary 2:1 seeding ratio (in weight) of timothy-red clover mixture taken in Hokkaido area seemed to be a little too high in timothy against red clover. By reducing timothy seed percentage, both plant may grow more favorably.
