Study On The Reproductive Characteristics And Seed Production Technology Of Smooth Bromegrass (Bromus Inermis Less.) & Alfalfa (Medicago Sativa L.)

The paper was conducted in a study for seed propagating characters and seed yields of smooth bromegrass, alfalfa in Chefeng, north-east of China in 2001-2003.The results showed that:Fertile tillers in smooth bromegrass arised from winter dormancy buds mainly, and gave birth to new buds formed in spring sometimes. Tillerng time was in summer-autumn briefly. The fertile tillers in next year were increased when applied nitrogen or N,P,K compound fertilizer. Thinning promoted gramineous tillering, enhanced fertile tillers in next year.Reproductive allocation of seeds of smooth bromegrass was 11.8-15.8%. It was a constant usually.21—30% reproductive allocation of panicle changes by application fertilizers and thinning. Reproductive allocation of alfalfa individual was in 3 - 19% that diversified due to the plant size.Over compensation belonged to raceme length, raceme number, pods of alfalfa as the plant density was decreased, equal compensation belonged to florets and 1000-seeds weight, over or lack of compensation belonged to seed yield.Optimal seed yield of smooth bromegrass depended on more fertile tillers and higher biomass, and for alfalfa relied on less plant density, strong spring shoots. It was a optimal seed yield for smooth brome canopy that leaf area equal to 1 approximately, leaf distribution was uniformity, transmission coefficient for radiation penetration in 25° was 0.76, transmission coefficient for defuse Penetration was 0.5, leaf angle was 78° ,and Extinction coefficient was less.Spikelets on panicle of bromegrass primarily located on low panicle. Florets and seeds per spikelet distributed on the upper panicle. Seed set was more on the low panicle than that on the upper panicle. Florets on low to upper raceme of alfalfa increased gradually, and florets laying on the mid raceme was the most.Seed moisture content of alfalfa decreased mildly during seed developing, declined more celerityly before mature. Dry matter increased gently in alfalfa seed developing and more quickly before ripe. After yellow fruit, germination of alfalfa was a constant that changed more less, but dehydrogenase increased and was the most in mature. Seed potency ascended and seed hard went down during seed developing mildly.Optimal seed yield of smooth bromegrass was got in 45-90kg/hm2 nitrogen applied in spring, 135(90/40)kg/hm2 nitrogen applied in autumn/spring, thinning 35-45cm per line with 50cm row space, and irrigating before recovering.Optimal seed yield of alfalfa was 1070kg/hm2 that was 1 times about more than the contrast as the plant density was 10 plants/m2, 140-170 shoots/m2. Application 3.5 kg/hm2Boron,0.12 kg/hm2 molybdenum,15 kg/hm2 magnesium got optimal seed yield. Seed set can be enhanced to 27.9% as applied boron.