Studies On The Effects Of Different Enviroments And Fertilizing Rates On Hay Yield And Isoflavone Content Of Trifolium Pratense Cv. Minshan

Environment and fertilizing rate, especially the nitrogen fertilizer, have a prominent influence on hay yield, quality and isoflavones content of red clover (Trifolium pratense L). In this paper, the effects of environment and N and P fertilization on hay yield, nutritive value, isoflavones content and yield Minshan red clover were studied. This experiment was carried out in Lanzhou, Minxian and Guanghe respectively. Following conclusions were drawn out:1. Growing stages of Trifolium pratense cv. Minshan were different in different areas. At the same planting conditions, longer growing period and more biomass occurred at Minxian site. And also the highest height of every growing stage was obtained in this site. Branches and hay yields have significant difference in three sites, and branches in Lanzhou were the most and hay yields in Minxian were the highest. Fertilizing rates had significantly effects on heights, branches and hay yield. Overall, heights, branches and hay yields were all higher under A₂B₃ (75 kg N/hm², 360 kg P₂O₅/hm²) and A₂B₂ (75 kg N/hm², 120 kg P₂O₅/hm²) treatments. It showed that they were suitable fertilizating rates for Minshan red clover growth.2. Effects of different environments on red clover quality were different. In minxian, CP content and Leaf to Stem Ratio (LSR) were the highest, and NDF and ADF contents were the lowest. So from the point of nutritive value, Minxian was the best place to grow Minshan red clover. In this area, quality of red clover hay was the best and comprehensive characteristic was outstanding. Along with the the growing of red clover, CP content increased, and NDF and ADF content decreased. Higher nutritive value was obtained while cutting at bud appearing stage to early-flowering stage. There was significant difference of fertilizing rates on red clover quality. And under the treatments of A3B3 (150 kg N/hm², 360 kg P₂O₅/hm²) and A3B2 (150 kg N/hm², 360 kg P₂O₅/hm²), quality was the best and P content was also higher.3. There was no significant influence of enviroment on isoflavone content. In three sites, formononetin (For) and biochanin A (Bio) contents were the highest. It showed that For and Bio were dominating isoflavone ingredients in Minshan red clover. But there was significant difference among isoflavone contents of leaf, stem and racemes. And isoflavone content of leaf was the highest and racemes were the lowest. No matter leaf, stem and racemes, For and Bio contents were also the highest. It showed furtherly, that For and Bio are dominating isoflavone ingredients in Minshan red clover. There was significant difference of isoflavone contents at different growing stage. At the bud -appearing stage it was the highest. Along with the growing of red clover, isoflavone content decreased and at full-flowering stage, it was the lowest. So, cutting red clover at bud appearing stage could get higher isoflavone content. There was significant influence of fertilizing rates on isoflavone contents. And higher isoflavones contents were obtained under the treatments of A₂B₂ (75 kg N/hm², 120 kg P₂O₅/hm²) and A₂B₁ (75 kg N/hm², 0 kg P₂O₅/hm²).4. Planting Minshan red clover in Minxian could get higher hay yield and isoflavone yield, and cutting at bud-appearing to early-flowering stage could get a higher nutritive value. So, Minxian was the best place to grow Minshan red clover. Higher isoflavone yields were obtained under the treatments of A1B3 (0 kg N/hm², 360 kg P₂O₅/hm²), A₂B₂ (75 kg N/hm², 120 kg P₂O₅/hm²), A₂B₁ (75 kg N/hm², 0 kg P₂O₅/hm²) and A₂B₃ (75 kg N/hm², 360 kg P₂O₅/hm²). It showed that isoflavone yield per unit area was the highest when no N applied or its rate was 75 kg N/hm², and P had no apparent influence on isoflovone yield of Minshan red clover.