氮水平和接种根瘤菌对大豆生长和生物固氮的影响
Effects of inoculation with rhizobia strains and nitrogen level on nodulation and plant growth in soybean

    大豆在全球廣泛種植,原因之一在於它為人畜提供了良好的蛋白質營養。同時,它也可作為含氮化肥的替代物。氮的有效性對這兩個用途有著重要影響。接種根瘤菌後,大豆植株可從土壤礦物質和生物固氮兩個途徑獲取氮素營養。研究表明,高氮肥投入會抑制植株生長和根瘤固氮的能力。但這種抑制造成的影響可能依不同氮水準和不同根瘤菌株系而異。因此,為了找出一個適宜的氮水準和高效的根瘤菌株系,我們對五個氮水準和兩種根瘤菌株系進行了大豆水培試驗。結果表明,過低或過高的氮水準抑制大豆植株生長和限制根瘤生物固氮的總量。在固氮能力方面,根瘤菌株系USDA110在全部氮水準處理中都比BXYD3株系更為高效。高產大豆或優質大豆綠肥應結合良好的氮肥利用率和高效的生物固氮能力,試驗證明,當前種植大豆時施氮過度的做法應當停止,另應廣泛接種高效根瘤菌株系,如USDA110。
 
      Soybean is grown around the world primarily as a protein source for human and livestock diet. The plant is also utilized as a nitrogen fertilizer substitute. Nitrogen availability is important in realizing the purposes. When inoculated with rhizobia, soybean plants can derive nitrogen from both minerals and biological nitrogen fixation (BNF). Studies have showed that high nitrogen fertilizers input will adversely affect plant growth and nodules’ ability to fix nitrogen gas. This inhibition may vary with different external nitrogen levels and inoculation with alternative rhizobium strains. Thus, it is necessary to find out an optimal level of inorganic nitrogen input and an efficient rhizobium strain. Our hydroponic experiment on soybean growth and BNF at five mineral nitrogen levels and with two rhizobium strains separately, confirmed that soybean growth is inhibited by extremely high or low external nitrogen levels, and BNF is similarly affected. It also concluded that the rhizobium strain of USDA110 is always more efficient than the strain of BXYD 3. High yield in soybean production or high value in green manure is a result of good efficiency of inorganic nitrogen utilization combining high benefit from BNF. Our results imply that excessive nitrogen fertilizer application should be prevented and inoculation with the rhizobium USDA110 should be adopted in order to achieve these goals.