本研究利用华北平原2年的田间定位试验，研究了条带深旋耕和控释尿素耦合对玉米产量和氮素利用效率的影响，及其氮素积累和产量形成的相关生理过程。与常规旋耕（RT）和免耕（NT）比，由于条带深旋耕（ST）使0-40 cm土层的土壤容重分别降低了10.5%和13.7%，从而显著提高了20-40 cm土层的土壤含水量和土壤矿质氮含量。与普通尿素（CU）比，控释尿素（CR）使开花期和成熟期0-40 cm土层的土壤矿质氮含量分别提高了12.4%和10.3%。因此，ST和CR显著提高了玉米根长和氮素总积累量，从而促进了叶片面积和干物质积累（特别是花后干物质积累）的增加，最终提高了玉米千粒重。ST处理产量比RT和NT处理分别提高了8.3%和11.0%，CR处理产量比CU处理提高8.9%。由于ST和CR耦合处理产量和氮素积累量的增加，显著提高了玉米氮素利用效率。综述可知，ST与CR结合可以通过改善土壤理化特性和氮素供应，进一步提高玉米产量和氮素利用效率，该措施可作为华北平原以及世界上其他类似地区的促进玉米可持续生产发展的有效措施。

Planting grass and legume mixtures on improved grasslands has the potential advantage of realizing both higher yields and lower environmental pollution by optimizing the balance between applied N fertilizer and the natural process of legume biological nitrogen fixation. However, the optimal level of N fertilization for grass-legume mixtures, to obtain the highest yield, quality, and contribution of N2 fixation, varies with species. A greenhouse pot experiment was conducted to study the temporal dynamics of N2 fixation of alfalfa (Medicago sativa L.) grown alone and in mixture with smooth bromegrass (Bromus inermis Leyss.) in response to the addition of fertilizer N. Three levels of N (0, 75, and 150 kg ha–1) were examined using 15N-labeled urea to evaluate N2 fixation via the 15N isotope dilution method. Treatments were designated N0 (0.001 g per pot), N75 (1.07 g per pot) and N150 (2.14 g per pot). Alfalfa grown alone did not benefit from the addition of fertilizer N; dry matter was not significantly increased. In contrast, dry weight and N content of smooth bromegrass grown alone was increased significantly by N application. When grown as a mixture, smooth bromegrass biomass was increased significantly by N application, resulted in a decrease in alfalfa biomass. In addition, individual alfalfa plant dry weight (shoots+roots) was significantly lower in the mixture than when grown alone at all N levels. Smooth bromegrass shoot and root dry weight were significantly higher when grown with alfalfa than when grown alone, regardless of N application level. When grown alone, alfalfa’s N2 fixation was reduced with N fertilization (R2=0.9376, P=0.0057). When grown in a mixture with smooth bromegrass, with 75 kg ha–1 of N fertilizer, the percentage of atmospheric N2 fixation contribution to total N in alfalfa (%Ndfa) had a maximum of 84.07 and 83.05% in the 2nd and 3rd harvests, respectively. Total 3-harvest %Ndfa was higher when alfalfa was grown in a mixture than when grown alone (shoots: |t|=3.39, P=0.0096; root: |t|=3.57, P=0.0073). We believe this was due to smooth bromegrass being better able to absorb available soil N (due to its fibrous root system), resulting in lower soil N availability and allowing alfalfa to develop an effective N2 fixing symbiosis prior to the 1st harvest. Once soil N levels were depleted, alfalfa was able to fix N2, resulting in the majority of its tissue N being derived from biological nitrogen fixation (BNF) in the 2nd and 3rd harvests. When grown in a mixture, with added N, alfalfa established an effective symbiosis earlier than when grown alone; in monoculture BNF did not contribute a significant portion of plant N in the N75 and N150 treatments, whereas in the mixture, BNF contributed 17.90 and 16.28% for these treatments respectively. Alfalfa has a higher BNF efficiency when grown in a mixture, initiating BNF earlier, and having higher N2 fixation due to less inhibition by soil-available N. For the greatest N-use-efficiency and sustainable production, grass-legume mixtures are recommended for improving grasslands, using a moderate amount of N fertilizer (75 kg N ha–1) to provide optimum benefits.