Optimizing nitrogen (N) management is an important factor for sustainable perennial biomass systems. However, N application is costly, both financially and environmentally. Our objectives were to determine: (1) N rate and plant spacing effects on yield and yield components of prairie cordgrass swards and (2) fertilizer N replacement value (FNRV) of kura clover in prairie cordgrass-kura clover binary mixtures. Plots were established in Illinois, Minnesota, South Dakota, and Wisconsin, USA, in 2010. Kura clover was transplanted on 30-cm centers in all treatments in which it was a component; prairie cordgrass seedlings were transplanted within the kura clover on 60- and 90-cm centers. Monoculture prairie cordgrass stands were established at the same population densities of mixed stands and fertilized with 0, 75, 150, or 225 kg N ha^-1. Biomass was harvested in the autumn from 2011 to 2013. N (urea), year, plant spacing, and year × plant spacing affected prairie cordgrass production at all locations. Prairie cordgrass yield increased with N application, but the response varied by location. N application tended to increase prairie cordgrass tiller density and consistently increased tiller mass. Prairie cordgrass yield with 0 N was equal to or less than the yield of prairie cordgrass/kura clover mixtures at all locations in 2011 and 2012; however, kura clover provided a FNRV of 25–82 kg N ha^-1 to prairie cordgrass in 2013. Kura clover has potential to provide N to prairie cordgrass in binary mixtures of these two species and on land that may not be easily farmed due to wetness.

优化氮（N）管理是可持续的多年生生物量系统的重要因素。然而，氮的施用在经济和环境上都是昂贵的。我们的目标是确定：（1）氮肥用量和株距对草原草草牧草产量和产量构成的影响，以及（2）草原草草-库拉草三叶草二元混合物中库拉草三叶草的氮素替代价值（FNRV）。2010年在美国伊利诺伊州，明尼苏达州，南达科他州和威斯康星州建立了试验区。在所有构成部分的处理中，将库拉三叶草移植到30厘米中心。在60厘米和90厘米中心的库拉三叶草内移植草原草丛幼苗。以相同种群密度的混交林建立了单作草原cord草林，并施以0、75、150或225 kg N ha的肥料^-1。2011年至2013年秋季收获了生物质。氮（尿素），年，植物间距和年×植物间距会影响所有地方的草绳草产量。施用氮肥可提高草原草的产量，但响应因地区而异。施用氮肥往往会增加草原草cord的分er密度，并持续增加分till质量。0 N时的草原草产量等于或低于2011年和2012年所有地区的草原草/库拉三叶草混合物的产量；但是，库拉三叶草在2013年为草原草提供了25–82 kg N ha ^-1的FNRV 。库拉三叶草有潜力以这两种物种的二元混合物以及在由于以下原因不易耕种的土地上为草原草提供氮。潮湿。