Switchgrass (Panicum virgatum) is one of the leading candidates for sustainable lignocellulosic biofuel production in North America. Most current management recommendations for switchgrass include applications of synthetic nitrogen (N) fertilizers to increase production, particularly when grown on marginal lands. However, this management can be costly to growers and have negative impacts on ecosystem functioning. Also, N-fertilization does not always result in higher yield in switchgrass and may have unintended effects on plant biomass quality, including cell wall composition, that can affect the efficiency of fermentation processes for biofuel production. Drought stress may reduce biomass responses to N-fertilization, further reducing the value of fertilizer application. To examine whether N-fertilization and reduced precipitation affected switchgrass productivity and cell wall composition, we conducted a two-year field experiment in mature stands of two switchgrass cultivars grown for bioenergy at the W.K. Kellogg Biological Station Long Term Ecological Research Site in Michigan, USA. Nitrogen was added at a rate of 56 kg N ha⁻¹ (urea and ammonium nitrate), and precipitation was reduced using rainout shelters. Overall, we did not observe any effect of N-fertilization on biomass production. However, under ambient rainfall conditions, N-fertilization altered switchgrass biomass quality by reducing hemicellulose. Reduced precipitation minimized the effects of N-fertilization on switchgrass cell wall composition. Switchgrass is a relatively drought-tolerant species, and our results indicate that this crop will be a viable bioenergy feedstock even in a changing climate. However, in this study, N-fertilization had no effect on biomass quality or quantity under drought conditions.

柳枝（（Panicum virgatum）是北美可持续木质纤维素生物燃料生产的主要候选人之一。当前对柳枝management的大多数管理建议包括施用合成氮（N）肥料以增加产量，特别是在边缘土地上种植时。但是，这种管理对种植者而言可能是昂贵的，并且会对生态系统的功能产生负面影响。同样，氮肥并不总是导致柳枝yield的更高产量，并且可能会对植物生物量质量（包括细胞壁组成）产生意想不到的影响，从而影响发酵过程生产生物燃料的效率。干旱胁迫可能会降低生物量对氮肥的响应，从而进一步降低施肥的价值。为了研究氮肥和减少的降水量是否影响柳枝productivity生产力和细胞壁组成，我们在美国密歇根州WK Kellogg生物站长期生态研究基地的两个柳枝for品种的成熟林分中进行了为期两年的田间试验，以获取生物能源。氮的添加量为56 kg N ha^-1（尿素和硝酸铵），使用防雨棚减少了降水。总体而言，我们没有观察到氮肥对生物量生产的任何影响。然而，在环境降雨条件下，氮肥通过减少半纤维素改变了柳枝biomass的生物量质量。减少的沉淀使氮肥对柳枝cell细胞壁组成的影响降到最低。柳枝is是一种相对耐旱的物种，我们的结果表明，即使在气候变化的情况下，这种作物也将是一种可行的生物能源原料。然而，在这项研究中，氮肥对干旱条件下的生物量质量或数量没有影响。