Perennial grasses are the promising source of bioenergy in South America which could provide several environmental benefits such as reduction in the greenhouse gasses emissions and reduction of nutrients and soil losses. Our objective was to determine the impact of N and P fertilization on biomass yield, N use efficiency (NUE), apparent N recovery (ANR), and nutrient removal (NR) on three perennial grasses: elephantgrass (Pennisetum purpureum Schum.), giant reed (Arundo donax L.), and switchgrass (Panicum virgatum L.). Four fertility treatments were evaluated in a 8-year field study in northwestern Uruguay: 1. control (No fertilizer), 2.100 kg N ha⁻¹ year⁻¹, 3.100 kg P₂O₅ ha⁻¹ year⁻¹, and 4.100 kg N + 100 kg P₂O₅ ha⁻¹ year⁻¹. Across years, elephantgrass had the highest biomass yield followed by giant reed and switchgrass (18.9, 16.3, and 14.1 Mg ha⁻¹, respectively). Biomass yield increased 46% when N fertilizer was added, compared to the control. A low response was detected for P fertilization on all grasses, probably for initial P soil content (≥9 g kg⁻¹). Elephantgrass had the highest NUE (70 kg kg⁻¹ N), however, it had the highest total NR on these eight years (899, 226, and 2800 kg ha⁻¹ for N–P–K, respectively) among the grasses, indicating a potential for increased fertilization input over time. Switchgrass had the lowest average ANR (19%) and NR (334, 45, and 166 kg ha⁻¹, respectively). Therefore, even though switchgrass presented the lowest biomass yield, it is an excellent option as low-input bioenergies grass for temperate regions.

多年生草是南美有希望的生物能源来源，它可以提供多种环境效益，例如减少温室气体排放以及减少养分和土壤流失。我们的目标是确定氮肥和磷肥对三种多年生禾草（象草，狼草（Pennisetum purpureum Schum））的生物量产量，氮利用效率（NUE），表观氮回收率（ANR）和养分去除（NR）的影响。芦苇（Arundo donax L.）和柳枝（（Panicum virgatum L.）。1.对照（无肥料），2.100千克Ñ公顷：四个生育治疗在西北部乌拉圭一个8年场研究中评价^-1年^-1，3.100公斤P ₂ ö₅公顷^-1年^-1，和4.100公斤N + 100公斤P ₂ ö ₅公顷^-1年^-1。多年来，大象草的生物量产量最高，其次是巨型芦苇和柳枝（（分别为18.9 Mg ha ^-1和14.1 Mg ha ^-1）。与对照相比，添加氮肥可使生物量增产46％。在所有草地上对磷施肥均检测到低响应，可能是对初始磷含量（≥9g kg ^-1）。象草的NUE最高（70 kg kg ^-1  N），但是，这八年来的总NR最高（899、226和2800 kg ha ^-1在草丛中分别为N–P–K），这表明随着时间的推移施肥输入量可能会增加。柳枝had的平均ANR（19％）和NR（分别为334、45和166 kg ha ^-1）最低。因此，即使柳枝presented的生物量产量最低，它还是温带地区低投入生物能源草的绝佳选择。