Although perennial bioenergy crops provide a potential for soil C sequestration, high fertilizer inputs are required to sustain yields. Land application of bioenergy byproducts can be an effective strategy to reduce the use of inorganic fertilizer. This study examined the impacts of elephantgrass [Pennisetum purpureum (L.) Schum.] bioenergy cropping and conventional pasture on soil C and N responses. Treatments included (a) bahiagrass + 50 kg N ha⁻¹ yr⁻¹ (BHG), (b) elephantgrass + 50 kg N ha⁻¹ yr⁻¹ (E50), (c) elephantgrass + 50 kg N ha⁻¹ yr⁻¹ + fermentation residual (E50FR), (d) elephantgrass + 50 kg N ha⁻¹ yr⁻¹ + biochar (E50BC), and (e) elephantgrass + 250 kg N ha⁻¹ yr⁻¹ (E250). Soil C and N responses occurred mainly at the 0‐ to 10‐cm depth. Biochar resulted in the largest increase in soil C stocks at the 0‐ to 10‐cm depth (5.8 Mg C ha⁻¹ in 2012 vs. 40 Mg C ha⁻¹ in 2016), but no differences were observed among the other treatments. Conversely, greater soil N stocks at the 0‐ to 10‐cm depth were associated with the BHG (0.8 and 0.34 Mg N ha⁻¹ for other treatments). Biochar favored N and C accumulation in the mineral‐associated (<53 μm) fraction, possibly from the accumulation of fine biochar fragments. In contrast, fermentation residual promoted C accumulation in unprotected light fraction. These results are supported by the δ¹³C signature and C/N ratios of the fractions. Results underscore the value of recycling biochar in bioenergy cropping systems as a means of improving C in coarse‐textured soils.

中文翻译：

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生物能源种植对佛罗里达Ultisol土壤碳和氮动态的短期影响

尽管多年生生物能源作物为固碳提供了潜力，但仍需要大量肥料以维持产量。在土地上使用生物能源副产品可以成为减少使用无机肥料的有效策略。本研究象草的影响[紫狼尾草（L.）舒姆。]生物能源作物和土壤C和N的反应常规牧场。处理包括：（a）百喜草+ 50千克氮公顷^-1 年^-1（BHG），（b）中象草+ 50千克氮公顷^-1 年^-1（E50），（C）象草+ 50千克氮公顷^-1 年^-1 +发酵残留物（E50FR），（d）象草+ 50 kg N ha ^-1  yr ^-1+生物炭（E50BC）和（e）象草+ 250千克N ha ^-1  yr ^-1（E250）。土壤的碳和氮响应主要发生在0到10厘米深度。生物炭在0至10 cm深度导致土壤碳储量增加最大（2012年为5.8 Mg C ha ^-1与2016年为40 Mg C ha ^-1），但在其他处理之间未观察到差异。相反，在0到10厘米深度处更多的土壤N储量与BHG相关（0.8和0.34 Mg N ha ^-1其他治疗）。生物炭有利于矿物相关（<53μm）部分中氮和碳的积累，这可能是由于细小的生物炭碎片的积累。相反，发酵残余物促进了C在无保护的轻馏分中的积累。这些结果是由δ支撑¹³的级分的Ç签名和C / N比。结果强调了在生物能源耕作系统中回收生物炭的价值，作为提高粗化土壤中碳含量的一种手段。