Department of Agricultural and Environmental Sciences, Tennessee State University, Nashville, TN, United States of America.
Department of Earth and Ocean Sciences, University of North Carolina Wilmington, Wilmington, NC, United States of America.
PLoS One. 2020 Mar 30;15(3):e0230688. doi: 10.1371/journal.pone.0230688. eCollection 2020.
Nitrogen (N) fertilization affects bioenergy crop growth and productivity and consequently carbon (C) and N contents in soil, it however remains unclear whether N fertilization and crop type individually or interactively influence soil organic carbon (SOC) and total N (TN). In a three-year long fertilization experiment in switchgrass (SG: Panicum virgatum L.) and gamagrass (GG: Tripsacum dactyloides L.) croplands in Middle Tennessee USA, soil samples (0-15cm) were collected in plots with no N input (NN), low N input (LN: 84 kg N ha-1 yr-1 in urea) and high N input (HN: 168 kg N ha-1 yr-1 in urea). Besides SOC and TN, the aboveground plant biomass was also quantified. In addition to a summary of published root morphology data based on a separated mesocosm experiment, the root leachable dissolved organic matter (DOM) of both crops was also measured using archived samples. Results showed no significant interaction of N fertilization and crop type on SOC, TN or plant aboveground biomass (ABG). Relative to NN, HN (not LN) significantly increased SOC and TN in both crops. Though SG showed a 15-68% significantly higher ABG than GG, GG showed a 9.3-12% significantly higher SOC and TN than SG. The positive linear relationships of SOC or TN with ABG were identified for SG. However, GG showed structurally more complex and less readily decomposed root DOM, a larger root volume, total root length and surface area than SG. Collectively, these suggested that intensive N fertilization could increase C and N stocks in bioenergy cropland soils but these effects may be more likely mediated by the aboveground biomass in SG and root chemistry and morphology in GG. Future studies are expected to examine the root characteristics in different bioenergy croplands under the field fertilization experiment.
氮（N）施肥会影响生物能源作物的生长和生产力，从而影响土壤中的碳（C）和 N 含量，但目前尚不清楚 N 施肥和作物类型是单独还是相互作用影响土壤有机碳（SOC）和总氮（TN）。在美国田纳西州中部的一项为期三年的柳枝稷（SG：Panicum virgatum L.）和大刍草（GG：Tripsacum dactyloides L.）农田的施肥试验中，在没有 N 输入（NN）、低 N 输入（LN：尿素中 84kgN/ha/yr）和高 N 输入（HN：尿素中 168kgN/ha/yr）的处理小区中采集了 0-15cm 土壤样品。除了 SOC 和 TN 外，还量化了地上植物生物量。除了基于单独的中尺度实验的已发表根系形态数据的摘要外，还使用存档样品测量了两种作物的根可溶溶解性有机质（DOM）。结果表明，N 施肥和作物类型之间没有显著的相互作用对 SOC、TN 或地上植物生物量（ABG）有影响。与 NN 相比，HN（而非 LN）显著增加了两种作物的 SOC 和 TN。尽管 SG 的 ABG 比 GG 高 15-68%，但 GG 的 SOC 和 TN 比 SG 高 9.3-12%。SG 的 SOC 或 TN 与 ABG 之间存在正线性关系。然而，GG 显示出结构上更复杂、分解速度更慢的根 DOM、更大的根体积、总根长和表面积，比 SG 高。总的来说，这些表明密集的 N 施肥可以增加生物能源农田土壤中的 C 和 N 储量，但这些影响更可能通过 SG 的地上生物量和 GG 的根化学和形态来介导。预计未来的研究将在田间施肥实验中检查不同生物能源农田的根特征。
