Inappropriate nitrogen (N) fertilization rate could cause yield and economic losses and negative environmental impacts. This study was conducted to explore optimum N rate for a promising biofuel crop ‐ bioenergy sorghum [Sorghum bicolor (L.) Moench]. The biogeochemical model, DAYCENT, was verified with an eight‐year field trial and then used to simulate the long‐term (35 years) effects of N fertilization on aboveground biomass carbon (C), soil organic C (SOC), carbon dioxide (CO₂), and nitrous oxide (N₂O) emissions. Associated with the simulated metrics, N use efficiency (NUE), net greenhouse gas (GHG) emissions, and net economic return to N (RTN) were calculated to determine the optimum N rate. The model was capable of reproducing the field measurements with r² of 0.57, 0.47, 0.55, and 0.34 for aboveground biomass C, SOC, CO₂, and N₂O, respectively. Projection with 0–350 kg N ha⁻¹ fertilization in increments of 70 kg N ha⁻¹ indicated positive responses of aboveground biomass C and SOC to increasing N but with little increase above 140 kg N ha⁻¹. Declining NUE and increasing net GHG emission at field scale were predicted as N rate increased. When considering GHG mitigation from fossil fuel replacement, net GHG emission decreased first and leveled off at a N rate of 70–140 kg N ha⁻¹ before increasing. Net economic RTN increased first and peaked when N rate was around 140 kg N ha⁻¹ before decreasing. Fertilization at 140 kg N ha⁻¹ was found to be optimal when using both GHG mitigation and economic criteria.

中文翻译：

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使用DAYCENT模拟氮肥的影响，以优化生物能源高粱生产的经济回报和环境服务

氮肥施用量不当会导致产量和经济损失以及对环境的不利影响。这项研究的目的是探索有前途的生物燃料作物-生物能源高粱[高粱双色（L.）Moench]的最佳氮含量。通过八年的田间试验验证了生物地球化学模型DAYCENT，然后将其用于模拟氮肥对地上生物量碳（C），土壤有机碳（SOC），二氧化碳（ CO ₂）和一氧化二氮（N ₂O）排放。与模拟指标相关联，可以计算出氮的利用效率（NUE），净温室气体（GHG）排放量和净经济收益率（RTN），以确定最佳氮肥利用率。该模型能够重现地上生物量C，SOC，CO ₂和N ₂ O的r ^2分别为0.57、0.47、0.55和0.34的现场测量结果。以0–350 kg N ha ^-1的施肥量以70 kg N ha ^-1的增量进行投影表明，地上生物量C和SOC对氮的增加具有正响应，但在140 kg N ha ^-1以上的增加很少。随着氮肥浓度的增加，预计NUE的下降和净规模GHG排放的增加。当考虑减少化石燃料替代产生的温室气体时，净温室气体排放量首先下降，并在增加之前以70-140 kg N ha ^-1的N速率稳定下来。净经济RTN首先增加，并在N率约为140 kg N ha ^-1之前达到峰值，然后下降。当同时使用温室气体减排和经济标准时，发现140 kg N ha ^-1的施肥是最佳的。