Maximizing nitrogen (N) use efficiency [NUE] is commonly identified as a key strategy to improve both agronomic and environmental outcomes; however, interpretation of NUE requires explicit consideration of crop N status. In this study, we derived a set of novel theoretical relationships between the nitrogen nutrition index [NNI] and NUE used to better interpret values for nitrogen uptake efficiency [NUpE] and nitrogen utilization efficiency [NUtE]. A small-plot trial for potato [Solanum tuberosum (L.) ‘Russet Burbank’] was conducted in 2016 and 2017 in Central Minnesota, USA, on a Hubbard loamy sand with six N rate, source, and timing treatments and two irrigation rate treatments. Impacts of treatments on NNI, NUpE, NUtE, NUE, biomass, harvest index, and potential N losses were interpreted within the context of a theoretical quantitative relationship between NUE and NNI. We found that for a constant NNI value, NUtE values increased non-linearly as biomass increased; at an NNI value of 1.0, this relationship defines the critical N utilization efficiency curve. As N rate increased from 40 to 270 kg N ha⁻¹, NUtE significantly decreased from 109.8–69.7 g g⁻¹ N, corresponding with a significant increase in both biomass (from 12.0–17.8 Mg ha⁻¹) and in NNI (from 0.520 to 0.973), respectively. Additionally, we found that potential N losses (e.g., leaching) decreased as NUpE increased, or as total N inputs decreased. Potential N loss was lower in 2016 than 2017 (135 and 187 kg N ha⁻¹, respectively) due to both greater NUpE and lower total N input from all sources in 2016 (0.602 g N g^-1 N and 339 kg N ha^-1, respectively) than in 2017 (0.526 g N g^-1 N and 395 kg N ha^-1, respectively). Interpreting NUE to evaluate agronomic and environmental outcomes requires separate consideration of its constituent factors (e.g., NUpE, NUtE, and HI) and explicit consideration of both NNI and biomass.

最大化氮（N）的利用效率[NUE]通常被认为是改善农艺和环境成果的关键策略。但是，对NUE的解释需要明确考虑作物的N状况。在这项研究中，我们得出了一套氮营养指数[NNI]和NUE之间的新型理论关系，用于更好地解释氮吸收效率[NUpE]和氮利用效率[NUtE]的值。马铃薯的小规模试验[马铃薯[L.]'Russet Burbank']于2016年和2017年在美国明尼苏达州中部的Hubbard壤质砂土上进行，氮肥，氮源，定时处理和两种灌溉速率处理均达到6种。在NUE和NNI之间的理论定量关系的背景下，解释了处理对NNI，NUpE，NUtE，NUE，生物量，收获指数和潜在氮损失的影响。我们发现，对于恒定的NNI值，NUtE值随着生物量的增加而非线性增加；在NNI值为1.0时，此关系定义了临界氮利用效率曲线。当氮含量从40 kg N ha ^-1增加到270 kg N ha ^-1时，NUtE从109.8–69.7 gg ^-1 N显着降低，与两种生物量均显着增加（从12.0–17.8 Mg ha ^-1）和NNI（从0.520到0.973）。另外，我们发现，随着NUpE的增加或总N输入的减少，潜在的N损失（例如，淋失）减少。由于2016年NUpE增加和所有来源的总氮输入量减少（0.602 g N g ^-1 N和339 kg N ha ^--），2016年潜在的N损失低于2017年（分别为135和187 kg N ha ^-1）^。分别比2017年增加¹（分别为0.526 g N g ^-1 N和395 kg N ha ^-1）。解释NUE以评估农艺和环境成果需要分别考虑其构成因素（例如NUpE，NUtE和HI），并明确考虑NNI和生物量。