The enigma of soil nitrogen balance sheets originally described by Allison in 1955 has endured for 65 years. Originally the accounting showed a positive balance between N gains and losses, which indicated a failure to measure all losses, widely suspected of being gaseous N emissions. Measurement of organic, inorganic and gaseous N forms derived from 15N-enriched nitrate added to soils under both anaerobic and aerobic conditions in small- to medium-scale short-term experiments in closed vessels without plants, demonstrated that it is possible to achieve a complete 15N balance. A recent partial N balance at the global scale of the three main cereal crops over a 50-year time span showed a negative balance between N gains and losses, indicating a failure to measure all N gains or to accurately measure net changes in total soil N to a sufficient soil depth. Therefore, if the enigma is to be resolved in a realistic agronomic setting, fundamental decisions need to be made regarding the approach to be adopted, the cereal crop to be studied, the nature of the measurements required and their temporal and spatial scales.

中文翻译：

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土壤氮平衡表之谜何在？

艾利森在 1955 年最初描述的土壤氮平衡表之谜已经持续了 65 年。最初的核算显示氮收益和损失之间存在正平衡，这表明未能衡量所有损失，广泛怀疑是气态氮排放。在没有植物的密闭容器中进行的中小型短期实验中，在厌氧和好氧条件下对土壤中添加的富含 15N 硝酸盐的有机、无机和气态氮形式的测量表明，有可能实现完全15N 平衡。最近 50 年时间跨度内三种主要谷类作物在全球范围内的部分氮平衡显示氮的收益和损失之间存在负平衡，表明未能测量所有 N 增益或准确测量土壤总 N 的净变化到足够的土壤深度。因此，如果要在现实的农艺环境中解开这个谜团，就需要就所采用的方法、要研究的谷物作物、所需测量的性质及其时空尺度做出基本决定。