Estimates of soil nitrogen (N) stocks are important for assessing potential nitrogen oxide emissions due to land-use changes and agricultural practices. No comprehensive data set exists for N stocks for the 850,000 km² of the semiarid Brazilian northeastern region, according to land use and soil classes. Changes in N stocks due to the conversion of caatinga to pasture or agriculture, in different soil classes, were quantified in 201 soil profiles down to 1 m deep, except in shallower soils (Leptosols, 50 cm; Luvisols, and Planosols, 80 cm). Acrisols, Arenosols, and Regosols had the larger N stocks (8.07 to 9.72 Mg ha⁻¹) than Ferralsols (6.10 Mg ha⁻¹), whose stocks were similar to those of the shallower soils (5.87 to 6.72 Mg ha⁻¹). The conversion of dense caatinga to agricultural fields caused reductions in 23% in N stocks. The soils of the semiarid Brazilian region accumulate 612 Tg of N in the top 1 m in the different classes of soils and land uses, being 226.8 Tg under dense caatinga, 145 Tg under open caatinga, 168 Tg under pastures, and 70 Tg under crop fields. This study contributes to elucidating N dynamics in different soil classes and land uses, and it is the most complete cover of soil N stocks in the semiarid region of Brazil. The results highlight the importance of preserving native vegetation and the need to identify and foster the adoption of agricultural management practices to maintain and restore soil N stocks.

对土壤氮（N）储量的估算对于评估由于土地利用变化和农业实践而产生的潜在氮氧化物排放非常重要。根据土地利用和土壤类别，没有关于巴西半干旱东北地区850,000 km ²的N储量的综合数据集。在不同土壤类型中，从caatea转换为牧场或农业而导致的N储量变化，在深度小于1 m的201种土壤剖面中进行了量化，但在较浅的土壤中（Leptosols，50 cm； Luvisols和Planosols，80 cm）除外。 。Acrisols，Arenosols和Regosols的N储量（8.07至9.72 Mg ha ^-1）大于Ferralsols（6.10 Mg ha ^-1），后者的储量与较浅土壤（5.87至6.72 Mg ha ^-1）相似。）。稠密的caatinga向农业领域的转化导致氮资源减少了23％。巴西半干旱地区的土壤在不同土壤和土地利用类别的前1 m中累积612 Tg的氮，在密集的caatinga下为226.8 Tg，在开放的caatinga下为145 Tg，在牧场下为168 Tg，在作物下为70 Tg领域。这项研究有助于阐明不同土壤类别和土地利用中的氮动态，它是巴西半干旱地区土壤氮储量最完整的覆盖面。结果强调了保护本地植被的重要性，以及确定和促进采用农业管理实践以维持和恢复土壤氮素储量的必要性。