Decline in soil organic carbon (SOC) is one of the most important causes of agricultural ecosystem degradation and food insecurity. Multiple agricultural management practices, such as fertilization and straw additions, affect cropland SOC; however, long-term effects of these practices remain ambiguous. In this study, we evaluated how mineral fertilizers, straw additions, and different tillage methods affected SOC and crop yields in a long-term field experiment (1985–2017) in the North China Plain (NCP). Nine treatments consisting of different tillage methods (CT:conventional tillage; NT: no-tillage) combined with applications of inorganic N (N₀, N₁ and N₂: 0 kg, 225 kg and 375 kg urea-N ha⁻¹ yr⁻¹), inorganic P (P₀, P₁ and P₂: 0 kg, 75 kg and 150 kg P₂O₅ ha⁻¹ yr⁻¹) and straw (S₀, S₁ and S₂: 0 kg, 2250 kg, and 4500 kg ha⁻¹ yr⁻¹) were established. CT-N₀-P₀-S₀ was the control treatment. In all treatments, the SOC content increased rapidly over the first 15 years, which was mainly due to the fact that these plots were wastelands before. The SOC content of treatments with straw additions generally increased faster than treatments without straw additions. Nutrient additions and conventional tillage increased crop yields whereas straw additions had variable effects, with highest crop yields in the CT-N₂-P₂-S₂ treatment. Long-term applications of mineral fertilizer and straw significantly affected SOC and yields (P < 0.0001). Straw additions contributed more than nutrient additions to the explained variance of SOC (19.7 %). P and N contributed most to the total explained variance of wheat yields (43.2 % and 40.9 %, respectively) and maize yields (30.5 % and 38.7 %, respectively). The climate accounted for 23.8 % of the total explained variance of maize yields, however, it contributed only 1.1 % for wheat yields (P = 0.0064). In addition, crop yields were positively correlated with SOC levels. This means that long-term applications of straw can feasibly improve SOC and crop yields, which can satisfy the economic needs of farmers and can also benefit the environment. CT-N₁-P₁-S₂ was eventually identified as the optimal treatment to preserve soil quality and reduce fertilizer use, thereby maintaining the sustainable development of the wheat-maize agricultural system in NCP.

土壤有机碳（SOC）的下降是农业生态系统退化和粮食不安全的最重要原因之一。施肥和添加秸秆等多种农业管理措施会影响农田土壤有机碳含量；但是，这些做法的长期影响仍然不明确。在这项研究中，我们通过华北平原（NCP）的长期田间试验（1985-2017），评估了矿物肥料，秸秆添加和不同耕作方法如何影响SOC和作物产量。九种处理方法，包括不同的耕作方法（CT：常规耕作； NT：免耕）与无机氮（N ₀，N ₁和N _2的施用量：0 kg，225 kg和375 kg尿素-N ha - ¹年）^-1），无机P（P ₀，P ₁和P ₂：0 kg，75 kg和150 kg P ₂ O ₅ ha ^-1 yr ^-1）和稻草（S ₀，S ₁和S ₂：0 kg，2250 kg ，并建立了4500 kg ha ^-1 yr ^-1）。CT-N ₀ -P ₀ -S ₀是对照治疗。在所有处理中，SOC含量在最初的15年中迅速增加，这主要是由于这些地块以前都是荒地。与不添加秸秆的处理相比，添加秸秆的处理的SOC含量通常增加更快。添加营养和常规耕作可提高作物产量，而添加秸秆则具有不同的影响，在CT-N ₂ -P ₂ -S _2中作物产量最高治疗。长期施用矿物肥料和秸秆会显着影响SOC和产量（P <0.0001）。秸秆的添加量比养分的添加量对SOC的解释差异更大（19.7％）。磷和氮对解释的小麦单产（分别为43.2％和40.9％）和玉米单产（分别为30.5％和38.7％）的总方差贡献最大。气候占解释的玉米单产总方差的23.8％，但是，其对小麦单产的贡献仅为1.1％（P = 0.0064）。此外，农作物产量与SOC水平呈正相关。这意味着长期使用秸秆可以切实提高土壤有机碳和农作物产量，既可以满足农民的经济需求，也可以使环境受益。CT-N ₁ -P ₁ -S ₂ 最终将其确定为保持土壤质量和减少肥料使用量的最佳方法，从而保持了NCP小麦-玉米农业系统的可持续发展。