Abstract The few available studies on maize biomass in soil of field experiments have shown that belowground maize biomass resides more than twice as long as aboveground residues. Our principal objective was to investigate the effect of maize crop residue incorporation on the long-term dynamics of soil organic carbon (SOC) for a selection of croplands with sandy to sandy loam texture in Flanders, Belgium. After a period of more than 20 years, we resampled 31 and 29 parcels that had either silage maize (MS, only belowground biomass input) or grain maize (MG, both above- and belowground biomass input) dominated crop rotations. Changes in maize-derived SOC (Cmaize) of MS and MG systems between 1993 and 2018 were evaluated by detecting SOC content and its δ13C value. In addition, a 140-day incubation experiment (at 20.5 °C) was carried out to compare the stability of Cmaize and the related nitrogen (N) mineralization between the MG and MS fields. After two decades, δ13C raised 2.4 and 2.6‰, while Cmaize increased 1.6 and 2.2 g kg−1 in MS and MG systems, respectively. The estimated average humification coefficient over this period of maize-C was 0.11 for the MS system, about twice as that of the MG system (0.06). This reconfirms findings of stronger contribution of belowground biomass versus aboveground residues to stabilized SOC pools over the medium to long term. By the end of the incubation, on average 10.4% and 11.6% of Cmaize had been decomposed in the MS and MG soils, respectively. These Cmaize mineralization rates were statistically equal for the two systems, which indicates that mainly belowground biomass remained in the soils. Also, net N mineralization was indifferent to the crop rotations (MS: 58.8 mg N kg−1 and MG: 52.6 mg N kg−1). To reconcile the two main observations in this study, we hypothesize that the lower preservation of shoot-C could be manifested on a shorter term. Detailed research is needed to determine the time scale of increased stabilization of root-C versus shoot-C under field conditions.

中文翻译：

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玉米的地上和地下碳输入对土壤有机碳的贡献：来自比利时农田 20 年后 13C/12C 解析重采样活动的结论

摘要 田间试验对土壤中玉米生物量的少数现有研究表明，地下玉米生物量的存在时间是地上残留物的两倍多。我们的主要目标是研究玉米作物残留物掺入对比利时佛兰德斯选择具有沙质至沙质壤土质地的农田土壤有机碳 (SOC) 长期动态的影响。经过 20 多年的时间，我们重新采样了 31 和 29 个地块，这些地块以青贮玉米（MS，仅地下生物量输入）或谷物玉米（MG，地上和地下生物量输入）主导作物轮作。通过检测 SOC 含量及其 δ13C 值，评估了 1993 年至 2018 年间 MS 和 MG 系统的玉米衍生 SOC（Cmaize）的变化。此外，还有一个 140 天的孵化实验（在 20. 5 °C) 进行了比较 Cmaize 的稳定性和 MG 和 MS 字段之间相关的氮 (N) 矿化。20 年后，在 MS 和 MG 系统中，δ13C 分别增加了 2.4 和 2.6‰，而 Cmaize 分别增加了 1.6 和 2.2 g kg-1。在此期间，MS 系统估计的玉米-C 平均腐殖化系数为 0.11，约为 MG 系统（0.06）的两倍。这再次证实了地下生物量与地上残留物对中长期稳定 SOC 库的更大贡献的发现。到孵化结束时，平均 10.4% 和 11.6% 的 Cmaize 在 MS 和 MG 土壤中被分解。这两个系统的这些 Cmaize 矿化率在统计上是相等的，这表明主要地下生物量保留在土壤中。还，净氮矿化与轮作无关（MS：58.8 mg N kg-1 和 MG：52.6 mg N kg-1）。为了调和本研究中的两个主要观察结果，我们假设茎 C 的较低保存可以在短期内表现出来。需要详细的研究来确定在田间条件下根 C 与地上部 C 稳定性增加的时间尺度。