Background

Phosphorus (P) fertilizer inputs can increase soil P availability, which improves soil carbon (C) cycling and microbial community structure. However, the potential mechanisms via which P drives soil organic carbon (SOC) and microbial regulation of aggregates formation and stabilization are still unclear.

Methods

A 10-year field experiment was conducted, including (1) CK, no fertilization; (2) NK, N and K fertilizer addition; (3) NP1K and (4) NP2K, NK with 28 and 56 kg P ha⁻¹ addition, respectively.

Results

Relative to NK treatment, long-term P fertilizer application significantly increased the proportion of >0.25 mm aggregates and mean weight diameter (MWD), which were increased by 16.4% and 18.0%, respectively. Scanning electron microscopy further confirmed that P addition resulted in better soil structure. Meanwhile, compared with NK treatment, the content of soil exchangeable Ca and SOC (especially stable C=C chemical speciation) was increased with P fertilizer addition, which could form organic-Ca complexes to improve aggregate stability. And compared with NK treatment, the relative abundance of copiotrophic bacteria (i.e., Actinobacteriota) involved in aggregate formation and stability was increased by 11.3% and 8.4% in NP1K and NP2K, respectively. Additionally, redundancy analysis indicated that the main factor for bacterial diversity was available P (AP).

Conclusion

Taken together, P fertilizer addition can increase the content of soil exchangeable Ca and SOC (especially C=C) to form organic Ca complexes, while AP improves the microbial community structure, thereby improving the stability of aggregate structure in saline alkali soil.

中文翻译：

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磷肥如何提高土壤团聚体的稳定性？十年受精实验的证据

背景

磷（P）肥料的投入可以增加土壤磷的利用率，从而改善土壤碳（C）循环和微生物群落结构。然而，磷驱动土壤有机碳（SOC）以及团聚体形成和稳定的微生物调节的潜在机制仍不清楚。

方法

进行了10年的田间试验，包括（1）CK，不施肥； (2) NK、N、K肥添加； (3) NP1K和(4) NP2K、NK，分别添加28和56 kg P ha ^-1。

结果

相对于NK处理，长期施用磷肥显着增加了>0.25 mm团聚体的比例和平均重量直径（MWD），分别增加了16.4%和18.0%。扫描电子显微镜进一步证实磷的添加导致了更好的土壤结构。同时，与NK处理相比，磷肥的添加增加了土壤交换性Ca和SOC（尤其是稳定的C=C化学形态）的含量，可形成有机钙复合物，提高团聚体稳定性。与NK处理相比，NP1K和NP2K中参与聚集体形成和稳定性的富营养菌（即放线菌）的相对丰度分别增加了11.3%和8.4%。此外，冗余分析表明细菌多样性的主要因素是有效磷（AP）。

结论

综合来看，磷肥的添加可以增加土壤交换性Ca和SOC（特别是C=C）的含量，形成有机Ca复合物，而AP则改善了微生物群落结构，从而提高了盐碱土团粒结构的稳定性。