Purpose

Biochar mediation of soil structure and carbon (C) sequestration has been tested, but the underlying mechanisms in this process are poorly understood. We investigated the effects of different organic matter applications on soil aggregation and associated C in Northeast China.

Materials and methods

Non-disrupted soil samples (0–20 cm in depth) were collected from the field improvement experiment (established in 2009) with four addition treatments: (1) corn straw (CS), (2) pig manure compost (PMC), (3) biochar from corncob (BIO), and (4) biochar-based compound fertilizer (BF), of which CS, PMC, and BIO were combined with extra mineral fertilizers including nitrogen (N), phosphorus (P), and potassium (K). Soil aggregate distribution and associated C concentrations were estimated using physical fractionation techniques.

Results and discussion

The CS and PMC additions increased mean weight diameter (MWD), large macroaggregate fractions (>2 mm), and small macroaggregate fractions (0.25–2 mm). In contrast, BIO and BF significantly increased silt + clay fractions (< 0.053 mm). Compared with CS and PMC, applying BIO and BF had limited benefits for soil aggregation. Nevertheless, BIO promoted fine and coarse particulate organic matter (POM) accumulation significantly, and BF promoted fine POM accumulation significantly (within small macroaggregates). The concentrations of mMPOM (POM occluded in microaggregates within small macroaggregates) in BF and mPOM (POM within microaggregates) in BIO were the highest (P < 0.05).

Conclusions

Biochar addition did not significantly improve soil structure compared to corn straw and pig manure compost treatments, but it was beneficial to SOC accumulation. Furthermore, C sequestration in the organic addition treatments was driven by the POM dynamics, and biochar debris was preferentially incorporated into the < 0.25 mm fractions.

中文翻译：

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三种有机资源和生物炭基复合肥对土壤团聚体和有机质的稳定作用

目的

已经对土壤结构和碳（C）固存的生物炭介导进行了测试，但对该过程的潜在机理了解甚少。我们调查了东北地区不同有机质施用对土壤团聚和相关碳的影响。

材料和方法

从田间改良试验（于2009年建立）中收集了未破坏的土壤样品（深度为0-20厘米），并进行了四种附加处理：（1）玉米秸秆（CS），（2）猪粪堆肥（PMC），（ 3）来自玉米芯（BIO）的生物炭，以及（4）基于生物炭的复合肥料（BF），其中CS，PMC和BIO与额外的矿物肥料（包括氮（N），磷（P）和钾（ K）。使用物理分馏技术估算土壤聚集体分布和相关的C浓度。

结果和讨论

CS和PMC的添加增加了平均重量直径（MWD），大颗粒总量（> 2 mm）和小颗粒总量（0.25-2 mm）。相反，BIO和BF显着增加了粉尘+粘土含量（<0.053 mm）。与CS和PMC相比，施用BIO和BF对土壤聚集的益处有限。但是，BIO显着促进了细颗粒有机物和粗颗粒有机物（POM）的积累，而BF显着促进了细POM的积累（在小颗粒聚集体中）。高炉中的mMPOM（小宏观聚集物中的微聚集物中的POM）和BIO中的mPOM（微聚集物中的POM）的浓度最高（P  <0.05）。

结论

与玉米秸秆和猪粪堆肥处理相比，添加生物炭不会显着改善土壤结构，但有利于SOC的积累。此外，有机加成处理中的C固存是受POM动力学驱动的，并且生物炭碎片优先掺入<0.25 mm的馏分中。