It was shown that the use of biochar provides many benefits to agriculture by improving the whole complex of soil properties, including soil structure. However, the diverse range of biochar effects depends on its physicochemical properties, its application rates, soil initial properties etc. The impacts of biochar, mainly its reapplication to soils and its interaction with nitrogen in relation to water-stable aggregates (WSA) did not receive much attention to date. The aims of the study were: (1) to evaluate the effect of initial application (in spring 2014) and reapplication (in spring 2018) of different biochar rates (B0, B10 and B20 t ha⁻¹) as well as application of biochar with N-fertilizer (40 to 240 kg N ha⁻¹ depending on the requirement of the cultivated crop) on the content of WSA as one of the most important indicators of soil structure quality, (2) to assess the interrelationships between the contents of soil organic matter (SOM) and WSA. The study was conducted in 2017–2019 as part of the field experiment with biochar on Haplic Luvisol at the experimental station of SUA in Nitra, Slovakia. Results showed that initial application as well as reapplication of biochar improved soil structure. The most favorable changes in soil structure were found in N0B20B treatment (with biochar reapplication) at which a significantly higher content of water-stable macro-aggregates (WSAma) (+15%) as well as content of WSAma size fractions of > 5 mm, 5–3 mm, 3–2 mm and 2–1 mm (+72%, +65%, +57% and +64%, respectively) was observed compared to the control. An increase in SOM content, due to both, initial biochar application and its reapplication, significantly supported the stability of soil aggregates, while organic matter including humic substances composition did not.

中文翻译：

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在土壤结构改良的背景下，初次施用和重新施用生物炭的重要性

结果表明，生物炭的使用通过改善整个土壤特性，包括土壤结构，为农业提供了许多好处。但是，生物炭作用的不同范围取决于其物理化学性质，其施用量，土壤的初始性质等。生物炭的影响（主要是其在土壤中的再施用以及与水稳定的骨料（WSA）有关的与氮的相互作用）并未受到影响。迄今为止引起了很多关注。研究的目的是：（1）评估不同生物炭比率（B0，B10和B20 t ha ^-1）的初始施用（2014年春季）和再施用（2018年春季）的效果以及生物炭的施用使用氮肥（40至240 kg N ha ^-1WSA含量是土壤结构质量最重要的指标之一，取决于耕作作物的需求。（2）评估土壤有机质（SOM）含量与WSA之间的相互关系。这项研究于2017-2019年进行，这是在斯洛伐克尼特拉（Nitra）的SUA实验站对Haplic Luvisol进行生物炭实地试验的一部分。结果表明，生物炭的初始施用和再施用可以改善土壤结构。在N0B20B处理（生物炭再施用）中发现了最有利的土壤结构变化，其中水稳性大型骨料（WSAma）含量高得多（+ 15％），并且WSAma粒度级分含量> 5 mm与对照组相比，观察到5–3 mm，3–2 mm和2-1 mm（分别为+72％，+ 65％，+ 57％和+ 64％）。