Soil structure governs the functions of soil in many ecosystems, including those dominated by agriculture, such as water and carbon storage, biomass production, and physical stability. Specifically in tropical and subtropical soils, the long-term impacts of different fertilizers on soil functionality and stability in no-till crops are poorly understood. Under subtropical climate conditions, we evaluated how 17 years of continuous fertilizer application (organic vs. inorganic) on no-till crops affected structure of a sandy loam texture, in terms of the pore size distribution and pore functionality for water storage and aeration, and the intra-aggregate pore geometry. The investigated long-term experiment was implemented in a randomized block design with four repetitions in Santa Maria, Brazil. Treatments were pig slurry (PS), cattle slurry (CS), pig deep litter (pig manure with rice husk; PDL), mineral fertilizer (MF), and an unfertilized control (CL) applied in a no-till system. Soil sampling was done in two depths (0–5 and 5–15 cm) to analyze (i) soil pore size distribution, soil water retention, air permeability and pore continuity indices in core samples (± 98 cm³); and (ii) the intra-aggregate pore system using X-ray computed tomography in macroaggregate samples (± 5 cm). The treatments had different impacts on soil pore functionality and intra-aggregate pore geometry. Only PDL application increased field capacity by around 34 % and the plant available water by about 36 % (compared to all other treatments). Soil air-filled porosity was not affected by fertilizer management in any of the layers. However, in the 0–5 cm layer, fertilizer management had a significant effect on soil air permeability which increased at −6, −10, and −33 kPa matric potential from 6.6, 14.4, and 16.1 µm in CL treatment to 29.5, 34.2, and 43.6 µm in PDL, respectively. The PS and PDL treatments increased the intra-aggregate porosity and provided a continuous, connected pore network. These fertilizers provided increased biomass productivity (PS and PDL) and soil organic matter content (higher in PDL only). Therefore, continuous application of fertilizer with higher carbon input, such as PDL, improved soil structural conditions and crop yield of sandy soil under subtropical climate.

中文翻译：

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长期高碳输入有机肥改善免耕沙土的孔隙几何形状和功能


土壤结构控制着许多生态系统中土壤的功能，包括以农业为主的生态系统，例如水和碳储存、生物量生产和物理稳定性。特别是在热带和亚热带土壤中，不同肥料对免耕作物土壤功能和稳定性的长期影响知之甚少。在亚热带气候条件下，我们评估了免耕作物连续施肥 17 年（有机肥料与无机肥料）如何影响沙壤土的结构，包括孔径分布和储水和通气的孔隙功能，以及聚集体内的孔隙几何形状。所研究的长期实验是在巴西圣玛丽亚以随机区组设计进行的，重复四次。处理方法包括猪粪（PS）、牛粪（CS）、猪深层垫料（带稻壳的猪粪；PDL）、矿物肥料（MF）和免耕系统中施用的未施肥对照（CL）。在两个深度（0-5 和 5-15 cm）进行土壤采样，以分析 (i) 岩心样品中的土壤孔径分布、土壤保水性、透气性和孔隙连续性指数 (± 98 cm3)； (ii) 使用 X 射线计算机断层扫描对大骨料样品进行骨料内部孔隙系统 (± 5 cm)。这些处理对土壤孔隙功能和骨料内孔隙几何形状有不同的影响。仅施用 PDL 即可使田间持水量增加约 34%，植物可用水量增加约 36%（与所有其他处理相比）。土壤充气孔隙度不受任何层肥料管理的影响。然而，在 0-5 cm 层，肥料管理对土壤透气性有显着影响，基质势从 6.6、14 增加到 -6、-10 和 -33 kPa。CL 处理中的 4 和 16.1 µm 分别达到 PDL 中的 29.5、34.2 和 43.6 µm。 PS 和 PDL 处理增加了骨料内孔隙率，并提供了连续、连通的孔隙网络。这些肥料提高了生物量生产力（PS 和 PDL）和土壤有机质含量（仅 PDL 较高）。因此，持续施用碳输入较高的肥料，如PDL，可以改善亚热带气候下沙土的土壤结构条件和作物产量。