Effects of different organic amendments on soil pore structure acquired by three‐dimensional investigation

Abstract

The application of organic amendments is an important way to improve soil structure. However, the differences in soil pore properties after adding various organic materials are not fully available, which is important for selecting the most suitable material for soil improvement. In this study, soil pore structures in a field experiment amended with different organic materials (maize straw [MS], cattle manure, mixture of MS and cattle manure, biochar, woody peat, and polyacrylamide [PAM]) were determined by digital image analysis and three‐dimensional (3D) investigation, and their changes were quantitatively evaluated. The results showed that all organic material applications reduced the soil bulk density and increased the field capacity and water‐stable macroaggregate content. The 3D information about the soil pore structure showed that MS return was closely related to pore shape parameters. Soil treated with PAM had a low channel and throat number, long channel length and large throat area, all of which affect soil solute migration and crop root growth. A straw and organic fertiliser mixture changed the medium and large porosity (>500 μm) percentage from 1.1% to 9.7%, and the connected/isolated porosity ratio (C/I ratio) increased by 4.7 times. Taken together, our results indicate that the application of organic amendments can effectively improve the soil microstructure in fluvo‐aquic soils of the Huanghuaihai Plain in China, which is consistent with macroscopic physical properties such as bulk density and field capacity. PAM addition can promote the redistribution of air, water and nutrients in the soil. Straw returning can significantly affect the soil pore shape. Among all organic amendments, a straw and organic fertiliser mixture had the most obvious effects on the soil structure, especially on improving soil connectivity. Highlights Computed tomography and digital image processing used to visualise and quantify pore structure of soil treated with organic materials. Applications of various organic amendments reduced bulk density of fluvo‐aquic soil. Field capacity and water‐stable macroaggregates were increased. Straw and organic fertiliser improved soil porosity and connectivity and increased numbers of macropores.

Maize/Soybean Intercropping with Straw Return Increases Crop Yield by Influencing the Biological Characteristics of Soil

“…For example, Song et al reported that straw return and intercropping increased the content of water-stabilized aggregates belonging to the 0.5–1.0 mm and 0.25–0.5 mm grain size classes when compared to a single topdressing pattern [ 33 ]. This could be attributed to the accumulation of a rich carbon source substantially increasing the content of soil water-stable aggregates after the decomposition of straw [ 34 ]. Dou et al found that a straw return treatment on three soil types—black soil and brown soil—led to a marked increase in their content of 0.25–2.0 mm and 0.25–1.0 mm water-stable aggregates vis à vis control soils lacking straw, with black and brown soils showing greater improvement in organic carbon content and stabilization of aggregates, resulting in higher crop benefits [ 35 ].…”

“…For example, Song et al reported that straw return and intercropping increased the content of water-stabilized aggregates belonging to the 0.5-1.0 mm and 0.25-0.5 mm grain size classes when compared to a single topdressing pattern [33]. This could be attributed to the accumulation of a rich carbon source substantially increasing the content of soil water-stable aggregates after the decomposition of straw [34]. Dou et al found that a The high and low contents of water-stable aggregates in soil are closely related to its resistance to impact and erosion [31].…”

Soil pore structure and its research methods: A review

“…The application of various organic fertilizers can reduce soil bulk density, improve soil pore structure in the field, improve soil porosity and connectivity, and increase the number of macropores. However, the specific effects of various organic materials are different, and the effect of straw plus organic ferti-https://doi.org/10.17221/64/2023-SWR lizer is the most obvious (Xuan et al 2022). Organic management (application of organic fertilizers while avoiding chemical fertilizers and pesticides) not only increases the total macroporosity in the soil to the optimal range for plant growth but also optimizes the pore size distribution by increasing the relative porosity of the transmission pores (50-500 μm) (Wang et al 2021a).…”

Soil physics matters for the land–water–food–climate nexus and sustainability

“…Application of organic amendments is another important way towards improving soil structure. According to a field experiment amended with different organic materials including maize straw, cattle manure, biochar, woody peat and polyacrylamide, Xuan et al (2022) quantified soil pore structure characteristics using a three‐dimensional digital image analysis methodology. They found that application of organic amendments generally reduced bulk density of fluvoaquic soil, and increased the field water capacity as well as the amount of water‐stable macroaggregates.…”