Abstract
BackgroundLong-term fertilisation has a large influence on soil physical and chemical properties in agro-ecosystems. The effects on the distribution of aggregates, however, are not fully understood. We determined the dynamic change of the distribution of aggregates and soil organic carbon (SOC) content over time in a long-term field experiment established in 1998 on the Loess Plateau of China and illustrated the relationship between them.MethodsWe determined SOC content and the distribution of aggregates in nine fertiliser treatments: manure (M); nitrogen (N); phosphorus (P); M and N; M, N, and P; M and P; N and P; bare land; and an unfertilised control. These parameters were then used for a path analysis and to analyse the fractal dimension (Dv).ResultsThe organic fertiliser increased SOC content. The proportions of 0.1–0.25 mm microaggregates and 0.25–0.5 mm macroaggregates were higher and the proportion of the 0.01–0.05 mm size class of the silt + clay fraction was lower in the treatments receiving organic fertiliser (M, MN, MNP, and MP) than that in the control, indicating that the addition of organic fertiliser promoted aggregation. The distribution of aggregates characterised by their fractal dimension (Dv), however, did not differ among the treatments.DiscussionDv was strongly correlated with the proportion of the <0.002 mm size class of the silt + clay fraction that did not differ significantly among the treatments. The change in the distribution of aggregates was strongly correlated with SOC content, which could produce organic polymer binding agents to increase the proportion of larger particles. Long-term application of organic fertiliser is thus necessary for the improvement and maintenance of soil quality in semi-arid agricultural land when residues are removed.
Highlights
Soil organic carbon (SOC) is important for the long-term sustainability of agro-ecosystems and the environment, because it promotes aggregation, improves soil physical properties and water retention, and increases productivity and the activity of soil organisms (Paradelo, Virto & Chenu, 2015; Haynes & Naidu, 1998)
soil organic carbon (SOC) content was significantly higher in the treatments receiving organic fertiliser (M, M and N (MN), M and P (MP), and MNP) than in the treatments receiving mineral fertiliser (N, N and P (NP), and P) or in bare land (BL) or CK
Dv could not distinguish among the various treatments, even though it can well describe the changes in the stability of aggregates and soil structure associated with vegetative succession (Xiao et al, 2014; Zhao et al, 2006), because Dv was positively correlated with the proportion of the
Summary
Soil organic carbon (SOC) is important for the long-term sustainability of agro-ecosystems and the environment, because it promotes aggregation, improves soil physical properties and water retention, and increases productivity and the activity of soil organisms (Paradelo, Virto & Chenu, 2015; Haynes & Naidu, 1998). We determined SOC content and the distribution of aggregates in nine fertiliser treatments: manure (M); nitrogen (N); phosphorus (P); M and N; M, N, and P; M and P; N and P; bare land; and an unfertilised control. These parameters were used for a path analysis and to analyse the fractal dimension (Dv). The change in the distribution of aggregates was strongly correlated with SOC content, which could produce organic polymer binding agents to increase the proportion of larger particles. Long-term application of organic fertiliser is necessary for the improvement and maintenance of soil quality in semi-arid agricultural land when residues are removed
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