Journal
JOURNAL OF SOILS AND SEDIMENTS
Volume 20, Issue 4, Pages 1824-1833Publisher
SPRINGER HEIDELBERG
DOI: 10.1007/s11368-019-02544-8
Keywords
Long-term fertilization; Organic carbon; Physical particle-sized fractionation; Soil aggregation; Total nitrogen
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Purpose Understanding the underlying mechanism of soil carbon (C) and nitrogen (N) accumulation is of great significance for soil C sequestration and climate change mitigation, as well as soil fertility improvement. The objective of this study was to evaluate the response of C and N accumulation in aggregates and fine soil particles to long-term mineral fertilizer and manure application. Materials and methods Five treatments from a long-term experiment with double maize cropping were examined in this study, i.e., (1) no fertilizer (control); (2) mineral nitrogen, phosphorus, and potassium application (NPK); (3) doubled application rate of the NPK (2NPK); (4) pig manure alone (M); and (5) mineral NPK fertilizers and manure combination (NPKM). By using physical particle-sized fractionation, we analyzed soil organic carbon (OC) and total nitrogen (N), and delta C-13 of OC in bulk soil and aggregates (53-2000 mu m) and, coarse silt-sized fraction (5-53 mu m), fine silt-sized fraction (2-5 mu m), and clay-sized fraction (< 2 mu m) under those five treatments. Results and discussion Fertilizer application for 24 years, particularly M and NPKM treatments, significantly increased the concentration and proportion of OC and total N associated with aggregates and clay-sized fraction as compared with control. Manure application significantly increased the proportion of OC by 6.6-7.8 points in aggregates, whereas it was by 22.6-25.0 points in clay-sized fraction. Clay-sized fraction-associated C and N showed a non-linear response to C and N accumulation in bulk soil, contributing approximately 47% and 69% to soil OC and total N, respectively. Moreover, the mass proportion of aggregates and the mass ratio of aggregates to fine soil particles increased significantly with C accumulation in fine silt-sized and clay-sized fraction. Conclusions Organic carbon and total nitrogen accumulation in soil clay-sized particles play important role in soil C and N sequestration in red soil. Our results also suggested that C accumulation in fine soil particles might benefit soil aggregation in intensive cropping system of South China.
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