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A long-term field experiment was established in 1990 to evaluate the impact of mineral fertilizer (N and NPK) and organic material (manure and crop residues) application on soil aggregation and organic carbon (C) accumulation in an intensively cultivated grey desert soil in northwestern China. The long-term addition of organic materials with balanced inorganic NPK inputs significantly increased the mass proportion of macroaggregates from 10% in the CK treatment to 34% and 24% in the 1.5MNPK and SNPK treatments (the application of inorganic NPK combined with organic sheep manure and the return of crop residues to the field, respectively). In contrast, the addition of inorganic fertilizer (the N and NPK treatments) had no obvious effect in promoting the percentage of macroaggregates. The application of inorganic fertilizer and abandonment (the CK 0 treatment) only sustained the soil organic carbon (SOC) content. However, the SOC contents were significantly increased by 197% and 19% in the 1.5MNPK and SNPK treatments, respectively, relative to the CK treatment over a 24-year period. Amending the soils with N and NPK mainly increased the organic C concentrations in the silt + clay fraction. In contrast, the application of manure accelerated the accumulation of organic C in all of the aggregate fractions, particularly by increasing the amount of C in the fine intra-aggregate particulate organic matter (iPOM) fraction rather than the coarse iPOM or the silt + clay subfraction. The organic C concentration in the silt + clay fraction was significantly correlated with the mass proportion of macroaggregates (R 2 = 0.9488, P 2 = 0.9477, P

The relationship between soil fauna and different fertilizer management practices is of growing concern. The aim of this research was to investigate the response of soil fauna to fertilization regimes, to explore the relationships among the community of soil animals, soil moisture and crop yields. The application of organic fertilizers (i.e., sheep manure or crop residues) increased crop yields and promoted the number of individuals and species of soil fauna owing to the exogenous organic matter that fertilizers provided for the survival and development of soil fauna. Furthermore, the treatments that applied sheep manure (i.e., sheep manure only or nitrogen, phosphorus, potassium and sheep manure plus) were significantly beneficial for increasing crop yields and diversity of soil fauna compared to treatments with crop residues returned (i.e., crop residues returned only or nitrogen, phosphorus, potassium and crop residues returned to the field) (p &lt, 0.05) due to the response of soil fauna to diverse exogenous nutrients and the effect of soil fertility. Therefore, the finding that soil fauna abundance is significantly positively correlated with soil moisture and crop yield may mean the effects of fertilizer applications on soil animals were partly masked by the soil moisture and crop yield.