Assessing the impact of soil aggregate size on mineralization of nitrogen in different soils, China

Abstract Soil aggregates play a critical role to support the development of soil nitrogen (N) pools, but the underlying mechanism by which soil aggregate size impacts N mineralization remains unclear. The objective of this study was to determine the effect of aggregate size in soil N mineralization through cultivation experiments of different type soils. The topsoil samples of ten typical profiles in different regions of China were collected, and a series of laboratory column incubation experiments were conducted to quantify the relationship between the distribution of soil aggregate size and the concentration and mass of mineral N (i.e., NH4-N and NO3-N) under N fertilizer addition. The results indicated that the weight of aggregate with different sizes was less affected by the intensity of fertilization, which was mainly influenced by the soil types. In most soils, the weight of soil aggregates of 1–0.5 mm accounted for the largest proportion of aggregates in the five categories (i.e., 5–2 mm, 2–1 mm, 1–0.5 mm, 0.5–0.25 mm, and  65% (highly responsive), 45%–65% (moderately responsive), and