Nitrogen Accumulation and Form over Time in Young Mine Soils
1994
Li, R. S. | Daniels, W. L.
Nitrogen deficiency is a common problem during reclamation of mine soils, and limited comprehensive information is available concerning the forms and characteristics of N in Appalachian mine soils. This chronosequence study was conducted to investigate the accumulation, distribution, and component change of N in mine soils over time. Fresh spoil, coal, natural forest soil and 10 mine soil sites with ages ranging from 1 to 30 yr were sampled and analyzed for N components. Young mine soils (> 10 yr) were dominated by seeded grass-legume vegetation, while the older sites supported native mixed hardwoods. There was a considerable amount of indigenous N in the fresh spoils (250–475 mg kg⁻¹), consisting primarily of fixed NH⁺₄ (Fix-N) held in micas and nonhydrolyzable organic N (NoHyOM-N) bound in coal. Both the Fix-N and NoHyOM-N fractions were geologic N, stable in chemical character, and unavailable to plants. With time, N accumulation occurred primarily in the surface 0 to 5 cm, associated with A horizon development. In this layer, soil total N and active N [Act-N, consisting of hydrolyzable organic N (HyOM-N) and exchangeable N (Exch-N)], were significantly correlated with site age. The corrected-N (Corr-N), which was obtained by subtraction of soil total N at 10 to 20 cm from soil total N at 0 to 5 cm at each site, had a much higher correlation coefficient with site age (r = 0.95, P < 0.0001) due to its correction for variation in soil indigenous N content among sites. The annual rate of N accumulation estimated by the Corr-N method was 60.5 mg N kg⁻¹ in soil (<2mm) or 23.4 kg N ha⁻¹ in the top 0 to 5 cm. The total C content of the mine soils was correlated with site age (r = 0.65, P < 0.05), while pH, N availability index, Fix-N, and NoHyOM-N were not.
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