Dynamics of Physical Organic Matter Fractions During De-inking Sludge Decomposition
- Alejandro Fierroa,
- Denis A. Angers *b and
- Chantal J. Beauchampa
Replenishment of soil C and N is essential for sustainable revegetation of minesoils. Our study investigated paper de-inking sludge as the organic amendment for revegetating an abandoned sandpit in Québec, Canada. Sludge was incorporated at 0 (check) and 105 Mg dry matter ha−1 before seeding tall wheatgrass (Agropyron elongatum (Host) Beauv.). Nitrogen (at 315, 630 and 945 kg N ha−1) and P (at 52.5 and 105 kg P ha−1) were also applied to all plots. Distribution of C and N was determined periodically in two sizes (<53 μm and >53 μm) and two densities (<1.8 g cm−3 and >1.8 g cm−3) of soil fractions during 823 d. After 823 d, C concentrations were 43 and 69% of those of Day 5, for the low and high N rates, respectively. With time, the proportion of C in the heavy (>1.8 g cm−3) fraction increased from 20 to 55%, but remained near 20% in the fine (<53 μm) fraction. Increasing N rates increased C conservation mainly in the coarse (>53 μm) fraction. The amount of N recovered in all fractions decreased after Day 86, in accordance with a previous litter bag study. Although inorganic N was positively correlated with total N in all fractions, the fine fraction was the best indicator of the size of the mineral N pool. Addition of sludge to the sandpit favored the restoration of C and N pools, and high levels of mineral N increased this effect. Residues became denser but remained relatively coarse during their decomposition.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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