Preservation of Plant Residues in Soils Differing in Unsaturated Protective Capacity
- Jan Hassink
This study tested the hypothesis that the decomposition of applied residue C in soil is not determined by soil texture per se but by the degree of saturation of the protective capacity of a soil. Soil protective capacity is defined as the maximum amount of C associated with clay and silt (<20 µm) in grassland and uncultivated soils. To test this hypothesis, 14C-labeled ryegrass (grown in a phytotron and continuously labeled with 14CO2; specific activity 546 Bq mg-1 C) was mixed with 11 soil samples differing in texture and saturation deficit, the latter being the difference between the actual and the maximum amount of C associated with the <20-µm fraction. After 3 d of incubation, the percentage of applied 14C that had respired showed a significant correlation (r = −0.85) with the saturation deficit. After 53 d of incubation, the amount of 14C respired showed a significant correlation with the saturation deficit of the fine-textured soils (r = −0.88), but not with those of coarse-textured soils. The correlation between 14CO2 production and soil texture was weak. The results confirm the hypothesis that the degree of saturation of the protective capacity of a soil predicts the decomposition rate of residue C better than does soil texture alone.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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