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Contributions of incorporated residue and living roots to aggregate‐associated and microbial carbon in two soils with different clay mineralogy
Author(s) -
Denef K.,
Six J.
Publication year - 2006
Publication title -
european journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 1351-0754
DOI - 10.1111/j.1365-2389.2005.00762.x
Subject(s) - residue (chemistry) , chemistry , soil water , kaolinite , illite , mollisol , clay minerals , agronomy , mineralogy , environmental chemistry , soil science , geology , organic chemistry , biology
Summary We conducted a study to investigate the role of aggregates in the stabilization of residue‐ and root‐derived C in an illitic Mollisol and a kaolinitic Oxisol under the following treatments: (i) incorporated residue, (ii) growing plants, and (iii) both incorporated residue and growing plants. Residue‐C dynamics were followed in soils incubated with 13 C‐labelled wheat residue with and without unlabelled growing wheat plants. Root‐C was traced by growing wheat plants with and without unlabelled wheat residue in a 13 CO 2 ‐labelling chamber. After 46 and 76 incubation days, residue‐ and root‐C were measured in four aggregate size classes and in microbial‐C. Both soils had greater residue‐derived than root‐derived total aggregate‐associated C at day 76, which we attributed to the larger residue‐C than root‐C inputs at the start of the experiment. On an aggregate basis, the ratio of residue‐derived over root‐derived C decreased in most size fractions over time, indicating a greater potential for longer‐term root‐C than residue‐C stabilization by aggregates in both soils. At both sampling days, all aggregates > 53 µm had greater residue‐C concentrations in the illitic soil than in the kaolinitic soil and this difference increased with increasing aggregate size. This suggested a greater affinity of illite clay than kaolinite clay to bind with fresh residue‐derived compounds into larger aggregates and hence a greater importance of aggregates in stabilizing residue‐C in illitic compared with kaolinitic soils. The stabilization of root‐C by aggregates was less affected by clay mineralogy and thus less dependent on the affinity of clay minerals to bind with root‐derived compounds.