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Plant rhizodeposition — an important source for carbon turnover in soils
Author(s) -
Hütsch Birgit W.,
Augustin Jürgen,
Merbach Wolfgang
Publication year - 2002
Publication title -
journal of plant nutrition and soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 1436-8730
DOI - 10.1002/1522-2624(200208)165:4<397::aid-jpln397>3.0.co;2-c
Subject(s) - sink (geography) , soil water , shoot , chemistry , agronomy , soil organic matter , root system , bulk soil , nitrogen , photosynthesis , nutrient , organic matter , botany , environmental science , biology , soil science , cartography , organic chemistry , geography
The soil organic matter plays a key role in ecological soil functions, and has to be considered as an important CO 2 sink on a global scale. Apart from crop residues (shoots and roots), left over on the field after harvest, carbon and nitrogen compounds are also released by plant roots into the soil during vegetation, and undergo several transformation processes. Up to now the knowledge about amount, composition, and turnover of these root‐borne compounds is still very limited. So far it could be demonstrated with different plant species, that up to 20 % of photosynthetically fixed C are released into the soil during vegetation period. These C amounts are ecological relevant. Depending on assimilate sink strength during ontogenesis, the C release varies with plant age. A large percentage of these root‐borne substances were rapidly respired by microorganisms (64—86 %). About 2—5 % of net C assimilation was kept in soil. The root exudates of maize were mainly water‐soluble (79 %), and in this fraction about 64 % carbohydrates, 22 % amino acids/amides and 14 % organic acids could be identified. Plant species and in some cases also plant cultivars varied strongly in their root exudation pattern. Under non‐sterile conditions the exuded compounds were rapidly stabilized in water‐insoluble forms and bound preferably to the soil clay fraction. The binding of root exudates to soil particles also improved soil structure by increasing aggregate stability. Future research should focus on quantification and characterization of root‐borne C compounds during the whole plant ontogenesis. Apart from pot experiments with 14 CO 2 labeling, it is necessary to conduct model field experiments with 13 CO 2 labeling in order to be able to distinguish between CO 2 originating from the soil C pool and rhizosphere respiration, originating from plant assimilates. Such a separation is necessary to assess if soils are sources or sinks of CO 2 . The incorporation of root‐borne C ( 14 C, 13 C) into soil organic matter of different stability is also of particular interest.