wAbstract
@Two native shrubs (Piliostigma reticulatum and Guiera
senegalensis) commonly coexist with crops in fields throughout
the Sahel but aboveground residue is annually coppiced and burned.
An alternative, with potential to improve soil quality, would
be non-thermal return of residues to soils but information is
needed on the potential of residues' to provide nutrients before
such systems can be adopted. The objective of this research was
to characterize carbon (C), net nitrogen (N) and phosphorus (P)
mineralization of shrub residues during decomposition in soil
beneath or outside shrub canopies. Two lab incubation (30 for
118 days) studies (1 for each shrub species/soil type system)
had a 2 by 4 factorial design with two soil sources (beneath or
outside the shrub canopy) and four residue soil amendments (leaf,
leaf+stem, beef manure, or control of soil only). Soils amended
with P. reticulatum or G. senegalensis leaf residues
immobilized N during the first 62 and 76 days, respectively, but
later had net release of inorganic N. The addition of stems to
leaf amendments for both shrub species resulted in net N immobilization
throughout the incubation. manure had positive but shrub residues
negative release of inorganic P. However, if the leached P released
at time zero is included in the summation, all amendments released
more P than the control. Cumulative net release of C, N or P over
the incubation was higher in soil originating from beneath than
outside the shrub canopy except for release of P from soil associated
with G. senegalensis. Residue chemistry was related to
nutrient release, particularly high lignin content of stems, which
corresponded to N immobilization. Our results suggest that none
of the shrub residues when added to soil would potentially provide
short-term plant available N and that additional fertilizer would
be required for optimal crop yield.
Keywords: Carbon; Nitrogen; Phosphorus; Immobilization; Mineralization;
Nutrient cycling; Guiera senegalensis; Piliostigma reticulatum;
Senegalx
1. Introduction
2. Materials and methods
@2.1. Study site
@2.2. Soil, shrub materials sampling and experimental design
@2.3. C, N and P mineralization
@2.4. Soil and plant analysis
@2.5. Kinetic models and statistics
3. Results
@3.1. Chemical composition of soil and plant materials
@3.2. Carbon mineralization
@3.3. Net N mineralization
@3.4. Net P mineralization
@3.5. Mineralization kinetics
4. Discussion
@4.1. Residue source, type and C mineralization
@4.2. Nitrogen and P mineralization
5. Conclusions and perspectives
Acknowledgments
References