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Maintenance of soil organic matter (SOM) is important for soil quality and agricultural productivity. However, little is known about the effects of management practices of different intensities on soil aggregation and SOM dynamics in tropical arable cropping systems of sub-Saharan Africa. We investigated the influence of land use practices and management intensity on soil aggregation and SOM dynamics across 12 long-term field experiments in eastern and western Africa. Aggregate size distribution and SOM were measured in arable systems under contrasting management intensities of high carbon, low carbon and a fallow. Aggregate stability indices and SOM were generally higher in the fallow compared to the arable systems. Fallowing and high carbon inputs in arable soils, significantly improved aggregate stability and carbon (C) and nitrogen (N) stabilization in whole soil, and in aggregate fractions. In contrast, no significant improvements in soil aggregation and C and N stabilization were found when organic inputs were either applied in low quantities or not applied at all, thus resulting in low carbon in soils. Our study showed that fallowing and long-term application of organic amendments alone or in combination with mineral fertilizers were the best among the practices tested in this study, for enhanced C and N stabilization in soils with the subsequent benefits of improving soil physical and chemical properties. These results emphasize the importance of management for sustaining soil quality. It is recommended that fallowing be an integral part of sustainable soil management strategies in these regions. Key words: Soil aggregation, soil organic matter, carbon, nitrogen, management intensity, Introduction Soil aggregate stability, that is the ability of soil aggregates to remain intact when subjected to some stress and soil organic matter (SOM) dynamics have lately received much attention [...]

Certain tree species qualify as multi-purpose trees because they grow quickly, produce food for humans and animals, are drought resistant, provide fuel and prevent erosion. The best of these are seed-pod bearing, or leguminous, and include the ability to fix nitrogen in roots nodules. These species include Prosopis, Leucaena leucocephala, Faidherbia albida, Parkinsonia aculeata, Cassia siamea, Cajanus cajan and Casuarina spp.

The preparation of a bacterial inoculum by starvation is discussed. This involved an investigation of the starvation-survival of a p-nitrophenol (PNP)-degrading isolate taken from an industrial waste lagoon. Changes in cell viability, morphology and its resuscitation on PNP and alternative organic substrates weredetermined as the isolate was subjected to nutrient deprivation. Results indicate that starvation causes the filaments to fragment into individual cells.