Soil macrofauna functional groups and their effects on soil structure, as related to agricultural management practices across agroecological zones of Sub-Saharan Africa

F.O. Ayuke

Research output: Thesisinternal PhD, WU

Abstract

This study aimed at understanding the effects of crop management practices on soil macrofauna and the links with soil aggregation and soil organic matter dynamics, which is key to the improvement of infertile or degrading soils in Sub-Sahara Africa. Soil macrofauna, especially earthworms and termites, are important components of the soil ecosystem and, as ecosystem engineers, they influence the formation and maintenance of soil structure and regulate soil processes, such as organic matter decomposition and nutrient dynamics. In comparison with natural systems, earthworm and termite diversity and abundance were low in fallow, high soil-carbon (C) and low soil-C arable treatments in 12 long-term trial fields across the sub-humid to semi-arid tropical zones in Eastern and Western Africa. Continuous crop production had significant negative effects on earthworm diversity, but little effect on termite diversity, as compared to long-term fallow. Agricultural management resulting in high soil C increased earthworm and termite diversity as compared to low-C soil.Long-term application of manure in combination with fertilizer resulted in higher earthworm diversity and biomass, associated with improved soil aggregation and enhanced C and N stabilization within this more stable soil structure. These practices therefore result in the dual benefits of improving soil physical and chemical properties. A micromorphological study of undisturbed soil thin sections showed that fallowing, conservation tillage plus residue application (in East Africa) and hand-hoeing plus manure (in West Africa) enhanced biogenic soil structure formation, resulting in a well developed soil structure and a continuous pore system characterized by many faunal channels. In contrast,intensive tillage and absence of organic inputs resulted in soil with less biogenic soil structural features. Farmers in Nyabeda, West-Kenya, were aware of the activities and nesting habits of termites, but 90% percent of the farmers perceived termites as pests.This study has shown that the soil macrofauna, especially earthworms, and, to a lesser extent termites, are important drivers of stable soil aggregation in Sub-Saharan agroecosystems, with beneficial effects on soil physical and chemical properties. However, their beneficial impact on soil aggregation is reduced with increasing management intensity and associated soil disturbance due to cultivation. This knowledge is important in designing agricultural management systems aimed at increasing long-term soil fertility in Sub-Saharan Africa.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Wageningen University
Supervisors/Advisors
  • Brussaard, Lijbert, Promotor
  • Pulleman, Mirjam, Co-promotor
  • Vanlauwe, B., Co-promotor, External person
  • Six, J., Co-promotor, External person
Award date11 Jun 2010
Place of Publication[S.l.
Print ISBNs9789085856870
Publication statusPublished - 2010

Keywords

  • farm management
  • crop management
  • soil structure
  • worm casts
  • termitaria
  • ant hills
  • agroecological zones
  • isoptera
  • earthworms
  • africa south of sahara
  • kenya
  • macrofauna

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