PK12:Soil macrofauna Biodiversity, Soil structure and Organic Resource Management in East and West African cropping systems
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The document discusses the role of soil macrofauna, particularly earthworms and termites, as ecosystem engineers that enhance soil structure and fertility in Sub-Saharan Africa. It examines how climate and agricultural management impact the biodiversity of these species, revealing that agricultural practices reduce their diversity compared to fallow systems. It concludes that effective agricultural management should aim to increase soil fertility while conserving soil biodiversity through integrated practices.
PK12:Soil macrofauna Biodiversity, Soil structure and Organic Resource Management in East and West African cropping systems
- 1. 5/27/2010 Soil macrofauna as ecosystems engineers Soil macrofauna Biodiversity, Soil structure and Organic Resource Management in East and West African Earthworms and termites are important cropping systems ecosystem engineers (Jones et al. 1994). Their role in sustainable crop Fredrick Ayukea*, b, Mirjam Pullemana, Lijbert Brussaarda, Johan Sixc, Bernard production includes: Vanlauweb Improve soil structure & water retention Earthworms Lavelle et al. 1998 Microbial Soil water content OM degradation Incorporate organic material into soil activities Improved Improve soil fertility through organic matter decomposition and nutrient Water Infiltration rate release *a Department of Soil Quality, Wageningen University, P.O Box 47, NL-6700 AA Wageningen, The Netherlands Nutrient uptake Clay transfer & b Tropical Soil Biology and Fertility (TSBF) Institute of CIAT, P.O Box 30677-00100, Nairobi, Kenya transformation N c Department of Plant Sciences, University of California, Davis, CA 95616, USA Termites (Courtesy of Soulemayne Konate) Objectives & Hypotheses Objectives continued: This study aimed at: 1. Assessing effects of climate and agricultural management on earthworm and termite biodiversity across SSA 2. Explore relations between soil macrofauna (earthworms and termites), soil aggregation and SOM dynamics in Hypotheses differently managed agro-ecosystems” Biodiversity of earthworms and termites will: Specifically: a) the extent to which soil macrofauna explains 1. Decrease with increasing temperature and decreasing differences in aggregation across a wide range of climatic precipitation and soil conditions in SSA, and b) compare these relationships between arable and 2. Be lower in agricultural than in fallow systems fallow systems representing different levels of management intensity. 3. Be higher under long-term agricultural management that had led to high-C soils than where it had led to low-C soils Materials & Methods Sub-humid AEZ Semi-arid AEZ Study sites Long-term trials across the sub-humid to semi-arid agroecological zones of East & Fallow West Africa Shrubland Bush Shrubland The trials differed in management of: Organic resources Mineral N High-C Rotation T. candida-maize S. siamea+NPK Millet-cowpea Tillage Low-C Maize, no input Maize, no input Millet, no input KENYA NIGERIA NIGER 1
- 2. 5/27/2010 Results Earthworms Soil macrofauna biodiversity Millsonia inermis, Saria, Burkina Faso 20 earthworm taxa in 3 families: Ocnerodrilidae (4 taxa) Acanthodrilidae (8 taxa) Eudrilidae (8 taxa) Earthworm and termite taxonomic richness and functional groups Termites based on monolith and transect methods Earthworm taxa Termite taxa Functional Functional Food Taxonomic group Taxonomic group group a group b type c Ocnerodrilidae Rhinotermitidae-Rhinotermitinae Nematogenia lacuum Endogeic Captotermes intermedias I WLG Gordiodrilus robustus Endogeic Schedorhinotermes lamanianus I WLG Gordiodrilus wemanus Endogeic Rhinotermitidae-Psammotermitinae Gordiodrilus marcusi Endogeic Psammotermes hybostoma I WLG Acanthodrilidae Termitidae-Nasutitermitinae Millsonia inermis Endogeic Nasutitermes spec II WLG Endogeic Trinevitermes spec II LG 20 termite taxa in two families: Millsonia guttata Dichogaster (Dt.) saliens Epigeic Termitidae-Macrotermitinae Dichogaster (Dt.) affinis Epigeic Ancistrotermes cavithorax II WLG Epigeic II FWLG Termitidae (17 taxa) Dichogaster (Dt.) bolaui Macrotermes nr. Vitrialatus Dichogaster (Dt.) modiglianii Di h t (Dt ) di li ii Epigeic E i i Macrotermes subhyalinus M t bh li II FWLG Dichogaster (Dt.) spec nov 1 Epigeic Macrotermes herus II FWLG Dichogaster (Dt.) spec nov 2 Epigeic Microtermes pusillas II FWLG Rhinotermitidae (3 taxa) Eudrilidae Polytoreutus annulatus Epigeic Macrotermes spp. Microtermes spp. II II FWLG FWLG Hyperiodrilus africanus Epigeic Odontotermes magdalenae II FWLG Hyperiodrilus spec nov Epigeic Odontotermes spp. II FWLG Eudrilus buettneri Epigeic Pseudacanthotermes spiniger II FLG Ephyriodrilus afroccidentalis Epigeic Pseudacanthotermes spp II FLSD Eminoscolex violaceus Epigeic Termitidae-Termitinae Stuhlamannia spec nov Epigeic Amitermes-Amitermes stephensoni II WLSD M. bellicosus, Tamale (Ghana) Lavellea spec nov Epigeic Microcerotermes parvulus II WLG Termes-Termes baculi III WS Cubitermes- Tubeculitermes spec IV S a Based on classification by Swift & Bignell (2001). (W=wood; L=leaf litter; S=soil; D=Dung/manure; F=fungus grower; G=dead/dry grass. bBased on classification by Eggleton et al. (2002). c based on field notes/observation. c based on observations by Kooyman & Onck (1987). RDA biplot on earthworm species abundance and environmental variables RDA biplot on termite species abundance and environmental variables Axis 1: temperature/altitudinal gradient Axis 1: precipitation/latitudinal gradient Axis 2: Soil C/latitudinal gradient Axis 2: temperature/texture/ longitudinal gradient. Axes partition sites that are cooler and are at high altitudes from lower relatively hotter altitudes More taxa occur on warmer/drier sides Earthworm taxa are less abundant on the higher, cooler altitudes characteristic of East African sites Axes mainly separate East & West Africa. 2
- 3. 5/27/2010 Shannon diversity indices across fallow and arable systems Treatment Arable system Soil Macrofauna and ecosystem functioning Fallow High-C Low-C P-value Earthworm diversity 0.13a 0.07b 0.02c <0.001 (H′) Termite diversity (H′) 0.08a 0.06a 0.03b 0.008 Factor analysis and factor pattern after varimax rotation Possible attributes: factor & multiple regression analysis Treatment Fallow Arable system Fallow system Factor I Factor II Factor I Factor II (n=36) Arable system (n=72) Termite Variable Factor I Factor II Factor I Factor II SOM, (abundance & Termite Shannon index −0.1 0.5 −0.1 0.2 Texture, biomass), Earthworm Shannon index 0.5 −0.4 −0.1 0.7 Climate, Termite Earthworm Termite abundance 0.2 0.6 0.2 0.7 Earthworm (Shannon (Shannon (Shannon diversity, diversity, Earthworm abundance 0.6 −0.3 0.0 0.7 Possible diversity & abundance & SOM, Texture, abundance and Termite biomass 0.3 0.7 0.3 0.6 attributes abundance) biomass) Climate biomass) Earthworm biomass −0.1 −0. 8 −0.2 0.6 Average t A temperature t −0.9 09 02 −0.2 −0.9 09 01 −0.1 Precipitation 0.7 0.1 0.7 0.0 Multiple regression analysis with aggregate fractions and factors with loading coefficients >0.05 Total organic C 1.0 0.1 1.0 0.0 (%variance accounted for by factors) Total Total organic N 1.0 0.1 1.0 0.0 macroaggregates Clay 0.9 0.3 0.9 −0.1 (sand corrected) 88.5 4.1 90.4 7.6 Sand −0.9 −0.1 −0.9 0.1 Microaggregates within Factor eigenvalues 5.6 2.0 5.1 2.4 macroaggregates (mM) 82.6 4.9 91.3 8.7 Explained variance (%) 45.9 17.8 42.6 20.0 Conclusions Conclusions continued: Macrofauna, especially earthworms, and to a lesser extent Differences in climate coincide with differences in soil types and geographical region. These factors are termites, are important drivers of stable soil aggregation, in associated with earthworm and termite diversity conjunction with climate, soil organic C content and soil texture in Sub-Saharan agroecosystems Agriculture has negative effects on earthworm and termite diversity as compared to long-term fallow The beneficial impact of earthworms and termites on soil aggregation is reduced with increasing management intensity Under continuous crop production, agricultural (e.g. soil disturbance due to cultivation) management that resulted in low-C soils had lower earthworm and termite diversity than agricultural management that had resulted in high-C soils Our results are important for designing agricultural management systems aimed at increasing long-term soil fertility in Sub-Saharan Africa. 3
- 4. 5/27/2010 Recommendations from this study: General recommendations: The agroecological conditions studied, i.e: As mineral and organic fertilizers are often limited in quantity and quality, soil fertility research has to focus on developing integrated management Long-term application of manure in combination with fertilizer strategies to address soil fertility decline (Integrated Soil Fertility Conservational tillage plus maize stover residue application; Management (ISFM) and Conservation Agriculture (CA)) Hand-hoeing plus manure affect faunal activities in different ways. Hence: As the soil biota are responsible for the key ecosystem functions of decomposition and nutrient cycling, soil organic matter synthesis and recommendation of these practices should be tailored to mineralization, soil structural modification, aggregate stabilization, ISFM f S meet the circumstances of target farmers & CA have to maximize beneficial soil biota. Although there is pressure on land in many parts of Sub-Saharan Africa fallowing (or similar practices) has to be an integral part of land management in view of the conservation of biodiversity for enhanced ecosystem functioning Acknowledgements WOTRO/NWO through Wageningen University for awarding the Scholarship and Research funds and Norman E. Borlaug LEAP through UC-Davis and the International Atomic Energy Agency (IAEA) for co-funding the research Collaborating Institutions TSBF-CIAT, KEFRI, Kenyatta University (Nairobi, Kenya) INERA, INERA IFDC (Burkina Faso) Others: IITA-Nigeria, SARI-Ghana, ICRISAT-Niger, KARI-Kenya, CHITEDZE Agricultural Inst. It was a teamwork for cooperating during periods of data collection Special thanks to all my promoters and in particular Prof. Lijbert Brussaard for sending me off on the long journey. 4