Impact of land use on nematode assemblage in three agro-ecological zones of Ghana

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Understanding the types of biological and nutritional degradations is critical in developing practical soil health management strategies in Ghana. To understand the types of biological and nutritional degradations in disturbed and undisturbed landscapes; and the impact of change in land use on soil physicochemical and biological properties, 90 farms (maize and tomato agro-systems) and nine undisturbed sites were sampled in 2012 and 2013 from the semi-deciduous forest, forest-savannah transition and guinea savannah agro-ecological zones of Ghana for laboratory investigations. Farmers were also interviewed to ascertain prevailing cultivation practices in the study areas. This study used nematode assemblage analysis to determine ecological disturbance (PPI, MI and ΣMI), community diversity (H′, λ, N0 and N1), and soil food web structure (BI, CI, SI and EI). Samples were also analysed for soil pH (H2O), organic carbon (OC) total nitrogen (%N), available nitrogen (NO3-+NH4+), P2O5, K2O5, Ca2+, Mg2+ and effective cation exchange capacity (ECEC) to evaluate the levels of physicochemical degradations. Results from the laboratory analysis of 396 and 99 samples for physicochemical and biological properties respectively, were analysed by Residual Maximum Likelihood (RELM) Linear Mixed Model (VSN International, 2011). Results from the study show that the soils were inherently poor, in terms of plant nutrients and naturally fragile, in terms of soil food web condition which were further worsened by cultivation practices. Most farmers continuously cultivated their fields for over 9 years in the Semi-Deciduous Forest and Forest-Savannah Transition zones yet their cultivation practices, were not directed towards maintaining good soil health. Soils from undisturbed sites of all the three agro-ecological zones recorded significantly higher maturity index (ΣMI) than soils from maize and tomato fields, indicating that the current cultivating practices are disturbing the soil’s ecosystem.
A thesis submitted to the Department Of Crop And Soil Sciences, Faculty of Agriculture KNUST, Kumasi in partial fulfilment of the requirement for the award of Master of Philosophy in Crop Protection (Nematology),