Abstract
Abstract. Soil degradation is a major threat for farmers of semi-arid north-central Namibia. Soil conservation practices can be promoted by the development of soil quality (SQ) evaluation toolboxes that provide ways to evaluate soil degradation. However, such toolboxes must be adapted to local conditions to reach farmers. Based on qualitative (interviews and soil descriptions) and quantitative (laboratory analyses) data, we developed a set of SQ indicators relevant for our study area that integrates farmers' field experiences (FFEs) and technical knowledge. We suggest using participatory mapping to delineate soil units (Oshikwanyama soil units, KwSUs) based on FFEs, which highlight mostly soil properties that integrate long-term productivity and soil hydrological characteristics (i.e. internal SQ). The actual SQ evaluation of a location depends on the KwSU described and is thereafter assessed by field soil texture (i.e. chemical fertility potential) and by soil colour shade (i.e. SOC status). This three-level information aims to reveal SQ improvement potential by comparing, for any location, (a) estimated clay content against median clay content (specific to KwSU) and (b) soil organic status against calculated optimal values (depends on clay content). The combination of farmers' and technical assessment cumulates advantages of both systems of knowledge, namely the integrated long-term knowledge of the farmers and a short- and medium-term SQ status assessment. The toolbox is a suggestion for evaluating SQ and aims to help farmers, rural development planners and researchers from all fields of studies understanding SQ issues in north-central Namibia. This suggested SQ toolbox is adapted to a restricted area of north-central Namibia, but similar tools could be developed in most areas where small-scale agriculture prevails.
Highlights
Soil degradation is a major cause of marginal agricultural productivity and food insecurity in sub-Saharan Africa (FAO and ITPS, 2015)
We aim to verify the benefits of using farmers’ field experiences (FFEs) for soil quality assessment, as the development of SQ estimation tools is vital for SQ management in areas where small-scale family agriculture represents a large proportion of land use
Knowledge and descriptions of these local soils were largely shared among the interviewed population, and we did not observe differences based on gender, generations, or studied eco-regions
Summary
Soil degradation is a major cause of marginal agricultural productivity and food insecurity in sub-Saharan Africa (FAO and ITPS, 2015). The state of environmental and soil degradation remains, unclear in the area (Newsham and Thomas, 2011). The selection of SQ indicators adapted to local conditions represents an important step towards sustainable soil management practices (Ditzler and Tugel, 2002). We consider that the SQ is a function of soil properties, intended land use, and management possibilities and goals (Andrews et al, 2004). This definition favours a use-dependent approach, which is in line with farmers’ and local administration’s needs. A bottom-up approach is vital as farmers are the key actors for developing and implementing soil management policy (Mairura et al, 2007)
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