Comparing Rainfall Use Efficiency Trends with Expert Judgments for Nation-Wide Land Degradation Assessments: The Case of Senegal

Sonneveld, B.G.J.S.; Bai, Z.G.; Ndiaye, Déthié Soumaré; Bindraban, P.S.

doi:10.5539/jsd.v5n8p116

Cited by 4 publications

(6 citation statements)

References 43 publications

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“…Of course, one could question the reliability of the expert judgments. However, as already stated, Sonneveld et al (2012) proved for Senegal that expert judgments were consistent in that experts gave the same erosion classification VS-Fast for land degradation assessment 629 for sites that had similar characteristics (soil, rainfall, land use) and with the same degree of land degradation. Figure 4 depicts by GAA the average VS-Fast score for each of the three classes that were assigned by the experts.…”

Section: Discussionsupporting

confidence: 62%

“…However, as already stated, Sonneveld et al . () proved for Senegal that expert judgments were consistent in that experts gave the same erosion classification for sites that had similar characteristics (soil, rainfall, land use) and with the same degree of land degradation.…”

Section: Resultsmentioning

confidence: 86%

“…Sonneveld () and Sonneveld & Dent () addressed these concerns and show that expert assessments are reasonably consistent, fairly reproducible while class boundaries can be interpreted quantitatively when ordered expert judgments are related to quantitative degradation assessments. The experts that were consulted in this study showed high consistency in their degradation assessments (Sonneveld et al ., ) and we considered them as a reliable source for the soil degradation assessment in this project.…”

Section: Introductionmentioning

confidence: 99%

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Using the VS‐Fast methodology for soil degradation assessment: a case study from Senegal

Sonneveld

McGarry

Ndiaye

2012

Soil Use and Management

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Soil degradation threatens sustainable food production and accelerates global warming. Poorer countries, whose agricultural sectors are highly dependent on their natural resource bases, are hit particularly hard by declining soil productivity. Calls for soil‐quality monitoring are therefore, justified and this could inform decision‐makers on the preparation of appropriate interventions. However, the provision of monitoring methodologies is not an easy task. Soil degradation affects several soil characteristics that at larger scales cannot be evaluated with models or remote‐sensing techniques. Therefore, this study focuses on investigating the use of field‐based soil assessment methodologies to differentiate degrees of soil degradation. Specifically, we test the Visual Soil Field Assessment Tool (VS‐Fast) for detecting and monitoring soil degradation using a cross‐section of 71 sites in Senegal, the soil quality of which were classed by local experts. We found low correlation between VS‐Fast classes and expert assessments. By using an ordered logit model to quantify class boundaries, we show that experts categorized areas as ‘degraded’ for a wider range and higher VS‐Fast scores than the corresponding VS‐Fast class. Yet, from general linear models and analysis of variance procedures we found that areas classed by experts as ‘degraded’ had statistically significant lower VS‐Fast scores compared to those that were judged as ‘normal’ and ‘good’, while differences of the VS‐Fast scores between the latter two were negligible. It is remarkable that the visual assessment, the cheaper component of the VS‐Fast score, performs better in differentiating degradation status than its measured counterpart. The results support the need to investigate the applicability of other VSA methodologies that only use field observations and tactile methods.

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Section: Discussionsupporting

confidence: 62%

Section: Resultsmentioning

confidence: 86%

Section: Introductionmentioning

confidence: 99%

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Using the VS‐Fast methodology for soil degradation assessment: a case study from Senegal

Sonneveld

McGarry

Ndiaye

2012

Soil Use and Management

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“…Sonneveld et al (2012) tested the consistency of these expert judgements by a cross-comparison of mapping units with identical characteristics for annual rainfall, soil suitability, slope, population density, and livestock density. The study concluded that experts had a high consistency in their judgement and gave reliable assessment on the degree of land degradation.…”

Section: Land Degradation In Senegalmentioning

confidence: 99%

Quantifying the impact of land degradation on crop production: the case of Senegal

2016

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Abstract. Land degradation has been a persistent problem in Senegal for more than a century and by now has become a serious impediment to long-term development. In this paper, we quantify the impact of land degradation on crop yields using the results of a nationwide land degradation assessment. For this, the study needs to address two issues. First, the land degradation assessment comprises qualitative expert judgements that have to be converted into more objective, quantitative terms. We propose a land degradation index and assess its plausibility. Second, observational data on soils, land use, and rainfall do not provide sufficient information to isolate the impact of land degradation. We, therefore, design a pseudo-experiment that for sites with otherwise similar circumstances compares the yield of a site with and one without land degradation. This pairing exercise is conducted under a gradual refining of the classification of circumstances, until a more or less stable response to land degradation is obtained. In this way, we hope to have controlled sufficiently for confounding variables that will bias the estimation of the impact of land degradation on crop yields. A small number of shared characteristics reveal tendencies of "severe" land degradation levels being associated with declining yields as compared to similar sites with "low" degradation levels. However, as we zoom in at more detail some exceptions come to the fore, in particular in areas without fertilizer application. Yet, our overall conclusion is that yield reduction is associated with higher levels of land degradation, irrespective of whether fertilizer is being applied or not.

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“…This resulted in more intensive forms of agriculture, while demand for fertile land gradually came to exceed availability (Mortimore et al, 2005), which gave rise to Senegal's first large wave of rural-urban migration in the period 1971-1980(Mbow et al, 2008. Reform policies undertaken in the 1980s and implemented as the Structural Adjustment Programme reduced the state involvement but had detrimental effects on soil fertility management as fertilizer subsidies were abolished, and even the application of locally produced phosphorus became too expensive for Senegalese farmers to use (Speirs and Olson, 1992).…”

Section: Land Degradation In Senegalmentioning

confidence: 99%

Quantifying the impact of land degradation on crop production: the case of Senegal

Sonneveld¹,

Keyzer²,

Ndiaye³

2015

Preprint

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Abstract. Land degradation has been a persistent problem in Senegal for a long time and by now has become a serious impediment to long term development. In this paper, we quantify the impact of land degradation on crop yields using the results of a nation-wide land degradation assessment. For this, the study needs to address two issues. First, the land degradation assessment comprises qualitative expert judgments that have to be converted into more objective, quantitative terms. We propose a land degradation index and assess its plausibility. Second, observational data on soils, land use and rainfall do not provide sufficient information to isolate the impact of land degradation. We, therefore, design a pseudo-experiment that for sites with otherwise similar circumstances compares the yield of a site with and one without land degradation. This pairing exercise is conducted under a gradual refining of the classification of circumstances, until a more or less stable response to land degradation is obtained, In this way, we hope to have controlled sufficiently for confounding variables that will bias the estimation of the impact of land degradation on crop yields. A small number of shared characteristics reveal tendencies of "severe" land degradation levels being associated with declining yields as compared to similar sites with "low" degradation levels. However, as we zoom in at more detail some exceptions come to the fore, in particular in areas without fertilizer application. Yet, our overall conclusion is that yield reduction is associated to higher levels of land degradation, irrespective of whether fertilizer is being applied or not.

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Comparing Rainfall Use Efficiency Trends with Expert Judgments for Nation-Wide Land Degradation Assessments: The Case of Senegal

Cited by 4 publications

References 43 publications

Using the VS‐Fast methodology for soil degradation assessment: a case study from Senegal

Using the VS‐Fast methodology for soil degradation assessment: a case study from Senegal

Quantifying the impact of land degradation on crop production: the case of Senegal

Quantifying the impact of land degradation on crop production: the case of Senegal

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