Keith Duncan Shepherd

• PhD
• Chief Scientist at Innovative Solutions for Decision Agriculture (iSDA)

I n September, a United Nations summit of heads of state will adopt the Sustainable Development Goals (SDGs) — a set of 17 goals and 169 targets to guide international development. A diverse range of indicators and monitoring strategies is being proposed, covering every dimension of development, from human well-being to the environment 1. Next week...

Degradation of land health - the capacity of land, relative to its potential, to sustain delivery of ecosystem services - is recognized as a major global problem in general terms, but remains poorly quantified, resulting in a lack of specific evidence to focus action. Land health surveillance and response is designed to overcome limitations of curr...

The trade-off between the growing need for large scale soil information and its high cost could be resolved by a widespread use of visible and infrared spectroscopy. A recent workshop by the European Commission - Joint Research Centre (EC-JRC) and the Food and Agriculture Organization (FAO), focused on the measures to foster the global monitoring o...

Development programs have typically neglected uncertainty and variability in terms of outcomes and socio-ecological context when promoting conservation agriculture (CA) throughout sub-Saharan Africa. We developed a simple Monte Carlo-based decision model, calibrated to global data-sets and parameterized to local conditions, to predict the range of...

Science-based approaches to agricultural and environmental management are needed to accelerate development progress in the world's poorest countries. We present a diagnostic surveillance framework modelled on medical diagnostic approaches for evidence-based management of agriculture and environment in developing countries. Infrared (IR) spectroscop...

Soils provide a range of essential ecosystem services for sustaining life, including climate regulation. Advanced technologies support the protection and restoration of this natural resource. We developed the first fine-resolution spectral grid of bare soils by processing a spatiotemporal satellite data cube spanning the globe. Landsat imagery prov...

Recent advances in hardware technology have enabled the development of handheld sensors with comparable performance to laboratory‐grade near‐infrared (NIR) spectroradiometers. In this study, we explored the effect of the uncertainty from the NeoSpectra Scanner Handheld NIR Analyzer (Si‐Ware) on estimating farm‐level soil organic carbon (SOC) stocks...

Crop models can improve our understanding of crop responses to environmental conditions and farming practices. However, uncertainties in model inputs can notably impact the quality of the outputs. This study aimed at quantifying the uncertainty in soil information and analyse how it propagates through the Quantitative Evaluation of Fertility of Tro...

This near-infrared spectral dataset consists of 2,106 diverse mineral soil samples scanned, on average, on six different units of the same low-cost commercially available handheld spectrophotometer. Most soil samples were selected from the USDA NRCS National Soil Survey Center-Kellogg Soil Survey Laboratory (NSSC-KSSL) soil archives to represent th...

Rapid and cost‐effective techniques for soil analysis are essential to guide sustainable land management and production agriculture. This study aimed at evaluating the performance and consistency of portable handheld Fourier‐transform near‐infrared spectrometers and the NeoSpectra scanners in estimating 12 common soil physical and chemical properti...

Given the importance of soil for the global carbon cycle, it is essential to understand not only how much carbon soil stores but also how long this carbon persists. Previous studies have shown that the amount and age of soil carbon are strongly affected by the interaction of climate, vegetation, and mineralogy. However, these findings are primarily...

With climate and land use changes, it is becoming increasingly important to understand not only how much carbon is and will be stored in soils, but also how long this C will remain in soils. Estimates of C age can provide useful information about the timescales on which C will respond to such changes. It is generally accepted that the interaction o...

Mid-infrared (MIR) spectroscopy is emerging as one of the most promising technologies, as it is a rapid and cost-effective alternative to routine laboratory analysis for many soil properties. This study was conducted to evaluate the potential of mid-infrared spectroscopy for the rapid and nondestructive measurement of some important soil properties...

There is growing global interest in the potential for soil reflectance spectroscopy to fill an urgent need for more data on soil properties for improved decision-making on soil security at local to global scales. This is driven by the capability of soil spectroscopy to estimate a wide range of soil properties from a rapid, inexpensive, and highly r...

Realistic targets for soil organic carbon (SOC) concentrations are needed, accounting for differences between soils and land uses. We assess the use of SOC/clay ratio for this purpose by comparing changes over time in (a) the National Soil Inventory of England and Wales, first sampled in 1978–1983 and resampled in 1994–2003, and (b) two long-term e...

In Kenya, where malnutrition and hidden hunger still pose a significant challenge to growth and development, beans are an essential source of food for most of the population. However, data on micronutrient in beans are limited, and although they are required in very small amounts, they are essential for growth and development of plants as well as h...

Adept use of fertilizers is critical if sustainable development goal two of zero hunger and agroecosystem resilience are to be achieved for African smallholder agroecosystems. These heterogeneous systems are characterized by poor soil health mainly attributed to soil nutrient depletion. However, conventional methods do not take into account spatial...

Digital soil mapping (DSM) approaches provide soil information by utilising the relationship between soil properties and environmental variables. Calibration of DSM models requires measurements that may often have substantial measurement errors which propagate to the DSM outputs and need to be accounted for. This study applied a geostatistical‐base...

With the increasing popularity of local blending of fertilisers, the fertiliser industry faces issues regarding quality control and fertiliser adulteration. Another problem is the contamination of fertilisers with trace elements that have been shown to subsequently accumulate in the soil and be taken up by plants, posing a danger to the environment...

Open access, high-resolution soil property maps have been created for Africa at 30 m resolution, using machine learning trained on over 100,000 analysed soil samples. Combined with other field-level information, iSDAsoil enables the possibility of site-specific agronomy advisory for smallholder farmers. Recent developments in remote sensing and mac...

Information on soil properties is crucial for soil preservation, the improvement of food security, and the provision of ecosystem services. In particular, for the African continent, spatially explicit information on soils and their ability to sustain these services is still scarce. To address data gaps, infrared spectroscopy has achieved great succ...

Using spectrometric methods for soil characterization

This paper presents an application of decision analysis to the strategic planning of agricultural assistance projects in developing countries. The paper describes a strategic planning methodology, leading from project design, specification, evaluation and appraisal to a recurrent portfolio decision. Particular focus is placed on the evaluation of a...

Determination of the concentration of nutrients in the plant is key information for evaluating crop nutrient removal, nutrient use efficiency, fertilizer recommendations guidelines, and in turn for improving food security and reducing environmental footprints of crop production. Diffuse infrared (IR) reflectance spectroscopy is a powerful, rapid, c...

Fire and overgrazing reduce aboveground biomass, leading to land degradation and potential impacts on soil organic carbon (SOC) and total nitrogen (TN) dynamics. However, empirical data are lacking on how prescribed burning and livestock exclusion impact SOC in the long-term. Here we analyse the effects of 19 years of prescribed annual burning and...

Soil organic carbon (SOC) stabilization and destabilization has been studied intensively. Yet, the factors which control SOC content across scales remain unclear. Earlier studies demonstrated that soil texture and geochemistry strongly affect SOC content. However, those findings primarily rely on data from temperate regions where soil mineralogy, w...

Forest and Landscape Restoration (FLR) is carried out with the objective of regaining ecological functions and enhancing human well-being through intervention in degrading ecosystems. However, uncertainties and risks related to FLR make it difficult to predict long-term outcomes and inform investment plans. We applied a Stochastic Impact Evaluation...

Recent compilations of global soil radiocarbon data suggest that current Earth System Models underestimate the mean age of soil carbon (C). The discrepancy between data-derived estimates and model calculations might be due to an inadequate representation of processes that control C persistence in soils-especially in understudied regions. Here, we i...

Soil property and class maps for the continent of Africa were so far only available at very generalised scales, with many countries not mapped at all. Thanks to an increasing quantity and availability of soil samples collected at field point locations by various government and/or NGO funded projects, it is now possible to produce detailed pan-Afric...

Information on soil properties is crucial for soil preservation, improving food security, and the provision of ecosystem services. Especially, for the African continent, spatially explicit information on soils and their ability to sustain these services is still scarce. To address data gaps, infrared spectroscopy has gained great success as a cost-...

While the principles of sustainable development are widely accepted, considering these principles effectively during implementation planning and performance measurement remains a challenge. We argue that predominantly-used results-based approaches, which monitor performance against pre-defined targets and indicators, are ill-suited to performance m...

Portable X-ray fluorescence (pXRF) and Diffuse Reflectance Fourier Transformed Mid-Infrared (DRIFT-MIR) spectroscopy are rapid and cost-effective analytical tools for material characterization. Here, we provide an assessment of these methods for the analysis of total Carbon, Nitrogen and total elemental composition of multiple elements in organic a...

Soil property and class maps for the continent of Africa were so far only available at very generalised scales, with many countries not mappedat all. Thanks to an increasing quantity and availability of soil samples collected at field point locations by various government and/or NGOfunded projects, it is now possible to produce detailed pan-African...

Earlier studies have demonstrated that soil texture and geochemistry strongly affect soil organic carbon (SOC) content. However, those findings primarily rely on data from temperate regions with soil mineralogy, weathering status and climatic conditions that generally differ from tropical and subtropical regions. We investigated soil properties and...

Soil mineral compositions are often complex and spatially diverse, with each mineral exhibiting characteristic chemical properties that determine the intrinsic total concentration of soil nutrients and their phyto-availability. Defining soil mineral-nutrient relationships is therefore important for understanding the inherent fertility of soils for...

Agricultural development projects have a poor track record of success mainly due to risks and uncertainty involved in implementation. Cost-benefit analysis can help allocate resources more effectively, but scarcity of data and high uncertainty makes it difficult to use standard approaches. Bayesian Networks (BN) offer a suitable modelling technolog...

Simple measures of appropriate levels of soil organic matter are needed for soil evaluation, management and monitoring, based on readily measurable soil properties. We test an index of soil organic matter based on the soil organic carbon (SOC) to clay ratio, defined by thresholds of SOC/clay ratio for specified levels of soil structural quality. Th...

Soil organic carbon (SOC) is a key component of terrestrial ecosystems. Experimental studies have shown that soil texture and geochemistry have a strong effect on carbon stocks. However, those findings primarily rely on data from temperate regions or use model approaches that are often based on limited data from tropical and subtropical regions. He...

A farm survey was conducted within a 100 km² sampling block to collect data on the spatial variation in unfertilized maize biovolume and grain yields in relation to soil organic carbon (SOC), total nitrogen, phosphorus and extractable cations. Key soil factors associated with crop performance were identified using stepwise multiple linear regressio...

Sustainable land management is at the heart of some of the most intractable challenges facing humanity in the 21st century. It is critical for tackling biodiversity loss, land degradation, climate change and the decline of ecosystem services. It underpins food production, livelihoods, dietary health, social equity, climate change adaptation, and ma...

Crops that grow on soils with higher fertility often have higher yields and higher tissue nutrient concentrations. Whether this is the case for all crops, and which soil and management factors, or combinations mostly affect yields and food nutrient concentration however, is poorly understood. Here, the main aim was to evaluate effects of soil and m...

Assessment and monitoring of soil resources is needed for ensuring environmental sustainability of rice production in sub-Saharan Africa (SSA). Diffuse reflectance spectroscopy has the potential to offer means to evaluate and monitor soils at large scale in an efficient, affordable and timely manner. However, its accuracy for predicting chemical an...

Human activities change the structure and function of the environment with cascading impacts on human health, a concept known as “planetary health.” Agroforestry—the management of trees with crops and livestock—alters microclimates, hydrology, biogeochemistry, and biodiversity. Besides the nutritional benefits of increased fruit consumption, howeve...

An adequate supply of micronutrients is essential for balanced plant growth. In Africa, micronutrient constraints are known to restrict crop productivity and impair human welfare and health. We analyzed a total of 816 topsoil and 796 subsoil samples from Sub-Saharan Africa, to provide baseline information on their readily available Al, B, Cd, Co, C...

Wood density is an important variable for accurate quantification of woody biomass and carbon stocks. Conventional destructive methods for wood density estimation are resource intensive, prohibiting their use, limiting the application of approaches that would minimize uncertainties in tree biomass estimates. We tested an alternative method involvin...

Highlights: • New answers to land degradation problems have been an agroforestry focus for four decades. • Plot-level experimentation following agronomic traditions proved to be a challenge due to lateral interactions. • Testing hypotheses at process level and analysing tree–soil–crop interactions led to synthetic simulation models. • Policy attent...

Minerals are the major component of most soils. Through direct inheritance from the parent material and subsequent alteration by chemical weathering, the soil mineral composition can be spatially diverse-reflecting the local geology, climate, and age of the soil. Each mineral present within the soil environment exhibits a characteristic chemical co...

X-ray powder diffraction (XRPD) is widely applied for the qualitative and quantitative analysis of soil mineralogy. In recent years, high-throughput XRPD has resulted in soil XRPD datasets containing thousands of samples. The efforts required for conventional approaches of soil XRPD data analysis are currently restrictive for such large data sets,...

Mango fruits contain substantial vitamins and dietary fibre. Vitamins vary among and within fruits depending on cultivar type and ripening stage. Conventional techniques of vitamins analysis are based on High Pressure Liquid Chromatography, which are costly and laborious. This study evaluated the potential of Fourier transform infrared-diffuse refl...

In the arid areas of Sub-Saharan Africa, perennial challenges of water scarcity and food insecurity are exacerbated by climate change and variability. The development of robust strategies to cope with the region's climatic challenges requires thorough consideration of uncertainty and risk in decision making. We demonstrate the use of probabilistic...

Improving fertilizer recommendations for farmers is essential to increase food security in smallholder landscapes. Currently, blanket recommendations are provided across agro-ecological zones, although fertilizer response and nutrient use efficiency by maize crop are spatially variable. We aimed to identify factors that could help to refine fertili...

A quantitative risk-based framework is presented for improving planning and performance management of agroforestry interventions at farm and project levels. The framework first identifies the goals of the various stakeholders involved and the intervention options being considered. Then the various on-site and off-site costs, benefits and risks asso...

Decision analysis tools can help to utilise available data and expert knowledge rather than requiring hard data from costly long-term fieldwork and experiments. They allow for the incorporation of disparate data sources and what might be considered 'imprecise' inputs to create a representation of the current understanding of cause and effect relati...

Soil properties are useful for assessing the potential of landscapes to provide terrestrial ecosystem services, but they are affected by anthropogenic activities and environmental factors including landscape attributes. This study assessed how soil properties are influenced by landscape attributes and their interactions in the highlands of Cameroon...

p>Designing and implementing biodiversity-based value chains can be a complex undertaking, especially in places where outcomes are uncertain and risks of project failure and cost overruns are high. We used the Stochastic Impact Evaluation (SIE) approach to guide the Intergovernmental Authority on Development (IGAD) on viable investment options in h...

Governments around the world have agreed to end hunger and food insecurity and to improve global nutrition, largely through changes to agriculture and food systems. However, they are faced with a lot of uncertainty when making policy decisions, since any agricultural changes will influence social and biophysical systems, which could yield either po...

The report outlines some Decision Analysis tools for the adaptation and application of Bayesian Networks to agriculture for nutrition development contexts. These are promising as effective strategies for dealing with complex systems, multiple impact pathways, uncertain and incomplete information and other current constraints to meaningful quantitat...

Controlled grazing management is considered as an effective strategy to enhance soil carbon sequestration, but empirical evidences are scarce. Particularly, the role of livestock exclusion related to soil carbon sequestration is not well understood in arid and semiarid savannas of Africa. We investigated the effectiveness of long-term (14–36 years...

Mangoes are fruits of nutritional importance in Kenya. The fruits vary in their sugars depending on cultivar type and ripening stage. Current methods of sugar content analysis are based on HPLC methods, which are accurate but expensive and time-consuming. We evaluated the potential of diffuse reflectance infrared Fourier transform (DRIFT) spectrosc...

Soil is a key input in agricultural production and analysis. This guidebook offers practical guidance for integrating spectral soil analysis into household survey operations, particularly in low-income, smallholder farmer contexts. It is geared toward survey practitioners and includes guidance on what to consider in evaluating competing methods for...

Most agricultural models do not adequately represent real-life development decisions, not least because they fail to consider the impact of the full range of biophysical, socioeconomic , political and cultural factors that affect decision outcomes. Many modelling exercises restrict their scope to system aspects that can be characterised with precis...

Uganda's agriculture is currently confronted with a major government decision, set to transform the country's farming landscape. The national development plan (Vision 2040) calls for a transition from small-scale farming, which currently supports the majority of Ugandans, to large-scale commercial agriculture. While this plan is likely to boost sta...

Spatial predictions of soil macro and micro-nutrient content across Sub-Saharan Africa at 250 m spatial resolution and for 0–30 cm depth interval are presented. Predictions were produced for 15 target nutrients: organic carbon (C) and total (organic) nitrogen (N), total phosphorus (P), and extractable—phosphorus (P), potassium (K), calcium (Ca), ma...

Accountability and adaptive management of recent global agreements such as the Sustainable Development Goals and Paris Climate Agreement, will in part rely on the ability to track progress toward the social and environmental targets they set. Current metrics and monitoring systems, however, are not yet up to the task. We argue that there is an impe...

In this study, the utility of regression-kriging was investigated in building prediction models for soil properties using mid-infrared (7498 to 600 cm− 1) spectral data for soil samples collected from Nyando, Nzoia and Yala catchment areas in Kenya, sampled at 0–20 cm and 20–50 cm depths. Using a systematic technique, 158 samples were selected for...

Understanding spatial variability of soil properties is essential to support land management decisions. However, despite the growing worldwide emphasis on integrated landscape management, soil variations resulting from land use changes have rarely been documented. The study used the land health surveillance concept in combination with simple geosta...

The conversion of forests to other forms of land use has profound effects on the distribution and supply of soil nutrients. Understanding the effects of land use on soil is essential for addressing agroecosystem transformation and sustainable land productivity. Although soil carbon stock has been previously examined in the humid forest zone of Came...

Mining activities contribute to an increase of specific metal contaminants in soils. This may adversely affect plant life and consequently impact on animal and human health. The objective of this study was to obtain the background metal concentrations in soils around the titanium mining in Kwale County for monitoring its environmental impacts. Fort...

Hyperion hyperspectral (VNIR-SWIR) satellite image data was used to map the spatial distribution of mineral precipitates at Lake Magadi area, in the southernmost part of the eastern Kenya rift, Kenya. Mapping was coupled with laboratory analysis, including visible near infrared diffuse reflectance spectroscopy (VNIR) measurements and X-ray diffract...

Soil aggregation is critical for assessing soil health; however, conventional aggregation measurement is laborious and expensive. The performance of near infrared diffuse reflectance spectroscopy (NIR) and basic soil properties for estimation of wet aggregation indices was investigated. Two samples sets representing different soils from across Lake...

In 2014, the USAID project ‘Grazing lands, livestock and climate resilient mitigation in Sub-Saharan Africa’ held two workshops, hosted by the Colorado State University, which brought together experts from around the world. Two reports resulted from these workshops, one an assessment of the state of the science, and the other an inventory of relate...

The PROSAM project aimed to take the participatory techniques described in the field of prototyping and combine them with quantitative mechanistic simulation models and household models to the level of the ecoregion. To do so, a GIS database has been established, three project sites were selected, and farming systems were characterized in these sit...

Successful implementation of major projects requires careful management of uncertainty and risk. Yet such uncertainty is rarely effectively calculated when analysing project costs and benefits. This paper presents a Bayesian network (BN) modelling framework to calculate the costs, benefits, and return on investment of a project over a specified tim...

Agricultural intensification has been recognized as one of the solutions to increase food production to feed the ever-increasing population in sub-Saharan Africa. This can partly be achieved if quantitative and up-to-date information on soil health indicators are not available. This study used the land health surveillance framework, which combines...

Soil provides ecosystem services, supports human health and habitation, stores carbon and regulates emissions of greenhouse gases. Unprecedented pressures on soil from degradation and urbanization are threatening agro- ecological balances and food security. It is important that we learn more about soil to sustainably manage and preserve it for futu...

We propose four methods for finding local subspaces in large spectral libraries. The proposed four methods include (a) Cosine angle spectral matching; (b) Hit quality index spectral matching; (c) self-organizing maps and (d) archetypal analysis methods. Then evaluate prediction accuracies for global and subspaces calibration models. These methods w...

Massive investments in climate change mitigation and adaptation are projected during coming decades. Many of these investments will seek to modify how land is managed. The return on both types of investments can be increased through an understanding of land potential: the potential of the land to support primary production and ecosystem services, a...

Soil provides ecosystem services, supports human health and habitation, stores carbon and regulates emissions of greenhouse gases. Unprecedented pressures on soil from degradation and urbanization are threatening agro-ecological balances and food security. It is important that we learn more about soil to sustainably manage and preserve it for futur...