Spectral soil analysis for fertilizer recommendations by coupling with QUEFTS for maize in East Africa: A sensitivity analysis

A - Papers appearing in refereed journals

Hassall, K. L., Gashaw-Asrat, T., Haefele, S. M. and Breure, T. 2023. Spectral soil analysis for fertilizer recommendations by coupling with QUEFTS for maize in East Africa: A sensitivity analysis. Geoderma. 432, p. 116397. https://doi.org/10.1016/j.geoderma.2023.116397

AuthorsHassall, K. L., Gashaw-Asrat, T., Haefele, S. M. and Breure, T.
Abstract

Laboratory analysis of soil properties is prohibitively expensive and difficult to scale across the soils in sub Saharan Africa. This results in a lack of soil-specific fertilizer recommendations, where recommendation can only be provided at a regional scale. This study aims to assess the feasibility of using spectral soil analysis to provide soil-specific fertilizer recommendations. Using a range of spectrometers [NeoSpectra Saucer (NIR), FieldSpec 4 (vis-NIR) with contact probe or mug light interface, FTIR Bruker Tensor 27 (MIR)], 346 archived soil samples (0–20 cm) with known soil chemical properties collected from Ethiopia, Kenya and Tanzania were scanned. Partial least square regression (PLSR) was used to develop prediction models for selected soil properties including pH, soil organic carbon (SOC), total nitrogen, Olsen P, and exchangeable K. These predicted properties, and associated uncertainty, were used to derive fertilizer recommendations for maize using the Quantitative Evaluation of the Fertility of Tropical Soils (QUEFTS) model parameters for sub-Saharan Africa. Most soil properties (pH, SOC, total nitrogen, and exchangeable K) were well predicted (Concordance Correlation Coefficient values between 0.88 and 0.96 and Ratio of Performance to Interquartile values between 1.4 and 5.9) by all the spectrometers but there were performance variations between soil properties and spec-
trometers. Use of the predicted soil data for the development of fertilizer recommendations gave promising results when compared to the recommendations obtained with the conventional soil analysis. For example, the least performing NeoSpectra Saucer over/under-estimated up to 8 and 24 kg ha-1N and P, respectively, though there was insignificant variation in estimation of P fertilizer among spectrometers. We conclude that spectral technology can be used to determine major soil properties with satisfactory precision, sufficient for specific fertilizer decision making in East Africa, possibly even with portable equipment in the field

KeywordsNIR; visNIR; MIR; QUEFTS model; PLSR model; East Africa
Year of Publication2023
JournalGeoderma
Journal citation432, p. 116397
Digital Object Identifier (DOI)https://doi.org/10.1016/j.geoderma.2023.116397
Open accessPublished as ‘gold’ (paid) open access
FunderOffice Chérifien des Phosphate (OCP)
Biotechnology and Biological Sciences Research Council
Funder project or codeGeoNutrition - tackling hidden hunger in Sub-Saharan Africa
Publisher's version
Output statusPublished
Publication dates
Online24 Feb 2023
Publication process dates
Accepted17 Feb 2023
PublisherElsevier Science Bv
ISSN0016-7061

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