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Review
. 2023 Sep:38:100708.
doi: 10.1016/j.gfs.2023.100708.

Inorganic fertilizer use and its association with rice yield gaps in sub-Saharan Africa

Jean-Martial Johnson  1   2 , Ali Ibrahim  3 , Elliott Ronald Dossou-Yovo  1 , Kalimuthu Senthilkumar  4 , Yasuhiro Tsujimoto  5 , Hidetoshi Asai  5 , Kazuki Saito  1   6
Affiliations
Review

Inorganic fertilizer use and its association with rice yield gaps in sub-Saharan Africa

Jean-Martial Johnson et al. Glob Food Sec. 2023 Sep.

Abstract

Where and which countries should receive higher priority for improving inorganic fertilizer use in rice fields in sub-Saharan Africa (SSA)? This study addressed this question by assessing the spatial variation in fertilizer use and its association with rice yield and yield gap in 24 SSA countries through a systematic literature review of peer-reviewed papers, theses, and grey literature published between 1995 and 2021. The results showed a large variation in N, P, and K fertilizer application rates and rice yield and an opportunity for narrowing the yield gap by increasing N and P rates, especially in irrigated rice systems. We identified clusters of sites/countries based on nutrient input and yield and suggested research and development strategies for improving yields and optimizing nutrient use efficiencies. Further research is essential to identify the factors causing low fertilizer use and the poor association between its use and yield in rainfed systems.

Keywords: Agroecological zone; Fertilizer use efficiency; Oryza spp.; Partial factor productivity; Yield gap.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Image 1
Graphical abstract
Fig. 1
Fig. 1
Location of the study sites (A) across five agroecological zones (Humid, Sub-Humid, Semi-Arid, Arid, and Highlands) and (B) in twenty-four sub-Saharan African countries.
Fig. 2
Fig. 2
Cumulative distribution probability of (A) N, (B) P, and (C) K fertilizer application rates (kg ha−1) from data points in irrigated lowland (IL), rainfed lowland (RL), and, rainfed upland (RU) retrieved from surveys/studies conducted in sub-Saharan Africa between 1995 and 2020. The dashed vertical red lines indicate the global average application rate for the corresponding nutrient.
Fig. 3
Fig. 3
Correlogram showing the relationships between nutrients (N, P, and K) application rates, rice grain yield, and relative yield gap in different studies in sub-Saharan Africa. The values displayed in the matrix are Spearman's rank correlation coefficients (ρ). Non-significant ρ (p < 0.05) are crossed out. Positive correlations are displayed in maroon (or dark red) and negative correlations in goldenrod. The color intensity (see color bar) of the square is proportional to the correlation coefficient.
Fig. 4
Fig. 4
Correlogram showing the relationships between nutrients (N, P, and K) application rates, rice grain yield, and relative yield gap in different studies across regions [West Africa (WA), Central Africa (CA), and, East and Southern Africa (ESA)] in sub-Saharan Africa. The values displayed in the matrix are Spearman's rank correlation coefficients (ρ). Non-significant ρ (p < 0.05) are crossed out. Positive correlations are displayed in maroon (or dark red) and negative correlations in goldenrod. The color intensity (see color bar) of the square is proportional to the correlation coefficient.
Fig. 5
Fig. 5
Correlogram showing the relationships between nutrients (N, P, and K) application rates, rice grain yield, and relative yield gap in different studies across growing environments [irrigated lowland (IL), rainfed lowland (RL), and, rainfed upland (RU)] in sub-Saharan Africa. The values displayed in the matrix are Spearman's rank correlation coefficients (ρ). Non-significant ρ (p < 0.05) are crossed out. Positive correlations are displayed in maroon (or dark red) and negative correlations in goldenrod. The color intensity (see color bar) of the square is proportional to the correlation coefficient.
Fig. 6
Fig. 6
Estimated parameters of multinomial logistic regression: effects of the nutrients application rates and the environmental conditions on the optimum levels of (A) PFPN, (B) PFPP, and (C) PFPK in different studies in sub-Saharan Africa. Empty dot symbols mean the regression coefficient is not significant (p > 0.05). The filled dot symbol means the regression coefficient is significant (p < 0.05).
Fig. 7
Fig. 7
Map displaying pie charts of clusters (combining actual yield and N application rate) for 24 sub-Saharan African countries. HYHN - High Yield and High N application rate; LYLN - Low Yield and Low N application rate; LYMN - Low Yield and Medium N application rate; MYHN -Medium Yield and High N application rate; MYLN - Medium Yield and Low N application rate; VHYVHN - Very High Yield and Very High N application rate.
See this image and copyright information in PMC

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