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Estimating nutrient concentrations and uptake in rice grain in sub-Saharan Africa using linear mixed-effects regression

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Title Estimating nutrient concentrations and uptake in rice grain in sub-Saharan Africa using linear mixed-effects regression
 
Creator Rakotoson, T.
Senthilkumar, Kalimuthu
Johnson, J.M.
Ibrahim, A.
Kihara, Job Maguta
Sila, Andrew M.
Saito, Kazuki
 
Subject production systems
soil properties
inorganic fertilizers
rice
 
Description Context or problem
Quantification of nutrient concentrations in rice grain is essential for evaluating nutrient uptake, use efficiency, and balance to develop fertilizer recommendation guidelines. Accurate estimation of nutrient concentrations without relying on plant laboratory analysis is needed in sub-Saharan Africa (SSA), where farmers do not generally have access to laboratories.

Objective or research question
The objectives are to 1) examine if the concentrations of macro- (N, P, K, Ca, Mg, S) and micronutrients (Fe, Mn, B, Cu) in rice grain can be estimated using agro-ecological zones (AEZ), production systems, soil properties, and mineral fertilizer application (N, P, and K) rates as predictor variables, and 2) to identify if nutrient uptakes estimated by best-fitted models with above variables provide improved prediction of actual nutrient uptakes (predicted nutrient concentrations x grain yield) compared to average-based uptakes (average nutrient concentrations in SSA x grain yield).

Methods
Cross-sectional data from 998 farmers’ fields across 20 countries across 4 AEZs (arid/semi-arid, humid, sub-humid, and highlands) in SSA and 3 different production systems: irrigated lowland, rainfed lowland, and rainfed upland were used to test hypotheses of nutrient concentration being estimable with a set of predictor variables among above-cited factors using linear mixed-effects regression models.

Results
All 10 nutrients were reasonably predicted [Nakagawa’s R2 ranging from 0.27 (Ca) to 0.79 (B), and modeling efficiency ranging from 0.178 (Ca) to 0.584 (B)]. However, only the estimation of K and B concentrations was satisfactory with a modeling efficiency superior to 0.5. The country variable contributed more to the variation of concentrations of these nutrients than AEZ and production systems in our best predictive models. There were greater positive relationships (up to 0.18 of difference in correlation coefficient R) between actual nutrient uptakes and model estimation-based uptakes than those between actual nutrient uptakes and average-based uptakes. Nevertheless, only the estimation of B uptake had significant improvement among all nutrients investigated.

Conclusions
Our findings suggest that with the exception of B associated with high model EF and an improved uptake over the average-based uptake, estimates of the macronutrient and micronutrient uptakes in rice grain can be obtained simply by using average concentrations of each nutrient at the regional scale for SSA.

Implications
Further investigation of other factors such as the timing of fertilizer applications, rice variety, occurrence of drought periods, and atmospheric CO2 concentration is warranted for improved prediction accuracy of nutrient concentrations.
 
Date 2023-08-01
2023-11-07T15:17:22Z
2023-11-07T15:17:22Z
 
Type Journal Article
 
Identifier Rakotoson, T., Senthilkumar, K., Johnson, J-M., Ibrahim, A., Kihara, J., Sila, A. and Saito, K. 2023. Estimating nutrient concentrations and uptake in rice grain in sub-Saharan Africa using linear mixed-effects regression. Field Crops Research 299:108987.
1872-6852
https://hdl.handle.net/10568/132801
https://doi.org/10.1016/j.fcr.2023.108987
 
Language en
 
Rights CC-BY-4.0
Open Access
 
Format 108987
application/pdf
 
Source Field Crops Research