Micronutrient deficiencies in African soils and the human nutritional nexus: opportunities with staple crops

Abstract

A synthesis of available agronomic datasets and peer-reviewed scientific literature was conducted to: (1) assess the status of micronutrients in sub-Saharan Africa (SSA) arable soils, (2) improve the understanding of the relations between soil quality/management and crop nutritional quality and (3) evaluate the potential profitability of application of secondary and micronutrients to key food crops in SSA, namely maize (Zea mays L.), beans (Phaseolus spp. and Vicia faba L.), wheat (Triticum aestivum L.) and rice (Oryza sativa L.). We found that there is evidence of widespread but varying micronutrient deficiencies in SSA arable soils and that simultaneous deficiencies of multiple elements (co-occurrence) are prevalent. Zinc (Zn) predominates the list of micronutrients that are deficient in SSA arable soils. Boron (B), iron (Fe), molybdenum (Mo) and copper (Cu) deficiencies are also common. Micronutrient fertilization/ agronomic biofortification increases micronutrient concentrations in edible plant organs, and it was profitable to apply fertilizers containing micronutrient elements in 60-80% of the cases. However, both the plant nutritional quality and profit had large variations. Possible causes of this variation may be differences in crop species and cultivars, fertilizer type and application methods, climate and initial soil conditions, and soil chemistry effects on nutrient availability for crop uptake. Therefore, micronutrient use efficiency can be improved by adapting the rates and types of fertilizers to site-specific soil and management conditions. To make region-wide nutritional changes using agronomic biofortification, major policy interventions are needed.

Viewpoint: Agri-nutrition research: Revisiting the contribution of maize and wheat to human nutrition and health

“…Soil characteristics and production systems affect crop macro- and micronutritional qualities for human consumption ( Herencia et al, 2011 , Kihara et al, 2020 , Lovegrove et al, 2020 , Shewry, 2018 , Shewry and Hey, 2015a ). More local knowledge is needed.…”

“…Agri-food systems thinking provides a robust platform for reshaping the agri-nutrition research agenda and to incorporate multi-disciplinary partnerships. There are ongoing wheat and maize systems research needs, which are to: accelerate plant breeding for nutritional quality and biofortified crop varieties, and scale up industrial fortification, both being proven strategies for enhancing the nutrient-intensity of major cereals among other crops ( HarvestPlus 2020 ); persist in crop productivity and sustainability research in diverse soil and production conditions and in the context of climate change, especially under the resource-constrained conditions of smallholder farmers ( Ritzema et al, 2017 , Kihara et al, 2020 ); enhance practices for processing, manufacturing, storage and distribution of natural, bio- and industrially enriched cereal foods to reduce losses and nutritional harm in terms of both quality and quantity ( Sharma et al, 2020b ); understand consumer behaviour at a disaggregated level: livelihood patterns and access to different foods among vulnerable groups, in different cultures, and in different production and marketing systems ( Haddad 2020 ); identify the inherent contradictions and resolve the trade-offs within cereal food systems concerning environmental sustainability, poverty reduction, profitability for actors and firms throughout the value chain, and improved nutrition and health of vulnerable populations. …”

“…persist in crop productivity and sustainability research in diverse soil and production conditions and in the context of climate change, especially under the resource-constrained conditions of smallholder farmers ( Ritzema et al, 2017 , Kihara et al, 2020 );…”

Improved Genetic Map Identified Major QTLs for Drought Tolerance- and Iron Deficiency Tolerance-Related Traits in Groundnut

“…In India, one-third of the cultivated area has calcareous soils that are deficient in iron, mostly distributed in the low rainfall areas, where groundnut is a major crop and suffers from iron deficiency (ID) or interveinal chlorosis leading to a significant decrease in pod yield (16–32%) [ 8 ]. In Sub-Saharan Africa (SSA) arable lands (over 50% of the world’s potential land for cultivation), iron is among the five predominant soil micronutrients being identified as important for crop productivity [ 9 ]. Acute iron deficiency can lead to plant death and even complete crop failure.…”

Increasing zinc concentration in maize grown under contrasting soil types in Malawi through agronomic biofortification: Trial protocol for a field experiment to detect small effect sizes

“…In Nigeria and Togo, Kihara et al. (2020) observed that application of Zn and other macronutrients caused an increase of about 20% in maize grain Zn concentration over a control treatment. In Pakistan, with seed priming, Harris et al.…”