The stakes could hardly be higher. The region’s population, now exceeding 1.2 billion, is projected to reach roughly 2.5 billion by 2050, yet crop productivity has stagnated or declined, with some analyses documenting a total factor productivity drop of 3.5 percent per year between 2008 and 2019. Smallholder farmers, who manage about 80 percent of the continent’s agricultural land in plots averaging less than two hectares, face a fundamental biophysical constraint: soil fertility depletion. Approximately 65 percent of agricultural land in the region is degraded, and annual nutrient mining of 22 to 26 kilograms of nitrogen per hectare far exceeds what farmers replace. Mineral fertilizer use averages a mere 9 to 17 kilograms per hectare, compared with a global average above 135 kilograms, and fertilizer prices run two to six times higher than in Asia or Europe because of import dependency and fragmented distribution networks.

Against this backdrop, researchers Marco E. Mng’ong’o and Philipina Shayo of Mbeya University of Science and Technology in Tanzania conducted a systematic review and meta-analysis following PRISMA 2020 guidelines, searching Web of Science, Scopus, PubMed and Google Scholar for field and controlled-environment studies across 28 Sub-Saharan African countries. Their final dataset encompassed 8,641 treatment-control comparisons covering staple crops such as maize, soybean, sorghum, wheat, pearl millet and cowpea. Using Hedges’ g as the standardized effect size within a random-effects model, they found a large positive pooled treatment effect of g = 0.91 (95 percent confidence interval: 0.83 to 0.99; P < 0.001), meaning bio-inputs and advanced materials consistently outperformed unamended controls. Even after correcting for publication bias with the trim-and-fill procedure, the effect remained large at g = 0.84.

The standout result concerned integration. Systems combining organic amendments, mineral fertilizers, microbial inoculants and improved germplasm under the umbrella of integrated soil fertility management produced the largest pooled effect of any category, g = 1.47 (95 percent CI: 1.18 to 1.76). This synergy reflects first principles of nutrient management: microbial inoculants amplify the efficiency of mineral inputs, while organic materials supply slow-release nutrients and build the soil health that sustains yields across successive seasons. Nanofertilizers ranked second among individual categories, with zinc oxide nanoparticles posting an effect size of g = 1.24, followed by plant growth-promoting rhizobacteria consortia at g = 0.91, Rhizobium inoculants at g = 0.82, arbuscular mycorrhizal fungi at g = 0.75, silicon dioxide nanoparticles at g = 0.88, biochar at g = 0.69, humic acids at g = 0.73 and seaweed biostimulants at g = 0.61.

The mechanisms behind these numbers are as varied as the technologies themselves. Rhizobial inoculants drive biological nitrogen fixation in legumes, raising nodule number by 48 percent and nitrogen fixation rates by 39 percent over uninoculated controls, while costing a fraction of equivalent mineral nitrogen. In northern Nigeria, legume inoculation added an average of 447 kilograms per hectare at an inoculant cost of roughly 4.50 to 6.46 dollars per hectare, against about 100 dollars for the same nitrogen from mineral fertilizer. Plant growth-promoting rhizobacteria, including Bacillus, Pseudomonas and Azospirillum strains, alleviate drought through ACC deaminase activity, exopolysaccharide production and osmoprotectant synthesis; under severe drought stress, co-inoculated maize showed 30.7 percent higher relative water content and 89 percent more aboveground biomass than drought-stressed controls.

Arbuscular mycorrhizal fungi extend the phosphorus depletion zone from the diffusion-limited two to four millimeters around roots to distances of up to 15 centimeters through hyphal networks, a decisive advantage in the phosphorus-poor Ferralsols and Acrisols that dominate the region. The analysis found mycorrhizal colonization was negatively correlated with soil available phosphorus, confirming these fungi deliver the most value where phosphorus is scarcest, which describes most smallholder fields. Dual inoculation with mycorrhiza and Rhizobium outperformed single inoculation, and cereal-legume intercropping raised land equivalent ratios to 1.2 to 1.9, with modeling suggesting 20-year intercropping scenarios can maintain soil organic carbon even without nitrogen fertilizer.

The nanotechnology results were arguably the most eye-catching. Nano-zinc oxide applications boosted sorghum grain yield by up to 183 percent under drought, improved grain nitrogen translocation by 84 percent and potassium acquisition by 123 percent through upregulation of abscisic acid and improved stomatal regulation. In rice exposed to heat waves, zinc oxide nanoparticles raised grain yield by 22.1 percent and grain protein by 11.8 percent. Silicon dioxide nanoparticle seed priming improved wheat spike length by 12 to 42 percent and biological yield by 21 to 64 percent under drought. Slow-release nanofertilizers extend nutrient availability to 40 to 50 days versus 4 to 10 days for conventional formulations, a critical advantage where 40 to 70 percent of applied nitrogen is lost before uptake. Biochar applied at 5 to 20 tonnes per hectare improved yields by an average of 42 percent, with the largest gains in drought-prone and saline soils, while simultaneously sequestering carbon and improving water retention.

Context, however, proved decisive. Rainfall regime was the strongest moderator of effect size: semi-arid environments receiving under 400 millimeters annually showed the highest relative gains (mean g = 1.18), while sub-humid zones showed more moderate responses (g = 0.76), indicating these technologies deliver the greatest marginal benefit under stress. Legumes responded most strongly to inoculants (g = 1.12), cereals intermediately (g = 0.88), and root and tuber crops responded better to biochar and integrated amendments. Combined seed and soil application outperformed single routes, and effect sizes grew with study duration at a rate of 0.14 per year, showing that soil-health-mediated benefits from biochar and integrated systems compound over seasons. Nutrient use efficiency rose by a mean of 28.4 percent for nitrogen and 35.2 percent for phosphorus, and zinc biofortification of grains reached up to 94 percent in drought-stressed sorghum, directly addressing micronutrient deficiencies affecting 24 to 66 percent of populations in several countries.

The authors are careful to temper enthusiasm with caution. Adoption rates remain below 5 percent for most categories, held back by inoculant viability losses of 30 to 80 percent in typical distribution chains, widespread farmer unawareness, and, for nanomaterials, prohibitive synthesis costs, absent regulatory frameworks and unresolved questions about the environmental fate and food-chain safety of engineered nanoparticles, whose ecotoxicology has been studied almost exclusively in temperate soils. Residual heterogeneity was high, with I-squared at 87.2 percent, and over 75 percent of studies came from East and West Africa, leaving Central Africa underrepresented. Most studies also spanned only one or two seasons, too short to capture the full soil-health dividends of biochar and integrated systems. The researchers call for multi-year, multi-site validation trials, modernized regulatory frameworks, quality assurance infrastructure, reformed input subsidy programs and retrained extension services. The message of the analysis is ultimately one of agency: the solutions to Africa’s food crisis largely exist, from living microbes to engineered nanoparticles, and the challenge now is building the enabling environment that delivers them to the 600 million food-insecure people who need them most.

Subject of Research: Effects of biofertilizers, nanofertilizers, biochar and biostimulants on crop yield and stress tolerance in Sub-Saharan Africa

Article Title: Smart inputs for stressed soils: assessment of biofertilizers, nanomaterials, biochar, and biostimulants for sustainable crop productivity in Sub-Saharan Africa

Article References: Mng’ong’o, M. E., & Shayo, P. (2026). Smart inputs for stressed soils: assessment of biofertilizers, nanomaterials, biochar, and biostimulants for sustainable crop productivity in Sub-Saharan Africa. Discover Agriculture, 4(1), Article 280. https://doi.org/10.1007/s44279-026-00748-4

Image Credits: AI Generated

DOI: 10.1007/s44279-026-00748-4

Keywords: biofertilizers, nanofertilizers, biochar, biostimulants, Sub-Saharan Africa, soil fertility, plant growth-promoting rhizobacteria, arbuscular mycorrhizal fungi, integrated soil fertility management, nutrient use efficiency, drought stress, smallholder farming

A groundbreaking review recently published in the journal Frontiers of Agricultural Science and Engineering synthesizes the state-of-the-art advancements in bio-based materials such as microbial inoculants, nanomaterials, and biochar. Led by Professor Gang Wang of China Agricultural University, this comprehensive research evaluates how these amendments interact synergistically with soil and crops to enhance nutrient use efficiency and overall plant growth. The study bridges experimental insights with applied agricultural practices, paving the way for more environmentally responsible farming models.

Plant growth-promoting rhizobacteria (PGPB) stand at the forefront of biological amendments, mediating crucial processes such as atmospheric nitrogen fixation and the solubilization of phosphate and potassium. These microbial agents optimize nutrient availability directly within the rhizosphere, facilitating more effective uptake by plant roots. Experiments demonstrate, for instance, that the co-inoculation of nitrogen-fixing bacteria with phosphorus-solubilizing strains markedly increases nitrogen and phosphorus absorption in wheat, which translates to improved yields.

Beyond nutrient acquisition, PGPB contribute to enhancing soil’s physical properties. The secretion of extracellular polymeric substances (EPS) by these bacteria not only stabilizes the soil matrix but improves its water retention capacity—a vital function in salt-affected soils. In such saline environments, enhanced water retention by EPS correlates with increased biomass production in crops like tomatoes, illustrating how microbiological interventions can mitigate abiotic stresses.

The role of PGPB extends into bioremediation as well. The contamination of soils with heavy metals presents significant challenges for sustainable agriculture. PGPB have been shown to facilitate the removal of toxic metals such as hexavalent chromium (Cr VI) via bioadsorption and microbial transformation mechanisms. This biological approach not only reduces soil toxicity but also lessens farmers’ dependence on chemical inputs, aligning agricultural productivity with environmental safety.

Nanotechnology introduces a new paradigm in precision agriculture, leveraging the unique physicochemical properties of nanomaterials to target and optimize nutrient delivery and plant protection. For example, magnetite (Fe3O4) nanoparticles have been reported to stimulate biological nitrogen fixation in leguminous crops such as soybeans, yielding significant improvements in both nitrogen utilization and crop productivity. This nanoscale intervention can strategically enhance key physiological processes.

Silica-based nanomaterials serve a dual function by physically impeding pathogenic invasion in plants. Applied to tomato crops, these nanostructures form a protective barrier that diminishes the occurrence of destructive stem blight. Such pathogen management through nanomaterials represents a sustainable alternative to conventional pesticide application, thus contributing to reduced chemical dependency.

Nano-engineered slow-release fertilizers epitomize advances in nutrient management technology. These formulations regulate nutrient release profiles, synchronizing supply with crop demand, thereby substantially improving nitrogen use efficiency. Compared to traditional fertilizers, nano slow-release variants achieve comparable or higher yields while reducing excessive nutrient application and subsequent environmental runoff.

Under abiotic stresses such as drought, nanomaterials have also been observed to modulate plant physiological responses. In wheat, for example, nano applications reduce malondialdehyde content—a biomarker of oxidative stress—by enhancing antioxidant defense mechanisms. This capacity to mitigate oxidative damage underpins the resilience of plants exposed to adverse conditions, supporting stable food production amid climate variability.

Biochar, produced from organic waste materials such as corn straw through pyrolysis, acts as a highly effective carbon carrier with a porous microstructure conducive to heavy metal adsorption. When biochar is enriched with phosphorus-solubilizing bacteria, it not only improves the availability of phosphorus in soil but also fosters soil aggregate formation. This enhances soil structure and boosts organic carbon storage, which are critical factors in maintaining soil fertility and combating degradation.

The interplay between biochar and microorganisms yields remarkable performance in contaminated site rehabilitation. For example, in mine soils laden with toxic heavy metals, the combined application of biochar alongside manganese-oxidizing bacteria synergistically elevates the removal rates of hazardous elements like lead and arsenic. Additionally, biochar’s inherent carbon sequestration capabilities contribute to mitigating the carbon footprint of agricultural landscapes.

Crucially, the combined usage of microbial inoculants, nanomaterials, and biochar demonstrates amplified benefits beyond their individual effects. In rice cultivation, the co-application of beneficial microbes with nanomaterials significantly improves nitrogen utilization, while the joint deployment of biochar with microorganisms restores enzymatic activities essential for soil health in degraded mining areas. This integrated approach leverages biochar as a scaffold that prolongs microbial viability and enables nanomaterials to precisely deliver nutrients and remediation agents.

Despite the demonstrated potential of bio-based amendments, several hurdles must be addressed for broad-scale adoption. Cost implications remain a primary concern, necessitating advancements in production methods and process engineering to make these technologies economically feasible for farmers worldwide. Furthermore, comprehensive environmental risk assessments are needed to ensure safety and to guide rational policy formulations that encourage the sustainable implementation of bio-based solutions in agriculture.

Looking forward, interdisciplinary collaborations that harness biotechnology, materials science, and agronomy will be pivotal to unlocking the full potential of bio-based material amendments. Through optimized formulations, regulatory oversight, and supportive policy frameworks, these green technologies can catalyze a transformative shift in agricultural paradigms—ensuring resilience, productivity, and ecological harmony in the face of global challenges.

Subject of Research: Not applicable
Article Title: Biomaterial amendments improve nutrient use efficiency and plant growth
News Publication Date: 14-Jan-2025
Web References: DOI: 10.15302/J-FASE-2024586
Image Credits: Ying LIU, Natasha MANZOOR, Miao HAN, Kun ZHU, Gang WANG