NutriLeads (Netherlands)

Soil fertility depletion, spatially variable nutrient limitations, and increasing climate variability are major constraints to crop productivity and resource conservation in Sub‑Saharan Africa (SSA). Sustainable nutrient management strategies that simultaneously improve crop yields, enhance soil health, and reduce nutrient losses are urgently needed to strengthen agricultural resilience. This study presents an integrated modelling framework for quantifying gaps in nitrogen (N), phosphorus (P), and potassium (K) fertilization under water‑limited conditions. The aim is to support site‑specific nutrient recommendations that improve fertilizer use efficiency while contributing to soil and water conservation.The framework combines three complementary models. INITIATOR simulates soil nutrient stocks and flows, providing a spatially explicit assessment of nutrient availability and potential depletion risks. WOFOST estimates water‑limited maize yield potential, capturing the influence of rainfall variability and soil moisture dynamics on attainable production. QUEFTS then models nutrient uptake and yield responses, enabling calculation of nutrient requirements that match crop demand without excess application. Together, these components enable a holistic evaluation of nutrient management in soil–crop–water systems on different management levels.The approach was applied to Uganda, a country characterized by strong agro‑ecological diversity, high interannual rainfall variability, and widespread soil degradation. Using 1 km resolution SoilGrids data and climate records from 2001–2024, spatially explicit water‑limited yield potentials were simulated for maize across the country. Fertilizer requirements were calculated based on median attainable yields for the period . Results reveal substantial geographic variation in nutrient availability, nutrient use efficiency, and fertilizer needs. In many areas, low soil nutrient stocks combined with high potential yield estimates lead to large fertilization gaps, while in other regions the gap is smaller due to relatively higher soil fertility or lower potential yields due to moisture constraints.These findings demonstrate that uniform fertilizer recommendations are unlikely to be effective under the diverse soil and climatic conditions of SSA. The proposed modelling framework provides a robust decision‑support tool for developing precision nutrient management strategies that align nutrient inputs with both crop demand and water availability. Such targeted approaches can help reduce nutrient losses to the environment, maintain soil fertility, and support sustainable intensification efforts across smallholder farming systems. This work highlights the potential of integrated soil–crop–climate modelling to guide context‑appropriate nutrient management solutions that enhance productivity while promoting soil and water conservation.

Earthworms play a crucial role in enhancing phosphorus (P) availability in soils by processing organic matter as well as mineral soil particles and associated P. This role could represent a lever to increase agronomic P use efficiency. However, if earthworms are employed to unlock soil P, soils will still need to be replenished with nutrients. This could be accomplished through the application of circular fertilisers. In this context, earthworms could help to mobilize P from emerging mineral fertilisers recovered from waste streams, such as struvite. Despite these potential benefits, the biotic influence of earthworms on P cycling remains poorly understood and the interactions between earthworms and emerging fertilisers are unknown. Here, we present results of two studies aiming at (1) testing an isotopic approach based on the oxygen isotopes ratio in phosphate (PO4) to study the biotic effect of earthworms on soil P cycling in arable soils; and (2) investigating the role of earthworms in mobilizing P from poorly soluble struvite. In a mesocosm experiment using straw and 18O-enriched water in the presence of soil-dwelling earthworms, we found that earthworms have a significant effect on the mineralization of P from organic residues in litter-amended soils with a low PO4 availability. We demonstrated that the 18O-isotopic approach provides a promising method to study the influence of earthworms on PO4 cycling. In a field study using struvite and ryegrass in the presence of multiple combinations of earthworm species, we showed that struvite performs comparably to conventional mineral P fertiliser in terms of plant P uptake, highlighting that struvite could be an efficient P fertiliser. The effect of earthworms on plant P uptake was significant but relatively small. These two studies emphasize that the effect of earthworms on P cycling is highly context dependent (e.g., soil P status and organic matter), with optimal efficiency observed in P-poor soils when a suitable food source is provided.

Human activities have drastically increased nitrogen (N) deposition onto forests globally. This may have alleviated N limitation and thus stimulated productivity and carbon (C) sequestration in aboveground woody biomass (AGWB), a stable C pool with long turnover times. This ‘carbon bonus’ of human N use partly offsets the climate impact of human‐induced N2O emissions, but its magnitude and spatial variation are uncertain. Here we used a meta‐regression approach to identify sources of heterogeneity in tree biomass C‐N response (additional C stored per unit of N) based on data from fertilization experiments in global forests. We identified important drivers of spatial variation in forest biomass C‐N response related to climate (potential evapotranspiration), soil fertility (N content) and tree characteristics (stand age), and used these relationships to quantify global spatial variation in N‐induced forest biomass C sequestration. Results show that N deposition enhances biomass C sequestration in only one‐third of global forests, mainly in the boreal region, while N reduces C sequestration in 5% of forests, mainly in the tropics. In the remaining 59% of global forests, N addition has no impact on biomass C sequestration. Average C‐N responses were 11 (4–21) kg C per kg N for boreal forests, 4 (0–8) kg C per kg N for temperate forests and 0 (−4 to 5) kg C per kg N for tropical forests. Our global estimate of the N‐induced forest biomass C sink of 41 (−53 to 159) Tg C yr−1 is substantially lower than previous estimates, mainly due to the absence of any response in most tropical forests (accounting for 58% of the global forest area). Overall, the N‐induced C sink in AGWB only offsets ~5% of the climate impact of N2O emissions (in terms of 100‐year global warming potential), and contributes ~1% to the gross forest C sink.

The human gut microbiome is currently recognized to play a vital role in human biology and development, with diet as a major modulator. Therefore, novel indigestible polysaccharides that confer a health benefit upon their fermentation by the microbiome are under investigation. Based on the recently demonstrated prebiotic potential of a carrot-derived pectin extract enriched for rhamnogalacturonan I (cRG-I), the current study aimed to assess the impact of cRG-I upon repeated administration using the M-SHIME technology (3 weeks at 3g cRG-I/d). Consistent effects across four simulated adult donors included enhanced levels of acetate (+21.1 mM), propionate (+17.6 mM), and to a lesser extent butyrate (+4.1 mM), coinciding with a marked increase of OTUs related to Bacteroides dorei and Prevotella species with versatile enzymatic potential likely allowing them to serve as primary degraders of cRG-I. These Bacteroidetes members are able to produce succinate, explaining the consistent increase of an OTU related to the succinate-converting Phascolarctobacterium faecium (+0.47 log10(cells/mL)). While the Bifidobacteriaceae family remained unaffected, a specific OTU related to Bifidobacterium longum increased significantly upon cRG-I treatment (+1.32 log10(cells/mL)). Additional monoculture experiments suggested that Bifidobacterium species are unable to ferment cRG-I structures as such and that B. longum probably feeds on arabinan and galactan side chains of cRG-I, released by aforementioned Bacteroidetes members. Overall, this study confirms the prebiotic potential of cRG-I and additionally highlights the marked consistency of the microbial changes observed across simulated subjects, suggesting the involvement of a specialized consortium in cRG-I fermentation by the human gut microbiome.