Ruggedizing Haber-Bosch: Allocation, Efficiency, and Resilience in Fertilizer-Dependent Food Systems Under Supply Shock

Abstract The closure of the Strait of Hormuz following the February 2026 conflict removed roughly one-third of globally traded seaborne fertilizer from the market, and the World Bank places the worst yield impact still ahead, in late 2026 into 2027. This paper argues that the most valuable response is not additional supply but better allocation of the supply that already exists, and it sets out the evidence for that claim. Crop response to applied nutrient varies by roughly an order of magnitude, and this has now been measured twice, independently, in two nutrients. Nitrogen response across sub-Saharan Africa ranges from 5 to 53 kg of grain per kg applied — varying between countries, within them, and within individual farms. For phosphorus, a sorption analysis using Langmuir parameters measured for four Sahelian soil series yields a ten-fold spread in the fraction of applied or released phosphorus reaching soil solution, and an eight-fold spread in the quantity required to reach a standard agronomic concentration: 17 kg P/ha on the most responsive soil, 140 kg P/ha on the least. The between-soil ratios are independent of soil-water assumptions. The same tonnage, allocated by soil response rather than spread uniformly, therefore does several times the work — with no new production, supply, subsidy, or technology. The paper classifies agricultural zones by nutrient-system properties rather than by region, on the argument that zones sharing measurable properties take the same prescription wherever they sit. Four classes are developed: legacy-rich and over-applied, where anthropogenic phosphorus signatures exceed 60% and application approaches 200 kg/ha; climate-exposed and import-linked, where monsoon-dependent staple production meets price transmission and producer export restrictions; nutrient-poor and allocation-limited, where signatures fall below 30% and application runs near 5 kg P/ha; and access-constrained, where conflict is the principal driver. The first and third classes are complementary — demand reduction in one frees supply for the other — and this grounds a two-sided reserve proposal in a mechanism rather than a gesture. The fourth class is stated honestly as beyond the reach of the agronomic interventions assessed here, and conflict is the principal driver in twelve of the thirteen hotspots identified in June 2026 monitoring. Seven interventions deployable within twelve months are assessed against current commercial and field-trial evidence, and technical deployability is distinguished throughout from farmer adoption, since soil-health practices deliver visible benefit slowly and farmers require short-term returns. Prior art is conceded in full: the 2006 Abuja target and the subsidy programmes that followed, the field's existing diagnosis of blanket national recommendations, and Integrated Soil Fertility Management as the framework this paper applies rather than proposes. The narrow contribution offered is a sorption-based method for quantifying the spatial targeting term, so that "target by soil" becomes a number per soil series rather than a principle. Two framings are explicitly rejected. Independence from mineral fertilizer is not treated as achievable: organic and biological sources alone cannot build or sustain soil fertility, and biomass transferred from elsewhere supplies roughly a tenth of requirement while degrading the source soil. And availability is not assumed to be the binding constraint everywhere, since most fertilizer produced in sub-Saharan Africa is currently exported for want of domestic demand. An appendix presents a longer-horizon nuclear-physics proposal for radiation-induced phosphorus release, scoped as a 5–20 year research direction, reporting the negative finding that pion capture offers no useful elemental selectivity toward phosphorus in soil, with a four-arm falsification test costing approximately $10 and a pre-registered kill condition. All near-term recommendations rely on established science. Released under CC BY 4.0 for unrestricted use by policy, humanitarian and research audiences.