Feeding the Future: Agroecological Pathways to Climate Adaptation and Food Security

Fertiliser use efficiency occupies a central but poorly interrogated position within climate-smart agriculture, where it is routinely presented as the instrument through which higher yields, lower greenhouse gas emissions and improved soil condition can be reconciled. This critical narrative review examines whether the published evidence supports that reconciliation. The state of knowledge is assessed across four domains: the conceptual behaviour of efficiency metrics, the emissions consequences of efficiency-oriented management, the performance of the principal technological and agronomic interventions, and the relationship between nutrient management and soil biological, chemical and physical function. Literature was identified through searches of open scholarly databases and citation indexes, supplemented by backward citation searching, and every retained source was verified against authoritative bibliographic records. The synthesis indicates that partial efficiency ratios can rise while environmental performance deteriorates, because the most commonly reported indicators are insensitive to soil nutrient depletion, to the substitution of imported for internally cycled nutrients, and to upstream manufacturing emissions. Direct nitrous oxide emissions respond to nitrogen surplus more predictably than to application rate alone, which weakens the case for rate reduction as a stand-alone strategy and strengthens the case for balance-based management. Enhanced-efficiency fertilisers, subsurface placement, decision-support-guided nutrient management and combined organic and mineral inputs all show measurable benefits, but effect sizes are strongly conditioned by soil texture, pH, moisture regime and baseline management, and several interventions transfer losses between pathways rather than eliminating them. Evidence connecting efficiency to soil health is the weakest of the three pillars, constrained by short experimental durations, inconsistent indicator selection and unresolved causal direction. Confidence in a universal triple-win narrative is therefore limited. Priorities include multi-season, multi-gas experiments with harmonised soil health measurement, surplus-based accounting at farm and landscape scales, and evaluation of interventions in the under-fertilised systems where they have been least tested.