The salinity challenge: macro-micro nutrients degradation, productivity loss, economic risks, and policy-technology directions in semi-arid regions

Soil salinization threatens significant agricultural lands globally, with semi-arid regions experiencing accelerated degradation due to climate change and unsustainable irrigation. Integrated analyses linking salinity, nutrition, and livelihoods remain rare. This systematic review quantified salinity effects on N, P, K, Fe, Zn, and B availability, economic impacts on smallholders, intervention effectiveness, and policy pathways for semi-arid regions. We searched Web of Science, Scopus, and Google Scholar (2015–2024) following PRISMA 2020 guidelines; meta-analysis included 47 studies on nutrient availability, quality-assessed using MMAT version 2018. At EC > 4 dS/m, macronutrient availability declined: N by 45% (95% CI: -52% to -38%), P by 60% (-68% to -52%), and K by 35% (-42% to -28%), with substantial heterogeneity (I² = 71–84%) and possible publication bias for P only. Micronutrient availability declined at EC 4–8 dS/m: Fe (-55% to -68%), Zn (-45% to -58%), B (-40% to -55%). Smallholders lose 25–50% of annual income (mean 37%, n = 28 studies), varying by region, farm size, and tenure status. Technical efficiency losses averaged 20%, indicating systemic constraints beyond fertilizer intensification. Biosaline technologies show high potential (B: C 1.4–2.8:1) but adoption remains < 10% due to market failures, knowledge gaps, and credit constraints. Context-specific thresholds replaced single EC benchmarks: legumes 2.8 dS/m, cereals 3.8–4.5 dS/m, halophytes > 8 dS/m. Breaking the salinity-poverty cycle requires integrated intervention addressing biophysical thresholds, economic incentives, institutional coordination, and climate adaptation, with priorities including phosphorus management, multi-stress-tolerant varieties, and scalable biosaline systems with secure tenure and long-term commitment.