Nanoparticle and Ionic Zn Promote Nutrient Loading of Sorghum Grain under Low NPK Fertilization

This study evaluated the effects of ZnO nanoparticles (NP) or Zn salt amendment on sorghum yield, macronutrient use efficiency, and grain Zn-enrichment. Amendments were through soil and foliar pathways, under "low" and "high" levels of nitrogen, phosphorus, and potassium (NPK). In soil and foliar amendments, grain yield was significantly (p ≤ 0.05) increased by both Zn types, albeit insignificantly with soil-applied Zn at low NPK. Across NPK levels and Zn exposure pathways, both Zn types increased N and K accumulation relative to control plants. Compared to N and K, both Zn types had a mixed effect on P accumulation, depending on NPK level and Zn exposure pathway, and permitted greater soil P retention. Both Zn types significantly (p ≤ 0.05) increased grain Zn content, irrespective of exposure pathway. These findings suggest a nanoenabled strategy for enhancing crop productivity, grain nutritional quality, and N use efficiency based on Zn micronutrient amendments, with potential implications for improved human and environmental health.