Enhancement of yield in cowpea (Vigna unguiculata) genotypes through nano-iron fertilization: a quantitative and qualitative assessment

To combat global mineral deficiencies, developing nutrient-dense crops like cowpea is essential. This study evaluates the impact of an iron nano-fertilizer (Fe3O4, 2 kg ha−1) on 12 cowpea lines (C1-C12) and the 'Mashhad' variety in four Iranian regions. Results revealed significant variation in genotypic responses to fertilizer across environments. Iron nano-fertilizer increased protein and iron content by 5.5% and 14%, respectively, in the Khomein region, where baseline accumulation was lowest. Genotypes C4 and C3 had the highest (1297 kg ha−1) and lowest (834 kg ha−1) yield, respectively, in conditions without iron application, while the best genotypes in conditions of iron application were genotypes C1 and C11 (1404 kg ha−1). Cluster analysis of the data under both conditions – with and without iron nano-fertilizer – classified the genotypes into two distinct groups. For fresh consumption, based on nitrogen and iron contents, the appropriate time to harvest the pods is in the middle of the seed filling duration. Overall, iron nano-fertilizer improved protein, iron, and nutritional value across genotypes. Further studies should determine its absorption, effects, and underlying mechanisms in different genotypes and locations to develop optimal applications for superior cowpea lines.