Enhancing Photosynthesis Pigment, Protein Content, Nutrient Uptake and Yield in Maize (Zea mays L.) Cultivars Using Vermicompost, Livestock Manure and Azotobacter chroococcum

In recent decades, the overuse of chemical fertilizers has posed significant environmental challenges worldwide, prompting a shift towards sustainable agricultural systems that emphasize bio-organic fertilizers to enhance soil and plant health. The split-plot experiment examined the effects of different fertilizer types (vermicompost (VC), livestock manure (LM), and Azotobacter chroococcum), cultivation times (June 19 and June 30, 2021; June 19 and June 30, 2022), and genetic cultivars (Single Cross 704 and Masil 703). The results showed a significant increase in Chl a, with an average increase of 1.44 mg g^-1 FW in 2021 and 1.42 mg g^-1 FW in 2022, Chl b, with an increase to 0.86 mg g^-1 FW in 2021 and constant levels in 2022, and total Chl, which increased to 2.3 mg g^-1 FW in 2021 after the application of VC and A. chroococcum. Similarly, carotenoid content increased significantly with VC application compared to the control group, with increases of 0.062 and 0.066 mg g^-1 FW in the two crop years, respectively. In addition, the first cultivation time showed higher levels of Chl a, Chl b, total Chl, carotenoids and nutrient uptake compared to the second cultivation time. In addition, the application of bio-organic fertiliser resulted in increased seed protein content, with the highest levels observed being 8.42% in 2021 and 8.69% in 2022. Seed nutrient uptake, particularly calcium (Ca) (21.96 mg kg^-1 DW), potassium (K) (270.7 mg kg^-1 DW), phosphorus (P) (19.94 mg kg^-1 DW) and iron (Fe) (1.76 mg kg^-1 DW), was significantly increased by VC and A. chroococcum, with further increases observed with VC application. Forage yield was significantly influenced by the experimental treatments, with VC and A. chroococcum showing the highest yields, reaching 80.94 t h^-1 and 79.75 t h^-1 respectively in 2021. Overall, the study highlights the potential benefits of VC and A. chroococcum in improving the nutritional content and yield of maize crops.