Role of biofertilizers and organic fertilizers in growth and productivity Maize (Zea mays L.) under constant levels of mineral fertilizers

A field experiment was conducted in one of the fields of Ibn Al-Bitar Vocational Preparatory School, located in Al-Husseiniya sub-district, Karbala Governorate, at 32°N latitude and 44°E longitude, during the fall season of 2024. The experiment was designed using a randomized complete block design (RCBD) in a factorial arrangement with three replications. The first factor included different levels of NPK fertilizer: the full recommended dose, three-quarters of the recommended dose, and half of the recommended dose, denoted as C1, C2, and C3, respectively. The second factor consisted of the following treatments: control, sheep manure at 4 tons ha-1, poultry manure at 4 tons ha-1, sheep manure at 4 tons ha-1 + EM1, poultry manure at 4 tons ha-1 + EM1, and EM1 alone, denoted as O1, O2, O3, O4, O5, and O6, respectively. The results indicated significant differences among the NPK fertilizer levels. The C1 treatment (full recommendation) outperformed other treatments in plant height, leaf area, total chlorophyll content, 500-grain weight, grain yield, and biological yield, with means of 183.83 cm, 4121.8 cm², 0.9505 mg g-1 fresh plant tissue, 195.51 g, 7.633 Mg ha-1, and 19.34 Mg ha-1, respectively. Similarly, organic and biofertilizer treatments showed significant effects, with O4 (sheep manure at 4 tons ha-1 + EM1) demonstrating the highest values for the aforementioned traits, recording 188.33 cm, 4094.5 cm², 1.0129 mg g-1 fresh plant tissue, 206.96 g, 8.833 Mg ha-1, and 21.68 Mg ha-1, respectively. The interaction between factors was also significant, with the C1O4 combination achieving the highest values in all studied traits. These findings suggest that the addition of organic matter, particularly the O4 treatment, resulted in a substantial improvement in maize growth and productivity.