Effect of humic and fulvic acids on the yield and quality traits of maize (Zea mays L.) cultivars

Humic acid enhances plant growth by improving enzyme activity, cell division, and root development, leading to higher biomass production. It also increases nutrient availability, buffers soil pH fluctuations, and prevents nutrient leaching. This study explores the impact of humic and fulvic acids on maize yield and quality to optimize their agricultural benefits. A field experiment on organic fertilizers was conducted during the spring season of 2022 in the Al-Hatra district, approximately 40 km from the city, by the Department of Field Crops Sciences, Al-Muthanna University, Al-Muthanna, Iraq. The factorial experiment included two factors. The first factor consisted of four maize cultivars (Zp, Maha, Forat, and Kaws), all of which are officially approved by the Ministry of Agriculture and sourced from the Agricultural Research Department, Maize Section. The second factor involved foliar application of four levels of organic fertilizer (a mixture of humic and fulvic acids) at rates of 10, 20, and 30 L/ha, in addition to a control treatment (no application). The results of the statistical analysis revealed significant differences among the levels of humic and fulvic acid application. The foliar application of 30 L/ha outperformed other treatments, achieving the highest values for 1000-seed weight (379.9 g), protein content (9.11%), and oil content (5.32%). Among the maize cultivars, Forat exhibited the longest ear length, averaging 20.98 cm, while Kaws recorded the highest 1000-seed weight (374.7 g) and grain yield (8.089 t/ha). Regarding the interaction effects, the combination of the highest application level (30 L/ha)