Effect of Humic Acid-Fortified Compound Fertilizer, Organic Amendment, and Biofertilization on Selected Growth Traits and Leaf Nitrogen, Phosphorus, and Potassium Concentrations in Barley. Murtada Reda Sadiq1, Basem Rahem Bader2*

• Murtada Reda Sadiq1, Basem Rahem Bader2

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This study aimed to assess the effects of a humic acid–enriched compound fertilizer, in combination with organic and biological amendments, on growth traits and foliar nutrient concentrations in barley. The field work took place on farmland affiliated with the College of Agriculture at the University of Diyala during the 2024–2025 season, using a randomized complete block design laid out as a factorial experiment with three replicates. The three experimental factors comprised a humic acid-fortified compound fertilizer at four application levels (0, 33, 66, and 100% of the recommended dose), an organic amendment at three levels (0, 2, and 4% of soil volume), and biofertilization with Pseudomonas fluorescens at two levels (with and without inoculation).

The recorded measurements included plant height, leaf area, number of spikes per plant, grain yield per plant, and the concentrations of nitrogen, phosphorus, and potassium in the leaves at the booting stage. A clear superiority of the A4B3C2 interaction was observed across nearly all traits. This combination gave the tallest plants at 91.96 cm, the largest leaf area reaching 30.67 cm², the highest spike count of 4.66 spikes per plant, and the greatest per-plant yield of 5.055 g. Compared with the A1B1C1 control, the increases amounted to 98.06% for plant height, 380.72% for leaf area, 366.00% for spike number per plant, and 494.01% for individual plant yield. Leaf nutrient levels at booting also peaked under this treatment, registering 4.66% nitrogen, 0.70% phosphorus, and 5.62% potassium—representing gains of 130.69%, 366.67%, and 73.46% respectively over the control values.

It can be concluded from these findings that an integrated fertilization strategy blending a humic acid-augmented compound fertilizer with organic matter and bacterial inoculants offers a sound, efficient approach for stimulating barley growth and improving its mineral nutrition. The underlying mechanisms likely involve a more balanced delivery of nutrients from the soil to the plant, enhanced fertilizer recovery efficiency, and broader improvements in those soil characteristics that govern nutrient release, including shifts in pH and greater rooting depth and root density, all of which feedback positively onto the traits examined here.

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