Effect of Different Levels of Nitrogen Fertilizer, Fungal Biofertilizer, and Algal Biofertilizer on Urease Enzyme Activity and Nutrient Availability for Barley (Hordeum vulgare L.)

• Hanan Awad Hammoud Al-Ziadi1, Allawi Abdulsada Japer Al-Murshidi2

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A field experiment was conducted at Al-Muthanna University research station in Al-Najmi district, north of Al-Muthanna Governorate, during the winter growing season (2025–2026). The study aimed to investigate the effects of Trichoderma harzianum, Chara sp. algae, and nitrogen mineral fertilizer applied at four levels (0, 25, 50, and 75% of the full nitrogen recommendation, equivalent to 0, 50, 100, and 150 kg N ha⁻¹ as urea 46%) on urease enzyme activity, soil NPK availability, plant growth, and grain yield of barley (Hordeum vulgare L.). The experiment was arranged in a randomized complete block design (RCBD) with three replicates. Results showed that dual inoculation with T. harzianum + Chara sp. (B3) significantly outperformed all other treatments across all studied parameters. Urease activity at 45 and 90 days after planting reached 124.00 and 116.67 μg N-NH₄⁺ g⁻¹ soil 2h⁻¹, respectively. Soil available nitrogen, phosphorus, and potassium were 20.57 mg N kg⁻¹ soil, 17.15 mg P kg⁻¹ soil, and 185.57 mg K kg⁻¹ soil, respectively. Plant height reached 101.31 cm and grain yield reached 7.70 Mg ha⁻¹. Application of nitrogen fertilizer at the 75% level (N3) recorded the highest urease activity (137.00 and 128.75 μg N-NH₄⁺ g⁻¹ soil 2h⁻¹ at 45 and 90 days, respectively), soil NPK (19.72 mg N kg⁻¹ soil, 16.27 mg P kg⁻¹ soil, 174.49 mg K kg⁻¹ soil), plant height (100.33 cm), and grain yield (7.27 Mg ha⁻¹).

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