Effects of Azotobacter as a Source of Nitrogen on Wheat Yield and Grain Protein

Abstract

Nitrogen (N) is a key nutrient that governs wheat productivity and grain quality; however, excessive reliance on synthetic N fertilizers poses economic and environmental challenges. Consequently, nitrogen-fixing biofertilizers such as Azotobacter have gained attention as environmentally friendly alternatives to urea. The research hypothesis was that Azotobacter inoculation could substitute a portion of chemical N fertilizer without reducing wheat yield and quality. The objective of this study was to evaluate the potential of Azotobacter in substituting nitrogenous fertilizers for improving wheat yield and grain protein content. A field experiment was conducted from November 2024 to April 2025. The treatments included an untreated control, Azotobacter only; Azotobacter + farmyard manure (FYM); FYM + 100% recommended N; Azotobacter + FYM + 25% N; 50% and 75% N supplied via urea. Phosphorus and potassium were applied uniformly in all treatments. Results showed differences (p ≤ 0.05) among the treatments for most yield and yield-contributing parameters, except harvest index and sterility. The treatment Azotobacter + FYM + 75% N recorded the highest number of effective tillers (301 m^-2), thousand-grain weight (50.3 g), grain yield (4393 kg ha^-1), straw yield (5048 kg ha^-1), and grain protein content (12.7%). Although this treatment produced 13.7% higher yield than FYM + 100% N, the yields were comparable, indicating that Azotobacter application can effectively replace up to 25% of chemical N fertilizer. Thus, the combined use of Azotobacter, FYM, and 75% N can be recommended for sustainable wheat production in the mid-hills of Nepal.