Effect of nitrogen and phosphorus fertilizers on yield and nutrient efficiency indices in maize under drought stress

Reduced use efficiency of important elements such as phosphorus and nitrogen has led to higher costs for corn production, reduced economic efficiency of fertilizers and greater environmental impacts due to increased use of these fertilizers. The use of nitrogen-stabilizing biological fertilizers is a potential alternative that can minimize these negative effects.

For this purpose, a split factorial layout with 4 replications based on randomized complete block design was conducted two consecutive years (2016 and 2017) at the Agricultural Research Station of Mehran in East of Ilam province. The studied factors included irrigation in 3 levels including non-stress, drought stress based on 75% and 50% field capacity. In sub-plots, two factors were factorial. The first sub-factor included nitrogen fertilizer at 100% fertilizer requirement (Net nitrogen) through urea, control and Azotobacter biological fertilizer. Another sub-factor included 100% phosphorus fertilizer (Net phosphorus) in the form of triple superphosphate, control and Pseudomonas biological fertilizer applied.

The results of this study showed that interaction of stress, nitrogen and phosphorus on seed yield were significant. The highest seed yield (11932 kg ha-1) was obtained in irrigation with Azotobacter and Pseudomonas. However, there was a significant difference at the same level of stress associated with Azotobacter and triple superphosphate (11873 kg ha-1) and irrigation treatment with Pseudomonas and urea (11318 kg ha-1). Furthermore, at all levels of stress and consumption of Azotobacter and triple superphosphate, grain yield increased compared to control treatment. The interaction of stress, nitrogen and Phosphorus had significant effect on nitrogen productivity. The highest nitrogen productivity was obtained in non-stress treatment and inoculation of Azotobacter and Pseudomonas with 54.04 kg kg -1. At all irrigation levels, Azotobacter inoculation along with Pseudomonas aeruginosa increased nitrogen productivity.

The results of this study showed that Pseudomonas and Azotobacter bacteria, both low (100% capacity) and severe (50% capacity) water stress conditions, possibly by increasing food absorption caused to increased the quantitative and qualitative yield of maize.