The effects of nitrogen and silicon biofertilizers on powdery mildew disease, physiological parameters and yield of wheat (Triticum aestivum L.)

In order to evaluate the effects of nitrogen and silicon (Si) plus biofertilizers on powdery mildew disease, physiological parameters and yield of wheat (Triticum aestivum L.) cv. N8019, a pot experiment was conducted in a factorial based randomized complete block design at Sari Agricultural Sciences and Natural Resources University during 2009. Treatments included biofertilizer in four levels (non-inoculation, Pseudomonas fluorescens + Bacillus subtilis, Azotobacter brasilense + Azospirillum lipoferum and Azospirillum + Pseudomona + Bacillus), three levels of nitrogen fertilizer (0, 35 and 70 kg nitrogen ha-1) and three levels of potassium silicate (0, 500 and 1000 mg/kg). Results showed that biofertilizers significantly increased both physiological parameters and grain yield of wheat compared to control. Maximum grain yield and leaf area (32.3 and 27.4 percent more than control) were recorded in those plants which received co-inoculation of Azotobacter + Azospirillum (Nitroxin). Furthermore, coinoculation of Pseudomonas with Bacillus (Barvar 2) plus either medium or maximum nitrogen fertilizer markedly improved chlorophyll a and chlorophyll b content. In the case of powdery mildew, the spraying of both 500 and 1000 ppm of silicon significantly reduced the amount of powdery mildew infection and percentage of infected plants compared to control.