Abstract
Owing to water scarcity and environmental hazards of synthetic fertilizers, reducing water and chemical N fertilizers is very urgent for sustainable agriculture. Thus, two field experiments were conducted to understand the physiological role of Azolla filiculoides Lam. extract (AE), as a promising biofertilizer, in enhancing growth, physiology, yield, N uptake efficiency (NUpE), N use efficiency (NUE) and irrigation water use efficiency (IWUE) in N-deficient maize plants under full and deficit irrigation. The experimental design was split plot with irrigation treatments as main plots and N treatments including full nitrogen (FN; 285 kg N ha(-1)), nitrogen deficiency (ND; 190 kg N ha(-1)) and ND (190 kg N ha(-1)) + AE (10% w/v) as subplots. At the vegetative stage, deficit irrigation was performed by withholding water from 26 to 56 days after sowing, while N-deficient plants received two-thirds of the total recommended N. N deficiency caused deleterious impacts on growth and yield of maize plants, particularly under deficit irrigation. However, results evidenced the role of Azolla extract, as an efficient biofertilizer, in combination with deficit irrigation in improving NUpE, NUE and IWUE without substantial decreases in grain and stover yields of N-deficient maize plants. Application of Azolla extract improved growth, yield attributes, irrigation water and N use efficiency via enhancing photosynthetic pigments, leaf water status, proline accumulation and N uptake with a reduction in membrane oxidative damage. Overall, the application of Azolla extract is an eco-friendly and cost-effective organic fertilizer to reduce more than 30% of urea fertilizer without affecting grain yield of maize plants.