Document Type : Research Article
Authors
1 Payame Noor University, Tehran
2 Moghan College of Agriculture and Natural Resources, University of Mohaghegh Ardabili
Abstract
Introduction: The excessive uses of chemical fertilizers have generated several environmental problems. Some of these problems can be tackled by use of Biofertilizer, which are natural, beneficial and ecologically friendly. The Biofertilizers provide nutrients to the plants and maintain soil structure. Biofertilizer is an alternative to mineral fertilizers for increasing soil productivity and plant growth in sustainable agriculture. Plant growth promoting rhizobacteria (PGPR) are a group of bacteria that actively colonize plant roots and increase plant growth and yield. There is a widespread distribution of PGPR that flourishes in different geographical habitats. These rhizobacteria significantly affect plant growth not only by increasing nutrient cycling, also by suppressing pathogens by producing antibiotics and siderophores or by bacterial and fungal antagonistic substances and/or by other plant hormones. Inoculation of plants with Azospirillum could result in significant changes in various growth parameters, such as increase in plant biomass, nutrient uptake, tissue N content, plant height, leaf size and root length of cereals. Thus, it has been shown that Azospirillum and Pseudomonas have the potential for agricultural exploitation and can be used as natural fertilizers. The divers array of bacteria including Pseudomonas, Azospirillum, Azotobacter, Bacillus, Klebsilla, Entrobacter and Serratia seem to promote plant growth. These bacteria are important components of the rhizosphere of many plants, and are known to colonize the rhizosphere of wheat, potato, maize, grasses, pea and cucumber. Strains of Pseudomonas putida and Pseudomonas fluorescens could increase root and shoot elongation in wheat. Azospirillum, Pseudomonas and Azotobacter strains could affect seed germination and seedling growth
Materials and Methods: To investigate yield, yield components and some qualitative and quantitative characteristics of safflower at different planting dates, a factorial experiment was conducted based on randomized completed block design with three replications in 2016 at the laboratory of Agricultural University of Payam Noor, Kosar (Kivi) branch. The first factor consists of three sowing dates (5 March, 20 April and 5 May) and the second factor involves the seeds inoculation with plant growth promoting rhizobacteria (no inoculation, seed inoculation with Azotobacter chorchorum strain 5 and Azosprilium lipoferum strain OF). The climate of studied region is semi-arid with 1350 meters altitude from sea level. Based on the soil test, pH was about 7.1, soil texture was loamy-sand and the depth of top soil was 70 cm. The experimental unit included six ridges of 25 cm in 6 m length. The plant density was 40 plants per m2. Each 1 gram bacteria have 107 no, we therefore used about 7 gr from each bacterium for seed inoculation. We also used Arabic gum to adhere the bacteria to the seed.
Results and Discussion: The results showed that the planting date had a significant effect on all characteristics, except brain to grain ratio and the ratio of skin to grain. The effect of seed inoculation with plant growth promoting rhizobacteria was statistically significant on plant height, stem diameter, number of main and sub main branches, seed oil and protein percentage. The maximum number of boll per plant, number of grain per boll, 1000-grain weight, grain yield, biological yield, harvest index, plant height and protein percent were achieved on the first planting date (5 April). The lowest amounts of these traits were obtained on the third planting date (5 May). The maximum oil percentage, number of primary and secondary branches and stem diameter were obtained on the first planting date and seed inoculation by Azotobacter. The lowest rates of these traits were obtained on the third planting date and no inoculation. Thus, seed priming with Azotobacter and first date (5 March) planting are recommendable to increase number of grain per boll, 1000-grain weight, grain yield, biological yield, harvest index, plant height and protein percent and other traits.
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