Effect of Plant Growth Promoting Rhizobacteria (PGPR) and Planting Pattern on Yield and Its Components of Rice (Oryza sativa L.) in Ilam Province, Iran
Abstract—Most parts of the world such as Iran are facing the excessive consumption of fertilizers, that are used to achieve high yield, but increase the cost of production of fertilizer and degradation of soil and water resources. This experiment was carried out to study the effect of PGPR and planting pattern on yield and yield components of rice (Oryza sativa L.) using split plot based on randomized complete block design with three replications in Ilam province, Iran. Bio-fertilizer including Azotobacter, Nitroxin and control treatment (without consumption) were designed as a main plot and planting pattern including 15 × 10, 15 × 15 and 15 × 20 and the number of plant in hill including 3, 4 and 5 plants in hill were considered as a sub-plots. The results showed that the effect of biofertilizers, planting pattern and the number of plants in hill were significant affect on yield and yield components. Interaction effect between bio-fertilizer and planting pattern had important difference on the number spikelet of panicle and harvest index. Interaction effect between bio-fertilizer and the number of plants in hill were significant affect on the number of spikelet per panicle. The maximum grain yield was obtained by inoculation with Nitroxin, planting pattern of 15 × 15 and 4 plants in hill with mean of 1110.6 g.m, 959.9 g.m and 928.4 g.m, respectively.
Growth promotion of plants by plant growth-promoting rhizobacteria under greenhouse and two different field soil conditions
Abstract This study was conducted with sugar beet in greenhouse and field at two soil type with different organic matter (containing 2.4 and 15.9% OM, referred as the low- and high-OM soil) conditions in order to investigate seed inoculation of sugar beet, with five N2-fixing and two phosphate solubilizing bacteria in comparison to control and mineral fertilizers (N and P) application. Three bacterial strains dissolved P; all bacterial strains fixed N2 and significantly increased growth of sugar beet. In the greenhouse, inoculations with PGPR increased sugar beet root weight by 2.8–46.7% depending on the species. Leaf, root and sugar yield were increased by the bacterial inoculation by 15.5–20.8, 12.3–16.1, and 9.8–14.7%, respectively, in the experiment of low- and high-OM soil. Plant growth responses were variable and dependent on the inoculants strain, soil organic matter content, growing stage, harvest date and growth parameter evaluated. The effect of PGPR was greater at early growth stages than at the later. Effective Bacillus species, such as OSU-142, RC07 and M-13, Paenibacillus polymyxa RC05, Pseudomonas putida RC06 and Rhodobacter capsulatus RC04 may be used in organic and sustainable agriculture.
N2 fixation in phototrophs: adaptation to a specialized way of life
Phototrophic diazotrophs include the photosynthetic green and purple bacteria, the heliobacteria, many cyanobacteria and the unusual chlorophyll-containing rhizobia that are found in the stem nodules of Aeschynomene spp. In this review, which concentrates on cyanobacteria, the interrelations between photosynthesis and N2 fixation are discussed. Photosynthesis can, in theory, directly provide the ATP and reductant needed to support N2 fixation but the link between these two processes is usually indirect, mediated through accumulated carbon reserves. In cyanobacteria, which possess an oxygenic photosynthesis, this serves to separate the O2 that is produced by photosynthesis from the O2-sensitive nitrogenase. However, in certain circumstances, oxygenic photosynthesis and N2 fixation coexist. Under these conditions, respiratory consumption of photosynthetically generated O2 may have an important role in minimizing O2-damage to nitrogenase.