Study of Viability of Phosphate Solubilizing Bacteria in Phosphate granules

sustainable development and the environment are interconnected. Sustainable agriculture is continuous utilization of a farm with respect to various aspects of environmental conditions by using fewer inputs (other than Bio-fertilizers). Phosphorus is one of the essential elements for the plants. Management of soil is possible by using biological fertilizers pillar of sustainable agriculture and providing some of the phosphorus needed by plants via bio-fertilizers. Phosphorus deficiency is extremely effective on the plant growth and productivity. The application of phosphorus fertilizers is expensive and dangerous. In addition, phosphorus in the soilmay become insoluble and will be unavailable to the plants. Studies showed that phosphate solubilizing bacteria in the soil rhizosphere are active and by root exudates solve insoluble phosphates such as tricalcium phosphate, and form absorbable P for plant. Consequently, the use of microbial fertilizers could reduce excessive use of chemical fertilizers and lead to decrease their harmful effects and protect the environment and conservation of available resources. The biological phosphate fertilizer industry uses sugar beet molasses as a binder and drying granules at high temperatures. Therefore, it is important to evaluate the durability of the bacteria in molasses at high temperature.
This study was designed as completely randomized design in a factorial arrangement.10 isolates were selected and the ratios of 50%, 25%, 15% and 10% of the apatite, organic matter, sulfur and soluble granule (ratio 1: 1 and 2: 1 bacteria and molasses), respectively, for each isolate was prepared. The final product was dried at 28 and 40 °C and remained for 4 months and population counted at first day and 10, 20, 30, 60, 90 and 120 days after the preparing. The population was counted by the serial dilution technique and cultured at Sperber media.
Comparing the average logarithm of population of bacteria in the granules indicated the highest proportion in the granules on the first day and the lowest population on 120 days (4 months), andthe ratio of 1: 1 inoculant and molasses had the largest population than the 2:1. The highest population was observed in 1:1 dried granules at 28 °C, but, some of 1:1 dried granules at 40 °C were consistent with the defined standards. Overall, bacteria I2-4, Z4 and C5-1 showed the greatest amount of population and the population had more power to maintain the standards among the isolates. The granules produced according to the defined standard (two-month period, 105 cell per gram of fertilizer) are dried at 28 °C in both 1: 1 and 2: 1 to the end of 4 months in the standard population. Granules dried at 40 °C for 1: 1 ratio of the population by the end of 4 months in the standard range. In the case of the most isolated granules at the ratio of 2:1 until the end of the second month, the population were within the standard range but at the end of the third month, they come lower than standard except I2-4, Z4 and C5-1. The total population of the granules was as following: Granules 1: 1, 28 °C> 2: 1, 28 °C> 1: 1, 40 °C> 2: 1, 40 °C. Considering to the fact that this standard is undefined for four months, but in this study, the population was 104 granules in the fourth month.
Based on the results, some of these conditions could keep their population and population decline was less. In general, it can be concluded that the granular organic fertilizer phosphorus in the industry of phosphate solubilizing bacteria with sugar beet molasses as a binder and drying at 40 °C can be used The results were positive and the granules can be cited to the production of this type of microbial fertilizer. Considering to the results, it was found that the proportion of molasses and inoculant, drying temperature and storage time were effective on viability of bacteria. Also, instead of using a train of bacteria, phosphate solubilizing bacteria, a combination of any of these bacteria in a field lead to better results. It is clear that by a comprehensive study, the molecular identification of bacteria, and detection of desire genetic loci and then gene transfer between bacteria for increasing of high temperature resistance by spour production and also, gene transfer between bacteria with high population and non-tolerance to sugerbeet molasses and tolerant bacteria to sugar beet molasses but low population; we can achieve bacteria with high population and high tolerance to sugar beet molasses and consequently achieve to favorable results. This result could decrease chemical phosphate fertilizers usage and their harmful effects and help to protect the environment and available resources.