The Production of Granulated Thiobacillus Biofertilizer by Native Facilities.

Inglés. The conjunction of calcareous parent materials and dry climate has resulted in the development of calcareous and alkali soils in large areas of Iran. Due to the high levels of Ca++ in soil solutions and high pH values, the soil nutrients, whose absorptions depend on pH, will become less available and thus limit the growth of crop plants. It has been a common practice in many regions of the world to use elemental sulfur as an acidifying source to lower pH and to improve the availability of some soil nutrients. In addition, the supply of sulfur used for the reclamation of sodium affected soils serves as a source of plant nutrient and more importantly acts as a disease controlling agent. Application of sulfur is one way to increase the availability of insoluble nutrients in calcareous and alkaline soils. Effectiveness of elemental sulfur depends on the activity of sulfur oxidizing bacteria especially, Thiobacillus genus. Sulfur application in agricultural practices deserves more consideration especially, since a large quantity of this material is produced in the country, where a great percentage of the farmlands are calcareous. A major requirement in utilizing elemental sulfur to lower soil pH is the presence and activity of sulfur oxidizing bacteria (especially the Thiobacilli) in the soils. The beneficial effects of sulfur application along with Thiobacillus bacteria for soil reclamation and improvement of soil nutrient availability have been demonstrated in various fields as well as greenhouse studies. In all such investigation, either pure cultures of Thiobacillus suspension or Thiobacillus bearing soils were utilized as inoculants, neither of which are applicable in a large scale use. On the other hand, the acid produced as a result of the oxidation of the sulfur material during the growth cycle or long-term maintenance phase of Thiobacillus would cause limitation on their growth and sharp declines in their population densities. The first part of the present research was aimed at the development of a carrier, suitable for a long-term maintenance of Thiobacillus bacteria as well as a source of inoculants to be used in the greenhouse and field experiments. For this the most effective sulfur oxidizing isolates of Thiobacillus bacteria indigenous to the soils of Iran were selected. The data on the generation time, the amount of acid produced, the lowest pH level, and the percentage of sulfur oxidation in the growing suspension of bacteria were 9.59 hrs, 26 me l-1, 2.75, and 24.17%, respectively. The surviving abilities of the bacteria in various carriers were tested using a completely randomized split-split-plot design with 12 treatments, 8 sampling times, and 3 replications. The effect of all treatments on carrier pH and bacterial population measured at constant time intervals during a 6-month period for different materials showed significant differences (1% level). At these time intervals the pH values and bacterial populations were higher at 4oC than at 25oC. Carrier 3 (30g perlite+120 g apatite+1% S by weight) contained the highest number of bacteria at 25oC while at 4oC it did not significantly differ from carriers 2, 4, and 5 in this respect. Carrier 3 maintained a large population of bacteria for a longer period of time, and in contrast to the other carriers, it contained a larger population during the 6-month trial at 25oC than at 4oC. Therefore, it was selected as the superior carrier. Carrier 6 showing the lowest numbers of bacteria at both temperatures was ranked the lowest...

Inglés. (Continue) To evaluate the possibility of partially substituting sulfur along Thiobacillus inoculum for phosphorus and micronutrient fertilizers, a randomized complete block factorial experiment was carried out on corn for two consecutive years. The treatments included four levels of sulfur (200, 400, 600 and 1000 kg/ha), four levels of Thiobacillus inoculum (at rates of 0, 1, 2 and 4 percent of sulfur) a control and balanced fertilization based on soil tests, during the first year. Following soil preparation and establishment of 72 plots measuring 5 * 2.4 m, each fertilizer was applied according to the treatment schedule, and finally a Single Cross 704 variety of corn was planted every 17.5 cm on rows 60 cm apart. Leaf samples were collected when the plants tasseled. At the end of the growing season the plants were harvested on two middle rows in 4.2 m2 sections, then the fresh weight, the dry weight, average length and weight of ears, as well as the concentrations of iron, zinc, copper, manganese and phosphorus were determined in the stems, leaves and grains. The treatments for the second year of the experiment included three levels of sulfur (200, 400 and 600 kg/ha), two levels of Thiobacillus inoculum (at the rates of 0 and 1% of sulfur w/w), a control, and balanced fertilization based on soil tests. Following fertilizer treatments on 24 plots prepared as the year before, corn was planted in the same way. Other cultivation practices, harvesting, irrigation, fertilizer application sampling and analysis, measurement of various other parameters, as well as statistical procedures were performed as in the first year. Data from the first year showed that there were no significant treatment effects with respect to weight and length of ears or the absorption of phosphorus, iron, zinc, copper and manganese in the shoots, even though the concentrations of phosphorus, iron, copper, zinc, and manganese in the shoots were significantly different for the different treatments. However none of the treatments were significantly different from the control or triple superphosphate with respect to the concentrations effects for the nutrients listed. This was true even though the treatments significantly affected the shoot dry weights. The dry weights for the control plot, optimal fertilization and treatment T4 (with the highest yield) were 30.62, 35.83 and 37.71 tons per hectare, respectively. With the last two treatments being statistically the same but significantly different from the control. Treatments T2, T4, T5, T7, T8, T10, T13, T14 and T15 were statistically the same as triple superphosphate treatment, while the rest of the treatments had the same statistical significance as the control. Data from the second year showed that there were no significant treatment effects with respect to dry weight and nutrients uptake in the shoots, even though the concentrations of phosphorus, iron, copper, zinc, and manganese in the shoots and seed were significantly different for the different treatments, and treatment T8 (optimal fertilization) was the best. In the 4th section of this research some perlite, rock-phosphate, elemental sulfur, and organic matters mixed with each other as different formulations. Then Thiobacillus bacterial suspension was added to these formulations and granulated. To evaluate the survival of Thiobacillus on samples, The Thiobacillus population was enumerated on them at time intervals by using colony count technique. The resuls indicated that only one of formulations could maintain one hundred thousands cell per one gram at about 2.5% moisture.