Morphophysiological and growth responses of sesame plant to combined use of sulfur and Thiobacillus

Sesame is an annual plant with a history of 5,000 years, apparently the oldest oilseed in the world. Due to the climatic conditions and characteristics of Iranian soils, it is very important to pay attention to the consumption of sulfur in agricultural lands. Lack of sulfur fertilizer consumption (such as simple superphosphate) containing in the last few years, consistent and intense cultivation of agricultural lands, the existence of sodic and saline-sodic soils, abundance and affordability of sulfur are the most important reasons for paying attention to sulfur consumption in Iran. The importance of this element in oilseed plants is more important. Sulfur must first be converted to sulfate ions to be absorbed by plants, which is caused by microorganisms such as chemoaulytotrophs, which use elemental sulfur as a source of energy. The most important of these microorganisms are Thiobacillus bacteria (Zhi-Hui et al., 2010). The realization of this depends on the existence of a significant population of Thiobacillus.
This study was conducted as complete randomized blocks design for factorial experiment with 3 replications on a farm in Karaj city (Alborz province) in the 2017-2018 agronomic year. In this experiment, sulfur fertilizer was used at three levels (including control level (S0), 100 Kg.ha-1 (S1) and 300 Kg.ha-1 (S2)); Thiobacillus bacteria was used at two levels (including no inoculation (T0) and inoculation with bacteria (T1)). Then plant height, yield and yield components and harvest index were calculated. To determine the content of chlorophyll and carotenoids before the end of the growing season, sampling of plant leaves was performed. Analysis of variance and mean comparisons of data (at a 5% probability level based on LSD test) were performed using SAS software (Ver. 9.4). MS Excel was also used to plot the diagrams.
The results showed that all the studied traits were significantly affected by the main effect of sulfur fertilizer and except for the plant height, all the studied traits were affected by the main effect of Thiobacillus. So that the highest amount of all the tested properties of sulfur fertilizer was 300 Kg.ha-1 in sesame. The use of Thiobacillus bacteria also significantly increased all the studied characteristics in sesame plants except plant height. The interaction of sulfur fertilizer and Thiobacillus bacterium also had significant effects on the number of capsules per plant, the number of seeds per capsule, grain yield, biological yield, chlorophyll a, chlorophyll b and total chlorophyll.
Due to the high level of lime in the soils of our country and the cheapness of sulfur resources in Iran, to reduce soil pH use sulfur fertilizer and to facilitate access to sulfur resources, increase oxidation of this fertilizer and increase the activity of beneficial soil microorganisms using bacteria Thiobacillus is recommended.