Effect of Sulfur, Thiobacillus bacteria and phosphorus on the yield and nutrient elements uptake of wheat in calcareous soil

Investigating the status of nutrients in calcareous soils shows that despite the abundance of some nutrients (such as phosphorus, iron, and zinc) in these soils, the available form of these nutrients is less than the amount required for plant growth, and the deficiency of nutrients is one of limiting factor in the production of plants especially wheat in these soils. Sulfur application and soil inoculation with Thiobacillus bacteria may improve the availability of nutrients in calcareous soils and consequently increase the plants growth. The purpose of this research was investigating the effect of sulfur application and Thiobacillus bacteria on the yield and nutrient uptake of wheat at different levels of phosphorus in a calcareous soil and in field conditions.
Material and In 2011 a factorial experiment arranged in a complete randomize block design consisting of three levels of sulfur along with Thiobacillus bacteria (without sulfur and Thiobacillus (S0T0), application of 500 Kg S 10 Kg Thiobacillus (S500T10), 1000 Kg S 20 Kg Thiobacillus (S1000T20) and 2000 Kg S 40 Kg Thiobacillus (S2000T40) per hectare) and three levels of triple super phosphate (without phosphorus (P0), 65 (P65%) and 100 (P100%) percent phosphorus recommended based on soil test) with three replication in field conditions. The leaf samples were collected before pollination and the content of phosphorus; zinc and iron were measured in them. After harvest, the yield components such as grain and straw yield, panicle length and 1000 seed weight in each treatment were determined. Then, from each plot, five kilograms of soil was taken from 0 to 15 cm depth and after dried out and sifted with a two-millimeter sieve, the concentration of phosphorus, zinc and iron of soil was determined in them.
With the application of sulfur along with Thiobacillus bacteria, the yield components and uptake of iron, zinc and phosphorus of wheat leaf increased compared to the control treatment, although the grain yield, straw yield and uptake of iron between the different levels of sulfur along with Thiobacillus bacteria showed a no significant difference. Using of phosphorus significantly increased the grain yield, straw yield, 1000 grain weight and uptake of iron and phosphorus of wheat leaf, but no significant difference was observed between treatments 65 (P65%) and 100 (P100%) percent phosphorus recommended based on soil test. In conditions of without phosphorus (P0), with consumption of 1000 kg ha-1 sulfur along with 20 kg ha-1 of Thiobacillus (S1000T20), grain yield, straw yield and panicle length increased compared with the control (124, 123 and 31% respectively), but with increasing levels of sulfur and bacteria, a decrease was observed in these parameters. The highest uptake of leaf iron and phosphorus were showed in combined treatments S1000T20 P100% and S2000T20 P65%, respectively. With the increase of sulfur along with Thiobacillus bacteria, Zn concentration and pH of soil decreased and the lowest values of these characteristics were observed at the highest levels of sulfur and bacteria. At all levels of phosphorus application, the consumption of 500 kg ha-1 sulfur along with 10 kg ha-1 Thiobacillus bacteria (S500T10) increased the phosphorus concentration in soil and highest contents of it was were obtained of combined treatments S500T10 P65% (31% more than S0T0 P0 treatment).
In conditions of without Sulfur and Thiobacillus bacteria (S0P0), consumption of 65 percent (P65%) phosphorus recommended based on soil test is appropriate for optimum yield for wheat. Consumption of 1000 kg ha-1 sulfur along with 20 kg ha-1 of Thiobacillus (S1000T20) in conditions of without phosphorus (P0), are recommended for use in agriculture and wheat yield increase.