Document Type : Research Paper
Authors
1
Assistant Prof
2
Researcher and Assistant Prof. at the Soil
3
Water Research Institute; respectively
Abstract
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. To evaluate the possibility of partially substituting sulfur along with 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. Where the last two treatments were 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.
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