Document Type : Research Paper
Authors
1 Dryland Agricultural Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Maragheh, Iran
2 Ministry of Agriculture-Jahad, Maragheh, Iran
Abstract
EXTENDED ABSTRACT
Introduction: Plant growth and development in calcareous soils and within calcareous soil patches face numerous constraints. Sulfur, as an essential nutrient element, in addition to its nutritional role, exerts positive effects on the properties of calcareous soils through pH reduction. Consequently, it is utilized as one of the most important acidifying agents for ameliorating calcareous soils and improving plant nutrition. This research was conducted to investigate the effects of mineral sulfur and sulfur-oxidizing bacteria (Thiobacillus with a population of more than 107 cells per gram) in combination with rotten farmyard manure on the properties of two types of calcareous soils and the performance of rainfed wheat.
Methodology: The experiment was conducted as a split-plot arrangement within a randomized complete block design (RCBD) in a dryland field in Hashtroud County during the 2023–2024 growing season. The treatments consisted of two soil types (low-lime soil (22%) and high-lime soil (39%)) as the main factor, and five soil amendments as the sub-factor: sulfur + Thiobacillus (S+TB), sulfur + Thiobacillus + farmyard manure (S+TB+FM), sulfur + farmyard manure (S+FM), farmyard manure alone (FM), and a control (C). Farmyard manure was applied at 4 t ha⁻¹, sulfur at 1 t·ha⁻¹, and Thiobacillus bacteria at 2% of the sulfur weight. Growth parameters, including plant height, 1000-grain weight, biological yield, and grain yield were measured. Additionally, soil chemical properties (pH, electrical conductivity (EC), calcium carbonate content, organic carbon, and available phosphorus and potassium) were analyzed at a depth of 0–25 cm.
Research findings: All soil amendment treatments significantly enhanced both grain and biological yields of wheat in both soil types. In the low-lime soil, the combined S+TB+FM treatment (sulfur + Thiobacillus + farmyard manure) proved to be the most effective, demonstrating significant reductions in lime content (from 21% to 17%) and soil pH (from 7.6 to 7.2), along with significant increases in organic carbon (from 0.27% to 0.40%) and available phosphorus (from 3.5 to 4.8 mg kg-1). These modifications resulted in significant improvements in wheat growth parameters, including increased plant height (from 76 to 100 cm), grain yield (from 1854 to 4355 kg ha-1, representing a 135% increase), biological yield (from 5984 to 10393 kg ha-1), and harvest index (from 31% to 42%). While sulfur-containing treatments were effective in both soil types, the effect of farmyard manure was more pronounced in low-lime soil compared to high-lime soil. Based on these findings, the combined S+TB+FM treatment (comprising 1 ton sulfur, 4 tons farmyard manure, and 2% Thiobacillus bacteria) is recommended as the optimal soil amendment strategy for improving wheat yield in low-lime soils.
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