نوع مقاله : مقاله پژوهشی
عنوان مقاله English
نویسندگان English
Introduction
Wheat (Triticum aestivum L.) is a strategic global crop, vital for food security, providing approximately 20-25% of the world's caloric intake and a significant share of dietary protein. With the global population projected to reach 9.6 billion by 2050, the implementation of sustainable agricultural practices has become imperative to meet escalating food demands without exacerbating environmental degradation. Traditional farming, heavily reliant on chemical fertilizers and pesticides, has led to soil and water pollution, threatening ecosystem health and human safety. In this context, soil microorganisms, particularly arbuscular mycorrhizal fungi (AMF), play a pivotal role in sustainable production by enhancing nutrient cycling and improving the bioavailability of essential elements like nitrogen and phosphorus. Nitrogen is a major yield-limiting factor in wheat production, with peak demand during tillering, heading, and grain filling stages. However, conventional nitrogen sources like urea are prone to leaching in light soils, contaminating groundwater. Bio-fertilizers and plant growth-promoting rhizobacteria (PGPR) offer a sustainable and eco-friendly alternative to chemical fertilizers, improving both targeted plant nutrition and soil physicochemical properties. Furthermore, plant hormones, such as cytokinins, act as chemical messengers and are crucial in mediating plant responses to environmental stresses. Cytokinins regulate key processes including cell division, chlorophyll synthesis, delay of senescence, and ultimately, yield enhancement. The Pishgam wheat cultivar, developed for cultivation under normal and limited irrigation in Iran's cold climates, has shown promising performance. However, limited information exists on its response to co-application of mycorrhizal fungi and cytokinin hormones. Therefore, this study was conducted to investigate the effects of different inoculation levels of mycorrhizal fungi, urea fertilizer, and cytokinin foliar application on the yield and yield components of irrigated Pishgam wheat.
Materials and Methods
The experiment was carried out during the 2022-2023 cropping season at the research farm of Islamic Azad University, Mahabad Branch, West Azerbaijan, Iran. The study was arranged as a factorial experiment based on a Randomized Complete Block Design (RCBD) with three replications. The experimental factors included: first, mycorrhizal organic fertilizer (containing mycorrhizal fungi) at three levels (2, 4, and 6 kg per 100 kg of seed); second, urea fertilizer from a urea source at three levels (0, 50, and 100 kg per hectare); and third, cytokinin foliar application (6-benzylaminopurine) at three stages (no application, application at flowering stage—Zadoks code 55, and application at the beginning of grain filling stage). The seeds of the Pishgam cultivar were disinfected with 70% ethanol and sodium hypochlorite before being inoculated based on the treatment groups. Soil analysis indicated a loamy clay texture with neutral to weak alkaline pH, negligible urea, and sufficient levels of phosphorus and potassium. Seeds were planted at a depth of 4 cm with a density of 180 kg.ha-1. Urea fertilizer was applied in two splits: one-third at planting and the remaining two-thirds at the beginning of stem elongation and before flowering. A 3 mM cytokinin solution was prepared and applied at a rate of 1.5 liters per plot using a hand sprayer, with Tween 20 added as a surfactant. Standard weed, pest, and disease management practices were uniformly applied. At physiological maturity, plants from a one-square-meter area per plot were harvested. Measured traits included plant height, flag leaf length, spike length, number of fertile spikes per square meter, number of grains per spike, thousand-kernel weight, biological yield, grain yield, and harvest index. Data were subjected to analysis of variance (ANOVA) using SAS software (version 9.4), and mean comparisons were performed using Duncan's Multiple Range Test at a 5% probability level.
Results and Discussion
The analysis of variance revealed that the interaction effects between the factors were highly significant. The interaction between mycorrhizal fungi and urea fertilizer significantly influenced flag leaf length, spike length, number of spikes per square meter, and biological yield. Similarly, the interaction between mycorrhizal fungi and cytokinin application had a significant effect on plant height, flag leaf length, grain yield, and harvest index. Furthermore, the interaction between urea fertilizer and cytokinin application timing significantly affected spike length, number of spikes per square meter, thousand-kernel weight, grain yield, and harvest index. The highest grain yield (approximately 12 tons.ha-1) was achieved with the combined application of 4 kg.ha-1 mycorrhiza, 50 kg.ha-1 urea, and cytokinin spraying at the flowering stage. This combination outperformed the control and other treatments, highlighting a strong synergistic effect. The results demonstrated that mycorrhizal inoculation, particularly at 4 kg.ha-1, significantly enhanced nutrient uptake, especially phosphorus, leading to improved photosynthetic capacity and longer flag leaf duration. Cytokinin application, especially at the flowering and grain filling stages, effectively delayed senescence, increased the number of fertile tillers, and improved grain filling efficiency. The combination of these treatments allowed for a substantial reduction in urea fertilizer input by 50% (from 100 to 50 kg.ha-1) without any compromise in yield, underscoring the role of bio-fertilizers and growth regulators in enhancing nutrient use efficiency. The improvement in yield components, including spike length, number of spikes per unit area, and thousand-kernel weight, was directly linked to better resource allocation and reduced oxidative stress under the integrated management approach.
Conclusion
The findings of this research conclusively show that the integrated application of mycorrhizal fungi (at an optimal rate of 4 kg.ha-1), reduced urea fertilizer (50 kg.ha-1), and cytokinin foliar spraying at critical reproductive stages (flowering and early grain filling) can significantly enhance the yield and yield components of Pishgam wheat. This management strategy works through multiple mechanisms: improved nutrient and water uptake via expanded root systems mediated by mycorrhizae, enhanced photosynthetic activity and delayed leaf senescence induced by cytokinins, and more efficient allocation of photo-assimilates to the grains. The study successfully demonstrates that it is possible to replace a significant portion of chemical urea fertilizer with organic amendments and growth regulators, thereby promoting a more sustainable and environmentally friendly wheat production system without sacrificing productivity. For achieving high and stable yields in wheat cultivation under similar agro-climatic conditions, it is highly recommended to adopt this integrated approach using 4 kg.ha-1 mycorrhizal seed inoculation, 50 kg/ha urea application, and cytokinin foliar spray at the flowering stage.
Acknowledgement
The authors of this article feel it necessary to sincerely express their gratitude for the cooperation and support of the officials of the Faculty of Agriculture and the laboratory experts at Islamic Azad University, Mahabad Branch, who extended their utmost assistance during various stages of this research.
کلیدواژهها English
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