Extended Abstract:
Introduction: Sweet corn (Zea mays L. var. Saccharata) is an improved cultivar of maize characterized by a mutation in the su allele located on chromosome four, which leads to elevated accumulation of soluble sugars in the endosperm. This trait enhances its nutritional and economic value, particularly in the food processing and livestock feed industries. With the significant expansion in the cultivation area of sweet corn, optimizing its nutritional management to boost yield and ensure production sustainability has become increasingly important. Among essential nutrients, phosphorus is the second most critical and limiting element after nitrogen. It plays a vital role in numerous physiological processes, including nucleic acid synthesis, ATP production, root development, and photosynthesis. However, phosphorus uptake by plants is often constrained by soil factors such as pH, aeration, moisture, organic matter, and microbial activity. Consequently, more than 80% of applied phosphorus fertilizers typically become immobilized in the soil, rendering them unavailable to plants. Moreover, excessive use of chemical phosphorus fertilizers has raised environmental concerns. In this context, sustainable and biological agricultural strategies—such as the use of arbuscular mycorrhizal fungi (AMF) and humic acid—are gaining attention as effective approaches to enhance phosphorus uptake and nutrient use efficiency. AMF improve fine root development, nutrient absorption, and stress tolerance, while humic acid enhances root growth, microbial activity, and nutrient availability. This study aimed to evaluate the synergistic effects of these inputs on yield and nutrient accumulation in sweet corn.

Materials and Methods: The experiment was conducted during the summer of 2023 to investigate the integrated effects of phosphorus fertilizer, Funneliformis mosseae (a species of arbuscular mycorrhizal fungi), and humic acid on sweet corn (hybrid RS-360) in Boyer-Ahmad region, southwestern Iran. The trial was laid out as a factorial experiment based on a randomized complete block design with three replications. The experimental treatments consisted of three factors: phosphorus applied at four levels (0, 50, 100, and 200 kg ha⁻¹ of phosphorus from triple superphosphate), AMF inoculation at two levels (non-inoculated and inoculated), and humic acid foliar spray at two levels (0 and 20 L ha⁻¹). The study evaluated a range of agronomic traits including yield components, grain yield, and macro- and micronutrient concentrations in both aerial parts and grain tissues.

Results: The findings revealed that application of up to 100 kg ha⁻¹ phosphorus led to the highest accumulation of phosphorus (60.32% increase) and potassium (23.02% increase) in aerial parts compared to the control. AMF inoculation resulted in a 27.31% increase in nitrogen and a 32.60% increase in phosphorus content in aerial tissues, relative to non-inoculated treatments. The highest phosphorus (1.87%) and potassium (3.24%) concentrations in grain were observed under the combined application of 100 kg ha⁻¹ phosphorus, AMF, and humic acid—representing a 1.1-

Received: Mar. 10, 2025; Revised: May. 31, 2025; Accepted: Jun. 01, 2025; Published Online: Sep 03, 2025.
* Corresponding Author: movahhedi1354@yu.ac.ir    
fold and 1.67-fold increase over the control, respectively. The highest canned grain yield (25,488 kg ha⁻¹) and the highest harvest index (17.05%) were obtained from the treatment combining 100 kg ha⁻¹ phosphorus with AMF. Increasing phosphorus levels beyond 100 kg ha⁻¹ had no significant effects on the measured traits, indicating a plateau in plant response. Both AMF inoculation and humic acid application significantly enhanced nutrient uptake and plant performance by improving root nutritional status. Among the yield components, the number of rows per ear was significantly influenced by the main effect of phosphorus, while the number of kernels per row responded significantly to the three-way interaction of phosphorus, AMF, and humic acid. In contrast, ear number per plant and 100-kernel weight were not significantly affected by the treatments, suggesting lower sensitivity of these traits to the nutritional interventions under the study conditions.

Conclusion: This study demonstrated that integrated application of organic and inorganic nutrient sources—including phosphorus fertilizer, AMF, and humic acid—can significantly enhance nutrient uptake efficiency, root development, and ultimately, the growth and yield of sweet corn. Notably, the combination of 100 kg ha⁻¹ phosphorus with bio-fertilizers produced the highest canned grain yield and harvest index. The results underscore the potential of sustainable nutrient management strategies, particularly the use of symbiotic fungi and organic compounds, in reducing chemical fertilizer dependency and improving productivity in cropping systems.
Ultimately, application of 100 kg ha⁻¹ phosphorus in combination with mycorrhizal fungi and humic acid improved the economic traits of sweet corn under the experimental conditions.