Functional Fertilizers Increase Yield and Enhance Aroma Quality by Modulating Volatile Compounds in Japonica Fragrant Rice Under Yunnan Field Conditions

Fertilizer management plays a critical role in regulating both yield and aroma quality in fragrant rice. However, the combined effects of functional fertilizers on these traits across different varieties and ecological conditions remain poorly understood. In this study, field experiments were conducted at two sites (Fumin and Dali) using two japonica fragrant rice varieties (Yunjing 37 and Liuxiangzi 1) under four fertilization treatments: T1 (conventional fertilization); T2 (compound fertilizer + silicon fertilizer); T3 (compound fertilizer + magnesium ammonium phosphate + amino acid-chelated calcium); and T4 (compound fertilizer + bio-organic fertilizer + zinc + amino acid water-soluble fertilizer). Compared with T1, silicon application (T2) significantly increased grain yield by 8.58–15.08%, primarily through synergistic increases in effective panicles and grains per panicle. Treatments T3 and T4 significantly enhanced grain 2-acetyl-1-pyrroline (2-AP) content by 18.32–32.67% and increased the diversity of volatile compounds. Correlation analysis revealed that 2-AP content was positively correlated with ketones (r = 0.373, p < 0.05) and alcohols (r = 0.363, p < 0.05), and negatively correlated with aldehydes and esters. Multifactor ANOVA showed no significant variety × treatment interaction for yield or 2-AP content (p > 0.05), indicating consistent responses across varieties. These results provide preliminary evidence that silicon fertilizer serves as an effective strategy for yield improvement, while combined application of calcium, magnesium, and amino acids enhances aroma quality by promoting the accumulation of 2-APm ketones, and alcohols. However, because treatments T3 and T4 contained multiple components, the individual contributions of Ca, Mg, or amino acids cannot be isolated. Multi-year trials are required to confirm the stability of these effects, featuring a differentiated fertilization strategy—silicon for yield and medium/trace elements for aroma—applicable across varieties, with site-specific variety selection further optimizing performance.