A New Organic-Inorganic Compound Fertilizer for Improving Growth, Yield, and 2-Acetyl-1-Pyrroline Biosynthesis of Fragrant Rice

Fragrant rice (<i>Oryza sativa</i> L.) is a high-valued rice type and possesses a unique aroma with 2-acetyl-1-pyrroline (2-AP) as the critical component. However, the cultivation measures in fragrant rice production are far from perfect. In this study, a new organic-inorganic compound fertilizer was made with organic matter, urea, superphosphate, potassium chloride, zinc sulfate, and lanthanum chloride. A four-year field experiment was conducted to investigate its effects on fragrant rice growth, yield formation, and 2-acetyl-1-pyrroline biosynthesis. Three treatments, i.e., (CK) no fertilizer was applied, (IF) the urea, superphosphate, and potassium chloride were applied at 234 kg ha⁻¹, 450 kg ha⁻¹ and 108 kg ha⁻¹, and (OICF) this new fertilizer composed of 10% organic matter, 26% urea, 50% superphosphate, 12% potassium chloride, 1.9% zinc sulfate, and 0.1% lanthanum chloride, was applied at 900 kg ha⁻¹, were adopted in the present study. Across four experimental years, the results showed that the grain yield in OICF treatment ranged between 5.86–8.29 t ha⁻¹, and was significantly (<i>p</i> < 0.05) higher than that in IF treatment and CK. The improvement in grain yield due to OICF treatment was explained by increased effective panicle number per m² and seed-setting rate. The highest or equally highest chlorophyll content and the net photosynthetic rate at 20, 40, 60, and 80 days after transplanting were recorded in OICF treatment among three treatments. OICF treatment also increased the aboveground biomass of fragrant rice compared with IF treatment and CK. Moreover, compared with CK and IF treatment, OICF treatment significantly (<i>p</i> < 0.05) increased grain 2-AP content by 30–38% and 10–21%, respectively. The contents of 2-AP related precursors, including proline and 1-pyrroline, also increased due to OICF treatment. This study provided a new organic-inorganic compound fertilizer and suggested that it could be used to achieve the goals of high yield and high grain 2-AP content in fragrant rice production.