Cadmium (Cd) pollution restricts the rice growth and poses a threat to human health. Nanosized selenium (NanoSe) is a new nano material. However, the effects of NanoSe application on aromatic rice performances under Cd pollution have not been reported. In this study, a pot experiment was conducted with two aromatic rice varieties and a soil Cd concentration of 30 mg/kg. Five NanoSe treatments were applied at distinct growth stages: (T1) at the initial panicle stage, (T2) at the heading stage, (T3) at the grain-filling stage, (T1+2) at both the panicle initial and heading stages, and (T1+3) at both the panicle initial and grain-filling stages. A control group (CK) was maintained without any application of Se. The results showed that, compared with CK, the T1+2 and T1+3 treatments significantly reduced the grain Cd content. All NanoSe treatments increased the grain Se content. The grain number per panicle, 1000-grain weight, and grain yield significantly increased due to NanoSe application under Cd pollution. The highest yield was recorded in T3 and T1+3 treatments. Compared with CK, all NanoSe treatments increased the grain 2-acetyl-1-pyrroline (2-AP) content and impacted the content of pyrroline-5-carboxylic acid and 1-pyrroline which are the precursors in 2-AP biosynthesis. In conclusion, the foliar application of NanoSe significantly reduced the Cd content, increased the Se content, and improved the grain yield and 2-AP content of aromatic rice. The best amendment was applying NanoSe at both the panicle initial and grain-filling stages.

With the existing model of chemical fertilizer application faces, improving grain yield and quality is challenging. Fragrant rice is known for its distinctive aroma and flavor, but it generally produces less grain than non-fragrant rice varieties. Limited research has been conducted on the potential of biochar as a solution for increasing the grain yield of fragrant rice. In a two-year field trial conducted in 2022 and 2023, two fragrant rice cultivars, Meixiangzhan2 (MXZ2) and Xiangyaxiangzhan (XYXZ), were selected as the experimental materials. These rice cultivars were subjected to four different rates of biochar application: no biochar treatment(T1); biochar with 0.375 t ha⁻¹ (T2); biochar with 0.75 t ha⁻¹ (T3); and biochar with 1.50 t ha⁻¹ (T4). The results showed that the grain yield of both cultivars increased to an extent in both 2022 and 2023 (an 8.57–33.77% increase for MXZ2; a 6.00–21.59% increase for XYXZ). Furthermore, under the T2, T3, and T4 treatments, there was an increase in the number of effective panicles, seed setting rate, 1000-grain weight, biomass accumulation, net photosynthetic rate, and intercellular CO₂ concentration. However, the transpiration rate and stomatal conductance decreased. The content of 2-acetyl-1-pyrroline (2-AP) increased with an increased rate of biochar application, and the highest content was observed under the T4 treatment (153.54–178.32 µg kg⁻¹ in 2022; 163.93–180.28 µg kg⁻¹ in 2023). The activities of proline dehydrogenase (PDH) and 1-pyrrolin-5-carboxylic acid synthase (P5CS), as well as the contents of proline (PRO), 1-pyrrolin-5-carboxylic acid (P5C), ∆1-pyrroline, and methylglyoxal, were improved under the T2, T3, and T4 treatments compared to the T1 treatment. Moreover, under the T2, T3, and T4 treatments, the brown rice rate, milled rice rate, and head rice rate increased, while the chalkiness degree and chalk rice rate decreased. Our correlation analysis showed that grain yield was positively correlated with total biomass accumulation, the number of grains per panicle, and the seed setting rate. Additionally, the content of 2-AP showed positive correlations with PRO, P5C, ∆1-pyrroline and methylglyoxal, and the activities of PDH and P5CS. In conclusion, applying biochar at a rate of 1.5 t ha⁻¹ can be more effective in increasing the grain yield and 2-AP content of fragrant rice.