Ratoon rice can improve rice yield by increasing the multiple cropping index in China. However, the greenhouse gas (CH₄ and N₂O) emission characteristics from ratoon rice fields and the cultivation methods to reduce CH₄ and N₂O emissions are rarely reported. This study first conducted the analysis of genotype differences in greenhouse gas emission fluxes using five strong ratoon ability rice varieties in 2020. Second, water management methods, including alternating the wet–dry irrigation (AWD) pattern and conventional flooding irrigation (CF) during the main season, were carried out in 2021. CH₄ and N₂O emission flux, agronomic traits, and rice yield during both main and ratoon seasons were investigated. The results showed that the CH₄ emission flux during the main and ratoon seasons was 157.05–470.73 kg·ha^–1 and 31.03–84.38 kg·ha^–1, respectively, and the total N₂O emission flux was 0.13–0.94 kg·ha^–1 in the ratoon rice system over the two seasons (RRSTS). Compared with the main season, the CH₄ emission flux during the ratoon season was significantly reduced, thus decreasing the greenhouse gas global warming potential (GWP) and greenhouse gas emission intensity (GHGI) in the ratoon rice system. Cliangyouhuazhan (CLYHZ) showed a high yield, and the lowest GWP and GHGI values among the five rice varieties in RRSTS. Compared with CF, the AWD pattern reduced the CH₄ emission flux during the main and ratoon seasons by 67.4–95.3 kg·ha^–1 and 1.7–5.1 kg·ha^–1, respectively, but increased the N₂O emission flux by 0.1–0.6 kg·ha^–1 during the RRSTS. Further, compared with CF, the AWD pattern had a declined GWP by 14.3–19.4% and GHGI by 30.3–34.3% during the RRSTS, which was attributed to the significant reduction in GWP and GHGI during the main season. The AWD pattern significantly increased rice yield by 21.9–22.9% during the RRSTS, especially for YX203. Correlation analysis showed that CH₄, GWP, and GHGI exhibited significant negative correlations with spikelet number per m² and the harvest index during the main and ratoon seasons. Collectively, selecting the high-yield, low-emission variety CLYHZ could significantly reduce greenhouse gas emissions from ratoon rice while maintaining a high yield. The AWD pattern could reduce total CH₄ emission during the main season, reducing the GWP and GHGI while increasing the ratoon rice system yield. It could be concluded that a variety of CLYHZ and AWD patterns are worthy of promotion and application to decrease greenhouse gas emissions in the ratoon rice area in the upper reaches of Yangtze River, China.

Biochar is beneficial as a clean, stable, and efficient soil amendment to improve rice quality and yield. However, there are few reports on the effects of no-tillage in combination with biochar application on rice growth, yield, and quality in regenerative rice systems. This study evaluated rice yield, grain quality, multiple antioxidant enzyme activities, and malondialdehyde content under four treatments: rotary tillage alone, rotary tillage + biochar application, no-tillage alone, and no-tillage + biochar. The results showed that the rice yield under no-tillage alone was 15% lower than that under rotary tillage alone, but that biochar application significantly increased rice yield by 10% and 20% under rotary tillage and no-tillage conditions, respectively, which might be attributed to the fact that biochar application increased panicle number, spikelet number per panicle, grain filling rate, and antioxidant enzyme activities. Additionally, biochar application also increased fine rice rate and protein content, meanwhile reducing chalkiness degree and chalky grain rate in both the main-season rice and ratoon-season rice. These results suggest that biochar application could enhance the yield and grain quality of ratoon rice, thus compensating for the no-tillage-induced yield loss. This study reveals the role of biochar in main-season rice and ratoon rice cultivation, providing a valuable reference for improved fertilizer utilization and cleaner agricultural production.

With the growing global demand for rice and the urgent need to enhance sustainable production, ratoon rice systems and selenium (Se) biofortification technologies have become important strategies. This study investigated the effects of the foliar application of ethylenediaminetetraacetic acid Se (EDTA-Se) during key growth stages of the main rice season on the yield, grain quality, and Se accumulation in ratoon rice. Two rice varieties—Fengliangyouxiang-1 (FLYX1) and Jinliangyouhuazhan (JLYHZ)—were selected for a two-year field experiment. A systematic analysis was performed on yield components, processing quality, appearance quality, nutritional quality, and Se speciation. The results showed that under an equivalent total amount of spraying EDTA-Se, the best effect on improving the yield, grain quality, and grain Se content of ratoon rice was observed at the heading stage and seven days after full heading. This treatment increased ratoon season yield by 6.45%, primarily due to enhanced grain filling rate (GF) and spikelets per panicle (SP). Processing quality was significantly improved; milled rice rate (MR) increased by 5.59–6.24% in FLYX1 and 3.38–3.52% in JLYHZ, while appearance quality also improved, with chalky grain rate (CGR) decreasing by 21.51–22.93% in FLYX1 and 14.50–14.53% in JLYHZ. These improvements were closely associated with elevated protein content and increased accumulation of selenomethionine (SM). Notably, FLYX1 exhibited higher efficiency in converting selenium to organic forms, whereas JLYHZ showed a greater accumulation of inorganic selenium, highlighting genotype-specific responses. This study confirmed that the foliar application of EDTA-Se during key growth phases of rice during the main season can synergistically optimize yield and quality in ratoon rice while achieving Se biofortification and providing a theoretical basis and technical support for improving the quality and efficiency of ratoon rice, as well as producing Se-enriched ratoon rice.

Rice‐crayfish system (RCS) is an integrated farming technology that benefits grain production, food safety, and green sustainable agricultural development. However, little is known about the effects of RCS on the biosynthesis of 2‐acetyl‐1‐pyrroline (2‐AP), a volatile aroma compound. The present study examined rice yield, 2‐AP content, and its biosynthesis enzyme activities in two rice cultivars Xiangyaxiangzhan (XYXZ) and Meixiangzhan‐2 (MXZ2) under rice‐crayfish system (RCS), rice‐crayfish system without crayfish (RCS‐NC), and traditional rice system (TRS). The results showed that the 2‐AP content was significantly higher in RCS than in RCS‐NC and TRS. In RCS, the contents of proline and Δ1‐pyrroline (2‐AP biosynthesis precursors) and the activities of rice aroma‐related enzymes proline dehydrogenase (ProDH), and Δ1 pyrroline‐5‐carboxylic acid synthetase (P5CS) were increased by 11.31%–12.55%, 19.53%–47.75%, 6.25%–8.98%, and 18.18%–51.26%, respectively, relative to those in RCS‐NC. Up‐regulation of P5CS2 and downregulation of BADH2 in RCS promoted 2‐AP biosynthesis in two rice cultivars. Overall, the increase in the levels of proline, Δ1‐pyrroline, ProDH, P5CS, P5CS2 gene and the decrease in BADH2 gene expression jointly led to the grain 2‐AP content increase. RCS also improved soil properties such as soil total nitrogen and total phosphorus contents. Overall, this study reveals that RCS is an environmentally‐friendly sustainable approach to improving aromatic rice traits.

Extreme meteorological events, particularly the summer heat‐drought compound events, increasingly threaten global rice production. In Southwest China, the precise synchronization of direct‐seeded rice phenology with favorable climatic windows is critical for yield and quality. However, the interactive effects of sowing date and variety selection on climate resilience and economic returns remain insufficiently quantified. This study evaluated 16 rice varieties across five sowing dates (S1–S5), with S1 commencing on April 25th and subsequent sowings spaced at 10‐day intervals in a representative heat‐drought region to optimize cultivation strategies. Results indicated that typical heat‐drought events concentrated from mid‐July to mid‐August. Delaying the sowing date effectively reduced high‐temperature exposure. Two‐line indica hybrid rice (2LIHR) generally outperformed inbred indica rice (IIR) and three‐line indica hybrid rice (3LIHR) in grain yield and quality. Specifically, the yield of 2LIHR was 2.17%–53.92% higher than that of IIR and 6.92%–18.42% higher than that of 3LIHR. This yield advantage was primarily attributable to its superior panicle number, spikelets per panicle, and grain filling rate. Furthermore, appropriate delayed sowing date can effectively improve rice quality, and 2LIHR exhibited significantly higher head rice yield and lower chalky grain percentage across all sowing dates. Comprehensive GGE biplot, cluster analysis, and PCA showed that Jingliangyou‐534 (JLY534) as the most stable and high‐yielding variety. Economic assessment revealed that optimized configurations significantly enhanced profitability; for instance, JLY534 at S3 increased net profit by 765.43% compared to the control. Conversely, the control suffered economic losses under S4. These findings demonstrate that the synergistic optimization of sowing dates and varieties significantly improves resource‐use efficiency and climate resilience, thereby providing a robust technical framework for enhancing food security and farmers' income in drought‐prone tropical and subtropical regions.