Brown spot (BS) disease poses a significant threat to rice cultivation globally, impacting millions of hectares annually. Research indicates that the severity of BS is closely linked to abiotic stresses and crop nutrition. A field experiment was conducted using transplanted (TP) and direct-seeded-rice (DSR) crop establishment methods to optimize the effective fungicide and nitrogen dose. The split-plot design was applied to study the effect of two factors (N-dose and fungicides) varying at different levels under two different crop establishment methods (TP and DSR) for two consecutive seasons (2021 and 2022). The BS severity was measured as the percent disease index (PDI), and the results of two seasons were pooled. The results indicated that all three factors significantly ( = 0.05) influenced the PDI and grain yield. The PDI under different fungicides was higher in DSR (30.20–88.90) than in TP rice (21.64–70.00). Similarly, increased N-dose altered the PDI negatively ( = 0.05) in both TP (32.16–46.12) and DSR (44.35–59.09) methods. The results indicated Tebuconazole 50% + Trifloxystrobin 25% WG (T) at 125% recommended dose of nitrogen as the best combination, as it recorded the lowest PDI of 21.6 and 30.2 in the TP and DSR, respectively. Similarly, all three factors interacted significantly ( = 0.05) and affected the final grain yield. Overall, the BS is more severe in DSR, and a higher dose of N reduces the BS severity in both TP and DSR. Therefore, N fertilizer management, especially in the DSR, is essential, along with a fungicide, for effective management of the brown spot disease.

中文翻译：

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两种种植方式下杀菌剂和施氮剂量的相互作用影响水稻褐斑病的严重程度


褐斑病（BS）对全球水稻种植构成重大威胁，每年影响数百万公顷土地。研究表明，BS 的严重程度与非生物胁迫和作物营养密切相关。采用移栽（TP）和直播水稻（DSR）作物种植方法进行田间试验，以优化有效杀菌剂和氮肥剂量。采用裂区设计研究连续两个季节（2021 年和 2022 年）两种不同作物种植方法（TP 和 DSR）下不同水平的两个因素（氮剂量和杀菌剂）的影响。 BS 严重程度以疾病指数百分比 (PDI) 来衡量，并将两个季节的结果汇总。结果表明，这三个因素均显着 ( = 0.05) 影响 PDI 和谷物产量。不同杀菌剂处理下的PDI，DSR（30.20-88.90）高于TP水稻（21.64-70.00）。同样，在 TP (32.16–46.12) 和 DSR (44.35–59.09) 方法中，增加 N 剂量对 PDI 产生负向改变 ( = 0.05)。结果表明，戊唑醇 50% + 肟菌酯 25% WG (T) 在 125% 推荐氮剂量下是最佳组合，因为它在 TP 和 DSR 中记录的最低 PDI 分别为 21.6 和 30.2。同样，所有三个因素显着相互作用 ( = 0.05) 并影响最终的粮食产量。总体而言，DSR 中的 BS 更严重，较高剂量的 N 会降低 TP 和 DSR 中 BS 的严重程度。因此，氮肥管理（特别是在 DSR 中）与杀菌剂一起对于有效管理褐斑病至关重要。