| Summary: | The study aimed to determine the effect of nitrogen rates and planting systems on the incidence and severity of rice blast under naturally infected rice plants and their relationship to rice yield performance. Recommended nitrogen rate for both direct seeding was 93.2kg/ha. Treatments consisted of 75% recommended-N rate, 100% recommended-N rate, 150% recommended-N, and existing farmer’s practice. Treatments were applied in a three-way splitted-N application at 14, 30, and 45 days after planting, respectively. The results indicate that rates of N fertilization affected disease incidence of the rice blast where the low-N application was generally lower than recommended-N rate, high-N rate, and farmer’s practice, both on jajar legowo 2:1 and broadcasted direct seeding. This study revealed that recommended-N application, although has a higher disease incidence than low-N application, could tolerate yield loss due to rice blast by producing more productive tillers, number of grains per panicle, and reducing the number of unfilled grains. This study generally showed that jajar legowo 2:1 direct seeding gave lower disease incidence and severity to the rice blast than broadcasted direct seeding. The study suggested an appropriate recommended-N rate and jajar legowo 2:1 direct seeding (double row) was incorporated into the rice blast management strategies.
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