Submitted to: Plant Disease Management Reports
Publication Type: Other
Publication Acceptance Date: 12/6/2010
Publication Date: 3/28/2011
Citation: Zhou, X., McClung, A.M., Cammack, J.L. 2011. Evaluation of effects of fertilizers on narrow brown leaf spot in organic rice, 2010. Plant Disease Management Reports. 5:FC051.
Technical Abstract: The experiment was established in a field of League soil (3% sand, 32% silt, and 64% clay) under organic management for many years at the Texas A&M University System's Agrilife Research and Extension Center, Beaumont. The experiment was conducted as a two factorial experimental design with five organic fertilizers and four application rates. The fertilizers were AgriCycle (4-2-3, N-P-K), Rhizogen (7-2-1), Nature Safe (13-0-0), Top Organic Fertilizer (4-2-2) and True Organic Fertilizer (12-3-0). Treatments were randomly arranged in each of three blocks. Plots were 20 ft long and 5 ft wide. Durana and Patriot clovers (6 lb/A) were planted on 13 Nov, 2009 and plowed down on 31 Mar, 2010. Plots received all fertilizer treatments on 7 Apr. Permanent flood was established on 8 Apr. Rice was water seeded at 180 lb/A on 9 Apr. Plots were irrigated as locally recommended. On 16 Jul, percentage of flag leaf blade area covered with lesions of narrow brown leaf spot was visually assessed for with a Horsfall-Barratt scale (0 to 11). Plots were harvested on 20 Jul, and grain yield adjusted to 12% grain moisture. All fertilizer treatments significantly reduced narrow brown leaf spot severity compared to the unfertilized control. For AgriCycle, disease severity tended to decrease as the rate of the fertilizer increased. When total nitrogen (N) amount, resulted from the application of AgriCycle, increased to 130 lb/A, disease decreased to a lowest level. Similar disease response patterns also were observed on the applications of all other fertilizers. Disease severity was not significantly different among different fertilizers at the same or similar rates of application. When disease severity was regressed against total N amount, narrow brown leaf spot severity linearly decreased with the increase of total amount of N applied (R2 =0.8, P < 0.0001). Applications of all fertilizers increased yield compared to the untreated control, with the trend pattern of increasing yield with the increase of total amount of N applied. Proper nutrient management is important not only for improving yield but also for effective management of narrow brown leaf spot.