On-farm evaluation of cultivar and seed treatment for control of organic rice diseases and weeds under water seeding production system in Jefferson County, Texas, 2018

摘要

The objective of this research was to validate proposed best management practices for optimizing yield while controlling disease and weed pressure in an organic rice water-seeding production system. An experiment was established on a grower's farm with League-type soil (sand 3%, silt 32%, clay 65%, and organic matter 4%) in Jefferson County, TX. The field was certified as organic and naturally infested with seedling and foliar disease pathogens and weeds after many years of organic rice production. Three treatments (see table) were arranged in a completely random design with four replications. Experimental units consisted of a strip plot 50 ft long and 22 ft wide. On 8 May, seeds of Cocodrie, susceptible to narrow brown leaf spot (NBLS) and brown spot, and Jasmine 85, susceptible to NBLS, were broadcast-planted into recently drained field at 80 and 120 lb/A, respectively. As a separate treatment, seeds of Jasmine 85 were treated with Sonata (Bacillus pumilus strain QST2808, Bayer CropScience LP, Research Triangle Park, NC) according the label instructions and air-dried prior to planting. Cocodrie using a seeding rate of 80 lb/A served as the standard farming practice control, whereas Jasmine 85 and its combination with Sonata seed treatment were treated as improved management practices. Permanent flood was established 1 week after seeding to control weeds. Irrigation, fertility and other agronomic practices followed the recommendations by the farmer. On 8 Jun, stand was counted as the number of seedlings in each of three quadrats (1.5 ft by 1.5 ft) randomly selected in each plot. Height of four seedlings randomly selected from each plot was measured. On 31 Aug, the severity of NBLS and brown spot was visually rated on a scale of 0 to 9 where 0 =no symptoms and 9 = most severe damage (100% leaf area covered with lesions and most portions of leaves dead). The incidence of sheath rot was rated as percentage of flag leaf sheaths with symptoms. Weed density was visually rated as percentage of plotarea covered with weeds. On 31 Aug, plots were manually harvested by cutting in a quadrat (3.3 ft by 3.3 ft) randomly selected from each plot. The plant samples were air dried and threshed using a rice thresher to determine grain yield. Rice yields wereadjusted to 12% moisture content. Before data analysis, NBLS and brown spot data were transformed first into the percent rank (0 to 100%) using an equation of [100/9*(disease severity - 9) + 100] and then transformed with the arcsine; sheath rot and weeddata were log transformed. All data were analyzed with the procedure of PROC GLM in SAS (version 9.4) and means were separated using Fisher's protected LSD test at 0.05.