ARS | Publication request: Disease severity of organic rice as affected by host resistance, fertility and tillage

Submitted to: Agricultural Experiment Station Publication
Publication Type: Other
Publication Acceptance Date: June 1, 2011
Publication Date: June 15, 2011
Citation: Zhou, X., McClung, A.M. 2011. Disease severity of organic rice as affected by host resistance, fertility and tillage. Texas Rice. XI(4):3-7.

Technical Abstract: Several studies were conducted to determine the effect of fertilizer inputs and tillage methods on disease incidence in an organic rice production system. The results of these studies suggest that organically produced rice is more vulnerable to infection of narrow brown leaf spot and brown spot. This is partially due to nitrogen deficiency as a result of using slow release organic fertilizers. In addition, in a study looking at different rates of organic fertilizer there was a clear association of increased severity of narrow brown leaf spot with decreased total N applied. However, some of the diseases, such as bacterial panicle blight, were less severe in organic rice compared to conventional rice. Therefore, developing cropping systems that enhance soil nutrient quality is a means of improving foliar disease control and yield under organic management. We evaluated the impact of tillage on the severity of straighthead, a physiological disease in rice, in an organic cropping system. Severe straighthead was found to occur in no-till organic production systems involved with the direct seeding of rice into a cover crop. These results suggest that straighthead may be related to decomposition of organic residues in flooded (anaerobic) soils. To prevent straighthead, highly susceptible varieties should be avoided and the rice crop should not be directly planted into fields with an abundance of decaying crop residues. Host resistance significantly affects disease severity, especially straighthead. In this study, several varieties, such as Tesanai 2, GP2, Wells, Jupiter, and Rondo, demonstrated resistance to multiple diseases including narrow brown leaf spot, straighthead and bacterial panicle blight. These varieties consistently produced the highest grain yields in these trials. Selection of varieties that are disease resistant and have high yield potential is the most effective method to minimize damages caused by diseases in organic rice production systems.