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Fusarium Foot Rot of Wheat and Peas as Influenced by Soil Applications of Anhydrous Ammonia and Ammonia-Potassium Azide Solutions. R. W. Smiley, Soil Scientist Research Assistant, Soil and Water Conservation Research Division, ARS, USDA, Pullman, Washington 99163, Senior author is currently Research Assistant, Department of Plant Pathology, Washington State University; R. J. Cook(2), and R. I. Papendick(3). (2)Pathologist, Plant Science Research Division, ARS, USDA, Pullman, Washington 99163; (3)Soil Scientist, Soil and Water Conservation Research Division, ARS, USDA, Pullman, Washington 99163. Phytopathology 62:86-91. Accepted for publication 3 August 1971. DOI: 10.1094/Phyto-62-86.

Populations of Fusarium roseum f. sp. cerealis ‘Culmorum’, F. solani f. sp. pisi, and saprophytic fusaria were reduced within the NH₃ retention zone in situ in the field following injection of the soil with liquid anhydrous NH₃ using a portable, hand-operated dispenser. However, little or no reduction in numbers of Fusarium propagules could be detected in the tillage layer when anhydrous NH₃ was applied to soil with a field applicator using different methods of placement at rates up to 224 kg N/hectare at each of three widely separated geographical locations during two different seasons. Chlamydospore germinability was markedly reduced by exposure to 400 or 600 µg NH₃-N/g of dry soil for 5 or 1 min, respectively. However, banding the NH₃ within the wheat row at comparable concentrations failed to control Fusarium root and foot rot of winter wheat. Potassium azide dissolved in NH₃ increased slightly the effectiveness of kill within the NH₃ retention zone in the laboratory, but was ineffective in the field. Failure of NH₃ to reduce the Fusarium population in the field was attributed primarily to insufficient distribution of NH₃ throughout the tillage layer. Nearly all treatments where N was applied caused increased incidence of Fusarium foot rot of wheat.