Effect of ryegrass root residues, knockdown herbicides, and fungicides on the emergence of barley in sandy soils

Abstract

Poor seedling emergence of 30 000 ha of winter crops occurred in Western Australia in 1984 after herbicides were used to kill weeds prior to sowing. In pot experiments to determine the possible cause(s), the emergence of barley seedlings was reduced by the presence of both herbicide treated and untreated ryegrass root residues in the soil. Fumigation of the soil with methy1 bromide or the application of a fungicide soil drench restored seedling emergence in the presence of ryegrass root residues, but benomyl drench was less effective than methyl bromide fumigant or furalaxyl soil drench. The effects of the residue, fumigant and furalaxyl were consistent in the 3 soils used but soif type affected the severity of the problem. In the presence of ryegrass root residues, Pythim species colonised the large roots and subsurface hypocotyl of barley seedlings. Metalaxyl seed dressing reduced the colonisation of barley seedlings by Pythim species and restored seedling emergence.