Influence of depth of soil disturbance on root growth dynamics of wheat seedlings associated with Rhizoctonia solani AG-8 disease severity in sandy and loamy sand soils of Western Australia

Rhizoctonia root rot (bare-patch disease) of cereals caused by Rhizoctonia solani AG-8 is reported to become more severe when the crop is sown under no-tillage practice. Disturbing the soil with tillage is an effective way to reduce the impact of disease. Glasshouse and field studies were conducted to evaluate the effects of the depth and intensity of soil disturbance and soil moisture conditions at the time of disturbance on rhizoctonia root rot of wheat (Triticum aestivum L. cv. Aroona) seedlings. Results of glasshouse studies showed that intensity of soil disturbance was important for reducing the disease if the soil was disturbed at the surface (0–5 cm). Disturbing the soil at 10–20 cm below the surface without disturbing the surface soil proved to be more effective in reducing the disease than surface disturbance even when the soil was disturbed at lower intensity. Total wheat root length and rooting depth increased when soil below the seed was disturbed. Disturbance of wet soil before sowing resulted in less reduction of root and shoot weights following inoculation with R. solani AG-8 than in relatively dry soil. Similar results were obtained from a field study conducted near Newdegate (WA, Australia) on a Orthic Solonetz soil (sandy loam), with tillage of the field soil 10–15 cm below the surface producing maximum dry root and shoot weights in a rhizoctonia patch area mapped in the previous year.