Effect of nitrogen and residual copper on the occurrence of Rhizoctonia bare patch in wheat grown near Esperance, Western Australia

Abstract

The area of rhizoctonia bare patch and the incidence and severity of rhizoctonia root rot (caused by Rhizoctonia solani Khnn) were reduced by the application of ammonium nitrate fertiliser. Residual copper (Cu) from a Cu fertiliser treatment in 1967 had no effect on the area of rhizoctonia bare patch or the incidence and severity of root rot. With no applied nitrogen (N), 17.6% (mean of residual Cu levels) of the plot was affected by patches while the area of plot affected by patches declined to 4.2% where 92 kg N/ha had been applied. The incidence and severity of rhizoctonia root rot declined from 45.9 and 27.0% to 32.7 and 9.1%, respectively, with the application of N fertiliser. The grain yield of wheat supplied with adequate Cu increased although the level of N fertiliser exceeded that considered adequate for plant nutrition. The response is explained by the control of rhizoctonia bare patch. The area of rhizoctonia patches and the incidence and severity of rhizoctonia root rot decreased with the application of N, and with adequate Cu fertiliser (2.2 kg Cu/ha), the grain yields increased. However, with marginal and deficient levels of applied Cu fertiliser, the application of N fertiliser induced Cu deficiency in wheat plants, and the grain yields declined although rhizoctonia patches were reduced.