Effect of sowing point design and tillage practice on the incidence of rhizoctonia root rot, take-all and cereal cyst nematode in wheat and barley

Effect of tillage treatments on the cereal root diseases, rhizoctonia root rot, take-all and cereal cyst nematode, and on grain yield of cereals were tested in 4 field experiments over 3 years. Conventionally cultivated treatments were compared with a range of direct-drill treatments using either a standard tined seed drill equipped with 10 cm sowing points, a specialised drill designed to give minimal soil disturbance or a standard tined seed drill equipped with a range of commercial or modified narrow points designed to provide soil disturbance from 0 to 5.0 cm below seed depth. Direct-drilled treatments that disturbed the soil below seed depth (DDD) and treatments that included 1 cultivation prior to sowing (CPS) resulted in a reduction of rhizoctonia root rot when compared with direct-drilled treatments that did not disturb the soil below seed depth (DDN). When seasonal conditions encouraged volunteer plant growth before sowing, a chemical fallow treatment applied 3 weeks before sowing significantly reduced rhizoctonia root rot in all direct-drilled plots. This was a significant factor in DDD treatments providing effective control of rhizoctonia root rot. Take-all was present in 3 of the 4 experiments. In 2 experiments, take-all was significantly higher in plots following DDN treatments than DDD or CPS treatments and in 1 experiment there was no effect of tillage. Cereal cyst nematode was present in 1 of the 4 experiments. The level of root damage from cereal cyst nematode was least in plots following DDN treatments, higher following DDD treatments and highest following CPS treatments. The influence of tillage practice on grain yield was closely related to the effect of tillage on cereal root disease when levels of disease were moderate to high. Where the incidence of root disease was low, grain yield differences due to tillage treatments were generally related to agronomic factors such as seed depth and seedbed condition.