INFLUENCE OF TIME OF TILLAGE ON GROWTH AND YIELD PARAMETERS OF SPRING CEREALS IN A COOL, HUMID CLIMATE

The suitability of spring mouldboard ploughing, and spring and fall chisel ploughing was compared with conventional fall mouldboard ploughing for the production of spring cereals over a 4 year period in the cool boreal, humid climate of Prince Edward Island, Canada where the growing season is relatively short. Adoption of spring primary tillage would allow improved soil management of the non-crop winter period (i.e. use of cover crops). The soil was a Tignish loam (10% clay), a Podzoluvisol. In each tillage treatment, primary tillage was conducted to the 25 cm soil depth. All secondary tillage (10 cm) was conducted in the spring using a rotary harrow for each treatment. Plant populations and plant biomass production from the early seedling to the heading stage were not consistently influenced by tillage treatment. Grain yield, which ranged from 1. 3 to 4.8 t ha-1 over the 4 year period, and yield components significantly differed each year but not consistently with any one tillage treatment. Mean grain mass tended to be greater for the chisel than the mouldboard treatments. Little difference was recorded in plant or grain accumulation of nitrogen, phosphorus or potassium. Plant response to additional nitrogen (25 kg N ha-1) applied at tillering was positive when growing season precipitation was optimum and showed a critical grain nitrogen concentration of 1.8%. Overall, shifting primary tillage from the fall to the spring had no detrimental effect on plant productivity and appears a promising strategy to allow retention of plant or residue soil cover in the winter period. This would reduce the potential for soil degradation in cool, humid regions with limited effective growing season (less than 100 days) for spring cereals.