EVALUATION OF SHALLOW TILLAGE FOR SPRING CEREALS ON A FINE SANDY LOAM .1. GROWTH AND YIELD COMPONENTS, N-ACCUMULATION AND TILLAGE ECONOMICS

Shallow tillage was assessed over a 4-year period for low-input production of spring cereals in Prince Edward Island. The soil was a Charlottetown fine sandy loam, an Orthic Podzol, which is marginally suitable for direct drilling. The tillage systems consisted of mouldboard ploughing, shallow tillage (rotary harrow, disc harrow) to the 10 cm soil depth, and direct-drilling. Plant populations were similar between tillage systems. Shallow tillage and direct-drilling produced similar grain yields as mouldboard ploughing when environmental conditions were optimum, but wet or very dry growing seasons favoured mouldboard ploughing and direct-drilling, respectively. Rotary harrowing prevented reduced plant growth rates prior to tillering and subsequently reduced accumulation of N in the plant and grain, associated with direct-drilling. Generally, the ability of plants to utilize N for growth was considered to be the main factor influencing N yield differences between tillage systems. In comparison to mouldboard ploughing, shallow tillage reduced machinery costs and energy requirements by 25-48% for seedbed production. In addition, shallow tillage had the advantage of timeliness and increased the potential area which could be prepared for seeding during the limited early spring period. Overall, shallow tillage removed some of the constraints associated with direct-drilling and provides an alternative, in rotational farming systems on fine sandy loams, to mouldboard ploughing.