Fertility issues and long-term no-till.
Johnston, A.M.. 2005. AB Reduced Tillage Linkages. Proceedings of Alberta Reduced Tillage Linkages.
Abstract
Direct-seeding systems are the most rapidly evolving tillage practice in western Canada, with an
estimated 63% of crop area in 2001 seeded with minimum or no-till in Alberta (Statistics
Canada, 2002). Because direct seeding encompasses a broad range of seeding and fertilization
methods, questions have arisen regarding the long-term impact of reduced tillage on soil fertility.
The impact of tillage on soil nutrient levels is largely determined by the nature of each specific
macronutrient, and the impact that the changes in the soil environment have on transformations
of the nutrient. Nutrients like nitrogen (N) and sulphur (S) are mobile in their dominant soil
forms, resulting in the lack of soil mixing having little impact on availability to plants. Less
mobile nutrients like phosphorus (P) and potassium (K) have the potential to become stratified
near the surface of the soil. Fertilizer placement of these less mobile nutrients can become
critical to plant uptake and yield optimization. Current soil testing methods are being challenged
to consider changes necessary to account for the evolving crop production and soil management
practices, in particular direct seeding and increased crop diversity in rotation. The ability to
estimate soil N supply with current soil testing methods appears to be limited in some situations
and innovative changes to soil testing will be required to improve the ability to predict soil
nutrient supply rates. An understand the how nutrients react in the soil, and are impacted by
changes in tillage practices, is critical to ensuring that crop production goals can be achieved by
balancing soil and fertilizer nutrient management.
