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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.