Why treating soil acidity crop by crop is no longer enough for prairie farmers

Long-term research from the University of Alberta has revealed that Western Canadian farmers should manage soil acidity across their entire multiyear rotation, rather than focusing on individual crops. A study published in the Canadian Journal of Plant Science examined how decades of fertilizer use, crop rotation, and lime applications affect soil acidity and nutrient availability over time.

The key finding was that liming legume forages not only improves their growth but also releases vital nitrogen for subsequent grain crops in the rotation. Managing soil acidity is crucial for maintaining productivity and preserving biological processes, as soil acidity has only recently become a concern for many farmers in Western Canada due to changing agricultural practices.

By not addressing soil acidity, farmers risk gradually decreasing soil fertility, which can affect the availability of nutrients and the activity of beneficial soil microorganisms. Different crops in the rotation have varying levels of sensitivity to soil acidity, with legumes like alfalfa benefiting most directly from liming. Although cereal crops like wheat and oats are less sensitive, they still gain indirect benefits by taking up more nitrogen when they follow alfalfa grown in limed soil.

However, alfalfa can also contribute to soil acidification by releasing acid into the soil as it absorbs positively charged nutrients like calcium and magnesium. Therefore, farmers need to consider the long-term consequences of different nutrient management strategies and regularly monitor and manage soil acidity. Regular soil testing should focus on plant-available nutrient levels in the top several inches of soil, as modern zero- or reduced-tillage systems may require different monitoring approaches.