There’s a concerning trend in Ontario’s soils: organic matter is being depleted.
The decrease may seem small — about 0.8% over 12 years — but organic matter is vital to soil’s water holding capacity, nutrient-cycling ability, and compaction resiliency, to name just a few roles. What’s more, replacing lost soil organic matter is a slow, tedious process; preserving it should be job one.
What’s causing the steady decline? Christine Brown, sustainability specialist for field crops, with the Ontario Ministry of Agriculture, Food and Rural Affairs, says that it’s due, in part, to the increase in soybeans in rotation.
If you’ve got water, you’ve got the opportunity for nutrients to move — Christine Brown
Unlike corn and wheat, which leave quite a bit of residue behind with even average yields, soybeans would need to yield about 158 bushels per acre in order to leave enough crop residue to maintain organic matter levels.
But all is not lost! You really can still grow soybeans AND maintain or even build soil organic matter, but it takes a little extra planning or work, including adding soil amendments. Amendments might be added manure or compost, or could mean growing cover crops. Each amendment is food for the soil bugs, but it’s important to understand which is a chocolate bar and which is bran cereal for soil life.