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A few days of warmer weather provide an opportunity to squeeze in some soil sampling. Soil tests are a basic practice of 4R Nutrient Stewardship. To hire someone to collect a composite sample and get a lab analysis on that sample will cost $100 to $200 per field – or around $1 per acre. (Less for larger fields.) This will be a good investment if it means better decisions on fertilizer rates for each field and better yields. (Last month’s quiz covers this nicely.)
Fertilizer Canada’s Fertilizer Use Survey (discussed in this article) shows a strong relationship between soil testing and overall yield. The survey found that 50.6 per cent of high-yield growers soil test for nitrogen every year. That compares to 29.5 per cent for moderate-yield farmers and 24.4 per cent for low-yield growers. The soil tests are an indicator of a higher level of management overall, and this often goes hand in hand with higher yields.
Ideally, growers will use an appropriate fertilizer rate for each field based on soil nutrient reserves and yield goals. Sampling after soil has cooled to less than 10°C can provide a close reflection of nitrogen levels in the spring prior to planting, and allow for more accurate fall fertilizer purchases. The Canola Encyclopedia has more on sampling techniques and strategies.