Experiment with three soils tests from one field

Submitted photo. The best time for fall sampling is after soil has cooled to at least 10°C.

Warren Ward, Canola Council of Canada

Want to take your fertilizer management up a notch? Here is a low-cost test that could provide some valuable insight into field variability: Choose an underperforming field and submit soil samples this fall from three target areas – hill tops, mid slopes and low spots.

The most common soil testing method is to submit one sample per field. The sample is based on 10 to 20 cores collected from mid-slope “average” areas, often split into 0-6” and 6-12” or 6-24” depths. Mid-slope areas are usually the most consistent, yield-wise, and account for most of the acres. So if farms are collecting one composite sample per field, this practice provides a good baseline fertilizer rate.

However, these mid-slope samples miss low-performing or inconsistent-performing hill tops and low areas. By spending a couple hundred dollars to collect and analyze two extra samples from one field, farms will gain new insight that could change the way they manage the farm.

For example, if soil analysis shows that hill tops are low in sulphur, farmers could spread extra sulphur on a few hills, since canola is a crop with relatively high sulphur requirements. Use those test hills as check strips, and see if they show a difference in next year’s combine yield map.

Consult with an agronomist to help decide how to use the results and whether targeted applications or check strips make sense.

Even if these extra two tests for one field don’t inspire a change in approach for 2024, they will provide some real numbers to quantify nutrient and soil variability. With that discovery, farms can start to see how, or if, that field variability might be enough to justify investment in a variable-rate system.

The best time to soil test

Soil sampling just prior to seeding provides the most accurate measure of nutrients available to the crop, but fall soil sampling can be almost as accurate and has various advantages:

            •           less time pressure to get samples collected and analyzed

            •           more time for fertilizer planning

            •           potential to buy the right amount of fertilizer at a lower price

The best time for fall sampling is after soil has cooled to at least 10°C. Cool soils reduce the microbial activity that can mobilize nutrients. Soil samples collected after this activity slows down will more closely reflect spring soil nitrate content.

Get funding for soil testing

Canola 4R Advantage provides funding for fertilizer best management practices (BMPs). The program can reimburse growers up to $20,000 for soil testing and, if growers choose, another $20,000 for consulting services to develop field zone mapping for variable rate nitrogen.

To participate, growers are required to have a 4R Nutrient Stewardship Plan developed and verified by a 4R designated agronomist that covers the BMPs included in the application.

The application deadline is November 30, 2023. This intake will cover expenses invoiced and paid by growers between April 1, 2023 and March 31, 2024. Visit canolacouncil.org/4r-advantage/ for program details, eligibility and the new application portal.

–Warren Ward is an agronomy specialist with the Canola Council of Canada.