A good time for a soil test

By Mitchell Japp, SaskBarley

I’m a fan of soil testing. But, many of the farms I talk to opt to test a portion of their acres each year rather than all fields. This is because they observe similar trends in their soil test results on well-known fields and across their farm. If there is a time to expand soil testing across most or, even better, all fields on a farm, it is prior to planting in 2022.

Following a drought, critical thinking suggests that any field that was fertilized for an average or greater yield, will have higher than normal residual nutrients in the soil. With yields as they are, it appears that the crop didn’t grow enough to use those nutrients and there hasn’t been enough moisture to cause leaching of mobile nutrients like nitrogen. Is that reflected in the soil?

The 2021 drought was far reaching, but local conditions varied. Some areas had significant snowfall in the 2020-21 winter, leading to good moisture conditions at seeding. Some areas had rain in late May – early June. Very few areas seem to have had rain between mid-June and mid-August. Despite the devastating heat and drought in late June and through July, nutrients may still have been taken up by the plant in areas that had starting soil moisture or received rain. In cereals like barley, most of the plant’s required nitrogen is taken up early in crop development, which may have been before the drought hit hard in some areas.

Seeding into dry soil can leave furrows that are not sufficiently closed to prevent nitrogen losses to volatilization. And, dry soils have reduced activity because many soil activities require water. Reduced soil activity will have affected processes like mineralization, ammonification and nitrification, so predicting stored soil nutrients will be more challenging without a soil test.

Harvest is finishing ahead of schedule this year. That leaves time for fall work like soil testing. The ideal time for soil testing is when soil temperatures are below 10°C and as close to freeze up as possible. Once the soil has cooled, all of the mineralization expected for this season will be captured in the soil test directly. Logistics will require soil testing to begin earlier, so determine if the testing lab will estimate additional mineralization, and if not, talk to your agronomist about what adjustments might be required.

There are a lot of unknowns in farming. Getting a soil test, especially after an exceptional year like 2021, can change soil nutrients from unknown to known. We don’t know what moisture conditions will be like next spring or growing season. A lot of crop planning happens in winter. Now is a good time to get a handle on soil nutrients to assist crop planning for 2022.