To measure soil moisture, you need a simple probe made by welding a 3/4 inch steel ball on one end of a 3.5 foot long 1/2 inch rod and welding a handle on the other end.
Mark the rod every six inches.
Push the probe into the ground in a single motion. It will stop penetrating when it hits dry soil or a rock.
Sample about 20 sites per field and record the average depth of moist soil. More samples might be needed in spring because of the variability caused by snowdrifts and water runoff.
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Storm dynamics and extreme rainfall
Besides moisture, instability and orographic lift, the next biggest factor that contributes to heavy or extreme rainfall is storm dynamics.
The amount of water in the soil can be determined (See Table 1) from the moisture depth.
You can forecast the amount of moisture the field will get during the growing season by turning to records. Some farmers might have their own long-term monthly rainfall records.
In Saskatchewan, each rural municipality maintains precipitation amounts.
Environment Canada has monthly rainfall averages on its website for hundreds of sites across the Prairies from 1971 to 2000. Visit www.climat.meteo.ec.gc.ca and click on climate normals and averages.
Using the calculations in Table 2, you can figure out the target yield of common crops.
These calculations assume the crop was fertilized at the recommended amount, that pressure from pests was minimal and air temperatures were average. A drawback is that the equations are based on varieties common before 1990 while today’s varieties have higher yield potentials.
