Page 119 - Nutrient Management Planning Guide

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Practical Use of Soil Analysis Results

Table 3.4.12 Qualitative Interpretation of Available Soil Moisture

Soil Texture Group

Depth of Moist Soil (cm) Dry Average Wet

Very Coarse 30–60 60–120 120+ Coarse 30–50 50–100 100+ Medium 15–30 30–60 60+ Fine & Very Fine 15–30 30–60 60+

Adapted from Brady and Buckman 1969

Determining Soil Available Moisture

Soil moisture can be assessed at the same time that fields are being soil sampled. The same rules regarding representative sampling apply to assessing soil moisture. Areas such as depressions, slopes, and knolls can be assessed separately for site-specific crop planning. Sample a minimum of 15 to 20 sites per field and record the average depth of moist soil. Spring sampling may require more sites within a field because of increased variability caused by snow trapping, snow drifting, water runoff, moisture migration within the soil and variations in ground frost, etc. Soil moisture can be determined by: using the “feel test” (Figure 3.1.5, Chapter 3.1) •

subjective visual evaluation •

measuring the depth of moist soil in a collected •

soil core

brown soil probe (Figure 3.4.4) •

Using the Brown Soil Probe to Determine Soil Moisture

To assess soil moisture depth, vigorously push the probe into the soil in one motion without turning and while applying weight to the handle. The probe will penetrate the soil and will stop when dry soil is reached. Record the depth into the soil that the probe was able to penetrate. Refer to Table 3.4.12 to determine available soil moisture. Stones, frozen soil or a dry surface layer may stop the probe as well, but these are easily detected.

Photo courtesy Crystal Korth and Len Kryzanowski, AF

Figure 3.4.4 Brown Soil Probe

The probe has a short section of a wood drill-bit welded to its end. When the probe is twisted clockwise, a small sample of soil can be obtained. This soil sample can be used to determine texture class and moisture by feel (see method in Chapter 3.1). To construct a soil moisture probe, weld a three-quarter inch steel ball on one end of a one metre long half-inch rod and weld a handle on the other end.