Maps:
The
amount of moisture within the soil root zone just prior to fall
freeze-up provides a good indication of what can be expected for
spring moisture. With snow cover and freezing temperatures, water use
has ceased and when precipitation is mostly in the form of snow, the
infiltration of water is limited. This is especially true in moist
soils where soil pores are mostly “sealed off”.
During the last week of October, Manitoba Agriculture, Food and Rural
Initiatives personnel collected soil samples at over 120 sites across
Southern Manitoba. Each site was chosen based on the soil properties
that best represent the area and the most common crop types in each
region. Samples were taken with a soil auger at five depths throughout
the root zone; 0-15cm, 15-30cm, 30-60cm, 60-90cm, and 90-120cm. Samples
were immediately placed in sealed containers and sent to be weighed,
oven dried, and re-weighed to establish their gravimetric moisture
content (mass of moisture in mass of dry soil).
Each
soil sample was classified based on its similarities to
well-characterized soils around Manitoba. This enabled us to assign a
bulk density, wilting point, field capacity, and available water holding
capacity value (plant available water) to each depth from each sampling
site. From there, soil moisture by weight was converted to percent soil
moisture by volume. Then available water and soil moisture as a percent
of available water holding capacity were calculated and are shown on the
maps.
For
more information, contact
Andy Nadler, Farm
Production Extension – Agro-Meteorologist, Crops Branch,
Manitoba Agriculture, Food, and Rural
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