Agronomists usually cringe at the use of the word “dirt” in place of “soil”. The term dirt is too bleak a description to pay proper credit to the dynamic interactions taking place underfoot. Soil is an entire galaxy of minerals, liquids and gases influenced by vegetation and bacteria coming together to create life.
When the buzzwords “soil health” pop up ad-nauseum in today's media cycle, scientists are referring to creating and maintaining a balance between all these interactions in harmony. Each piece of the puzzle in its proper place, frequency, and abundance in order to optimize food production potential for crops and livestock (A.K.A. life). Most people have heard the saying “humans owe our existence on earth to 6 inches of topsoil and the fact it rains”. It’s simple but true.
Soils characterized by having good structure, provide the optimum potential for crop production. Sand, silt, clay and organic matter are negatively charged soil particles which rely on the proper balance of positively charged salts like calcium, magnesium, potassium to bind them. This forms larger aggregates that allow for good root penetration and water infiltration.
The last two summers here in Alberta our soils have been subject to extended heatwaves reducing our groundwater and surface water reserves. Water is a huge buffer of the overarching soil health picture that can mask or minimize many underlying soil issues. One of these waters influenced soil health issues is salinity.
Soil salinity isn’t always as obvious as white surface crusting. Salt-affected soils may seem to appear out of the blue, but they are lurking in the depths of the earth, building over time, and waiting for the right conditions. Usually going undiagnosed until symptoms are expressed in the vegetation.
When the water table rises to within 6 feet of the soil surface, that soil moisture is now close enough to be impacted by evaporation. The evaporation pulls the soil moisture up and out, leaving salts behind in the rooting zone. So, when Alberta experiences heat and drought as it has in the previous two years, crops are at higher risk of being negatively affected by high levels of salt.
30% of Alberta’s arable land is considered salt affected. What causes high levels of salt is typically the soil’s natural Glacial Till parent material being high in accumulated salts. When the soil is unbalanced and overwhelmed by these salts, the soil bonds that are between particles of sand, silt and clay are broken apart from their aggregates and soil structure is ruined. Each time the soil aggregates get a saltwater bath from fluctuating soil moisture levels more salts accumulate near the soil surface and in the rooting zone. Once the ground dries again this leaves an impenetrable hardpan or crust restricting root growth.
Managing these soil issues starts with a soil test to determine soil properties such as texture, pH, electric conductivity, nutrient and salt levels. From that point we can apply agronomic strategies such as planting salt tolerant crops and forages, till/no-till, soil amendments such as lime.
As we approach next season, soil moisture reserves will be a big factor to keep our eye on when getting our crops established and off to a running start.
A reminder now that winter is upon us, stop in and make a crop plan with our expert agronomy team, the coffee is always on!
Submitted by Calvin Ireland, C.C.A, Agronomist with Central Alberta Co-op (Lacombe)