The interest and adoption of variable rate fertilizer technology (VRFT) has increased dramatically in recent years. Industry agronomists and farmers have been and will continue to be on a steady learning curve to understand when and how to best utilize this technology. Before farmers can fully understand how to adopt VRFT, they need to develop a very good understanding of the types and amounts of soil variability in their fields.
A major factor that affects soil variability of fields is the type of parent geological material (PGM), which is the geologically deposited mixture of sand, silt, clay and stones. About 12,000 years ago, almost all of the Prairie region was covered by a massive glacial ice sheet about a mile thick. The parent material of many soils across the Prairies is called glacial till, which is the material left after glacial retreat. This heterogeneous material is a mixture of sand, silt, clay and stones. Soil texture (the proportions of sand, silt and clay) can be highly variable in glacial till but often is fine textured, as is the case with clay loam. The topography of glacially deposited soils ranges from gently rolling to very rolling or hummocky. Glacial till deposits are often moderately stony.
When topography is quite rolling, soil variability is primarily a result of slope position. Poorer soil moisture conditions on upper slope positions have meant less plant growth and less organic matter added to soils in upper slope versus lower slope positions over hundreds of years of soil development. Soils have been affected by greater erosion on upper slopes and deposition in lower slope positions. Sometimes soils are variable across landscape due to differences in geologic deposition. Soils may be quite sandy at one end of a field but higher in clay in another area. Sometimes the parent material may be high in sodium and Solonetzic soils have developed due to the high presences of sodium.
So there are a number of factors that can cause a profound range of different types of soil variation in cultivated fields