Trafficability is the term used to describe the suitability of soils to field operations. While in the past much of our focus was on the traction properties of power driven equipment, the adoption of track and quad-driven wheel tractors has allowed us to shift the focus to the timing of field operations to optimize soil tilth and help build a good seed bed.
The point at which optimum soil tilth occurs is determined by many factors, including the soil moisture content, the sand, silt, and clay portions, as well as organic matter and the mineral materials from which the soil is made up. However, as for soil tilth, we can aggregate most of these factors into a single characteristic that we will call the consistency of the soil. One method of estimating soil consistency is to take a small handful of moist soil and try to mold it in your hand. The degree to which you can form a ball or ribbon (called plasticity) from a sample drawn directly from a soil probe or taken off a shovel can help you estimate how close you may be to optimal conditions for tillage or planting.
Because soil moisture content affects the consistency of the soil, it can also greatly determine whether tillage will have a positive or negative effect on the soil. A soil that is too wet when tilled (too plastic) is likely to exhibit compressive stresses that form clods that may become an obstacle to obtaining good seed to soil contact. As soil that is too dry (no plasticity) when tilled could have its structure fractured, becoming susceptible to erosion and soil compaction.
Morning Farm Report’s Tractor Time uses precise data on precipitation and soil type to make theses kinds of calculations. This information is then sent to growers who have subscribed to the Tractor Time service so that they have up-to-date information on conditions in each of their fields on a daily basis.
Now that planting season is upon us, we will be looking for good soil moisture content to facilitate seed germination. Although corn can germinate with 25 to 30% moisture, the optimum for soybean will be closer to 50% soil moisture. Throughout most of the Midwest we should be hitting those moisture levels with ease this spring. That means that for most growers their first concern may be getting good seed-soil contact in fields or low spots that have been worked a bit wet. Those areas will need your attention and perhaps require a follow-up visit to determine emergence rates.