Understanding Soil Mechanics to Improve Winter-Feeding Areas and Production

Steve Higgins and Morgan Hayes

Soils directly affect beef and forage production, yet active soils management is limited. Understanding soil mechanics and management in winter-feeding areas could improve beef cattle production, with less effort on the producer and cattle. This publication is intended to guide evaluating soil strength for winter-feeding areas, the pollution potential of winter-feeding areas, and to provide solutions for correcting structural deficiencies and reducing mud on both the ground and on the cattle.

Addressing these challenges is important because of the cyclical and repetitive nature of beef and forage production problems. Every winter and spring, beef cattle producers complain that too much hay is wasted, which requires more hay production and storage. Other common complaints include poor gains, weak calves, loss of body condition, and mortalities. In spring, technical assistance requests are often related to reducing or eliminating mud, weeds, erosion, and compaction (if the producer knows about it) due to winter hay feeding. If pasture renovation is conducted, winter-feeding areas might incur additional costs and labor for equipment, seed, fertilizer, chemicals, and fuel.

Geotechnical engineers or others who study soil mechanics usually refer to soil as the soil material from the subsoil to bedrock. To them, “soil” is the building material on which the foundations of structures and buildings such as farm roads, barns, buildings, and houses, are situated. To an engineer, topsoil has an agricultural value, but it has no structural value because it essentially has no load bearing strength. That is why contractors and builders scrape off topsoil to a depth of 4 to 12 inches to get to a compactible clay layer or remove all material to bedrock.

Using winter feeding as an example, a producer should look up the soil hydrologic grouping (A, B, C, D) to quickly and easily determine the suitability for winter feeding. Select soil hydrologic groups A and B   for this kind of use because these are well-drained soils. Selection standards for winter-feeding areas require that soils have a moderately low runoff potential when thoroughly wet (hydrologic soil group B). Choose soil with a good infiltration rate, but not so great that the infiltrated water passes immediately through the soil profile.  Sandy soils often demonstrate these very high infiltration rates. The goal is to filter the water as it passes through the soil profile. Inadequate infiltration is also not good, because it increases runoff potential without any filtering. Be aware when using hydrologic classifications that existing soil properties will change with time because of animal treading, tractor traffic, compaction, erosion, organic matter content, and soil phosphorus levels, etc. Long term use may require periodic re-location.

Once the producer has identified possible locations for winter feeding the next step is to rule out any low-lying areas, particularly those along floodplains. Even though sites may provide well drained conditions, these areas should be avoided if flooding periodically occurs or if they are in close proximity to a water body. Also exclude areas where streams of stormwater flow through the winter-feeding area or where ephemeral ponding occurs. These areas will often collect additional water originating from upland watershed areas. Moisture levels from a rising water table and drainage can easily shift a soil from a friable (workable) to plastic (moldable) to a liquid state. Plasticity in soil refers to soil that can be formed and reformed into shapes similar to clay used in pottery. Plasticity requires moderate water content; whereas dry soils will crumble - moderately wet soil particles will adhere to other particles.  The liquid state for soils occurs when the moisture content is greater than the plastic state can handle.  A liquid consistency can cause soil to shift, flow, or move offsite. The soil particles become suspended in the liquid water. This liquid state causes erosion.  

Solar radiation should be used during winter feeding to dry and stiffen soil. Shade from buildings, structures, and trees can interfere with solar energy and lower wind speeds across the area. High humidity tends to be concentrated in low-lying areas and is most common overnight and in the morning as the sun rises. During a typical day, humidity will be lowest when high temperatures are reached in midafternoon. To leverage these trends, orienting your winter-feeding area on slopes with a southern exposure is best.  If southern exposures are not easily accessible, western, then eastern aspects should be chosen over northern aspects.

The slope for a winter-feeding area should be less than 4%. A vegetative buffer or area that maintains good vegetative cover should be provided downhill from the winter-feeding area prior to entering a water body.  The vegetation can filter solids/organic matter and trap potential pathogens in the manure, while allowing nutrients to infiltrate into the soil profile and boost yields for the vegetation being grown. A standard setback minimum distance from a water body   located downhill from a winter-feeding area is 100 feet. A steeper slope requires a significantly greater setback. The number of cattle being fed as a group is a criterion that also affects the setback distance.      

Selecting an ideal site is the first step. But even with good siting, well drained soils, with time (and depending on stocking rates) can erode, compact, and modify inherent soil properties. These conditions are predictable based on measured values applied to soil engineering concepts. To keep a winter-feeding area in the same site for a longer term might mean using an adaptive strategy such as installing an all-weather surface, which should be designed to increase the load-bearing capacity of the surface, while reducing mud creation.  Gravel and geotextile fabric, concrete, or appropriate similar structural materials are examples of all-weather surfaces.

The benefits of understanding a soil’s physical properties can be invaluable to a beef producer. Engineering properties are used to determine a soil’s suitability for septic systems, manure application, burial sites, roads, the ability to corrode steel and concrete materials, and as a structural material. Engineering concepts are no less important as a critical part of the planning process for the beef producer designing infrastructure improvements like winter-feeding areas. These plans can prevent structural failure and limit future management difficulties on a farm, which means improved feeding situations, compliance with environmental regulations and sustainability for the operation.