Cover crops are considered one of the most effective and economical ways to improve soil health. Grazing them can be a way to turn them into a profit for your operation. It is important, however, to avoid causing excessive compaction that could negatively affect following crop yield and increase runoff and erosion.
Sjoerd Duiker, soil management specialist with Penn State Extension, offers some tips on how to avoid excessive compaction when grazing cover crops:
First use continuous no-till. A no-till soil resists compaction better than a tilled soil. Even two or three years after a tillage event, the soil will still be softer, causing greater pugging by the grazing animals. The high organic matter content near the surface in continuous no-till is not easily compacted. Make sure the cover crop stand is dense. A dense cover crop has a robust root system that will help resist compaction.
And rotating with perennials is important. Perennial crops such as orchard grass, fescue, bromegrass, alfalfa or red clover improve soil beyond what is possible with an annual. The effect of the perennial lasts many years. Rotation with tap-rooted crops such as alfalfa, red clover, sweet clover or chicory helps improve subsoil porosity.
It is important to feed the “underground herd.” That means stimulating fungal and bacterial activity and promoting soil animals like earthworms that create macro-pores in the soil.
Leave sufficient crop residue after grazing to feed the soil. Healthy soil with high biological activity will more quickly bounce back from any compaction that is caused.
Have a movable water source. Most compaction is typically caused near the water source. By moving it regularly, you limit the potential for soil compaction.
Monitor soil moisture conditions and do not graze in areas that are too wet. You can use a ball test to determine if the soil is fit for the animals to be on it by grabbing a handful of surface soil and kneading it in your hand. If it forms a ball, the soil is too wet. If soil conditions are marginal, you should consider if there are fields on your farm that drain more quickly than others. You might have sandy or shaly soil, which drains more quickly, that might be ready sooner than limestone soil or soil with a seasonally high water table.
Steeply sloping soils can also be problematic in wet times of the year. When hoofs start skidding down the slope or create ridges, it is time to move the animals to more level fields.
Move animals more frequently when soil is wet to reduce the time of exposure. This means you pack the herd into a smaller area, but they are in there for a shorter period. Back-fencing is a good idea no matter what, so that the animals don’t go back over an area that has already been grazed.
Move animals to perennial pastures with tough root systems if conditions are wet. You will quickly notice the difference between tough-rooted species like tall, chewing or red fescue pasture and annual cover crops that have a smaller root system. The perennial grass withstands compaction a lot better. Pull the animals off if you expect them to cause severe compaction. This is a means of last resort, but it is preferred over mudding up your field.