If you find
Your soil has relatively low biological activity
Your soil is hard
Your soil has poor water infiltration
Your soil has low biological fertility
Grazing shock is the effect on a plant of being grazed hard or slashed and it’s a great way to build soil and improve pasture quality.
Because there is now less plant above the ground, there is less root needed to support the top.
So the plant sheds roots.
The loss of roots leaves gaps and food for soil organisms and for future root growth.
It’s a great way to build soil and improve pasture quality by feeding the soil.
This is where some of the benefit comes from the Short hard graze part of a Short on, long off rotation.
When animals hard graze a plant or when it is cut for hay, the plant goes into the plant equivalent of a state of shock.
The top (the part of the plant above the ground) is now much smaller and cannot support as great a volume of roots. The roots need nutrients from the leaves just as the leaves need nutrients from the roots.
Plus the plant no longer needs as much nutrient or water that the roots were getting from the soil.
So, to save energy the plant drops off some of the roots it no longer needs.
First it withdraws nutrients from the root in much the same way as a deciduous tree does from the leaves it sheds in the fall. When it can draw no more back, it cuts off the root.
Any nutrients that are still in the roots are left for soil organisms.
The root has become thinner and shorter in the process and so leaves a gap in the soil that enlarges as the root breaks down after being shed.
This is often the right size for earthworms and other soil organisms and it allows better gas exchange and water infiltration.
Grazing shock is more common on farms that have electric fences, but it’s not given by the electric fence.
Grazing shock is an important technique in managing pasture, because it allows you to provide
- dead organic matter
- a different environment
- a range of nutrients
- substances that help to glue soil into crumbs and
- soil tunnels.
These all suit soil organisms and encourage them to multiply.
The process builds soil structure by releasing substances that help to glue soil into crumbs.
Hard grazing and enough rest time are two of the things you need to get the full benefit from grazing shock. Electric fencing is often cheaper and quicker than other forms of fencing and as a result makes it more likely that you will use grazing shock effectively and to your advantage.
Grazing shock is enhanced by
- sufficiently large mobs of animals to ensure a short hard graze
- small enough areas being grazed at any one time to ensure a short hard graze
- mixed mobs — such as of sheep and cattle or cattle and goats to ensure that all plants are grazed and Selective grazing is minimized
- long rest time for the pasture to get the benefit and recover fully
- adequate nutrition to allow high levels of growth and biological activity to support the new growth