Thursday, June 21, 2018

Grass Management for Electric Fence

Grass contacting the lower conductors of an electrified poultry fence.

We've all had it happen. Grass contact. Every blade of grass acts as a small leak in the fence. As you go down the fence line, those leaks add up to significant energy loss.

How can we manage ourselves out of this situation?

  1. Mow. For fences moved daily, weekly or monthly, mow the grass before installation. Set your mower to cut the grass below the height of your lowest strand. 
  2. Trample the grass. Drive or walk the fence line several times to knock down the grass. Anecdotal evidence suggests that the grass will grow horizontally at first before vertically. Giving the grazer some leeway before grass contact occurs. 
  3. Spray. Not popular among grass farmers who spend so much time and energy trying to grow grass. Why bother killing it? I would only do this along permanent fences in an effort to keep off the brush growth.
  4. Adjust the height of your lowest strand. Folks that use multi-strand fences can easily adjust the height of their lowest conductor by sliding the insulator up the fiberglass post (away from power drinking grass).  
  5. Choose an appropriate energizer. Appropriate means a unit with enough output to overcome the weed load. For reference, a 1joule (output) energizer should power 2000' of weed laden fence, or 3-6 rolls of netting.
Other points of note:
  • The longer the blade of grass the longer the pathway from the fence to ground. The added resistance (and maturity of the plant) makes it a poor conductor. 
  • Short, lush plants are more conductive than their longer, older counter parts. They make better pathways to ground. 
  • Don't forget energizer grounding. If the grass is green, not contacting your fence, but you have an inadequate pulse, you may not have enough grounding to redirect the full-power of the pulse back to the energizer. Increasing the ground field increases the ability of the pulse to travel through the soil, back to the energizer.

What to avoid:
We covered what you can do, here's a "What you must NOT do".
If using electroplastic conductors (tape/twine/rope), do not use high impedance, continuous current or weed burner fence energizer.
The shape and duration of the pulse from these energizers is quite different from the pulse from low impedance energizers. The pulse from high impedance, weed burner or continuous lasts a touch longer and creates a little more heat. What does plastic do when it's heated? It melts. Combine melted plastic with grass contact (which creates a spark) and you have the recipe for a grass fire.

Stay away from energizers that claim both low impedance and continuous current. They are not a low-impedance unit that's safe to use with electroplastic conductors (and or tall grass).