Why is this a bad idea? Growing animal feed grains over septic drain-field

On our steep and rocky property, one of the only flat and exceedingly fertile spots is our septic drain field. We grow all sorts of trees, shrubs and vines on our hillsides, and have numerous raised beds for veggies and herbs. We really have nowhere other than the septic drain field that it makes sense to devote to barley, corn, quinoa, or other calorie rich foods, and for obvious reasons this would be for chickens rather than people. I am aware however that its important to have the right kind of things growing over a drain-field to absorb the nutrients, and for the depth of the soil above the outlet pipes to be within a certain range. I also do not want to be digging in that too much!

So the theoretical plan is:

- Scalp the current grass and weeds on the drain field with a brush cutter to weaken them and leave the green material to decompose
- Place a thin layer of twigs down to help balance c-n and aid drainage and water/nutrient retention
- Bury this all in 4” of purchased but inexpensive bulk compost from an organic landscaper
- Immediately plant corn and quinoa for bird food
- Stay on top of weeding resurgent grasses until the canopy is formed
- Plant barley in the fall for a winter crop

It seems like if we have a fast growing plant on there at all times, and we don’t bury things so deep as to create anaerobic conditions in he drain field, we should be ok, no?  Other concerns could be contaminants going into the septic, but its just my wife and I, and we use no toxic products and eat almost entirely organic. As it stands now I think the forest below our septic probably absorbs virtually all of the runoff, but it just seems like a way to help close a nutrient loops.

Is this just a crappy idea? Please share your thoughts!

I don't remember the details on what type of plants work best over a septic field, but it seems like, if you want to minimize digging, perennial crops might be a better option. Personally, I'd be inclined to go with white clover, alfalfa, perennial grains of some kind, perennial flax, and some kind of perennial green leafy things like sorrel.

I think the biggest worry is damaging the septic field. That is potentially a very expensive error.

I don't think any deep rooted plant would be a good idea in a septic field. The roots would invade the piping and clog it up.

Grass is usually what's grown. I suppose many grains could be grown as well, since they are also grasses with shallow roots.

Cultivation for seeding would be a big challenge. Equipment is basically out of the question, IMO.  Depending on how the field is constructed, there may be shallow layers of geotextile (fancy landscape fabric) covering trenches of washed gravel). Damaging the fabric means that soil/silt will infiltrate and clog things up.

Harvesting too would have to be done by hand.

Danger of contamination? The only one I can see is direct contact (boots, hands) from working on the field itself. If the field seems spongy or squishy when you walk on it, I would rapidly abandon the idea.

My longwinded 2c.

Good points, especially about perennials, which are my preference anyhow, and about grass’ ideal root depth and low soil disturbance maintenance.

This would have been a lot of hand work for a little feed grain, so its probably not worth the work or risks to the septic system drain field (I wasn’t considering anywhere very close to the septic tank itself). It grows abundant biomass with some decent diversity of grasses and weeds as it is, and i could always chop and toss this to chickens.

Feel free to add your own “Why is this a bad idea?” questions. Thanks!

Read about Vetiver Grass,
it filters many bad things out but keeps it in the roots. The stalks are not poisoned and young stalks can be used as fodder.
But Vetiver grass has very long vertical roots (12' and even deeper) and should be planted in a safe distance to the pipes and not above to avoid clogging.

Another example of perennials in septic fields are fruit circles (example Banana circles or Papaya circles)
The sewage water breaks down with the organic matter in the center and the short rooted plants and trees feed on the nutrients of the outer circle.
(They need to be short rooted that they not reach out into the center of the circle)