Lignin Content after Chop and Drop

Hey fellow permies,

I've been doing research to prepare to give a couple workshops on a "lens" for No Mow + Permaculture, and I've come across some useful info and a question that the community may be able to help with.

I've developed a set of techniques specifically for the average residential grower to use their landscape's meager outputs as valuable inputs, while transitioning their lawn to a food forest. The relevant portion of this is that it involves some use of "No Mow" as the landscape progresses through succession. I encourage people to grow this grassy biomass in order to begin to build soil, fertilize soil, and use it to make fertilizer.

In the aspect that is building soil, I've gone down a lignin rabbit hole. Lignin is wood. It takes a long time to break down. It is a super-essential ingredient to build healthy humus, fungal communities, attract beneficial organisms, create a soil composition that has air/water pores, etc. There is some amount of lignin in all plants, ranging from about 7% in grasses, to 40%+ in hardwoods.

My point is to use the No Mow as a source of elements like lignin to build soil. (It may be useful to note here that 95% of the biomass of plants comes from the air. So, when the plant is chopped or otherwise added to the soil, it is a net gain for the soil.)

In pursuing this point I used the devil (AI) to create these useful graphs (attached). What I glean from them is that lignin content in grass increases with age, and thus it's probably best to chop and drop it at the end of summer - fall. This coincides with leaf fall.

The question that I have which is hard to solve is this:

Do you think if a grass is chop and dropped earlier in the season, it will have a higher lignin content than a grass that wasn't?

In research, it was said that more stems = more lignin. I wonder if chop and dropping - or otherwise pruning - an herbaceous perennial like might cause it to produce more stems and thus a higher lignin content than the same grass that wasn't pruned. I'm sure this would vary with species and/or grass classes. It's a bit synonymous with saying that the chop and dropped plant has more biomass at the end of the season than the non chopped plant. I haven't been able to find scientific studies with this nuance, But I think the answer is that most will produce more biomass after chop and drop.

Anyway, I thought this was interesting info and and question, I look forward to your perspectives -

If you're more interested in this idea, I made a video awhile back about it, called No Mow Permaculture:

If cutting grass caused there to be more individual blades of grass, I would hypothesis that you would see more lignin at the end of the season than if you didn't cut it even with the small loss of maturing time. I however do not have evidence backing this up at the current moment.

Grass takes a little bit of time to polymerize lignin. I think it starts building up in content over a few weeks (As the grass matures). The longer it matures, the more lignin accumulates, the more fiber content that exists.

I suppose the question I would have is what specific grasses are you hoping to use to develop biomass?

If you want more of a rabbit hole, I would recommend looking into papermaking science research. There is a lot of information on lignin and fiber development for all sorts of pulps and woods. Bahia grass is a frequently used plant for fiber pulp so there is a ton of scientific research on it for example.

Timothy Norton wrote:
Grass takes a little bit of time to polymerize lignin. I think it starts building up in content over a few weeks (As the grass matures). The longer it matures, the more lignin accumulates, the more fiber content that exists.

I suppose the question I would have is what specific grasses are you hoping to use to develop biomass?

Yeah lignin definitely takes some time to form and accumulate, so it would really only work for species that would have a decent growth cycle after chopping. I think a warm season grass is an easy example. Even though they are largely dormant in the spring of a temperate climate like mine, if they are chopped in spring, and thus produce more "stems" over the season, I would think the resulting biomass/lignin would be greater than one not chopped.

For a cool season grass, they don't grow much over the summer and thus might not accumulate much lignin, even after being chopped. - But they might produce more lignin in their cool-fall-season growth cycle, which would mean it's best to harvest in late fall.

Thanks for your reply and another rabbit hole I definitely don't need right now lol

Undisturbed grasslands accumulate a lot of organic matter in soils, some from leaf litter, but also from root and rhizome material.  So the lignin content of the leaves is only part of the story.  Relative lignin content in leaves goes up in the late season in part b/c carbohydrates and nitrogen compounds are translocated out to seeds, rhizomes, or both.

I do not understand the y axis on your graphs, although the patterns look reasonable.
(ps I worked on related  issues years ago).

I don't see lignin as a bad thing.

Lignin can benefit soil by acting as a carbon source for microbes thus benefiting in soil health and helping with moisture retention.

I believe in using the chop and drop techniques and so this makes it sound even better.

Douglas Campbell wrote:
I do not understand the y axis on your graphs, although the patterns look reasonable.
(ps I worked on related  issues years ago).

Y axis just shows relative lignin - relative to the few different plant types it displays. (Trees have more than grass, etc.)

I'm definitely on board with lignin not being the only metric, but it is the most useful metric for above-ground biomass (No Mow), and it's easy to explain how chopping and dropping it builds soil on the surface.

Anne Miller wrote:I don't see lignin as a bad thing.

Lignin can benefit soil by acting as a carbon source for microbes thus benefiting in soil health and helping with moisture retention.

I believe in using the chop and drop techniques and so this makes it sound even better.

Did I imply it's bad? Quite the opposite.

I guess your comment makes me think of the people who till in wood chips (lignin) into their soil, thereby locking nitrogen. That is bad.

The chop and drop aspect is literal - I just leave the lignin/biomass/refuse on the soil surface to decompose and attract all those organisms and fungi. In this way it really acts like a mulch until it breaks down.

No, that was just my perspective.

A word of warning on your graphs - AI is still generally bad at things related to maths and numbers, including generating graphs. It will confidently lie to you and give you no clue that it has done so. If you want to use a graph like this I recommend that you find the original data source and either use their graphs or build your own.