Poor wet soil - fine mulch/the exception to the rule of clearing cut vegetation?

Amy
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Poor wet soil - fine mulch/the exception to the rule of clearing cut vegetation?

Post by Amy »

Protection of wet ground?
My question arises from a starting point of specific areas of land with unfertilised, poor, deep, permanently damp solid clay, with a natural vegetation cover of soft and sharp rush, wood club-rush where soil has been disturbed, yorkshire fog, fleabane and similar wet loving flowering plants. Some of these areas are permanently waterlogged i.e. a bog with perhaps 2 inches of almost peaty soil above the water table, and some other adjacent areas have springs running for 3/4 of the year but dry to a damp state in summer.

The Rule
We meadow makers are told that the fundamental rule is to Cut And Clear the vegetation every year to reduce fertility and allow flowering and other plants to compete with the grasses. However, if the land is naturally poor with a species rich seedbank, surely reducing the already low level of fertility is not the major concern?

Add humus for improvement?
Instead of removing vegetation, should I be considering leaving some of it to rot down and add humus to the soil, to aerate it and encourage soil creatures?

Bare wet earth v. mulch
I usually cut and clear by strimmer in the wet areas, and by flail mower collector in the drier areas, from September to mid October, as there is a lot of the late flowering fleabane and devil's bit scabious in some areas. The drier areas cut in September, produce a flush of new grass growth for ponies coming in in late November, but the wet areas cut in October don't produce much new growth until the following spring. If I strip the vegetation every year, am I not exposing more soil to the rains and potential run off, and reducing the food for the soil creatures, reducing the biomass of the topsoil and encouraging anaerobic conditions?

Mulch v. fertility
The RHS advises gardeners that adding new mulch to a flower bed, does not add many extra nutrients, and the value of mulch lies more in the improvement of the soil texture.

If I leave a fine and shallow mushed up mulch of the existing bog vegetation, then surely that would only be recycling the present degree of fertility, not adding to it?

Mulch and water holding capacity
But then - the RHS also says that adding mulch improves the water holding capability of the top soil - so if the top soil is already frequently very wet, what does that mean?

To summarise
When my strimmer mulches up the bog vegetation, would it not be good to leave a shallow layer of fine mulch which will rot down quickly, (far far more quickly than the adjacent areas of untouched rush and flower stems,) instead of raking up as much as possible and aiming to clear everything? I would still remove the long swathes of rush and flower stems which do smother other plants and shade out anything beneath.

I have been advised to cut and clear a third of the bog vegetation every year, so this must leave 2/3 to slowly rot down in a natural smothering way, with flattened stems over winter for the wildlife. My question concerns the 1/3 which is cut in rotation each year.

Also - protection against poaching
Where I have winter springs, I am putting those long swathes of cut vegetation on top of these different waterlogged areas (not the bog), to protect them from light poaching by red deer jumping a fence and Exmoor ponies walking alongside it. (I appreciate it is not ideal to have the ponies in winter, but this is the only time I can have them.) My reasoning is that it is better to protect the structure of the soil with a mat of vegetation, and, there are probably loads of rush seeds in the ground any way.

Finally, for the rest of the fields, which are drier - but naturally low in fertility, with a good mix and expanse of flowering plants threaded through what is mostly yorkshire fog, creeping bent and cocksfoot - would an occasional shallow fine mulch from the existing vegetation, be a good conditioner for the unforgiving clay beneath?

Would this not be applicable to any land - would it not be a good thing to improve the soil by cutting the existing vegetation and then leaving some of it as a fine mulch, say one year in 3, or at different times of the year?

Your thoughts please?
Alice
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Re: Poor wet soil - fine mulch/the exception to the rule of clearing cut vegetation?

Post by Alice »

My thoughts are that it is clear you know your piece of land very well, and you should go with your gut instinct. It is good to keep the ground covered over the winter, specially if there is some 'peaty' soil - that needs protecting to stop it degrading and releasing its carbon into the atmosphere.
I suggest you give it a try for a few seasons. If the species you are trying to keep and promote carry on coming back then you are doing it right!

The argument about fertility is, I think, mainly aimed at normal soil (if there is such a thing!), where if there is too much fertility you end up with nettles and docks. Extra fertility comes from the photosynthesis making fresh plant material each year but it sounds as though this is not your major concern.

Give it a try!
Amy
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Re: Poor wet soil - fine mulch/the exception to the rule of clearing cut vegetation?

Post by Amy »

Thank you, Alice.
Your dissertation sounds very interesting. I'd love to hear about it.

I've left a partial shallow mulch now in selected places for this winter, as I was concerned to see a cut by the flail mower in mid October, left bare soil in between the cut grass and flower stalks which may not be covered with regrowth over winter.

Generally, I just wonder if removing all the cut green matter every year could be counterproductive once a meadow has been established and the soil nutrients are low. In nature the green matter gets recycled, whether by overwintered standing stems, or dung - with meadow makers it does not.
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Re: Poor wet soil - fine mulch/the exception to the rule of clearing cut vegetation?

Post by Lucy Cornwall »

Hi Amy,

With regards to removing vegetation on your meadow, I think it is potentially quite important so to keep the nutrients low on the whole, although I'm sure a few patches wouldn't be too detrimental.

You say there is a lot of Yorkshire fog, creeping bent and cock's-foot in the sward. These are vigorous grasses and any rotting vegetation will feed these plants and they will continue to dominate. Ideally you want to have more finer meadow grasses and a bit more space for flowering plants.

I think the RHS advice on managing flowering beds is quite different to a meadow ecosystem, and the input of mulch to feed and improve the soil is really important in a garden flower bed, but not so in a perennial species-rich grassland system. In a meadow the diversity of plants and natural shedding of plant matter throughout the season should protect the soil and help to keep its structure.

In terms of poaching and soil protection, perhaps you could try making a slightly higher cut in September which would leave some low growth to protect the soil, and in early spring making a tighter cut? I am aware this is a lot more work and perhaps not possible.

It sounds like you have been doing lots of great work getting to know your meadow.
I hope my advice/knowledge is helpful.

Many thanks,
Lucy
nickygradyscott
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Re: Poor wet soil - fine mulch/the exception to the rule of clearing cut vegetation?

Post by nickygradyscott »

I think in this case I would be inclined to leave it to nature to decide - our meadow goes down to a wet common which has ponies and cattle grazing. It is on the edge of Dartmoor and is peaty soil. We have an abundance or orchids, ragged robin, Bog bean - in fact a Bio Blitz was done on it and it has an amazing variety of flora. There is no cutting or removing except by grazing and its been managed like that as long as I've known. My biggest concern is that the commoners have brought in diggers to deepen channels to drain parts of the common in one place destroying Devil's bit scabious and the Marsh Fritillary colony that was there. (totally illegal!) I would research how the land was managed previously.
The RHS comments on mulching are typical. Mulch and compost do not add much in the way of fertility it is true but then the most important thing - in my opinion and many others - in gardening is minimum disturbance of soil. Every time we dig carbon is released back into the atmosphere. Mulching keeps the soil profile intact and the ecology of the soil is maintained. Soil health is the aim. Healthy soils produce healthy plants and healthy plants produce healthy animals and people and healthy gut flora. But in this situation it's difficult to advise because if it cannot be managed with animals grazing then some random scything may be beneficial to help maintain a mosaic of habitats. and if in areas of thick grassy growth (Yorkshire fog - cocksfoot) it could be good to remove - but be aware these areas can be great for harvest mice and even dormice)
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Re: Poor wet soil - fine mulch/the exception to the rule of clearing cut vegetation?

Post by Alice »

Amy wrote: Sun Oct 22, 2023 7:49 pm Thank you, Alice.
Your dissertation sounds very interesting. I'd love to hear about it.
Your situation is a wonderful example of how simplistic 'rules' on how things should be done cannot fit every situation! Thank you for showing an interest in my dissertation. In it was trying to understand how 'reducing fertility' relates to soil carbon and climate change. If you're still interested, I did a ~40 min talk on my project and posted it on YouTube. You can find it (and a link to the full dissertation) here:
https://gsestudents.wordpress.com/2023/ ... /#more-600
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