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Steep slope strategies  RSS feed

 
Bruno Brusini
Posts: 5
Location: Macaronesia (Canary Is.)
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Hello, Permies!

After throughoutly looking for land, our group has finally come across a good candidate for our permaculture project. Our intention is to create, step by step, a permaculture homestead for self-sustainability, and whatever the future may bring. We'd love to evolve our farm, over a decade, into a permaculture experimental farm encompassing different fields, ranging from a common natural agriculture production to educative and cultural activities and native species reforesting.

Zone is 10a, subtropical climate at higher elevation (1250m/4100ft AMSL), facing NNE to ESE. Total surface is 7ha.
The only present vegetation are isolated chestnut and nut trees, and after the rain season weeds like thistles and dandelions sprout, just to be mowed down by the pasture animals afterwards. In the tiny 'valleys' between opposite slopes there are some unidentified trees. The owner says it's alamos, although I doubt it since they have laurel like leaves. It used to be an agriculture farm +15 years ago, nowadays used as pasture grounds for sheep and goats. Since it's pretty much bare soil, erosion has made a significant impact and is noticeable at plain sight. There are isn't any natural or man-made infrastructure to prevent or slow down erosion, except for two partially knocked down retaining walls.


This piece of land is pretty challenging because of its slope. While there's flat/gentle slope ground, most of the surface of the plot is within steeper slopes, ranging from 25% to 50% slope. I don't know whether there's a word in English for this kind of hilly terrain, in Spanish I'd say it's a 'loma' or 'cerro'. We aren't able to make traditional terraces, since it's has the lowest level of landscape protection (a completely arbitrary calification, by the way). Right now, our main concern is how to manage those slopes in order to rebuild soil and make them productive over time, hopefully reducing the slope to a manageable, safe for working steepness. I have done some research on possible strategies, such as alley farming and on contour deep rooted vegetation which would act as a barrier for erosion, building a terrace over time. Most of the searches I've done end up leading to man-made terraces, which are out of the question at the moment. I would love to hear which general courses of action or strategies you guys and gals deem convenient, or what you've done in similar situations.

Cheers!
Brus
 
Rene Nijstad
Posts: 184
Location: La Mesa, Cundinamarca, Colombia
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Hi Brus,

Congratulations on finding a suitable piece of land! Your description sounds like it will indeed keep you busy for quite some time. Does planning for a decade means that initially you will only work on it during holidays until the land is sufficiently restored?

I am not sure why you think that terraces have the lowest level of landscape protection, because in my personal experience they seem to have the highest level. So if you maybe could say more about that, it would satisfy the curiosity I feel now.

A few things I can think of you could do:
- bad erosion probably means you've got some (deep) gullies going down the slopes. You can build gabions in those, using rocks. That will prevent them from getting deeper, it will trap sediment behind them and create pockets of wet soil like that.
- if you have enough rocks, instead of vegetation planted in lines on contour, you can also lay down shallow rock walls. They will have the same effect. Trapped sediment will build up slower than behind gabions, because this method depends on sheetflow of water over the terrain instead of the highly concentrated flow you get in the gullies, but it might help over time.
- to help need small trees survive you could dig small circular shaped mini terraces, with a low wall in half a circle to prevent the edges from eroding away. If you can give each of those an overflow protected with rocks, excess water in heavier rains can drain away safely.
- if the small terraces mentioned above are also out of the question, then just dig a hole next to or above any tree you plant, so water can collect in it during the rainy season. These holes will either fill up with sediment or erode away over time, but they will help to gather more water for some time to help small trees establish.

Thistles generally point to compacted soils. That's something you might have to deal with to make your project work out.

I'm still curious about the why no terraces...
 
Angela Aragon
Posts: 50
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Congrats on your property acquisition. One solution you might consider is planting double hedgerows on contour, with a distance of about 1/2 to 1 meter between the pairs. Fast-growing legumes, such as Lucaena or Glyricidia are ideal for this purpose. If you have rocks/stones around, you can put them in between the rows to increase the gabion effect. Plant the trees very close together, around 10 cm apart, and then keep them trimmed to about waist level. Drop the trimmings on the land above the hedgerow. Put other trimmings up there to if you have them.

Swales do not work well on slopes greater than 20%. However, this technique, called SALT (sloping agricultural land technology), does. Over time, you eventually will wind up with a natural set of terraces, without having to dig at all, and with fertile soil.
 
Bruno Brusini
Posts: 5
Location: Macaronesia (Canary Is.)
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Hi Rene,

Thank you very much for your answer!

Regarding terraces, I think I expressed myself incorrectly. We're limited by the town council planning, who have marked the land as Protected Landscape Space (Espacio de protecci√≥n paisaj√≠stica or EPP). From what I've seen town councils across the island tend to put this kind of protection to hilly areas in their municipality to prevent [some] high visual impact human activities on the slopes. One of the limitations included in EPPs are creating terraces, as well as and many other earthworks. Luckily, building water holding infrastructure is allowed. There are other important limitations, as well. However, laws are made for general cases, and these include traditional agriculture. Since we're aiming to establish a proper PC regenerative farm, our project is at the same time (according to town council ordinances) an ideal and limited candidate for activities in an EPP. Given the health of the land and bare soil, one would hardly think that's a protected landscape, especially with a medium-voltage tower sitting on top of the main hill   : 

We'll be able to work full time on the farm, and we have considered prioritizing a 1ha area to establish the core of our homestead during the initial years, in the flattest land spaces that conveniently sit halfway uphill. We'll be initially taking an easy approach on zones 4-5, which are 'forced' by slope and current accesses, and will have much of sitting, observing and letting be, except for the needed early actions to help it start rehealing.

Yes, you're right! The soil is definitely compacted where the dry thristles are, trampled for years. Thank you for your suggestions!
 
Bruno Brusini
Posts: 5
Location: Macaronesia (Canary Is.)
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Angela Aragon wrote:Congrats on your property acquisition. One solution you might consider is planting double hedgerows on contour, with a distance of about 1/2 to 1 meter between the pairs. Fast-growing legumes, such as Lucaena or Glyricidia are ideal for this purpose. If you have rocks/stones around, you can put them in between the rows to increase the gabion effect. Plant the trees very close together, around 10 cm apart, and then keep them trimmed to about waist level. Drop the trimmings on the land above the hedgerow. Put other trimmings up there to if you have them.

Swales do not work well on slopes greater than 20%. However, this technique, called SALT (sloping agricultural land technology), does. Over time, you eventually will wind up with a natural set of terraces, without having to dig at all, and with fertile soil.


Thank you Angela for your suggestions!

We haven't acquired the property, we're waiting on some paperwork, which also gives us more time for planning and observing.
 
Roberto pokachinni
pollinator
Posts: 1507
Location: Fraser Headwaters, B.C., Zone3, Latitude 53N, Altitude 2750', Boreal/Temperate Rainforest-transition
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I will select a few quotes from your post and then discuss:  1.)
a permaculture experimental farm encompassing different fields, ranging from a common natural agriculture production to educative and cultural activities and native species reforesting.


2.)
like thistles and dandelions sprout, just to be mowed down by the pasture animals afterwards.


3.)
n the tiny 'valleys' between opposite slopes there are some unidentified trees


4.)[quotenowadays used as pasture grounds for sheep and goats. Since it's pretty much bare soil, erosion has made a significant impact and is noticeable at plain sight.]

5.)
There are isn't any natural or man-made infrastructure to prevent or slow down erosion, except for two partially knocked down retaining walls.


6.)
most of the surface of the plot is within steeper slopes, ranging from 25% to 50% slope.


7.)
I have done some research on possible strategies, such as alley farming and on contour deep rooted vegetation which would act as a barrier for erosion, building a terrace over time. 


1.)In regards particularly to your desire for native species reforesting, that is what you should primarily focus on these steep slopes.  They are too steep for most agricultural systems, and any animal impact will significantly degrade slope stability.  Less than 25% slope is the place for terracing, swales, and intensive food/animal production.  The more you reforest the steep slopes, and gain a complete vegetation cover, the more your lower areas will benefit from the increased water retention. 

2.)So in regards to the pasture animals mowing down dandelion and thistle (tap rooted plants) that are trying to heal your landscape... you have to create a better management pattern for these animals, particularly getting them off the steep slopes.  They are probably a primary reason why quote 4.) is so important for you to look at.  The erosion is very likely a result of improper grazing.  If you are to have animals graze in a desert then you need to come up with a holistic plan where the animals are utilized to benefit the landscape, not degrade it, and only on lower lesser sloped ground.

3.)Whatever trees you have, you should try to stabilize the landscape around them, and catch water towards them, and make any effort to increase catchment of debris/nutrients above them/around them. Nurture them and utilize them as the foundation of your future system.
4.)See remarks under 2.)...
5.)Can you tell what damaged the walls? Water?  Animals?  Did it look like the retaining walls were effective when they were complete?  If so, rebuild them.  If not, utilize the materials to create systems that will work for you, concentrating on slowing water flow in the areas where it seems it will flow the fastest (steep gullies).  Brush dams are very effective at stopping erosion in these gullies as well.
6.)As already mentioned, this is very steep for agriculture, but not for forest/nature.  If you focus all of your horticulture/agriculture on the flatter land, and do so in an intensive pattern, then you will have far more production with less effort than trying to make the steeper slopes productive for food.
7.)Deep rooted vegetation is the way to go.  Plant as many deep rooted hardy trees as you can get onto your steep slopes.  Gambion and brush dam your gullies and their deposition zones, and plant trees there as well. 

In regards to your entire post, I highly recommend that you watch the following video, which has much to offer your situation.
  
 
Roberto pokachinni
pollinator
Posts: 1507
Location: Fraser Headwaters, B.C., Zone3, Latitude 53N, Altitude 2750', Boreal/Temperate Rainforest-transition
104
bike books food preservation forest garden fungi hugelkultur solar trees woodworking
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Also, in regards to deep rooted species that you should be encouraging on your slope, utilize the dandelions and thistles; particularly the former. 

If you do not allow the animals to graze these, they will form the foundation for your rehabilitation of ground cover. 

Plant Cardoon and artichokes as a replacement in the thistle niche. 

When you see a dandelion, this is a good place to seed out other plants which will benefit from the micro-climate provided.  A dandelion can live several years, nurturing other plants like clovers (or maybe alfalfa?), plantains, oregano, thyme, salvia et cetera.  These hardy plants can pioneer your slope, stabilizing the ground further. 

If you begin concentrating your planting of these near the top of your slope, you will gain more rapid seed dispersal through gravity.  The other best place is around your existing trees, or trees you are planting.  The next best after that is around or near your gambions.  Also, if you import dandelion, breaking up roots and planting the pieces, you can multiply the crop and make greater gains.  Put a dandelion root and put some other seeds around it.  Any radish/mustard species will greatly encourage beneficial insects/pollinators, as will carrot/parsley family.  Again, self seeding annuals will be best benefited by being planted on the upper parts of the slope, or top of gullies.   
 
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