Hugelkultur berm

At the back of our garden is a high rocky area. It makes a great back wall – beautiful, fun to climb, and a sanctuary for lots of birds, geckos and plants. When it rains, the water rushes off these rocks and erodes a lot of soil from the gently sloping field at the foot.

One technique that is used to prevent erosion is digging swales and building berms – that is, digging a ditch and piling the mud next to it on the downhill side. The water rolling downhill lands in the ditch, soaks into the ground under the berm, watering trees or shrubs that are planted in the berm, and soaking into the water table. The water is slowed down as it goes downhill so that the land can benefit from it, and so that the soil is not eroded.

Another permaculture technique that involves making hills is Hugelkultur – farming in a hill. The hill is made by piling branches or tree trunks and putting soil and plants over then. The wood breaks down, supplying nutrients to the plants, and it also absorbs water like a sponge which it stores for the plants to access even in times of drought.

A principal of permaculture is that each element should perform many functions. So, I am combining hugelkultur and swales/berms to slow down water off the rocks at the back of the garden.  I’m calling it a Hugelberm!

In a recent storm, a tree fell down quite near this area, which was handy!

Longnan  Longnan Henry, who helps me each week in

the garden, chopped the branches off so I could use them for the Hugelberm.  

01

Step One: Identifying the site for the berm

In this photo, taken from in the maize field,  you can see the high rocks at the back.  The rain runs down these rocks through the field and erodes the soil as seen in the foreground where the soil is completely eroded and bare rock exposed.  The tree branches have been placed in the centre of the photo, so that the Hugelberm will be between the field and the rocks.  

 02

Step 2: Laying the tree branches

The view from sideways – the tree branches the length of the field.  The rocks are to the right (uphill), the maize field to the left (downhill).

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Step 3: Digging the ditch and covering the branches with the soil

I cut the grass about half a foot uphill of the tree branches and Longnan and I  dug a ditch the entire length of the field.  This will catch the water flowing down hill, allowing it to soak under the berm and into the water table.  The soil that was removed was used to cover the tree branches.  As it was not enough, more was taken from a compost pile I made recently.  

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Step 4: Planting and mulcing the berm

I transplanted some wild plants taken from the foot of the rocks  onto the berm. My thinking was that these are hardy perennial plants so they would do well in a rough and ready environment and not need much tending. 

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I also planted some papaya seedlings that I had growing in my fenced garden.  I hope that the tree branches will retain moisture as they decompose, adding nutrients and moisture for the papaya and other plants.  

These are the useful wild plants that I transplanted from the base of the rocks to the top of the Hugelberm.

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Cassia mimosoides

and

Tephrosia pedicellata

Nitrogen fixers to help fertilise the soil naturally.

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Oldelandia croymbosa

Edible shoots and leaves.  When cooked with other leaves they help to tenderise them.

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Emilia sonchifolia

The whole plant, flowers, leaves etc can be eaten raw or cooked. The flower heads are chewed and kept in the mouth for 10 minutes to prevent tooth decay.

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Guizotia  (Hausa abamacha)

An edible leaf in the sunflower family that produces beautiful small, yellow flowers at the end of the rainy season.

Finally (for now) I covered the berm with some straw from my goat house, rich in urine and goat manure. This is to stop the soil being washed away the next time it rains.

04-Optimized  IMG_7560-Optimized  Longnan standing next to the completed “Hugelberm”

Future plans:

-Observe and photograph the Hugelberm in a rainstorm and adapt as necessary.

-Build up the soil and plant life on the Hugelberm, possibly adding other plants like bananas.

-Build up the soil downhill from the Hugelberm by covering the exposed rock with compost.

-Observe the effectiveness of the Hugelberm to 1) slow water 2) prevent soil erosion 3) act as a source of water to trees planted in it throughout the dry season 4) act as a green barrier in the face of bushfires coming down from the rocks in the dry season.

UPDATE 11th Sept 2015

The week after the Hugelberm was finished, we had some showers of rain, but then on Friday 11th we had  a huge storm which gave me the opportunity of photographing the ditch at full capacity – it works!

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On the right of each photo you can see how the rain washing down the rocks is being held back in the ditch rather than rushing across the cornfield.  It will seep gently under the Hugelberm and soak down into the water table.  There were a few leaks on the downward side which I will plug with some more soil and possibly rocks, but on the whole, I was very pleased at how it held the water back in such a big storm.

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