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  • Sarah

From erosion to sponge

Erosion is a the wearing away process of an earthen surface where soil particles are moved or entirely removed due to natural processes as wind and flowing water. Although the natural origin of erosion, human activity can reenforce the erosion process by for example the complete deforestation of a terrain and tilling practices that expose bare ground.


The impacts of erosion are the inability of soil to store water and nutrients, increased runoff of water and nutrients and the exposure of subsoil among others.


Fortunately, this process can be prevented in order to maintain a spongey soil that soaks up water and nutrients. So how did I manage to make a sponge out of my eroding soil?


There exist many different types of soil, such as clay, sand and silt, which all have different compositions and structures. Therefore, the measures one wants to take to prevent erosion will predominantly be dependent on the type of soil found on the eroding land.


My soil is clay, which consists of smallest particles that are most densely distributed in the soil structure relative to other soil types. Clay drains with difficulty, but it is good at incapsulating nutrients. This post will discuss the techniques I took to prevent erosion on my land.


Before:

Swales dug in April 2021 and the start of the hügelkultur beds


After:

Swales and hügelkultur beds in March 2023

1. Hydration


Firstly, we have to slow down the water running down the land. As said before, clay is very dense and will not easily soak when water is running down the hill. Therefore we will want the water to run down the longest and highest way possible without accumulating it. I have used three techniques on my land to achieve this; swales, grey water and irrigation.


Before even building the house, I had already began digging swales. These are trenches along the land’s contour (all points are at the same height above sea level) lined with the pile of dug out soil on the downhill side of the trench. This method works good for me because the land is sloping but not too steep, in the latter case you might prefer terracing.


Later, when I built the house, I focused on using the grey water (rainwater first used in the shower and sinks) to fill up the swales. This is the perfect spot in the swale to plant trees and plants that love some extra water!


After using the hügelkultur technique, basically accumulating any organic matter (from tree trunks to hay) under the swales and planting these same little hills with pioneering trees and shrubs, I installed a drip irrigation system. I will write another post specified on installing an irrigation system and how much and frequently you should irrigate. For now, it is just important to know that watering the hügelkultur beds speeds up the decomposition of the organic matter and thus the creation of the huge anti-erosion sponge!



April 2023, Greywater outlet leading to a swale where the water is received by Mint, Corontillo (native), Chrysanthemum, Maqui (native), Quillay (native), Lavender, Rosemary and Horsetail.


2. Nutrition


Nutrients are the food for microorganisms that will process all the organic matter. These microbes are indispensable as they make little tunnels that brings oxygen and water to the roots of plants and trees. I have punctured the earth with a digging fork and drilled holes in the tree trunks to invite microorganisms and have the nutrients wash into the hügelkultur hills.


Then you can add any soil amendment you have at hand, such as compost, dry livestock manure, green manure, bokashi etc. Afterwards I turned on the drip irrigation to let the nutrients soak into the ground, but you can also apply them before a drizzle or light rain.


Last but not least, I planted some leguminous crops, shrubs and trees that are known to attract nitrogen fixing bacteria to their roots. I’ve sown lupin, acacia, scotch broom and peas, but there are many other options. The nitrogen fixing bacteria pass nitrogen onto the plant, which can then pass it on to the other plants without nitrogen fixing bacteria.



October 2022, irrigation attached up to a wire, white lupin as a nitrogen fixer and mulch covering the topsoil.


3. Cover the topsoil


As said before, bare ground is extremely vulnerable to erosion. Planting cover crops and mulching are good techniques to protect the nutrient rich top layer of the earth. Moreover, they will also help to capture humidity and slow down the evaporation of the soil. Choose the prevailing cover crops by observing what grows naturally in your environment and use the clippings of abundant grasses, shrubs and trees as a blanket for the topsoil (i.e. mulching).


Conclusion


Erosion is equivalent to losing living soil which sustains all the flora and fauna dear to our homes. In this post I have explained my actions to prevent erosion. These anti-erosion steps are never really finished. You will have to repeat them over and over to until the soil has regained its regenerative capacity, which is when it is functioning like a forest again. For this to happen you have to go further than just preventing erosion, namely the ecosystem must be restored. The next blog post will discuss ecosystem restauration techniques and my own experiences.


Thank you for reading this post and please leave your comments and questions below!


Sources:


Vivero Regeneracion - VR Consultora. Rehabilitación ecosistémica, agroecología, asesorías particulares, capacitaciones.


La Floresta Pullay – jardín vivero. Plantas para climas mediterráneos zonas costeras, educación medio ambiental y talleres de poda, riego y fertilización.

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