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PUR Lab Case study – Soil erosion

DeviceThe PUR Lab is working on the assessment of ecosystemic services provided by trees. Among them is soil erosion.

In Peru, Alto Huayabamba, during one year of monitoring we have measured:

– 53 tons of soil losses/ha on bare soil;
– 11,8 tons of soil losses/ha on reforested area;
– 0,2 tons of soil losses/ha on secondary forest (full covered land).

This means that our tree planting reforestation model allows a reduction of 78% in soil losses!

STAKES

2015 was declared by FAO the international year of soils. Soil loss problematic is one major issue, as soil formation is very long (thousand of years are needed to form only a few centimeters of soil depth!) and 25 to 40 billion tonnes of topsoil are lost every year (FAO, 2015). Something is wrong in the equation…

The consequences for farmers and communities are important: lost of fertility, landslide, sediments accumulation in rivers, depletion of deep water reservoirs, water pollution. So, let’s try to avoid that.

FIELD STUDIES

In Peru, Guatemala and Honduras, PUR Lab measures soil losses and run-off in order to assess the impact of agroforestry systems on reducing such. The measurements are done using 10 m² prototype watershed with a collecting recipient. The erosion plots are installed in different landscapes: bare soil (Peru, Guatemala and Honduras), coffee mono-cropping (Guatemala), reforested area (Peru), and agroforestry (Peru, Guatemala and Honduras).

In total, we installed 3 plots in Peru, 6 in Guatemala (2 repetitions per land use) and 6 in Honduras (3 repetition per land use). On each project, the declivity must be the same for all. We measure run-off volume (how much water) and sediments concentration (how much soil) after each rain. An automatic rain fall gauge registers precipitation events.

After each measurement, we can calculate the run-off in liters and soil loss in kg/ha. Finally, the data analysis allows to assess the relationship between all the parameters determining soil loss and run-off.

NEXT STEPS

We will get the first year of measurement results from Guatemala and second year of measurement from Peru in 2017, and measurement will continue during 4 more years.

Our results are expected to allow us to develop training materials for farmers on agroforestry benefits, and partners. Add to that, these studies allow us to work with local and international universities.

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