World Soil Day is held annually on 5 December as a means to focus attention on the importance of healthy soil and to advocate for the sustainable management of soil resources. The theme for 2019 is Stop Soil Erosion, Save Our Future.
Soil erosion is the washing or blowing away (by water or wind) of the top layer of soil. Topsoil is the most fertile layer because it contains the most organic, nutrient-rich materials. Once this nutrient-rich layer is gone, few plants will grow in the soil again.
It can take up to 1,000 years to produce just 2-3cm of soil, but over 33% of the Earth’s soils are already degraded and 90% could become degraded by 2050, according to the UN Food and Agriculture Organisation.
Soil erosion can lead up to a 50% loss in crop yields.
We smallholders need to examine our veld and livestock management for practices which might lead to soil erosion, such as:
- Overstocking and overgrazing;
- Inappropriate farming techniques such as deep ploughing land 2 or 3 times a year to produce annual crops;
- Lack of crop rotation;
- Planting crops down the contour instead of along it.
Water erosion takes different forms, including sheet, rill and gully (dongas) erosion. Wind erosion happens when the land has dried out due to lack of rain and where it is flat enough for the wind to carry away particles of soil.
Factors such as the slope of the land, soil texture and structure, the amount of organic material, vegetation and land use will also influence soil erosion.
There are many approaches to prevent soil erosion from taking place.
We should consider reduced tillage and no-till methods of cultivation. These methods protect the soil surface and reduce runoff.
Once we have planted we should apply mulch. Mulching means spreading material such as decaying leaves, grass clippings, bark, wood chips or compost around the plants, to form a protective cover over the soil surface.
Cover crops are crops, usually grasses or legumes, which are planted between, or sometimes with, regular crops, primarily to protect and improve the soil. That protection helps to reduce erosion.
We can leave unploughed grass strips between ploughed lands (strip cropping). We can also make sure that there are always plants growing on the soil, and that the soil is rich in humus.
If you have livestock on your land, reduce them considerably to give the veld a chance to recover. Find out more about appropriate stocking rates and grazing intensities.
Extreme weather events due to climate change leave our land more vulnerable ~ preventing soil erosion forms an essential aspect of our veld management.