Soil erosion destroys the soil and the environment

Erosion of agricultural soil occurs in Denmark and can be a threat to soil quality and the environment.

2014.12.13 | Janne Hansen

Erosion of arable land is a problem in some places in Denmark. Photo: Preben Olsen

Wind, water and soil tillage erode our farmland. Erosion of the cultivated soil is a common problem in Denmark and is a threat to soil quality, to its status as a growth medium and to the environment.

- There is a notable shortage of studies on the level of erosion that can be considered acceptable for reasons of sustainability as well as for farm economy and for society in general, says Associate Professor Goswin Heckrath from the Department of Agroecology at Aarhus University. He will be presenting some of the available knowledge about erosion of farmland and about the impact of farmland erosion at the 2015 Plant Congress to be held in Herning, Denmark, in January 2015.

The concept of soil erosion is often unspecified, but includes erosion caused by wind, water and tillage. It is important to understand the differences between the terms.

- A distinction between erosion forms is important since not only the causes and harmful effects but also the initiatives required to protect the soil and the environment will be different, says Goswin Heckrath.

Wind and water

When the wind blows over the cultivated land it can erode the soil. In previous times roughly 500,000 hectares of agricultural land were exposed to wind erosion and an annual soil loss of more than 10 tonnes per hectare was not uncommon. Things have improved considerably since then, with the introduction of winter crops and windbreaks reducing significantly the risk of wind erosion.

Erosion caused by water can also be a problem. This depends on a complex interaction of topography, climate, specific soil type and soil management factors. Studies show that this has occurred particularly on fields with winter crops and in ploughed fields.

- Approximately 25 percent of the surveyed fields where erosion occurred had an annual erosion rate of 1.5 tonnes per hectare – and this is probably an underestimation, says Goswin Heckrath. Maize is particularly vulnerable to water erosion associated with heavy rainfall in the spring and early summer – and maize is more widely used now than when the survey was conducted.

Erosion caused by soil tillage occurs when a hilly area is ploughed or otherwise intensively worked. Tillage erosion acts as an efficient conveyor belt that moves soil from hilltops to hollows within the field, with little change happening in the middle part of the slopes. Annual soil loss is typically 20 tonnes per hectare.

A well-structured soil suffers less erosion

Crop management factors also influence soil erosion. Especially soil tillage and crop cover are important. Plant roots contribute to the mechanical strength of the soil, and in combination with a limited disturbance of the soil they form the basis for the protective effect against erosion bestowed by conservation tillage or direct drilling.

Critical soil erosion rates for sustainability have been defined internationally in relation to soil development and have been set at 1.4 tonnes per hectare per year, corresponding to approximately 0.1 mm soil per year. This level is exceeded locally in many places in Denmark.

- On heavily eroded areas, water and wind erosion leads to the loss of fine-grained material, organic matter and nutrients. This is detrimental to the soil structure, the water-holding capacity and the environment. In the long term these conditions will affect the growth potential of the soil. Since tillage erosion occurs on all hilly terrain that is farmed and causes a significant redistribution of the soil, this type of erosion can in the long term result in severe soil degradation, reveals Goswin Heckrath.

Read more about the 2015 Plant Congress to be held 14-15 January 2015 in Herning, Denmark.

For further information please contact: Associate Professor Goswin Heckrath, Department of Agroecology, e-mail: goswin.heckrath@agro.au.dk, telephone: +45 8715 7759

DCA