Research into bush encroachment impact soil health

The Perivoli Rangeland Institute is conducting research on the impact of bush encroachment, bush control and grazing management on soil organic carbon (SOC).

According to a statement issued by Assellah David of the Bush Control and Biogas Utilisation Project, 10 university students and graduates from the University of Namibia (Unam), the Namibia University of Science and Technology (Nust), and the University of the North West in South Africa are travelling to around 30 farms in Namibia to collect data from up to five sites per farm.

“Currently, we don’t have scientific consensus on whether bush harvesting decreases or increases soil organic carbon,” Evert Strydom, the programme director at the Perivoli Rangeland Institute, says.

The Perivoli Rangeland Institute is run by the Perivoli Climate Trust, a Namibian-registered trust, which is funded by the Perivoli Foundation, a United Kingdom charity.

“We do know that bush control can initially shock the eco-system, depending on the extent of the treatment, which can result in an initial drop in SOC.

“After that, depending on grazing management and bush aftercare regimes, the preferential perennial grasses could return. Then SOC would increase.”

At least 45 million hectares of land in Namibia is bush-encroached and the research aims to establish its impact.

Apart from soil samples to see what lies beneath, the researchers will also collect information on grasses and bushes.

According to the researchers, soils rich in organic matter are better at holding nutrients and water and in making these resources available to plants.

The carbon content of the soil is one of the most important readily measurable indicators of soil health.

Building it up is a slow process, but SOC could deplete rapidly, if the land is mismanaged, the researchers say.

The statement says information from the field would be entered into a database, and soil samples would be analysed at the agriculture laboratory of the Ministry of Agriculture, Water and Land Reform.

Final results are expected in November.

Strydom says sequestering carbon in the soil is seen as a way to mitigate climate change by reducing atmospheric carbon dioxide.

The reasoning is that small increases of SOC over very large areas in agricultural and rangelands will significantly reduce atmospheric carbon dioxide.

“We consider this study to be just the beginning for our organisation.

“For Namibia, this is the start of a larger long-term research programme into the status of our soils and for the continuous tracking of our impact.

“We are working with the industry and the government to refine our Namibian soil research methodology, setting up a farmer research network and going bigger with more international donor funds,” Strydom says.

He says the teams will come back to the farms every year to measure impact over time.

Ndeshi Ndapulamo (23) is a graduate in environmental biology from Unam and she is the team leader of the operation at farm Elandshoek south of Tsumeb, with four graduates and students from Unam and Nust.

“We work great together as a team. Everybody is willing to do the work,” she says.
– email: matthew@namibian.com.na