School of Agricultural, Earth and Environmental Sciences

Professor Kevin Kirkman at the NutNet site at Ukulinga Research Farm.

Ukulinga Research Farm Part of Global Study

Ukulinga Research Farm at UKZN is the only research site in Africa that forms part of a research network recently featured in Nature Communications, in an article that described the first ‘global-scale experiment to realistically determine the available nitrogen in grasslands on six continents.’

Professor Kevin Kirkman from Grassland Science at UKZN is one of the authors of the study that contributes to a better understanding of nutrient cycles in grasslands. According to lead author Anita Risch from the Swiss Federal Institute for Forest, Snow and Landscape Research WSL, grasslands cover ‘almost a third of the earth’s surface and have enormous significance for nutrient cycles, including the carbon cycle and the greenhouse gas CO2.’

The study concerns soil nitrogen mineralisation, an important process for productivity and nutrient cycling. By examining the balance between mineralisation and immobilisation under various soil and climate conditions, researchers were able to produce a field-based global-scale assessment of soil nitrogen mineralisation that analysed the drivers of this process across 30 grasslands worldwide, linking their data to factors such as temperature, soil clay content and microbial mass. The study demonstrated that field measurements differed considerably from laboratory measurements.

‘We now better understand what happens in the nitrogen cycle under natural conditions worldwide. This is important if we want to understand the impact of man-made global changes such as over-fertilisation of ecosystems,’ said Risch.

Risch and colleagues from the Nutrient Network (NutNet) project employed the same equipment and methods to measure nitrogen conversion in 30 natural grassland ecosystems worldwide directly in the soil. NutNet collaborators reproduced identical experiments on sites across nine countries to observe the results.

‘The long-term experiments at Ukulinga are increasingly recognised and contributing to global ecological studies,’ said Kirkman of the long-term mowing and burning trials that have been running at Ukulinga since the 1950s, making them one of the longest-running ecological experiments in the world.

Words and Photograph: Christine Cuénod